Precaval Right Renal Arteries: Prevalence and Morphologic Associations at Spiral CT

PURPOSE: To determine the prevalence and morphologic associations of precaval right renal arteries at spiral computed tomography (CT). MATERIALS AND METHODS: The authors retrospectively reviewed 186 arterial phase contrast material-enhanced spiral CT scans of the abdomen (5.0-mm section thickness in 97 scans, 2.5 mm in 89 scans) obtained during a 2-year period to identify patients with precaval right renal arteries. During routine interpretation of CT scans at daily readout, the authors prospectively identified 39 additional patients with precaval right renal arteries. All cases were evaluated for anatomic variants and associated clinical findings. Fisher exact analysis and X2 analysis were performed to compare the frequency of anatomic variants between patients with and those without precaval renal arteries. RESULTS: Nine of 186 patients had precaval right renal arteries, for a prevalence of 5%. In the 48 patients with precaval renal arteries, 52 precaval arteries were found, of which 48 were accessory and four were dominant. Fourteen patients had right pelviectasis to the level of the precaval artery, and three of these had a clinical diagnosis of right ureteropelvic junction obstruction. Eighteen (35%) of the 52 precaval renal arteries arose from the anterior aspect of the aorta (within 30° of the midline). The lower pole of the right kidney was rotated anteriorly in two (22%) of nine and 13 (33%) of 39 patients with precaval renal arteries in the retrospective and prospective groups, respectively, compared with four (2%) of 177 patients without precaval arteries (P < .05 and P < .001, respectively). CONCLUSION: On the basis of these results, precaval right renal arteries appear to be more common than previously reported. Anterior rotation of the lower pole of the right kidney should prompt a search for precaval renal arteries.