Improved pelvicalyceal visualization with multidetector computed tomography urography; comparison with helical computed tomography.

Our aim was to compare the quality of pelvicalyceal visualization on computed tomography (CT) urography using a small intravenous contrast material dose, hydration, and high-resolution multidetector CT (MDCT) with that of conventional helical CT. The test (MDCT) group (49 consecutive patients, 98 kidneys) was scanned 5 min following an intravenous bolus of 30 ml of iodinated contrast material. The control (helical CT) group (50 consecutive patients, 95 kidneys) was scanned 5 min following injection of 120-150 ml of intravenous contrast material. Enhancement and quality of calyceal detail were measured using a five-scale grading system (1 for no detail, 5 for cupped calyces). Calyceal attenuation was substantial in both groups (more than 220 Hounsfield units, HU) but less in the test group compared with the control group (mean 475 and 920 HU, respectively), p<0.0001. In the test group, the calyceal attenuation was less than 500 HU in the majority of cases (65/98 kidneys), while the opposite was true for the control group, where calyceal attenuation was more than 750 HU in 50/95 kidneys (p<0.001). The quality of calyceal detail was 3.4/5 in the test group compared with 1.8/5 in the control group (p<0.0001). The combination of hydration, low-contrast dose, and the high image resolution achieved with MDCT significantly improves calyceal visualization in CT urography.