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.