PEM POCUS Series: Pediatric Ocular Ultrasound for Optic Nerve Evaluation


Read this tutorial on the use of point of care ultrasonography (POCUS) for pediatric ocular ultrasonography for optic nerve evaluation. Then test your skills on the ALiEMU course page to receive your PEM POCUS badge worth 2 hours of ALiEMU course credit.

 

PATIENT CASE: Child with a Headache

Madeline is a 15-year-old female presenting to the Emergency Department with chief complaint of a headache for 1 week. She has been struggling with headaches for more than a year. The headache has been intermittent and tends to develop close to the end of the day, but it does improve with sleep. She denies photophobia, but has been complaining of blurry vision over the last week for which she is scheduled to see an ophthalmologist. Her medications include ibuprofen as needed for the headache and a daily medication for her acne.

Vital Signs

Vital SignFinding
Temperature97°F
Heart rate78 bpm
Blood pressure130/85
Respiratory rate14
Oxygen saturation (room air)100%
Weight200 lbs (90.1 kg)

Exam

Overall she is well appearing. She has a normal cardiac, respiratory, abdominal, and neurological examination including the cranial nerves.

On ocular examination, she has normal extra-ocular movements and a pupillary examination.

  • Visual acuity: Right eye 20/30, left eye 20/25
  • No visual field deficits
  • You attempt to evaluate her optic discs with an ophthalmoscope. Although not confident, you believe she has blurring of the optic disc margins bilaterally.

Given your examination findings, you request an ophthalmology evaluation and consider head imaging. While waiting, you decide to perform an ocular point of care ultrasound (POCUS) examination.


Why perform an ocular POCUS?

Ocular POCUS can be performed for various complaints, and it can provide valuable information. This especially is true in cases where the physical examination is difficult to perform such as from lack of patient cooperation, sensitivity to light, or pain. In resource-limited settings and when access to advanced diagnostic imaging or an ophthalmologist could be delayed or unavailable, ocular POCUS can be easily performed and provide information within minutes. 

Indications to performing ocular POCUS include:

  • Visual changes
  • Acute loss of vision
  • Ocular trauma
  • Non-traumatic eye pain
  • Evaluation for increased intracranial pressure (ICP)

IMPORTANT NOTE: Ocular POCUS should not be performed when there is a concern for globe rupture to avoid applying pressure on the eye and exacerbating loss of intraocular contents. 

Figure 1: Hockey stick linear transducer that can be used for ocular point of care ultrasonography
Figure 2. Linear transducer to use for ocular point of care ultrasonography

Step-By-Step Technique

  • The examination can be performed with the patient in the supine position or with the head of the bed slightly elevated
  • A high frequency linear transducer (Figures 1 & 2) should be used, preferably with a smaller footprint
  • A copious amount of gel should be applied to a closed eye
    • Different types of gel could be used such as the regular water-soluble ultrasound gel, sterile gel/surgical lube, and commercially available ocular-specific ultrasound gel. All these are safe, easy to clean, and do not irritate the eye.

Pro Tip: A tegaderm placed over a closed eye could be used to keep the gel from going into the eye. A tegaderm placed over a closed eye could be used to keep the gel from going into the eye depending on the patient’s preference.

  • Ultrasound Setup: Ideally use the ocular preset. The ocular setting lowers both mechanical and thermal indices, thus decreasing the amount of ocular exposure to the energy released from the transducer. Set the depth at 4-5 cm. This will allow imaging of the globe and the orbit behind the eyeball.

Pro Tip: If your POCUS machine does not have an ocular preset, a musculoskeletal or small parts preset could be used after turning down the dynamic range and mechanical index. Figure 3 is an example of how this could be done on a Mindray TE7 ultrasound machine.

Figure 3: To change the mechanical index (highlighted in the left upper corner), press on image, then slide the A.power down. Note as you are reducing the A.power, the mechanical index decreases. A mechanical index around 26% is sufficient.
ocular ultrasound transducer probe over eye
  • Provider Positioning: Anchoring is important when performing an ocular examination to avoid applying pressure on the eyeball. Place 2 or 3 fingers on the patient’s forehead, nasal bridge, or temple (Figure 4, left). Please note: Applying high pressure to the eye can induce the oculocardiac reflex leading to bradycardia. It can also stimulate nausea and vomiting.
  • Ultrasound Views: The ocular POCUS exam can be performed in transverse and sagittal orientations (Figure 5).
    • Transverse: place the transducer on the closed eyelids with the marker towards the patient’s right. Fan the probe until you identify the optic nerve.
    • Sagittal: with the transducer in transverse, turn it 90 degrees until the marker is pointing to the forehead. Tilt Fan the probe until you identify the optic nerve.
Figure 5: Transducer positioning while performing ocular POCUS in the sagittal (left) and transverse (right) orientation

Pro Tip: If the optic nerve cannot be seen, ask the patient to move the eye from one side to another. The optic nerve will move in the opposite direction (opposite to the patient gaze).


Normal Anatomy

Figure 6: A transverse ocular POCUS showing the hypoechoic eyelid anterior, the anechoic anterior chamber, hyperechoic iris, the hypoechoic lens with hyperechoic anterior and posterior edges, anechoic posterior chamber, and a hyperechoic retina. The optic nerve is appreciated posterior to the retina as a hypoechoic structure that may run vertically or at an angle.
Video 1: Normal ocular POCUS with a view of a straight optic nerve
Video 2: Another ocular POCUS showing a normal optic nerve and disc

Assessment of the Optic Disc

The optic disc is where the optic nerve enters the eyeball. On POCUS, it normally appears smooth and in-line with the retina. Sometimes a small elevation is noted at the optic disc. This is called Optic Disc Elevation (ODE). It can be measured from the base of the optic disc to its peak at the widest area. It normally measures < 1 mm (figure 7). If the ODE is > 1 mm, this indicates papilledema and increased ICP. Of note, normal ranges are still an active area of study, see table in Ocular POCUS: Facts and Literature Review section for more information.

Figure 7: Look at the optic disc. Is it elevated? When measured, it was 0.08 cm (0.8 mm).

Assessment of the optic nerve sheath diameter (ONSD)

  • The optic nerve is covered with the optic nerve sheath that is made up of the 3 layers of meninges surrounding the brain (dura mater, arachnoid mater, and pia mater). Pressure in the subarachnoid space is transmitted to the optic nerve sheath. ONSD (which is the hyperechoic membrane covering the hypoechoic optic nerve) can be measured 3 mm behind the retina (Figures 8 & 9 below). This measurement should done from the outer wall of the optic nerve sheath (hyperechoic sheath) to the outer wall of the sheath on the other side.
    • Do not include the shadow outside the ONSD in the measurement.
    • Identify the trajectory of the optic nerve because this measurement has to be done perpendicular to the nerve’s axis. 
  • Although definitive ONSD normal ranges are still an active area of research, a rough guide for a normal ONSD measurement is:
    • Infants less than 1 year: ONSD <4 mm
    • Children older than 1 year: ONSD <4.5 mm
Figure 8: Identification of the optic nerve, sheath, and disc
Figure 9: Measuring the ONSD 0.3 cm (3 mm) behind retina results in an ONSD of 0.385 cm (3.85 mm)
  • Use color doppler to identify the central retinal vessels that run in the middle of the optic nerve. This will help identify the axis/direction of the optic nerve. However, care should be taken to limited duration of color doppler use (Figure 10).

Pro Tip: ONSD normative values are not well established in pediatrics. Multiple studies attempted to set normal cutoffs for ONSD in various age groups. While measurement more than 5 mm in adults is considered abnormal, a value of 4 mm for infants and 4.5 mm in older children is used as the cut off [1]. The are different cutoffs that are used in the literature with variable sensitivity and specificity. See literature review section. ONSD is also highly operator dependent. An inappropriate technique in measuring the ONSD can lead to under- or over-estimation of the diameter. 


Ocular POCUS: Abnormal Ultrasound Findings


Optic Disc Elevation (ODE)

When ODE is >1 mm, it suggests papilledema, which is concerning for an increased ICP. The following figures and videos below illustrate abnormal ODE measurements. Note that normal ODE ranges are an active area of study.

Optic Nerve Sheath Diameter (ONSD)

Assessment of the optic nerve can provide information about intracranial pressure. Increased ICP is suggested when you see an enlarged ONSD.

