Objectives. To describe our experience with precaval right renal arteries and discuss a theory of development of this unusual vascular variant. The right renal artery typically passes dorsal to the inferior vena cava and is thought to represent a consistent anatomic relationship. Methods. Three cases of precaval renal arteries were identified during laparoscopic and endourologic procedures. The intraoperative and radiologic anatomic findings were recorded. The embryologic origins of the kidney and renal artery were reviewed to postulate a mechanism for the precaval location of a renal artery. Results. In all cases, the precaval renal artery was an accessory vessel to the lower pole. Computed tomography demonstrated the location of the accessory artery ventral to the vena cava; the superior "main" renal artery was dorsal to the vena cava. In addition, bifid collecting systems (ie, pelves) were present, and the renal contours suggested nearly complete fusion of two renal moieties, with normal location and rotation of the kidney. No other cases of precaval renal arteries were recorded in urologic operative reports during the past 5 years at the University of California, San Francisco. Conclusions. The precaval renal artery is a rare but important variant of renal vascular anatomy. Several associated findings on computed tomography (bifid collecting system, enlarged kidney) may suggest its presence. The embryologic origin is likely due to the late, incomplete division of the ureteral bud during the eighth week of gestation. The renal artery to the lower pole develops and persists after the posterior cardinal vein has become the inferior vena cava but before gonadal descent.
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