Circumcaval ureter - Congenital vascular cause of obstructive hydronephrosis

Clinical History

A 25-year-old male patient, with known hypertension, seizures disorder and mental
retardation, presented with right flank pain and intermittent high grade fever.
Laboratory investigations showed anaemia, leukocytosis, and urine was positive for erythrocytes and pus cells. His renal profile was normal with no growth on culture after 48 hours of incubation.

Imaging Findings

Ultrasound KUB revealed enlarged right kidney, moderate hydronephrosis and focal polar areas of altered echogenicity. Proximal right ureter was dilated without any additional anomaly.
CT urography revealed enlarged right kidney with renal parenchyma showing patchy nephrogram and focal areas of reduced enhancement. Right ureter was kinked at the level of the third lumbar vertebra with resultant moderate right hydronephrosis and proximal hydro-ureter. The proximal ureter demonstrated a ‘reverse J’ configuration; ureter distal to the L3 vertebral body encircled the IVC from behind, assuming a normal course lateral to the IVC, anterior to the iliac vessels, before opening into the urinary bladder. Left kidney was normal in size with normal contrast enhancement and excretion. No hydronephrosis / radiodense calculus was seen. Left ureter was normal in course and calibre and urinary bladder was distended showing normal wall thickness with no evidence of radiodense calculus or mass lesion.

Discussion

Circumcaval ureter is a rare congenital anomaly wherein the ureter encircles the IVC. It results from venous malformation of the infra-renal IVC.

A definitive right-sided infrarenal IVC forms from the right supracardinal vein. If the posterior cardinal vein in the lumbar portion fails to atrophy and forms the right-side IVC, the ureter is trapped dorsally to it. This occurs, as the right posterior cardinal vein is positioned ventral to the ureter in the definitive inferior vena cava, so the developing right ureter courses behind to the IVC [1].

The anomaly is congenital and is usually silent till hydronephrosis becomes symptomatic presenting commonly in the 3rd and 4th decade [2, 3]. The patient presents with complaints of right flank pain and discomfort, other symptoms include urinary tract infections, gross haematuria, urolithiasis, or fever [3, 4].

Circumcaval ureters have been classified into two clinical types depending upon their radiological appearance [4, 5]. Type 1 (also named ‘‘low loop’’, more common), characterized by ‘‘S shaped” or “fish-hook’’ or “reverse J” or “sea horse” deformity of ureter at the level of the third lumbar vertebra. Type 2 variant (also called ‘‘high loop’’, rare), characterized by a ‘‘sickle-shaped’’ curve, with the point of obstruction lateral margin of the IVC.

Intravenous urography demonstrates medial deviation of ureter with a sharp hook or kink at L3 vertebral level and non-opacified distal ureter. However, other causes of medial deviation of ureter, retroperitoneal fibrosis, retroperitoneal tumour and prior surgery, cannot be excluded on intravenous urography alone [6]. CT urography, especially the delayed excretory images, are helpful in demonstrating the course of the ureter as it encircles the IVC, as in our case. It is also helpful in diagnosing anomalies and pathologies that might be associated with this condition [4]. The anomalies associated are Horseshoe kidney, double IVC and left retrocaval ureter with Goldenhar syndrome [7, 8].

The choice of surgical treatment depends upon the grade of hydronephrosis, impairment of kidney function, and type of circumcaval ureter. The open ureterostomy is the gold standard surgical option. Laparoscopic surgery involves transposition and re-anastomosis (uretero-ureterostomy) of the circumcaval ureter by two main approaches, transabdominal and retroperitoneal [5].

Circumcaval ureter is a rare anomaly resulting from malformation of infra-renal venous system, in which the right ureter encircles the IVC resulting in obstructive hydronephrosis. CT urography is the modality of choice and laparoscopic transposition with re-anastomosis of right ureter the treatment of choice.

Differential Diagnosis List

Final Diagnosis

Circumcaval ureter

URL:	https://eurorad.org/case/13574
DOI:	10.1594/EURORAD/CASE.13574
ISSN:	1563-4086