Figure 11: Optic disc elevation can be seen as bulging of the hyperechoic optic disc into the posterior chamber, measured as 1.56 mm (normal is >1 mm elevation)
Video 2: Ocular ultrasound with bulging optic disc, concerning for papilledema
Figure 12: Ocular ultrasound label showing the elevated optic disc from Video 2

 

Video 3: Ocular POCUS showing elevated ODE and abnormal ONSD measurements for a 6-year-old patient
Figure 13: Labeled measurement of the optic disc elevation (ODE) from Video 3.
Figure 14: The optic nerve sheath diameter (ONSD) is 4.5 mm in Video 3, as measured 3 mm posterior to the retina. This is at the upper limit of normal for the age range.

Pseudopapilledema is a mimicker

Pro Tip: Pseudopapilledema (anomalous elevation of one or both optic discs without edema of the optic nerve) is a mimicker of papilledema and can be caused by a number of conditions including:

  • Optic nerve head drusen: Calcified deposits in the optic disc appear hyperechoic with posterior shadowing, and cause swelling (Video 4, Figure 15)
  • Congenital anomalies
  • Vitreopapillary traction
  • Systemic disease

In these mimic cases, the POCUS ODE is typically <1 mm, whileas true papilledema is ≥1 mm. If the findings are equivocal, providers should perform additional evaluation for papilledema and elevated ICP.

Video 4: Optic disc drusen
Figure 15: Optic disc drusen with hyperechoic calcium deposits of the optic disc with posterior shadowing. The ODE measurement is <1 mm.

Ocular POCUS: Facts and Literature Review

Ocular POCUS has been used in the Emergency Department for detection of various ocular conditions, including increased ICP. The American Academy of Pediatrics (AAP) supported its use for ocular evaluation in its policy statement [2].

Optic Disc Elevation (ODE)

ODE has been reported as a method for detection of increased ICP with decent accuracy. There has been multiple attempts to assess the quantitative measurement of ODE and its correlation with increased ICP (table 1). This is an area of ongoing research with early studies limited by small sample sizes.

StudySensitivitySpecificityComments
Teismann et al 2013 [3]At 0.6 mm cut off: 82%
(95% CI 48-98%)

At 1 mm cut off: 73%
(95% CI 39-94%)
At 0.6 mm cut off: 76% (95% CI 50-93%)

At 1 mm cut off: 100% (95% CI 81-100%)
Sample size: 14 adults

These measurements were compared to ophthalmology-performed fundus exam. Only 6 of 14 patients had papilledema.
Tessaro et al 2021 [4]At 0.66 mm cut off (for mean of ODE of both eyes): 96%
(95% CI 79–100%) 
93% (95% CI 79–100%)Sample size: 40 children (mean age 11.4 years)

26/40 patients had increased ICP.
Table 1: Literature about optic disc elevation measurements using ultrasonography

Optic Nerve Sheath Diameter (ONSD)

Normal values for ONSD have been established in adults [5]. It is still a controversial topic in children. The current standard is that an ONSD >4 mm in infants and 4.5 mm in children older than 1 year is considered abnormal, based on pediatric study of 102 healthy children [1]. There have been multiple studies to assess the sensitivity and specificity of this exam (table 2). 

StudyAbnormal ONSD ifSensitivitySpecificityComments
Blaivas et al 2003 [5]>5 mm100%95%Sample size: 34 adults

This is an adult study comparing ONSD on POCUS with CT results.
Le et al 2009 [6]>4 mm for infants

>4.5 mm for children >1 year old
83% (95% CI 60-94%)38% (95% CI 23-54%)Sample size: 64 children

24/64 patients had confirmed ICP based on CT, MRI, or direct ICP monitoring.
Marchese et al 2018 [7]>4.5 mm90% (95% CI 67–98%)57% (95% CI 43–70%)Sample size: 76 children

20/76 patients had concern for optic nerve swelling on ophthalmology exam. The test characteristics of ONSD changed with increasing or decreasing cutoffs or adding ODE as another marker for increased ICP.
Table 2: Studies assessing correlation of optic nerve sheath diameter (ONSD) measurements with increased intracranial pressure (ICP)

Case Resolution

You perform an ocular POCUS exam with a linear probe. The following image was obtained. What do you see?

Figure 16. Ocular ultrasound of patient case

ED Course

This patient’s POCUS showed optic disc swelling with optic disc elevation and an enlarged optic nerve sheath diameter suggesting elevated ICP. The brain MRI was normal without signs of hydrocephalus. Ophthalmology evaluation confirmed the presence of papilledema. After consulting with neurology, an ultrasound-assisted lumbar puncture (LP) was performed. The patient’s opening pressure was 35 mm H2O. CSF was removed until a goal pressure of 25 mm H2O was achieved. The patient was diagnosed with idiopathic intracranial hypertension (formerly known as pseudotumor cerebri). The patient symptoms were resolved after the LP. She was admitted for further evaluation and management.

Hospital Course

The patient was evaluated by neurology while on the inpatient unit. She was started on acetazolamide and discharged home. After multiple follow-up visits at the neurology clinic, her symptoms continue to be well-controlled.

Learn More…

References

  1. Ballantyne J, Hollman AS, Hamilton R, et al. Transorbital optic nerve sheath ultrasonography in normal children. Clin Radiol. 1999 Nov;54(11):740-2. PMID: 10580764.
  2. Marin JR, Lewiss RE; American Academy of Pediatrics, Committee on Pediatric Emergency Medicine; Society for Academic Emergency Medicine, Academy of Emergency Ultrasound; American College of Emergency Physicians, Pediatric Emergency Medicine Committee; World Interactive Network Focused on Critical Ultrasound. Point-of-care ultrasonography by pediatric emergency medicine physicians. Pediatrics. 2015 Apr;135(4):e1113-22. PMID: 25825532.
  3. Teismann N, Lenaghan P, Nolan R, Stein J, Green A. Point-of-care ocular ultrasound to detect optic disc swelling. Acad Emerg Med. 2013 Sep;20(9):920-5. PMID: 24050798.
  4. Tessaro MO, Friedman N, Al-Sani F, Gauthey M, Maguire B, Davis A. Pediatric point-of-care ultrasound of optic disc elevation for increased intracranial pressure: A pilot study. Am J Emerg Med. 2021 May 21;49:18-23. PMID: 34051397.
  5. Blaivas M, Theodoro D, Sierzenski PR. Elevated intracranial pressure detected by bedside emergency ultrasonography of the optic nerve sheath. Acad Emerg Med. 2003 Apr;10(4):376-81. PMID: 12670853.
  6. Le A, Hoehn ME, Smith ME, et al. Bedside sonographic measurement of optic nerve sheath diameter as a predictor of increased intracranial pressure in children. Ann Emerg Med. 2009 Jun;53(6):785-91. PMID: 19167786.
  7. Marchese RF, Mistry RD, Binenbaum G, et al. Identification of Optic Nerve Swelling Using Point-of-Care Ocular Ultrasound in Children. Pediatr Emerg Care. 2018 Aug;34(8):531-536. PMID: 28146012.
By |2021-06-23T12:54:16-07:00Jun 17, 2021|Pediatrics, PEM POCUS|

PEM POCUS Series: Pediatric Peripheral IV Access

PEM POCUS peripheral IV ultrasound badge

Read this tutorial on the use of point of care ultrasonography (POCUS) for pediatric peripheral IV placement. Then test your skills on the ALiEMU course page to receive your PEM POCUS badge worth 2 hours of ALiEMU course credit.


PATIENT CASE: Child with Sickle Cell Pain

Abigail is a 10-year-old girl with known sickle cell disease, who presents with severe atraumatic pain in her hips and back. She is afebrile, but tachycardic and tachypneic with 10/10 pain. Nurses have made several attempts but have been unsuccessful in establishing a peripheral IV(PIV) for giving IV fluids and medications. They now ask you to obtain access. You decide to perform an ultrasound-guided PIV placement. 

Exam

Vital SignFinding
Temperature37.6C
Heart rate135 bpm
Blood pressure135/90
Respiratory rate23
Oxygen saturation (room air)99%
  • General: Well-developed, appears in significant distress due to pain.
  • Cardiovascular: Tachycardic with regular rhythm, good distal pulses, and capillary refill
  • Pulmonary: Tachypneic without retractions; good aeration without wheezes, rales, crackles.
  • Abdomen: Soft, normal bowel sounds
  • Neurologic: Alert and oriented x3 with GCS 15; no focal deficits on cranial and sensorimotor exam

What are some potential challenges in peripheral IV placement?

