Opacification of the urinary tract in portal venous spiral CT without delayed scans

In portal venous spiral CT there is no visible renal contrast excretion wit hin the usual period of scanning. To opacify collecting systems additional delayed scanning is required. We administered an ex; tra pre-dose of contra st medium before the main portal venous bolus in order to opacify the urina ry tract and studied its effects on liver attenuation. In 32 patients exami ned first by non-contrast spiral CT 20 mi of a non-ionic IV CM were injecte d. Five minutes later, orientating cuts in the liver and along the urinary tract were obtained. Immediately thereafter, a 120- ml bolus was administer ed at 3 ml/s for portal venous phase helical CT (60-s delay craniocaudad). The quality of renal excretion was graded visually (excellent, fair, poor, none). Hepatic attenuation measurements were performed at comparable region s of interest. In all patients 20 ml CM opacified the renal pelvis after 5 min. Depiction of the ureters was excellent in 14, fair in 11 and poor or n one in 7 cases. There was little effect on mean hepatic attenuation by the 20-ml pre-bolus after 5 min: mean enhancement 2.3 HU (range -0.6 to 7.8 PIU ). Mean hepatic enhance ment after the 120-ml portal venous bolus ranged be tween 23.6 and 74.1 HU (mean 51.5 HU). When opacification of the urinary tr act is necessary, pre-administration of a 20-mi bolus 5 min before portal v enous scanning may save an extra delayed spiral. The effects on hepatic enh ancement are negligible.