[An unusual cause of acute pyelonephritis: the retrocaval ureter].

Retrocaval ureter is a rare congenital malformation in which the proximal right ureter courses toward the midline on the posterior aspect of the inferior vena cava before emerging medial and anterior to this structure and then descending into the pelvis. This anatomical anomaly may be asymptomatic or manifest clinically, usually starting from the fourth decade of life, with flank pain, pyelonephritis, gross hematuria or other rarer signs. We describe the case of a young woman being hospitalized because of acute pyelonephritis; she had previously complained of flank pain associated with episodes of high fever. Computed tomography of the abdomen identified the malformation. The patient underwent surgical correction by laparoscopy and, at one year of follow-up, did not show any further clinical problem.