Many emergency physicians (EPs) order “confirmatory” abdominal computed tomography (CT) in young flank pain patients, despite a high clinical suspicion of renal colic and the risk of radiation exposure. We measured the adverse outcome rate among flank pain patients identified as not requiring abdominal CT by the EP on a data form, regardless of whether CT was eventually ordered. Our secondary objective was to describe diagnoses other than renal colic identified by CT in this population.

We conducted a prospective observational study at two community EDs. We asked staff EPs to complete a data sheet on patients ages 18 to 50 years with a first episode of flank pain, recording 1) if the flank pain was consistent with renal colic and 2) if the EP felt abdominal CT was indicated. Adverse outcomes (defined a priori as urgent surgical procedures, disability, or death) were assessed by research assistants at 4 weeks using telephone follow-up and a hospital records search.

We enrolled 389 patients; 353 completed follow-up (91%). The average age was 38.8 years, and 72.0% were male. Of 212 patients identified in the “CT not indicated” group, 2 had another diagnosis identified (unruptured diverticulitis and a ruptured ovarian cyst), but none had adverse outcomes (95% CI 0-1.4).

Adverse events were rare (< 1.5%) among patients < 50 years old with flank pain when CT was not required according to the clinical assessment of the EP. Future research should assess the adverse outcomes of withholding CT in low-risk patients using a larger patient sample.