Idiopathic retroperitoneal fibrosis
Left loin pain
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Delayed scans revealed a sizable left perinephric contrast extravasation (urinoma) with associated pericalyceal urine traces (surrounding the upper and middle calyces, but sparing the inferior ones) and intense surrounding fat stranding with thickening of the perirenal fascia.
Mild to moderate dilatation of the left renal pelvicalyceal system and upper third of the left ureter. The middle thirds of both ureters are medialized running in line with the edge of the vertebral body rather than in line with the tips of the transverse processes. The dilated upper third of the left ureter is tortuous followed by abrupt non-visualization of the left ureteric lumen, which has become encased by abnormal periaortic soft tissue.
The distal 7 cm of the aorta until its bifurcation are surrounded by a rather thick enhancing soft tissue mantle reaching ~2.5 cm in thickness. Few tiny subcentimeter lymph nodes are seen.
Two left renal upper polar simple cysts measuring 2 cm each.
Normal CT features of the right kidney, pelvicalyceal system and ureter.
The liver shows a small segment III hemangioma measuring 1.2 x 1.0 cm. A gallbladder stone is seen measuring 1.5 cm.
Features of a ruptured upper calyceal system of the left kidney with associated sizable urinoma secondary to a high grade left ureteric obstruction caused by idiopathic retroperitoneal fibrosis. The middle thirds of both ureters are medialized running in line with the lateral edge of vertebral bodies rather than the tips of transverse processes which is a key feature of the disease.
Idiopathic retroperitoneal fibrosis is a chronic inflammatory periaortic condition that usually presents with ureteric obstruction which can be unilateral or bilateral. Peripelvic extravasation is a complication of high-grade ureteric obstruction and can extend inferiorly in the retroperitoneal space along the ureter. It is usually secondary to an obstructing ureteric stone unlike this case with resultant increased pressure in the renal pelvis.