Comparative analysis and interobserver variation of unenhanced computed tomography and intravenous urography in the diagnosis of acute flank pain.

OBJECTIVES The purpose of this study was to compare unenhanced computed tomography (UECT) to intravenous urography (IVU) for detecting urinary tract calculi, signs of obstruction and non-renal causes in the assessment of acute flank pain, and in their interobserver agreement. PATIENTS AND METHODS In this prospective study, carried out at a university hospital over a period of 1 year, 36 patients (27 males and 9 females) participated. Mean age was 44 +/- 15 years (range: 14-73 years). The patients presented with acute flank pain and underwent UECT and IVU. The images were blindly evaluated by 2 experienced radiologists and the two techniques compared using the two-tailed McNemar's test for matched pairs; p values <0.05 were considered significant. RESULTS UECT detected stones in 11 (30.6%) patients, while IVU found them in only 8 (22.2%). The increased detection by UECT was due to its ability to detect smaller stones (<6 mm). UECT was also found to be better than IVU in determining calculus position, in detecting primary or secondary signs of obstruction and in identifying non-urinary causes of flank pain. The overall average of agreement, as indicated by kappa values, was 0.88 for UECT and 0.61 for IVU. CONCLUSION UECT showed better detectability and interobserver agreement tan IVU, suggesting that UECT could replace IVU as the first imaging modality in the evaluation of acute renal colic.