  • Dehydration: Veins may collapse as a result of dehydration, making them harder to identify and cannulate.
  • Vein mobility: Veins are more mobile than arteries. Particularly mobile veins can “roll” or move during cannulation attempts.
  • Overlying soft tissue: Large body habitus can interfere with visualization of veins.
  • Vein size: Some patients, especially infants, have small veins.
  • Repeated venipuncture: Some patients with chronic conditions, such as sickle cell disease, often require frequent venipuncture. Repeated venipuncture can cause veins to change morphologically over time, making them difficult to identify and cannulate.

How can POCUS be helpful in obtaining IV access?

  • Direct visualization and guidance: Real-time visualization of IV catheter/needle in real-time as it approaches and cannulates the vessel.
  • Surrounding anatomy: Visualization of surrounding structures (e.g., nerves, arteries, other veins) which may not be apparent on visual examination.
  • Differentiating vein from artery: Distinguishing between different types of vessels.

Ultrasound-Guided Peripheral IV Access: Normal Findings

1. Differentiating Veins from Arteries

Veins and arteries can be difficult to distinguish. Below is a table to help differentiate using ultrasonography. 

CharacteristicVeinsArteries
DiameterTypically larger than arteries (is dependent on fluid status)Relatively fixed in size, round in shape
Wall ThicknessThinThick
CompressibilityEasyMore difficult
Color Doppler FlowNon-pulsatilePulsatile
Vessel ValvesPresent (but not always visible)Absent
Table 1. Anatomical and ultrasonography differences between veins and arteries
  • Compressibility: Typically, veins are easily compressed, while arteries with their thick walls are more difficult to compress.  
Video 1: Ultrasound clip of a vein being compressed
  • Color Doppler Flow: Color Doppler can be used to differentiate pulsatile from non-pulsatile flow. Red and blue colors do NOT correlate with venous or arterial blood flow. Instead, the colors represent the direction of flow. A helpful acronym is BART – “Blue Away, Red Towards.”
Video 2: Ultrasound clip of a vein (red) with non-pulsatile flow and artery (blue) with pulsatile flow

2. Identifying Nerves

Nerves can be confused with blood vessels when looking on ultrasound. The following are ways to identify a nerve.

  • Honeycomb appearance: Classically nerves appear in cross-section with small hypoechoic (dark) areas separated by hyperechoic (bright) septae.
Video 3: Ultrasound clip of nerve (left) and artery (right). The nerve has a honeycomb appearance with several hypoechoic (dark) areas separated by hyperechoic (bright) septae whereas the artery is more uniformly hypoechoic. There is also a needle entering from the left of the screen. See below labeled still image of same anatomical structures below.
peripheral IV ultrasound nerve artery
Figure 1: Ultrasound still image with labeled nerve and artery. See Videos 3 and 4 for ultrasound videos of same structures with and without doppler flow. 
  •  No Color Doppler flow: While Color Doppler can be used to assess for pulsatile and non-pulsatile flow of arteries and nerves, respectively, nerves should not demonstrate any flow. 
Video 4: Ultrasound clip of nerve (left) and artery (right) with color Doppler. This is a clip of the same location on the same patient in Video 3 and Figure 1. The nerve (center of yellow box) shows no flow under color Doppler. In contrast, the artery (partially captured at right of yellow box) demonstrates pulsatile flow. 
  • AnisotropyThis ultrasound artifact is exhibited by nerves (as well as tendons and ligaments), whereby the nerve changes brightness depending on the angle of ultrasound beam.
Video 5: Ultrasound clip of nerve exhibiting anisotropy. The brightness of the nerve (in center, labeled in Figure 2 below) changes with the angle of the probe.

PEM POCUS peripheral IV anisotropy ultrasound
Figure 2: Still image from Video 5 above with nerve highlighted in yellow. 

Fun fact: Certain gemstones like tiger’s eye and figured woods like flamed maple exhibit chatoyance which is analogous to anisotropy, but occurs under visible light, rather than ultrasound beams like anisotropy.

gemstone anisotropy
Figure 3: Image of Tiger’s eye gemstone. These gemstones exhibit chatoyance, a characteristic of light reflection which is analogous to “anisotropy” under ultrasound. (Image: Benjamint444 [CC BY-SA])

3. Needle Artifact

Needles exhibit ultrasound artifacts which can help with identification.

  • Ring down artifact:  This resonance artifact describes when ultrasound beams encounter trapped gas and create a spotlight effect.  See additional information on Radiopaedia.org.
  • Reverberation artifact:  This artifact describes when ultrasound beams reflect back and forth between two strong parallel reflectors and the machine interprets additional objects deeper than the actual object.  See additional information on Radiopaedia.org.
Video 6: Ultrasound clip of needle in water bath with both ring down and reverberation artifacts. The tip of the needle appears to have a spotlight beam shining down,  this is an example of ring down artifact from trapped air at the needle tip. This video also demonstrates reverberation artifact where there appears to be a deeper hyperechoic (bright) needle at the bottom left of the video seen best at the beginning of the clip.

TECHNIQUE

Vein Selection: Upper Extremity

Typically, pediatric patients receive a peripheral IV in the upper extremity in one of 2 locations: 

  1. Antecubital fossa (Figure 4):
    • Access superficial veins, which includes the basilic, cephalic, and median cubital veins. 
    • Tip: Beware of tortuously curved paths of veins, branch points, and nearby nerves.
arm anatomy vein
Figure 4: Diagram of venous anatomy of the arm focused on antecubital fossa. The antecubital fossa area (the inside of the elbow) is shown in the blue box. Adapted from image By OpenStax College – Anatomy & Physiology, Connexions Web site. Jun 19, 2013. [CC BY 3.0]
  1. Upper arm near medial bicipital groove (Figure 5):
    • Access the deep brachial vein or more proximal aspect of the basilic vein.
upper arm vein anatomy
Figure 5: Diagram of venous anatomy of the upper extremity. By OpenStax College – Anatomy & Physiology, Connexions Web site. Jun 19, 2013. [CC BY 3.0]

Vein Selection: Lower Extremity

If unable obtain upper extremity access, the lower extremity can also be accessed. This is more typically performed in infants and young children. 

  • Lower medial leg (Figures 6, 7): This site allows for access to thegreat saphenous vein. 
leg vascular anatomy
Figure 6: Diagram of veins of the leg. Blausen.com staff (2014). “Medical gallery of Blausen Medical 2014“. WikiJournal of Medicine 1 (2). [CC BY 3.0]
Figure 7: Diagram of veins of the lower leg. Adapted from image by Blausen.com staff (2014). “Medical gallery of Blausen Medical 2014”. WikiJournal of Medicine 1 (2). [CC BY 3.0]

Set up for success

  • Prior to starting the procedure, set up the room for optimal visualization. 
  • Place ultrasound system monitor in direct line of site with the angiocatheter.
ultrasound set up position peripheral IV
Figure 8: Ultrasound machine positioning such that the probe, patient, and screen are in one line of sight.
  • Apply tourniquet around the extremity.
  • Use the high-frequency linear transducer (Figure 9) to identify potential veins before the procedure to map out the course, depth, and size of veins. Initial scanning can be done without sterile precautions. 
    • The best vein: The ideal vein is large, superficial, not near other anatomic structures, and relatively straight.
    • Depth: Set an appropriate depth on the ultrasound monitor such that the target vein is centered on the screen.
ultrasound linear probe
Figure 9: A high-frequency linear probe
  • Tip: Pre-scan multiple areas on both arms (or legs) to find the optimal site for ultrasound-guided peripheral IV placement. 
  • Cleaning and probe covers
    • Clean off any non-sterile gel from the patient’s skin.
    • Prepare the skin with chlorhexidine or an alcohol swab.
    • Use a single-use probe cover.
      • Consider a Tegaderm patch, sterile glove, condom, or sterile probe cover.
      • For further discussion of the relevant literature around probe covers, see this ALiEM post.
    • Use sterile ultrasound gel between the skin and the covered probe.
linear ultrasound probe cover glove
Figure 10: Sterile glove as a makeshift probe cover. Here the entire probe fits into a single finger of a sterile glove. For another method of using a sterile glove as a probe cover see this Trick of the Trade.

Probe Positioning

  • Proper orientation and terminology
    • In this procedure, there are 3 objects to coordinate in space. All of these relationships should be in a perpendicular or parallel orientation (not oblique). 
      • The vein
      • The probe
      • The needle 
    • The needle should always be parallel with (i.e., directly overlying) the vein. This leaves two other positional relationships: probe/vein and probe/needle. 
      • Probe/vein: The probe is either transverse or longitudinal relative to the vein (Figure 11).
      • Probe/needle:The needle is either out of plane (i.e., perpendicular) or in plane (i.e., parallel) relative to the length of probe. When using the transverse orientation, the needle is typically also perpendicular, or out of plane, with the length of the probe. Conversely, when using longitudinal orientation, the needle will be parallel, or in plane, with the probe.
ultrasound short and long axis linear probe
Figure 11: Labeled axes of linear ultrasound probe

POCUS-Guided IV Cannulation Technique

There are 2 approaches in using POCUS for cannulating peripheral veins based on if the operator is using the transverse or longitudinal orientation.

