Radiological Diagnosis

Circumcaval ureter

IVU showed moderate right hydronephrosis with characteristic 'reversed J' appearance of the proximal ureter [Figure - 1]. CT at the level of the lower pole of the right kidney showed the dilated proximal right ureter lateral to the inferior vena cava [Figure - 2]A. Section slightly lower revealed the ureter sweeping medially behind the inferior vena cava [Figure - 2]B

The patient underwent surgery and excision with end to end anastomosis of the ureter was done.

While most deviations of the ureter are caused by pathologic processes in the retroperitoneum, one congenital anomaly, circumcaval ureter, results in a pathognomonic ureteral course. The IVC develops embryologically from persisting portions of the posterior cardinal, subcardinal and supracardinal veins. Normally, the suprarenal IVC derives from the right subcardinal vein, and the infrarenal IVC from the right supracardinal vein. Circumcaval ureter results from formation of the infrarenal IVC from the persistent right posterior cardinal vein rather than from the right supracardinal vein. The right ureter is carried medially by the migration of the posterior cardinal vein towards the developing IVC [1].

The initial upper course of the normal ureter is determined by the position of the kidney. Allowing for differences in renal position between left and right sides, most ureters start at the second and third lumbar body. They then either immediately cross the psoas muscle or descend for a variable distance along the lateral margin of the psoas muscle before ascending this muscle to run along the edge of the vertebral bodies. The ureters subsequent course is usually over the outer thirds of the transverse processes of the lumbar bodies. However, variations are seen and positions between the top of the transverse processes and the pedicles of the vertebral bodies are usually normal. The position of the ureters in the pelvis is generally a gentle curve convex laterally, more or less following the contour of the inner margin of the iliac bone. Finally, the ureter courses obliquely to traverse the trigone of the urinary bladder [2].

Symptoms of circumcaval ureter is related to the degree of ureteral obstruction [1]. Due to chronic obstruction the ureteral walls begin to decompensate and are distended. Decompensation continues, and ureteral luminal radius and length are increased until the dilated and tortuous ureter that is the hallmark of chronic obstruction results [3].

The typical pattern of circumcaval ureter on urography is a tortuous, dilated proximal right ureter with hydronephrosis. The course of the proximal ureter is described as having a "reverse J' configuration before it courses behind and around the IVC and then descends medial to the ipsilateral lumbar pedicle. This severe medial deviation is the hallmark of circumcaval ureter. Confirmation of the diagnosis can be made with CT, which shows the ureter passing posterior and medial to the IVC [1].