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) a s the primary investigation of choice for suspected acute renal colic in cl inical urological practice. Patients and Methods Between 1 August 1997 and 31 July 1998, all patients a ttending 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 spira l CT. The effective radiation dose and financial cost of unenhanced spiral CT and standard three-film emergency intravenous urography (IVU) were calcu lated. Results In all, 116 patients were assessed, 63 of whom had calculi and rela ted 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 rena l 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 d ose 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, anat omically accurate diagnosis of urinary tract calculi and in the present ser ies had a sensitivity of 98% and a specificity of 97%. CT provided an alter native diagnosis in 6% of patients. These advantages must be weighed agains t the threefold greater radiation dose of unenhanced spiral CT than with th ree-film IVU, and in practice the requirement for a radiologist to interpre t routine axial scans.