  1. Transverse orientation: This view is particularly helpful for keeping adjacent structures in view and requires less precision to keep the vein in view. It is important to keep in mind the distance the needle must travel to successfully enter the vein, which will depend on the angle of the needle and the depth of the vein. Videos 7 and 8 show the transverse orientation ultrasound views. Note that in this view, once the needle passes into the plane of the ultrasound beam,  it can be difficult to distinguish the tip of the needle from the shaft. 
Video 7: Ultrasound clip of a phantom model vein in transverse orientation with vein cannulation at end of clip. The needle can be identified based on the ring down artifact as it passes into the plane of the ultrasound beam.

Video 8: Ultrasound clip of a patient’s vein in transverse orientation with vein cannulation. The vessel is in the top center of the screen. The needle is the bright white (hyperechoic) dot entering it, seen out of plane.
  • Transverse technique (out of plane) with dynamic needle tip visualization: The shaft of the needle can appear indistinguishable from the tip of needle in the transverse or out-of-plane approach. The dynamic needle tip visualization technique allows the operator to continuously identify the location of the tip of the needle. 
    • As soon as the skin is entered, slide the probe closer towards the tip of the needle. 
    • Advance the probe just beyond the tip of the needle. As soon as the needle is no longer in view (i.e., just beyond the tip), it is clear where tip of the needle is. 
    • Hold the probe steady just beyond the needle tip, and advance the needle forward, returning it into the field of view. 
    • Advanced the probe just beyond the tip of the needle again.
    • Repeat the previous steps until the needle is visualized entering the vein.
      • Tip: Make small movements and attempt to keep the vein in the center of the screen. For beginners with this technique, it is recommended to alternate moving either the probe or the needle, one at a time.
Video 9: Ultrasound clip of a phantom model in transverse orientation with vein cannulation using dynamic needle tip visualization. The operator alternates moving the probe just beyond the tip of the needle and advancing the needle toward the vessel until cannulation. 

Video 10: Demonstration of the dynamic needle tip visualization technique, showing alternating movements of the probe and needle
  1. Longitudinal orientation: Conceptually, this orientation is more straightforward (probe, vein and needle are all parallel), but the precision involved requires a steady hand and a stationary patient. The needle must stay parallel to the probe within the slice thickness of the ultrasound beam. This value will vary depending on the machine and the probe, but is on the order of millimeters. Video 12 demonstrates the importance of maintaining the vein and needle parallel to the ultrasound beam or else the vein and/or needle disappears from view.
Video 11: Ultrasound clip with needle in and out of view using the longitudinal orientation technique. Being slightly out-of-plane makes it difficult to visualize the needle and needle tip. Of note, this needle has a guidewire extended past the needle tip which is curved slightly upward from the length of the needle.
  • Longitudinal (in plane) technique
    • Align the probe parallel to the vein. Ideally, the vein should be the same depth and thickness across the screen. 
    • Introduce the needle in-plane (parallel) to the probe marker at a shallow angle. Depending on the depth and size of the vein, this may be close to parallel with the skin.
    • Maintain visualization of the needle tip as it enters the vessel.
    • Tip: If it is unclear where the needle tip is, first stop moving the needle and assess if the probe has drifted or rotated. While keeping the needle still, make corrections with the probe until the needle and needle tip is once again visualized in plane. 

Video 12: Ultrasound clip of needle cannulating vessel in longitudinal view using in-plane technique

After Cannulation

After the needle tip is visualized entering the vein and a flash of blood appears in the hub of the needle, advance the needle forward an additional 1-2 mm before threading the catheter. Why? The catheter does not extend fully to the tip of the needle. Thus the needle must be advanced past the initial flash of blood to ensure that the catheter has also penetrated the vein. If there is resistance when threading the angiocatheter into the vein, reassess the needle tip position using the ultrasound and confirm the needle is still positioned intravascularly. 

Peripheral IV catheter with needle
Figure 12: Typical angiocatheter for peripheral IV access. The first few millimeters of the needle tip extend beyond the catheter.

After successful threading, retract the needle, attach pre-primed IV tubing, and flush and lock the tubing. Secure the catheter in place.

LITERATURE REVIEW

There have been many studies evaluating ultrasound-guided peripheral IVs in patients, and below are several key articles involving pediatric patients. Overall, ultrasound-guidance appears to be helpful in pediatric patients with difficult access, but the exact technique involved and the experience of the operator likely have an effect. 

YearAuthorsTitleMajor Findings
2009Doniger et al. [1]Randomized controlled trial of ultrasound-guided peripheral intravenous catheter placement versus traditional techniques in difficult-access pediatric patientsUltrasound-guided peripheral IV placement in difficult-access patients took less time, was more often successful, and required fewer needle re-directions.
2010Oakley and Wong [2]Ultrasound-assisted peripheral vascular access in a paediatric EDUltrasound-guidance was associated with slightly increased success rates in peripheral IV placement. This effect was more pronounced in cases with difficult-access patient.
2018Otani et al. [3]Ultrasound-guided peripheral intravenous access placement for children in the emergency department In contrast to many other publications on ultrasound-guided peripheral IV procedures, the authors report a LOWER success rate for patients that had one failed IV attempt, as compared to the conventional method. An important potential confounder was that this study used a “dual-operator” method, in which one clinician operates the ultrasound, and the other places the IV. 
2018Desai et al. [4]Longevity and complication rates of ultrasound guided versus traditional peripheral intravenous catheters in a pediatric emergency departmentUltrasound-guided peripheral IVs had a longer catheter survival time compared with traditionally-placed peripheral IVs. Complications from the peripheral IVs were similar between the two groups. 
Table: Key literature on pediatric cases studying ultrasound-guided peripheral IV access

References [click to expand] +

  1. Doniger SJ, Ishimine P, Fox JC, Kanegaye JT. Randomized Controlled Trial of Ultrasound-Guided Peripheral Intravenous Catheter Placement Versus Traditional Techniques in Difficult-Access Pediatric Patients. Pediatr Emerg Care. 2009;25(3):154-9. doi:10.1097/pec.0b013e31819a8946.
  2. Oakley E, Wong A-M. Ultrasound-assisted peripheral vascular access in a paediatric ED. Emerg Med Australas. 2010;22(2):166-70. doi:10.1111/j.1742-6723.2010.01281.x.
  3. Otani T, Morikawa Y, Hayakawa I, et al. Ultrasound-guided peripheral intravenous access placement for children in the emergency department. Eur JPediatr. 2018;177(10):1443-49. doi:10.1007/s00431-018-3201-3.
  4. Desai K, Vinograd AM, Abbadessa MKF, Chen AE. Longevity and Complication Rates of Ultrasound Guided Versus Traditional Peripheral Intravenous Catheters in a Pediatric Emergency Department. J Assoc Vascular Access. 2018;23(3):149-54. doi:10.1016/j.java.2018.06.002.

CASE RESOLUTION

Using POCUS, you begin by visualizing Abigail’s veins at the antecubital fossa and are able to identify the basilic and cephalic veins. Tracing the basilic vein proximally, you note that it is relatively large and straight; however, you see a honeycomb-like structure nearby it, which displays anisotropy and appears to be a nerve. You opt instead to follow the cephalic vein. There do not appear to be any nerves or other vessels nearby. You clean her skin appropriately and apply a sterile glove over the probe, and apply sterile gel. After these preparations, you re-identify the vessel in the transverse plane, use dynamic needle tip visualization with an out-of-plane approach, and successfully guide the tip of the needle into the vein. 

Video 13: Ultrasound clip of a vein in transverse orientation being successfully cannulated.

After visualizing the tip of the needle in the vein, you slightly advance the needle another 2 mm and then thread the catheter. You are able to obtain bloodwork. After flushing the catheter and cleaning the surrounding skin, you secure the catheter. Abigail is now able to get pain medications and fluids.

She soon feels much improved after 3 hours. Her laboratory results are similar to her baseline values. She is able to return home with ongoing management as an outpatient basis with close follow-up. 

The PEM POCUS series was created by the UCSF Division of Pediatric Emergency Medicine to help advance pediatric care by the thoughtful use of bedside ultrasonography.

