Welcome to another ultrasound-based case, part of the “Ultrasound For The Win!” (#US4TW) Case Series. In this peer-reviewed case series, we focus on a real clinical case where bedside ultrasound changed the management or aided in the diagnosis. In this case, a 46-year-old woman presents with acute right-sided abdominal and flank pain.

Case Presentation

An otherwise healthy 46-year-old female presents to the ED with 6 hours of right-sided abdominal pain. She complains of pain in the right lower quadrant radiating to the right flank. She is noted to be febrile, but appears well. Review of systems is positive for dysuria, but she denies nausea, vomiting, diarrhea, vaginal discharge or bleeding. She denies history of abdominal surgeries. On examination, she has tenderness to palpation at the right lower quadrant without rebound or guarding and no CVA tenderness.


BP: 123/65 mmHg
P: 87 bpm
RR: 20 respirations/min
O2: 100% room air
T: 38.7° C (101.7° F)

Differential Diagnosis

  • Appendicitis
  • Ectopic pregnancy
  • Gastroenteritis
  • Nephrolithiasis
  • Ovarian torsion
  • Pyelonephritis
  • Urinary tract infection

Labs were significant for a leukocytosis (WBC 18.8), and the pregnancy test was negative. A Computed Tomography (CT) with intravenous contrast to look for appendicitis was ordered. A urinalysis was positive for leukocytes, small blood, 620 white blood cells/hpf, and many bacteria.

At this point in the patient’s workup, it was change of shift and the patient was signed out as “follow-up CT to rule out appendicitis; if negative treat for urinary tract infection/pyelonephritis.”

The oncoming provider, upon re-evaluating the patient, performed a point-of-care focused renal ultrasound.

Point-Of-Care Renal Ultrasound

Figure 1a. Ultrasound of the right kidney reveals moderate hydronephrosis.

Figure 1a. Ultrasound of the right kidney reveals moderate hydronephrosis.

Figure 1b. Right kidney with moderate hydronephrosis (blue arrow). Renal cortex (#), medullary pyramid (+), and renal sinus (*) can also be identified.

Figure 1b. Right kidney with moderate hydronephrosis (blue arrow). Renal cortex (#), medullary pyramid (+), and renal sinus (*) can also be identified.

Figure 2. Right kidney with color doppler, confirming no flow in anechoic areas consistent with hydronephrosis.

Figure 2. Right kidney with color doppler, confirming no flow in anechoic areas consistent with hydronephrosis.

Figure 3. Normal left kidney with no evidence of hydronephrosis.

Figure 3. Normal left kidney with no evidence of hydronephrosis.

Ultrasound Image Quality Assurance (QA)

The images obtained show the standard views that should be obtained when performing a focused point-of-care renal study. A curvilinear probe is used and positioned in a coronal plane. These views should be very familiar to emergency physicians, as they are similar to the right upper quadrant (RUQ) and left upper quadrant (LUQ) views of a FAST. Both kidneys are scanned fully in both planes, using the liver and spleen as your acoustic windows.

The primary indication for performing a focused bedside renal study in the Emergency Department is to look for hydronephrosis, which is classified into one of three grades – mild (Figure 4a), moderate (Figure 4b), or severe (Figure 4c). Mild hydronephrosis appears as a dilation of the renal pelvis, moderate hydronephrosis as a dilation of the renal pelvis and calyces, and severe hydronephrosis as a ballooning of the calyces and thinning of the renal cortex.1

Figure 4a. Mild hydronephrosis

Figure 4a. Mild hydronephrosis.

Figure 4b. Moderate hydronephrosis

Figure 4b. Moderate hydronephrosis.

Figure 4c. Severe hydronephrosis

Figure 4c. Severe hydronephrosis.

A common pitfall is mistaking normal renal vasculature for hydronephrosis (Figure 5a), both of which will appear anechoic (black) on a B-mode or grayscale clip. Placing color doppler over the area will help to distinguish these from one another. Renal vasculature will demonstrate flow with color doppler (Figure 5b), whereas hydronephrosis will remain anechoic without flow.

Figure 5a

Figure 5a. Normal renal vasculature that can commonly be mistaken as hydronephrosis.

Figure 5b

Figure 5b. Color doppler demonstrating flow, indicating this is normal renal vasculature.

Disposition and Case Conclusion

Given the findings of moderate right-sided hydronephrosis on the point-of-care ultrasound, the CT was changed from a contrast study to a non-contrast flank CT study, given the concern for an obstructed and infected stone.

