Accuracy is about 30% lower than for contrast-enhanced computed tomography.

Intravenous contrast­-enhanced CT is the imaging procedure of choice for evaluating patients with acute abdominal pain, but clinicians sometimes consider withholding intravenous contrast due to concerns about renal toxicity or hypersensitivity. Investigators used a novel technique to compare the diagnostic accuracy of unenhanced CT scans with contrast­-enhanced scans by digitally subtracting the contrast effect. Six radiologists interpreted the unenhanced versions of the scans, and their diagnostic findings were compared with consensus interpretation of the contrast­enhanced versions by other radiologists.

A total of 201 consecutive contrast­ enhanced CT scans ordered for acute abdominal pain at a single US institution were evaluated, resulting in 104 primary diagnoses and 17 actionable secondary diagnoses. The overall accuracy of the pooled readings of the unenhanced scans by the six radiologists for both primary and secondary diagnoses was 70% when compared with the reference readings of the enhanced scans. 

Comment: Risk for renal toxicity with intravenous contrast is extremely low, except in patients with severe kidney disease, and risk mitigation strategies exist for managing known contrast hypersensitivity. The marked reduction in diagnostic accuracy of unenhanced CT scans suggests their use should be highly selective (e.g. when a ureteral stone is the probable cause of the pain) and generally infrequent.

Thomas L. Schwenk, MD, Professor Emeritus, Family and Community Medicine, University of Nevada School of Medicine, Reno, USA.

Shaish H, et al. Diagnostic accuracy of unenhanced computed tomography for evaluation of acute abdominal pain in the emergency department. JAMA Surg 2023 May 3; e-pub (https://doi.org/10.1001/jamasurg.2023.1112).

This summary is taken from the following Journal Watch titles: General Medicine, Ambulatory Medicine, Hospital Medicine, Emergency Medicine.