Read other PEM POCUS tutorials. Learn more about bedside ultrasonography on the ALiEM Ultrasound for the Win series.

By |2021-05-27T10:14:48-07:00May 24, 2021|PEM POCUS, Ultrasound|

PEM POCUS Series: Hip Effusion

Read this tutorial on the use of point of care ultrasonography (POCUS) for pediatric hip effusion. Then test your skills on the ALiEMU course page to receive your PEM POCUS badge worth 2 hours of ALiEMU course credit.


PATIENT CASE: Child with a Limp

Sarah is a 4-year-old girl who comes into the emergency department complaining of a limp for the last day. She had an upper respiratory infection which started a week ago for which she had been taking acetaminophen and ibuprofen with her last dose of either being 2 days ago. Those symptoms have improved. Yesterday, she started complaining of diffuse right leg pain primarily at her hip, thigh, and knee. Today, her parents noted she was walking with a limp.

On arrival, her vital signs are:

Vital SignFinding
Temperature100.1F
Heart rate100 bpm
Blood pressure97/50
Respiratory rate19
Oxygen saturation (room air)100%

She is well appearing and walks with an antalgic gait favoring the left leg. She has a normal HEENT, neck, cardiac, respiratory, abdominal, and back examination. She points to her right anterior thigh when you ask her where her pain is. She has limited range of motion with internal and external rotation of her right hip and complains of pain. She cries when you palpate any part of her leg, but is able to range her knee, ankle, and foot fully. She has 2+ dorsalis pedis and posterior tibialis pulses and intact sensation to light touch throughout. 

Given her pain with range of motion at her hip, you order a hip radiograph, but while waiting for it, decide to perform a hip point of care ultrasound (POCUS) examination.

PEDIATRIC HIP EFFUSION: Ultrasound Technique

It can be difficult for children to locate the exact area of pain and often hip pain can present with referred knee and thigh pain. A thorough physical examination along with hip POCUS can help localize the area of discomfort. When we use POCUS to evaluate the hip, we are primarily looking for a joint effusion in the synovial space. This is best visualized anterior to the femoral neck.  

hip anatomy hip effusion
Figure 2. Hip anatomy with target landmark being the femoral neck (red arrow) 

Technique

  1. The patient should be positioned supine.
    • Depending on the age of the child, the child can be positioned supine in the guardian’s lap while undergoing the examination. 
    • Offering the child a toy, book, or phone/tablet for distraction during the examination can also help ease anxiety.
  2. Use a linear high frequency transducer with a wide footprint.
  3. Place the transducer along the anterior hip.
    • Use the greater trochanter as a lateral landmark and place the probe on top of the femoral head and neck (Figure 3)
  4. Aim the probe marker towards the patient’s umbilicus.
hip effusion ultrasound
Figure 3. Linear transducer at the hip with probe marker (red dot) aimed towards the patient’s umbilicus
  1. Identify the anatomical landmarks on ultrasound (figure 4) 
    • Hip muscles: Sartorius, quadriceps, and iliopsoas
    • Bones: Femoral head, femoral neck
  2. The area of interest in looking for a hip effusion is the synovial space anterior to the femoral neck and NOT anterior to the femoral head. This area is also referred to as the anterior synovial recess.
Figure 4. Ultrasound image showing the normal landmarks for a pediatric hip without an effusion and the location of the femoral head (X) and synovial space (circle) with the linear transducer positioned overlying and longitudinal to the femoral neck
  • Tips:
    • It is often helpful to ultrasound the unaffected side as a comparison.
    • Be aware of the patient’s comfort throughout the examination.

ABNORMAL ULTRASOUND FINDINGS

A hip effusion will appear anechoic (black) in the synovial space anterior to the femoral neck (anterior synovial recess). Measure the distance between the anterior surface of the femoral neck and the posterior surface of the iliopsoas muscle. Examples are illustrated in figures 5 and 6.

hip effusion PEM POCUS ultrasound

There have been different methods used to assess if an effusion is present including:​1,2​

  • Measured effusion is >0.5 cm 
  • Measured effusion with >0.2 cm difference compared to the contralateral hip
  • Gestalt view with the anterior synovial recess areas appearing asymmetric compared to the other hip

Limitations of the Hip POCUS

Note that hip POCUS does not tell you the cause of an effusion but rather only whether an effusion is present or not. Effusions can result from infectious, inflammatory, and traumatic etiologies, and thus it is important to take into account the context of the patient’s presentation. 

References

  1. Vieira R, Levy J. Bedside ultrasonography to identify hip effusions in pediatric patients. Ann Emerg Med. 2010;55(3):284-289. PMID 19695738
  2. Cruz C, Vieira R, Mannix R, Monuteaux M, Levy J. Point-of-care hip ultrasound in a pediatric emergency department. Am J Emerg Med. 2018;36(7):1174-7. PMID 29223689 

FACTS and LITERATURE REVIEW

There have been multiple case reports of hip POCUS identifying hip effusions in children with fractures, septic joints, and in the work up of children with limps.​1–3​ There are limited studies examining the accuracy of hip POCUS compared to radiology-performed ultrasound in children (table 1).

StudyNSensitivitySpecificityComments
Vieira et al., Ann Emerg Med, 2010​4​2885%93%If the pediatric emergency physician had a high confidence in ultrasound accuracy, the sensitivity increased to 90% and specificity to 100%
Cruz et al., Am J Emerg Med, 2018​5​51685%98%For each additional hip POCUS performed, the odds of an accurate scan increased by 2.4%. 
Table 1. Published studies comparing pediatric hip POCUS to radiology-performed ultrasound

 

References [click to expand] +

  1. Deanehan J, Gallagher R, Vieira R, Levy J. Bedside hip ultrasonography in the pediatric emergency department: a tool to guide management in patients presenting with limp. Pediatr Emerg Care. 2014;30(4):285-287. PMID 24694889
  2. Garrison J, Nguyen M, Marin J. Emergency Department Point-of-Care Hip Ultrasound and Its Role in the Diagnosis of Septic Hip Arthritis: A Case Report. Pediatr Emerg Care. 2016;32(8):555-557. PMID 27490732
  3. Tsung J, Blaivas M. Emergency department diagnosis of pediatric hip effusion and guided arthrocentesis using point-of-care ultrasound. J Emerg Med. 2008;35(4):393-399. PMID 18403170 
  4. Vieira R, Levy J. Bedside ultrasonography to identify hip effusions in pediatric patients. Ann Emerg Med. 2010;55(3):284-289. PMID 19695738
  5. Cruz C, Vieira R, Mannix R, Monuteaux M, Levy J. Point-of-care hip ultrasound in a pediatric emergency department. Am J Emerg Med. 2018;36(7):1174-1177. PMID 29223689 

CASE RESOLUTION

The patient’s hip plain film radiographs are unremarkable. You decide to incorporate hip POCUS to your evaluation. You place a linear, high-frequency transducer and visualize the patient’s bilateral hips. You observe the following:

Right Hip (Affected Side) POCUS Video and Key View

Though the child complained of hip, knee, and thigh pain, your POCUS evaluation identifies a right hip effusion which helps you narrow the location of her pain.

Video 1. A hip POCUS of the case patient’s right hip (affected side)

 

PEM POCUS hip effusion
Figure 7. Right (affected side) hip POCUS with a hip effusion measuring 0.77 cm

Left Hip (Normal Side) POCUS Video and Key View

Video 2. A hip POCUS of the case patient’s left hip (unaffected side) for comparison

 

PEM POCUS hip no effusion normal
Figure 8. Left (unaffected side) hip POCUS with no effusion

ED Course

The patient’s labs result, and she has reassuring labs, which include a serum WBC 8.3 x109/L and ESR 34 mm/hr. The patient receives ibuprofen during her visit and within 1 hour is able to walk without a significant limp and states she feels better. The patient’s family notes they have spent the last few weeks of summer in a Lyme-endemic region, and so you send off Lyme titers.

Given the resolution of limp, lack of fever, and reassuring lab values, you do not believe the patient has a septic joint. Her effusion is more likely the result of a transient tenosynovitis. You recommend close pediatrician follow-up.

Pediatrician Clinic Follow-Up

At her pediatrician clinic visit 1 week later, her Lyme titers return negative, and the patient continues to be limp-free.  

 

The PEM POCUS series was created by the UCSF Division of Pediatric Emergency Medicine to help advance pediatric care by the thoughtful use of bedside ultrasonography.

Read other PEM POCUS tutorials. Learn more about bedside ultrasonography on the ALiEM Ultrasound for the Win series.