The CT abdomen and pelvis revealed a large, 7.37 mm obstructing renal calculus in the mid right ureter with upstream moderate hydroureteronephrosis and perinephric stranding due to infectious or inflammatory etiology.

CT renal colic kidney stone

Figure 6. CT showing 7.37 mm obstructing renal calculus in the mid right ureter

The patient was given IV antibiotics, and urology was consulted. She was taken to the OR for cystoscopy and right ureteral stent placement for urgent decompression. On post-op day 3, the patient was discharged to home in stable condition, afebrile, and with her pain well controlled.

Patients presenting to the ED with flank or kidney pain account for over 2 million annual ED visits in the US.1 CT is often the initial imaging study of choice given its high sensitivity (97%) and specificity (96%) for diagnosing nephrolithiasis.2 However, there has been a concerning 10-fold increase in the use of CT for diagnosis of kidney stones over the past 15 years, with no change in frequency of diagnosis or hospital admissions.3

Point-of-care renal ultrasound can play a vital role in the diagnosis and management of patients who present to the ED with abdominal or flank pain. The primary indication for renal ultrasound in the ED is to assess for hydronephrosis, an indirect sign of ureteral obstruction. Although ultrasound is poorly sensitive for directly imaging stones, one study revealed that resulting hydronephrosis may be easier to identify in patients with larger stones (90% sensitivity for detecting hydronephrosis with stones >6 mm, compared with 75% sensitivity with stones <6 mm).4 This can be reassuring in the clinical setting of uncomplicated ureterolithiasis, as smaller stones are likely to pass on their own without intervention, and “missing” hydronephrosis with these smaller stones is unlikely to change clinical outcomes.

A recent large multi-center study published in the New England Journal of Medicine found that ultrasonography should be used as the initial imaging modality for patients with suspected nephrolithiasis, with further imaging studies performed based on the findings and discretion of the clinician.5 Patients enrolled in the study were randomized to one of three initial imaging modalities:

  1. Point-of-care ultrasonography by an emergency physician
  2. Radiology-performed ultrasonography
  3. CT

Comparison of the three groups at 30 days showed no statistically significant difference in high-risk diagnoses with complications, serious adverse events, pain control, return ED visits, hospitalizations, or diagnostic accuracy.5

In this case, the point-of-care ultrasound and clinical picture gave concern for complicated ureterolithiasis (i.e. a potentially obstructed and infected stone requiring urologic intervention), and thus a CT was rightfully obtained.

Take Home Points

  1. Consider ultrasonography as the initial imaging modality in patients who present with a strong suspicion for nephrolithiasis, especially in younger and female patients.
  2. Although CT has a higher sensitivity for kidney stones than ultrasonography, this increased sensitivity does not necessarily improve diagnostic accuracy or decrease serious adverse events.5
  3. Point-of-care ultrasonography by Emergency Physicians for identifying hydronephrosis has a moderate sensitivity (72.6%) and specificity (73.3%), with much higher sensitivity (92.7%) in those with additional ultrasound fellowship training.1
  4. The use of color doppler can help distinguish hydronephrosis from normal renal vasculature.

*Note: All identifying information and certain aspects of the case have been changed to maintain patient confidentiality and protected health information (PHI).


  1. Herbst M, Rosenberg G, Daniels B, et al. Effect of provider experience on clinician-performed ultrasonography for hydronephrosis in patients with suspected renal colic. Ann Emerg Med. 2014;64(3):269-276. [PubMed]
  2. Dalziel P, Noble V. Bedside ultrasound and the assessment of renal colic: a review. Emerg Med J. 2013;30(1):3-8. [PubMed]
  3. Moore C, Scoutt L. Sonography first for acute flank pain? J Ultrasound Med. 2012;31(11):1703-1711. [PubMed]
  4. Riddell J, Case A, Wopat R, et al. Sensitivity of emergency bedside ultrasound to detect hydronephrosis in patients with computed tomography-proven stones. West J Emerg Med. 2014;15(1):96-100. [PubMed]
  5. Smith-Bindman R, Aubin C, Bailitz J, et al. Ultrasonography versus computed tomography for suspected nephrolithiasis. N Engl J Med. 2014;371(12):1100-1110. [PubMed]

Jeffrey Shih, MD, RDMS

Director, Emergency Ultrasound Fellowship Program
Scarborough Health Network;
Editor, Ultrasound for the Win Series
Academic Life in Emergency Medicine


I'm Director of Emergency Ultrasound Fellowship @ TSH ER Doc @UofT @SickKidsNews. Author of https://t.co/1UwRjjxgYW @Yale @MayoClinicEM Alum. LITFL & @ALiEMteam Editor