The defect known as retrocaval ureter is an uncommon congenital condition resulting from the aberrant development of infrarenal veins (IVC) from anteriorly positioned subcardinal veins rather than posteriorly located supracardinal veins. A portion of the proximal ureter becomes entrapped, causing the ureter to coil around the IVC. As a result, other names for it include preureteral vena cava and circumcaval ureter [2].

The retrocaval ureter is a rare malformation whose exact frequency is unknown; its incidence is thought to be of the order of 1 per 1,000 births [3]. The anomaly is about three times more common in men, and the age at diagnosis is usually between 20 and 40. Uncertainty about its frequency stems from the fact that it is usually asymptomatic. Currently, imaging tests such as abdominal computed tomography (CT) or magnetic resonance imaging (MRI) are making incidental diagnoses increasingly frequent [1].

The retrocaval ureter has different anatomical types, depending on the position of the crossing of the ureter around the vein vena cava. Radiological examination helps to define the morphology of the malformation, as defined by Bateson and Atkinson [4]. Two types of retrocave ureter have been defined:

- Type 1, the most common form, corresponds to an abrupt hook-shaped trajectory at L3; radiologically, there is an inverted J image on ureterography.

- Type 2 is described as a progressive coiling of the ureter, in which case the initial portion of the ureter is retrocave.

In this case, the abnormality was type 1 and the obstruction was at the right side beside the lateral margin of the IVC at the level of lumbar vertebrae L2–L3.

Patients usually present with symptoms associated with ureteral obstruction and hydronephrosis, such as right lumbar pain, recurrent urinary tract infections and renal lithiasis. In the present case, the patient presented with intermittent low-back pain with no hematuria [5].

Imaging is an essential aspect of the diagnostic and pre-therapeutic work-up of a retrocaval ureter. Each morphological examination (ureteral opacification by Intravenous Urography [IVU], retrograde ureteropyelography, URO-CT or abdominal MRI) helps to determine the level of the anomaly, the extent of dilatation and the local anatomical conditions. Renal scintigraphy is used to assess the functional value of the kidney in cases of obstructive syndrome associated with renal atrophy [1].

Surgical intervention is required in symptomatic patients or those with worsening renal function [5].

Nephrectomy is justified in symptomatic patients whose kidney is destroyed, with a low functional value on scintigraphy, in order to avoid complications [1].

Conservative surgical treatment is indicated for all symptomatic patients with preserved homolateral renal function.

The principle of conservative surgery on the retrocave ureter is to restore the normal anatomical situation, by unhooking the ureter from the inferior vena cava. This may be achieved by sectioning and anastomosing the ureter, or sectioning and anastomosing the inferior vena cava (a technique now abandoned). This may or may not be combined with resection of the retrocaval ureter. Surgery may be performed open, laparoscopic transperitoneally, laparoscopic retroperitoneally, or robot-assisted [1].