By |2021-07-21T18:55:01-07:00May 17, 2021|Orthopedic, PEM POCUS, Ultrasound|

PEM POCUS Series: Intussusception

Read this tutorial on the use of point of care ultrasonography (POCUS) for pediatric intussusception. Then test your skills on the ALiEMU course page to receive your PEM POCUS badge worth 2 hours of ALiEMU course credit.

 


PATIENT CASE

Johnny is a 2-year-old boy who comes into the emergency department for abdominal pain for the last day. His parents are concerned that he has been having intermittent abdominal pain and has seemed very tired all day. Parents deny bloody stool.

On arrival, his vital signs are:

Vital SignFinding
Temperature36.9C
Heart rate110 bpm
Blood pressure97/50
Respiratory rate22
Oxygen saturation (room air)99%

He is tired appearing, and his abdominal exam is soft but diffusely tender. Given his intermittent abdominal pain, you decide to perform an intussusception point of care ultrasound (POCUS) exam.

ULTRASOUND TECHNIQUE

Intussusception is when one part of the bowel telescopes, or gets stuck, in another part of the bowel. Typically intussusception refers to ileocolic intussusception where the ileum becomes stuck in the colon. To perform the ultrasound, start in the right lower quadrant and trace the colon. See below for a step-by-step technique.

intussusception
Overview of sequential ultrasound transducer positioning on the anterior abdomen to assess for intussusception

Technique

  • The patient should be positioned supine.
  • To aid in comforting the child, the child can be positioned supine in the parent’s lap while undergoing the scan. Having the parent or another provider offer a toy, book, or phone/tablet to distract the child during the scan can also help ease anxiety.
  • Begin in the right lower quadrant (RLQ), using a high frequency linear probe with the probe marker to patient’s right.
  • First, identify the anatomical landmarks in the RLQ (see ultrasound images below):
    • Psoas muscle (green) laterally
    • Right iliac vessels (blue)
    • Abdominal muscles (red)
    • Bladder (yellow) medially

Ultrasound image: Anterior Abdomen (RLQ) View

intussusception RLQ ultrasound

Ultrasound Image: Anterior Abdomen RLQ (More Medial) View

PEM POCUS intussusception RLQ More Medial
  • Perform graded compression, with slow steady pressure to displace bowel gas
  • Follow the colon from the RLQ to right upper quadrant (RUQ) until the liver (purple) and gallbladder are identified

Ultrasound Image: Anterior Abdomen (RUQ) View

PEM POCUS intussusception RUQ
  • Rotate the probe marker to patient’s head and scan the entire length of the transverse colon.
  • Rotate the probe marker back to patient’s right and scan the entire length of the descending colon, making sure to scan all four quadrants.
  • Save representative video clips and still images of each quadrant.
  • If an intussusception is found, measure its diameter in transverse view and note in which quadrant(s) it is found.
  • At the end of scan, if you have found an intussusception, re-image the abdomen to make sure it was not transient.
  • The provider should maintain awareness of the patient’s comfort throughout the scan.

INTUSSUSCEPTION CLASSIC FINDINGS

Normal (no intussusception)

https://www.youtube.com/watch?v=6TYEo1jZUwU&feature=emb_title
Normal: There is no target or sandwich sign, but rather just folded normal bowel. (To replay, press circular arrow in bottom left corner)

Abnormal findings

  • Look for findings of a sandwich sign (or pseudo-kidney sign) in the longitudinal view and target sign (or donut sign) in the transverse view.
  • If visualized, measure the diameter of the intussusception in short axis (transverse) and note which in which quadrant(s) it is located.

Sandwich Sign

https://www.youtube.com/watch?v=MK3WvUbdsgM&feature=emb_title
Anterior abdomen ultrasound: Intussusception – Presence of a sandwich sign (long axis view) and target sign (short axis view)

Target Sign

Intussusception diameter ultrasound
Measurement: The diameter of an intussusception (i.e., target sign) in transverse view involves measuring the distance from outer wall to outer wall.

Additional Anterior Abdominal Ultrasound Videos

Pro Tip
It can be difficult to distinguish intussusception of the small bowel-small bowel (i.e., when the ileum or part of the small bowel telescopes into itself) versus ileocolic (i.e., when the ileum becomes telescopes into the colon). The former often does not require a procedure for reduction, while the latter typically does. If the target sign diameter is <2 cm and transient, a small bowel-small bowel intussusception should be suspected. The length of the intussusception, or how many quadrants are involved, can also be measured for an idea of how much bowel is involved.

Small bowel-small bowel intussusception

https://www.youtube.com/watch?v=Po7wef5sVFw&feature=emb_title
Small bowel-small bowel intussusception – Note the small size of the target lesion. Because the ultrasound video scans to a depth of 3.3 cm (see bottom right side of the screen), the target sign appears to be approximately only 1 cm in diameter.

 

https://www.youtube.com/watch?v=AFrdsZFIV_U&feature=emb_title
Small bowel-small bowel intussusception – There is a target sign, but it is small (<2 cm) with a small fat (white) core.

 

Ileo-colic intussusception

https://www.youtube.com/watch?v=Iw3UQfLBmPo&feature=emb_title
Ileo-colic intussusception with classic target sign – Note the lymph nodes (black) inside the mesenteric fat (white) in the center of the target.

FACTS and LITERATURE REVIEW

Mimickers of Intussusception

There are additional pathologies that can be mistaken for intussusception such as an intussuscepted appendix, appendicitis surrounded by abscess, and Meckel’s diverticulum, which are beyond the scope of this course. Any concerning finding for intussusception should be followed by a confirmatory study by the radiology department.

Benefits of intussusception POCUS scans

Although few studies have looked at point of care ultrasonography (POCUS) for intussusception, the existing studies have shown excellent test characteristics and a decreased length of stay with using POCUS.

Two studies assessed the test characteristics of the intussusception POCUS.

PublicationStudy MethodologySensitivitySpecificity
Riera et al. (2012)​1​This journal publication was a prospective study of 82 patients who underwent POCUS by pediatric emergency medicine (PEM) providers. The gold standard was a comprehensive radiology ultrasound.85%97%
Trigylidas et al. (2017) ​2​This abstract reported a retrospective study of 105 intussusception POCUS scans by PEM providers. The gold standard was either a direct radiology over-read of the POCUS scans or a radiology department ultrasound.96.2%92.6%
Lin-Martore et al. (2020)6This systematic review and meta analysis included 1,303 patients and 6 studies.94.9%99.1%
Bergmann et al. (2021)7This prospective study of 256 children across 17 sites (35 sonologists) compared POCUS and radiology performed ultrasound using a gold standard of clinically important intussusception which was defined as an intussusception that required radiographic or surgical reduction during or within 7 days of the incident ED visit.96.6%98%

In terms of ED length of stay (LOS), Kim et al. (2017) reported that after the introduction of an intussusception POCUS scanning protocol, the LOS decreased by >200 minutes.​3​

Differentiating small bowel-small bowel from ileocolic intussusception

In general, true ileocolic intussusceptions are:

  • Found on the right side of the abdomen
  • >2 cm in diameter
  • Have mesenteric fat (which is white) and lymph nodes in the center
  • Do not self resolve

There have been studies looking at distinguishing small bowel-small bowel from ileocolic intussusception. These, however, have been radiology-based and not POCUS studies, making generalizability to the ED setting challenging. Thus, if there is a concern for an intussusception, a radiology ultrasound should be ordered.

One small study with 27 patients by Wiersma et al. (2006) found that small bowel-small bowel intussusceptions had a smaller mean diameter and length compared to ileocolic intussusceptions.​4​

Type of intussusception# of patients and scansMean diameter (range)Mean length (range)Location
Small bowel-small bowel10 patients, 11 scans1.5 cm (1.1-2.5 cm)2.5 cm (1.5-6 cm)Distributed throughout the abdomen (6 paraumbilical, 2 RUQ, 2 RLQ, 1 LLQ)
Ileocolic14 patients, 16 scans3.7 cm (3-5.5 cm)8.2 cm (5-12.5 cm)All on right side of abdomen

Lioubashevsky et al 2013​5​ had a larger sample size (174 patients) with similar findings. The authors also measured the ratio of the inner fat core to the intussusception outer wall and identified the presence or absence of lymph nodes within the lesion.

