Normal renal sonogram identifies renal colic patients at low risk for urologic intervention: a prospective cohort study.

INTRODUCTION Determining which patients with ureterolithiasis are likely to require urologic intervention is a common challenge in the emergency department (ED). The objective was to determine if normal renal sonogram could identify low-risk renal colic patients, who were defined as not requiring urologic intervention within 90 days of their initial ED visit and can be managed conservatively. METHODS This was a prospective cohort study involving adult patients presenting to the EDs of a tertiary care centre with suspected renal colic over a 20-month period. Renal ultrasonography (US) was performed in the diagnostic imaging department by trained ultrasonographers, and the results were categorized into four mutually exclusive groups: normal, suggestive of ureterolithiasis, visualized ureteric stone, or findings unrelated to urolithiasis. Electronic medical records were reviewed to determine if patients received urologic intervention within 90 days of their ED visit. RESULTS Of 610 patients enrolled, 341 (55.9%) had US for suspected renal colic. Of those, 105 (30.8%) were classified as normal; none of these patients underwent urologic intervention within 90 days of their ED visit. Ninety (26.4%) US results were classified as suggestive, and nine (10%) patients received urologic intervention. A total of 139 (40.8%) US results were classified as visualized ureteric stone, and 34 (24.5%) patients had urologic intervention. Seven (2.1%) US results were classified as findings unrelated to urolithiasis, and none of these patients required urologic intervention. The rate of urologic intervention was significantly lower in those with normal US results (p<0.001) than in those with abnormal findings. CONCLUSION A normal renal sonogram predicts a low likelihood for urologic intervention within 90 days for adult ED patients with suspected renal colic.