Computed tomography (CT) is increasingly available across U.S. Emergency Departments and has changed the practice of medicine. However, it is coupled with potential side-effects from radiation and contrast media. Emergency Medicine is beginning to make a concerted effort to identify clinical scenarios in which CT may be unnecessary, producing outcomes research and validated clinical decision rules. Renal colic and pulmonary embolism, in particular, seem amenable to this area of investigation. The ACEP E-QUAL Network podcast, a partnership with ALiEM to promote clinical practice improvements, reviewed this topic with experts Dr. Chris Moore (Emory University) and Dr. Jeffrey Kline (Indiana University). We present highlights from their discussion with Dr. Jason Woods.

First Time Flank Pain

It is common for EPs to evaluate a patient’s first occurrence of acute flank pain with a CT. The seminal paper on this topic, from 1996, showed CT to have a sensitivity of 97% and specificity of 96% for diagnosing ureteral stones in patients in whom the diagnosis is uncertain.1 Soon after, CT replaced IV pyelography. However, CT is often obtained for patients in whom a diagnosis of nephrolithiasis is highly likely. Should this be our standard of care? In the podcast, Dr. Chris Moore gives a well-referenced answer, and concludes that there is a paucity of evidence for obtaining a CT for highly suspected nephrolithiasis in first time flank pain.

The Relevance of Radiation

It is possible to identify a kidney stone with either a non-contrast CT or one with a minimal dose of radiation. These limit the potential risks associated with contrast and radiation, and likelihood of a identifying an incidental finding. The American Urological Society, American College of Radiation, and American College of Emergency Physicians all recommend that a CT performed for acute flank pain be completed with a reduced dose of contrast. However, there is significant variation across the U.S. with regard to the dose of contrast included in a CT “stone protocol.” Ultimately, it is the responsibility of the EP to discuss protocols with colleagues from radiology. For help, the Dose Optimization for Stone Evaluation (DOSE) project, funded by AHRQ, is available to provide CT best practice techniques to EDs nationwide.

An ED Patient’s PE Risk Profile

The risk factors for PE are different in ED patients versus the general population. For example, obesity, tobacco use, and atrial fibrillation increase the risk of PE in the general population, but not in ED patients.

What are some points from the history and physical that should raise the suspicion for PE in an ED patient, and contribute to any decision to obtain a CT-PE?:

  • Recent surgery or limb immobility
  • Prior VTE
  • Active cancer
  • Estrogen use (and the post-partum period, in particular, is a powerful predictor)
  • Pleuritic pain or dyspnea
  • HR > 100 bpm or an oxygen saturation < 95% on room air
Clinical Decision Rules:
It is helpful to be familiar with the components of a clinical decision rule; however, when applying a rule to a patient encounter, reference these variables on either a computer or smart phone. Memory is prone to human error, and even a seasoned emergency physician can make a mistake.

Learn more about the E-QUAL Network!

Smith R, Verga M, McCarthy S, Rosenfield A. Diagnosis of acute flank pain: value of unenhanced helical CT. AJR Am J Roentgenol. 1996;166(1):97-101. [PubMed]
Derek Monette, MD

Derek Monette, MD

ALiEM Deputy Editor-in-Chief
Medical Education Research Fellow
Department of Emergency Medicine
Massachusetts General Hospital