Unenhanced helical computerized tomography for the evaluation of patients with acute flank pain.

PURPOSE: We determined the value of unenhanced helical computerized tomography (CT) in the diagnosis of acute flank pain in 105 patients evaluated for suspected stone disease.

MATERIALS AND METHODS: Noncontrasted spiral CT was done in 105 consecutive patients seen in our emergency department to evaluate acute flank pain. All CT studies were reviewed for the presence of ureteral or renal calculi, perinephric or periureteral stranding, presence and degree of pelvicalicectasis or other radiological findings. If necessary, an excretory urogram was performed to confirm the presence or absence of urinary stones. Patients were followed to determine clinical outcome including the need for urological intervention.

RESULTS: Of the 49 patients determined to have stones 24 (49%) had spontaneous stone passage, 10 (20%) had improved symptoms without documented stone passage and 14 (29%) required surgical intervention. In 29 of 51 patients (57%) with negative CT readings for stone disease a diagnosis was established by other intra-abdominal findings. In 21 patients (41%) no clinical diagnosis could be established, and 1 scan in a patient with a distal ureteral calculus was interpreted as falsely positive. These findings yielded a sensitivity of 98%, specificity 98% and overall accuracy 96% for diagnosing ureteral stones.

CONCLUSIONS: Despite the limitations of helical CT in evaluating renal function and nonobstructing ureteral calculi, noncontrasted CT is a sensitive imaging modality for the detection of urinary tract calculi and obstruction. The majority of our patients required no further imaging to determine the need for urological intervention. At our institution spiral CT has become the standard method to evaluate patients with acute flank pain leading to more rapid turnover in the emergency department at similar or even reduced cost to conventional excretory urography.