Combined vascular-excretory phase MDCT angiography in the preoperative evaluation of renal donors.

OBJECTIVE

The objective of our study was to test a dose reduction protocol that uses combined vascular-excretory phase scanning achieved by split IV contrast injection and compare it with conventional multiphase MDCT angiography (MDCTA) in evaluating potential renal donors.

MATERIALS AND METHODS

This study is a review of MDCTA examinations of 54 potential renal donors scanned on 16- and 64-MDCT. The IV bolus was split: 50 mL was administered 3 minutes before scanning and a second injection of 70-100 mL was administered at a rate of 4-6 mL/s, with CT angiography started by bolus tracking. The second vascular (venous) phase was acquired 20 seconds later. Two readers reviewed the two phases, assessed vascular and parenchymal anatomy and variants or abnormalities, graded the added value of the venous phase on a 5-point scale, and took attenuation measurements in Hounsfield units. The operative notes of 39 subjects were reviewed as the reference standard for anatomic findings and compared with CT reports.

RESULTS

All of the relevant anatomy findings, according to the operative notes, were accurately depicted by MDCTA, and all were well recognized on the arterial phase. The arterial phase combined information from the arterial, venous, parenchymal, and excretory phases. The venous phase was inferior to the arterial phase in assessing the renal arteries without additional venous, parenchymal, or excretory phase information. The mean renal artery attenuation was 355 HU in the first phase versus 173 HU in the second phase (p<0.0001). The mean renal vein attenuation was not significantly different between the two phases. The parenchymal system and excretory system were equally well depicted in both vascular phases.

CONCLUSION

Split-bolus contrast injection and combined vascular-excretory phase scanning are adequate for studying potential renal donors and result in a marked decrease in multiphase scanning and, thus, in radiation dose.