Retrocaval ureter or preureteral vena cava: Lest we forget this rare cause of hydronephrosis.

Retrocaval ureter or circumcaval ureter is a rare congenital abnormality arising from dysgenesis of the inferior vena cava (IVC) that results in the right ureter coursing behind and medial to the IVC. The ideal nomenclature for the anomaly is preureteral vena cava, keeping in mind the aberrant embryology. It can result in hydronephrosis and is a rare cause of long-standing cyclical pain abdomen. Ultrasound, intravenous urography, nuclear scintigraphy, computed tomography urography (CTU) and magnetic resonance urography (MRU) have been used in the diagnosis of this abnormality but CTU, with its ability to depict the abnormality in three dimensions gives the most "wholesome" solution to its diagnosis. When symptomatic, the condition is treated surgically, either by laparoscopic or open surgery. The characteristic imaging findings that can help clinch the diagnosis are described as a reminder for this infrequently encountered cause for pain abdomen and hydronephrosis.