[Usefulness of renal CT scan for analysis of nutcracker phenomenon]

Among 24 patients with confirmed left renal bleeding, 11 were diagnosed of having nutcracker phenomenon (NP) on the basis of the results of renal venography and pull-back pressure from the left renal vein to the inferior vena cava. Renal CT scan was performed for these 11 patients, and its usefulness as a means of diagnostic analysis was studied. The following results were obtained. 1. The left kidney was scanned at 5-mm intervals. The mean distance between the anterior surface of the abdominal aorta (Ao) and the posterior surface of the superior mesenteric artery (SMA) was 4.5 +/- 0.6 mm in the NP group, while it was 13.9 +/- 6.4 mm in the control group (p < 0.01). 2. Regarding the morphology of the left renal vein (LRV), tapering dilatation, i.e., funnel-like dilatation, from the left side of Ao was seen in the NP group. In the control group, the left renal vein showed a club-like shape continuing to the inferior vena cava and showed no dilatation. 3. Vascular structures indicative of collateral vessels were observed around the LRV in the NP group. If renal CT scan is performed at 5-mm intervals, the following CT finding are thought to be indicative of the nutcracker phenomenon; (1) a distance of 5 mm or less between Ao and SMA and (2) tapered dilatation of the LRV. This study suggests that renal CT scan is useful for diagnostic analysis of the nutcracker phenomenon.