Type of Intussusception# of patientsMean diameter (range)Mean length (range)Ratio of fat core to the intussusception outer wall% of patients with lymph nodes in the lesion
Small bowel-small bowel57 patients1.4 cm 
(1.1-2.5 cm)
2.5 cm 
(1.5-6 cm)
<114%
Ileocolic143 patients2.6 cm 
(1.3-4 cm)
8.2 cm 
(5-12.5 cm)
>189.5%

References [click to expand] +

  1. Riera A, Hsiao A, Langhan M, Goodman T, Chen L. Diagnosis of intussusception by physician novice sonographers in the emergency department. Ann Emerg Med. 2012;60(3):264-268. PMID 22424652
  2. Trigylidas TE, Kelly JC, Hegenbarth MA, Kennedy C, Patel L, O’Rourke K. 395 Pediatric Emergency Medicine-Performed Point-of-Care Ultrasound (POCUS) for the Diagnosis of Intussusception. Annals of Emergency Medicine. October 2017:S155. DOI
  3. Kim J, Lee J, Kwon J, Cho H, Lee J, Ryu J. Point-of-Care Ultrasound Could Streamline the Emergency Department Workflow of Clinically Nonspecific Intussusception. Pediatr Emerg Care. September 2017. PMID 28926507
  4. Wiersma F, Allema J, Holscher H. Ileoileal intussusception in children: ultrasonographic differentiation from ileocolic intussusception. Pediatr Radiol. 2006;36(11):1177-1181. PMID 17019589
  5. Lioubashevsky N, Hiller N, Rozovsky K, Segev L, Simanovsky N. Ileocolic versus small-bowel intussusception in children: can US enable reliable differentiation? Radiology. 2013;269(1):266-271. PMID 23801771
  6. Lin-Martore M, Kornblith AE, Kohn MA, Gottlieb M. Diagnostic Accuracy of Point-of-Care Ultrasound for Intussusception in Children Presenting to the Emergency Department: A Systematic Review and Meta-analysis. West J Emerg Med. 2020 Jul 2;21(4):1008-1016. doi: 10.5811/westjem.2020.4.46241. PMID: 32726276.
  7. Bergmann KR, Arroyo AC, Tessaro MO, et al; P2Network. Diagnostic Accuracy of Point-of-Care Ultrasound for Intussusception: A Multicenter, Noninferiority Study of Paired Diagnostic Tests. Ann Emerg Med. 2021 Jul 2:S0196-0644(21)00340-1. doi: 10.1016/j.annemergmed.2021.04.033. Epub ahead of print. PMID: 34226072.

Case Resolution

You place a linear, high-frequency probe on the right side of the patient’s abdomen. You perform a bedside ultrasound scan, viewing transversely and longitudinally through the upper and lower abdomen. You observe the following:

https://www.youtube.com/watch?v=tQRLWPc8Heo

What is the diagnosis?

This is an intussusception!

The intussusceptum (red) is the part of the bowel that has telescoped into the intussuscipiens (blue). When ileum becomes trapped in the colon, this can lead to ischemia and necrosis over time. This is what causes the classic “currant jelly stools”, which are bloody stools.

Tip: The classic triad of colicky abdominal pain, palpable mass and bloody stool are present in less than 50% of patients, and intussusception should be suspected for patients with vomiting, abdominal pain, and/or lethargy.​1​

Hospital course

Johnny underwent an air enema reduction in the Radiology department, which successfully reduced the ileocolic intussusception.

Reference

  1. Daneman A, Alton D. Intussusception. Issues and controversies related to diagnosis and reduction. Radiol Clin North Am. 1996;34(4):743-756. PMID 8677307.

The PEM POCUS series was created by the UCSF Division of Pediatric Emergency Medicine to help advance pediatric care by the thoughtful use of bedside ultrasonography.

Learn more about bedside ultrasonography on the ALiEM Ultrasound for the Win series

By |2021-07-31T07:17:48-07:00May 10, 2021|Gastrointestinal, PEM POCUS, Ultrasound|

EMRad: Can’t Miss Pediatric Elbow Injuries

 

Have you ever been working a shift at 3 am and wondered, “Am I missing something? I’ll just splint and instruct the patient to follow up with their PCP in 1 week.” This can be a reasonable approach, especially if you’re concerned there could be a fracture. But we can do better. Enter the “Can’t Miss” series: a series organized by body part that will help identify common and catastrophic injuries. This list is not meant to be a comprehensive review of each body part, but rather to highlight and improve your sensitivity for these potentially catastrophic injuries. We reviewed the approach to the pediatric elbow previously. Now, the “Can’t Miss” pediatric elbow injuries. (more…)

By |2021-04-10T10:24:46-07:00Apr 5, 2021|EMRad, Orthopedic, Pediatrics, Radiology, Trauma|

EMRad: Radiologic Approach to the Pediatric Traumatic Elbow X-ray

This is EMRad, a series aimed at providing “just in time” approaches to commonly ordered radiology studies in the emergency department [1]. When applicable, it will provide pertinent measurements specific to management, and offer a framework for when to get an additional view, if appropriate. We recently covered the adult elbow, here we will cover the approach to the pediatric elbow.

Learning Objectives

  1. Interpret traumatic pediatric elbow x-rays using a standard approach
  2. Identify clinical scenarios in which an additional view might improve pathology diagnosis

Why the pediatric elbow matters and the radiology rule of 2’s

The Pediatric Elbow

  • 10% of all pediatric fractures involve the elbow [2].
  • Missed injuries can cause significant deformity, pain, or functional/neurologic complications [2].

Before we begin: Make sure to employ the rule of 2’s [3]

  • 2 views: One view is never enough.
  • 2 abnormalities: If you see one abnormality, look for another.
  • 2 joints: Image above and below (especially for forearm and leg).
  • 2 sides: If unsure regarding a potential pathologic finding, compare to another side.
  • 2 occasions: Always compare with old x-rays if available.
  • 2 visits: Bring the patient back for repeat films.

An approach to the traumatic pediatric elbow x-ray

  1. Adequacy / Alignment
  2. Effusions or Fat Pads
  3. Bones, Growth Plates, and Ossification Centers
  4. Consider an additional view

1.   Adequacy / Alignment

2.   Effusions or Fat Pads

  • An anterior fat pad can be normal, but is considered pathologic if excessively prominent (usually around ≥20 degrees from the humerus, or “sail sign”).
  • A clearly visualized posterior fat pad is always pathologic.
  • If either the sail sign or posterior fat pad is present, consider a supracondylar fracture or intra-articular fracture (e.g. lateral condyle fracture )

Sail sign

Figure 1: Measurement of apical angle of the anterior fat pad ≥ 20 degrees, concerning for sail sign. There is also a visible posterior fat pad. Case courtesy of Dr. Ian Bickle, Radiopaedia.org. Annotations by Daniel Ichwan, MD.

3.   Bones, Growth Plates, and Ossification Centers

Elbow x-ray

Figure 2: Lateral and AP x-rays of the elbow demonstrating humerus (green), radius (violet), and ulna (blue). Case courtesy of Dr. Jeremy Jones, Radiopaedia.org. Annotations by Daniel Ichwan, MD.

  • Immature bones with open growth plates (physes) are susceptible to injuries (Salter-Harris fractures) with important growth implications.
    • The Salter-Harris classification is as follows below:
      • Salter-Harris Type 1 (“Slipped”) – epiphysis (part of bone between the growth plate and adjacent joint) separates from metaphysis (neck portion of a long bone).
        • Pearl: Can appear radiographically normal, but tender on physical exam.
        • Requires splinting and ortho follow-up.
      • Type 2 (“Above”) – involves metaphysis (“above the physis”).
        • Requires splinting and ortho follow-up.
      • Type 3 (“Lower”) – involves epiphysis (“below the physis”).
        • Consult orthopedics in the department.
      • Type 4 (“Through”) – involves both the metaphysis and epiphysis.
        • Consult orthopedics in the department.
      • Type 5 (“Erasure”) – crushing of physis. May appear normal or focal narrowing of physis.
        • Consult orthopedics in the department

Figure 3: Salter-Harris Classification. Case courtesy of Dr. Matt Skalski, Radiopaedia.org.

  • Pediatric bones have a stronger periosteum than the underlying incompletely ossified bones.
    • Watch out for bowing, torus, greenstick, or avulsion injuries.
  • Trace each bone’s cortex carefully on both AP and lateral views.
  • Pay close attention to all aspects of the humerus, radius, and ulna.
  • Locate each expected ossification center per the patient’s age.
    • If there is one missing or seemingly prematurely present, consider a fracture.

