One year's clinical experience with unenhanced spiral computed tomography for the assessment of acute loin pain suggestive of renal colic

Objective To assess the use of unenhanced spiral computed tomography (CT) as the primary investigation of choice for suspected acute renal colic in clinical urological practice. Patients and Methods Between 1 August 1997 and 31 July 1998, all patients attending a hospital accident and emergency department with acute loin pain suggestive of renal colic underwent a physical examination, urine analysis, plain abdominal radiography (if clinically indicated) and unenhanced spiral CT. The effective radiation dose and financial cost of unenhanced spiral CT and standard three-film emergency intravenous urography (IVU) were calculated. Results In all, 116 patients were assessed, 63 of whom had calculi and related secondary phenomena of obstruction identified on unenhanced spiral CT. There were two false-positive and one false-negative result. An alternative urinary tract diagnosis was made in four patients, including two with renal cell carcinoma and one ureteric transitional cell carcinoma. Causes other than in the urinary tract were diagnosed in three patients, i.e. two with ovarian cyst and one with sigmoid diverticulitis. The effective radiation dose of unenhanced spiral CT was 4.7 mSa and that for three-film IVU was 1.5 mSv. The costs of both. IVU and unenhanced spiral CT were identical. Conclusions Unenhanced spiral CT allows a rapid, contrast-medium-free, anatomically accurate diagnosis of urinary tract calculi and in the present series had a sensitivity of 98% and a specificity of 97%. CT provided an alternative diagnosis in 6% of patients. These advantages must be weighed against the threefold greater radiation dose of unenhanced spiral CT than with three-film IVU, and in practice the requirement for a radiologist to interpret routine axial scans.