[Multislice CT urography (MSCTU): evaluation of a modified scan protocol for optimized opacification of the collecting system].

PURPOSE

To retrospectively quantify opacification of the urinary tract using a MSCTU protocol based on furosemide and individual adaptation of urographic acquisition delay.

MATERIALS AND METHODS

MSCTU examinations obtained from 4-row and 16-row CT scanners in 53 patients (35 men, 18 women, average age 59) were independently reviewed by two radiologists. MSCTUs were performed using a low-dose injection of furosemide. No fixed scan delay for urographic image acquisition was applied. The urographic timing was individually adapted by performing low-dose test images of the distal ureters to display their current opacification. Image analysis included grading of the opacification of the segmented collecting system. The average urographic delay was calculated. Stratified comparisons of mean scores were assessed using the Friedman and Wilcoxon tests. The inter-observer kappa value was calculated.

RESULTS

The calculated median scan delay for patients with normal serum-creatinine levels (n = 51) was 418 sec (mean 447 sec; SD, 118 sec). The median number of acquired test images was 2 (range 1 - 6 images). The opacification analysis demonstrated that 98 % of the ICS, 90 % of the proximal, 86 % of the middle, and 83 % of the distal ureteral segments showed opacification greater than 90 %. 9.5 % of the distal ureteral segments could not be visualized. Statistics did not show significant opacification differences between proximal, middle, and distal ureteral segments (p > 0.05). The two observers were largely in agreement (kappa coefficient r = 0.81).

CONCLUSION

The analyzed MSCTU technique based on furosemide and scan delay timing by means of test images reliably lead to a homogenous opacification of the entire upper urinary tract. It features the individual adaptation of MSCTU to the excretory rate of the kidneys.