Figure 4: Ossification centers on (a) AP pediatric elbow x-ray (case courtesy of Dr. Leonardo Lustosa, Radiopaedia.org) and (b) lateral pediatric elbow x-ray. Note that not all ossification centers are visible in this view (case courtesy of Dr. Ian Bickle, Radiopaedia.org. Figure 6 (b) annotations by Daniel Ichwan, MD

 

Table 1: Order and timing of appearance of elbow ossification centers. Some people remember this order by using the mnemonic “CRITOE”: capitellum, radial head, internal (medial) epicondyle, trochlea, olecranon, and external (lateral) epicondyle.

4.  Consider an Additional View

Oblique View

  • When: Sometimes included as the 3rd view in a series
  • Why: This is better at seeing the radiocapitellar joint, medial epicondyle, radioulnar joint, and coronoid process. Consider obtaining this view if there is a high suspicion for a subtle lateral condyle fracture or radial head fracture.

Elbow xray

Figure 6: Lateral oblique x-ray of the elbow. Case courtesy of Dr. Craig Hacking, Radiopaedia.org.

X-rays of Contralateral Elbow

  • Given variation among patients, sometimes it might be necessary to image the contralateral extremity to clarify whether the questionable finding is pathologic or actually normal.

References

  1. Schiller, P. et al. Radiology Education in Medical School and Residency. The views and needs of program directors. Academic Radiology, Vol 25, No 10, October 2018. PMID: 29748045
  2. DeFroda SF, Hansen H, Gil JA, Hawari AH, Cruz AI Jr. Radiographic Evaluation of Common Pediatric Elbow Injuries. Orthop Rev (Pavia). 2017;9(1):7030. Published 2017 Feb 20. PMID: 28286625
  3. Chan O. Introduction: ABCs and Rules of 2. In: ABC of Emergency Radiology. John Wiley & Sons, Ltd; 2013:1-10.
  4. Blumberg SM, Kunkov S, Crain EF, Goldman HS. The predictive value of a normal radiographic anterior fat pad sign following elbow trauma in children. Pediatr Emerg Care. 2011 Jul;27(7):596-600. PMID: 21712751
  5. Black KL, Duffy C, Hopkins-Mann C, Ogunnaiki-Joseph D, Moro-Sutherland D. Musculoskeletal Disorders in Children. In: Tintinalli JE, Stapczynski J, Ma O, Yealy DM, Meckler GD, Cline DM. eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8e. McGraw-Hill; Accessed December 22, 2020. https://accessmedicine.mhmedical.com/content.aspx?bookid=1658&sectionid=109408415
By |2021-05-15T12:49:15-07:00Mar 19, 2021|EMRad, Orthopedic, Pediatrics, Radiology, Trauma|

Computerized Adaptive Screen for Suicidal Youth (CASSY) study

CASSY PECARN suicide screening tool

Adolescent suicide rates in the United States, partly augmented by the COVID-19 pandemic, are steadily increasing [1, 2]. A commonly used screening tool is the 4-question Ask Suicide-Screening Questions (ASQ) instrument, which has a sensitivity and specificity of 60% and 92.7%, respectively, in predicting suicide-related events within 3 months. This was derived from a retrospective study of 15,003 pediatric patients (age 10-18 years) [3]. Given the morbidity and mortality associated with suicide attempts, is there a better screening tool with a higher sensitivity than 60%, while also maintaining adequate specificity? A higher sensitivity rate ensures that we have fewer misses.

The CASSY tool

In JAMA Psychiatry 2021, the Pediatric Emergency Care Applied Research Network (PECARN) researchers report derivation and external validation data for their suicide screening tool, called the Computerized Adaptive Screen for Suicidal Youth (CASSY) [4]. This publication was actually two studies in one: a derivation of the tool and then an external validation.

Terminology

This paper assumes that the reader understands certain predictive analytics methodologies and test design concepts. Let’s briefly review some of the foundational terminology used:

  • Item response theory [Wikipedia]: “It is a theory of testing based on the relationship between individuals’ performances on a test item and the test takers’ levels of performance on an overall measure of the ability that item was designed to measure.” Of note, each item may be weighted differently based on how well it correlates with the overall outcome measure, which in this study was suicide attempt within 3 months.
  • Computerized adaptive testing [Wikipedia]: This computer testing strategy, also known as tailored testing, presents questions based on the individual’s response to a prior question.
  • Receiver operator characteristics (ROC): “The performance of a diagnostic test in the case of a binary predictor can be evaluated using the measures of sensitivity and specificity. However, in many instances, we encounter predictors that are measured on a continuous or ordinal scale. In such cases, it is desirable to assess performance of a diagnostic test over the range of possible cutpoints for the predictor variable. This is achieved by a receiver operating characteristic (ROC) curve that includes all the possible decision thresholds from a diagnostic test result.” [5] In other words, test sensitivities can be calculated for set specificities of, for instance, 70%, 80%, and 90%. Based on the purpose of the diagnostic test, the binary predictor threshold would be set accordingly.
  • Area under the curve (AUC): Calculating the AUC for the ROC is an effective means to determine a diagnostic test’s accuracy. The AUC ranges from 0 to 1 with 0.5 meaning no discrimination (i.e., the test can not diagnose patients with and without the disease based on the test). Generally, an AUC value of 0.7-0.8 is acceptable, 0.8 to 0.9 is excellent, and >0.9 is outstanding [5].

Study 1: CASSY derivation

A total of 6,536 adolescents (age 12-17 years) from 13 PECARN emergency departments were enrolled and a subset were randomly received follow-up in 3 months to assess for a suicide attempt. These patients responded to 92 questions on a computer tablet. Using a multidimensional item response theory approach, the more correlated questions (72) were used to create the CASSY tool.

Test characteristic results:

  • AUC: 0.89 (excellent)
  • Using the ROC curve, the CASSY sensitivity was 83% and 61% for the fixed specificity of 80% and 90%, respectively.

Study 2: CASSY validation

A total of 4,050 adolescents from 14 PECARN emergency departments were enrolled, and all received 3-month follow-up assessing for a suicide attempt. These patients completed the CASSY tool, as well as a subset of questions from study 1 for comparison. The frequency of questions used in the adaptive screen are itemized in the paper.

Test characteristic results:

  • AUC 0.87 (excellent)
  • Using the ROC curve and at the 80% specificity cutoff from study 1, the CASSY sensitivity was 82.4% and specificity was 72.5%.

CASSY figure ROC

Limitations

Although there was strong study rigor by deriving and independently validating the tool in separate, multicenter populations, it should be noted that generalizability may be affected.

  1. The study was conducted in academic pediatric emergency departments.
  2. There was quite a few patients who were lost to follow up (27.1% in study 1, 30.5% in study 2), which may have skewed the results.
  3. Selection bias may have occurred because of patients declining to participate in the study (62% enrollment rate in study 1, 62.2% in study 2)

Bottom line

The CASSY tool accurately serves as a screening predictive tool for adolescents at risk for a suicide attempt in 3 months. Rather than having patients complete exhaustively long (and practically unfeasible) screening questions in the emergency department, this computerized adaptive tool required only a mean of 11 questions, which took a median time of 1.4 minutes (IQR 0.98-2.06 minutes) to complete.

How can you implement CASSY in your emergency department?

We asked the authors this question, and the answer is in the podcast below.

Podcast

Listen more with author Dr. Jacqueline Grupp-Phelan talking with ALiEM podcast host, Dr. Dina Wallin, about this landmark paper and behind-the-scenes issues not included on the paper.

This blog post was expert peer-reviewed by Drs. King and Grupp-Phelan, who authored the paper.

References

  1. Hill RM, Rufino K, Kurian S, Saxena J, Saxena K, Williams L. Suicide Ideation and Attempts in a Pediatric Emergency Department Before and During COVID-19 [published online ahead of print, 2020 Dec 16]. Pediatrics. 2020;e2020029280. PMID: 33328339
  2. Centers for Disease Control and Prevention. Web-based Injury Statistics Query and Reporting System (WISQARS). Published 2020.
  3. DeVylder JE,Ryan TC, Cwik M, et al. Assessment of selective and universal screening for suicide risk in a pediatric emergency department. JAMA Netw Open. 2019;2(10):e1914070-e1914070. PMID 31651971
  4. King CA, Brent D, Grupp-Phelan J, et al. Prospective Development and Validation of the Computerized Adaptive Screen for Suicidal Youth [published online ahead of print, 2021 Feb 3]. JAMA Psychiatry. 2021; 10.1001/jamapsychiatry.2020.4576. doi:10.1001/jamapsychiatry.2020.4576. PMID 33533908
  5. Mandrekar JN. Receiver operating characteristic curve in diagnostic test assessment. J Thorac Oncol. 2010;5(9):1315-1316. doi:10.1097/JTO. 0b013e3181ec173d

Listen to all the PECARN podcasts

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