Urinoma

A urinoma, also pararenal pseudocyst, is an encapsulated collection of extravasated urine and typically found in the area adjacent to the kidneys or to extend into the retroperitoneum. A urinoma, also pararenal pseudocyst, is an encapsulated collection of extravasated urine and typically found in the area adjacent to the kidneys or to extend into the retroperitoneum. A urinoma is the result of a breach of the integrity of the pelvis or calices of the kidney or of the ureter. The urine collection in the perirenal fat causes an inflammatory response with lipolysis resulting in its fibrous encapsulation. Urinomas are usually caused by blunt trauma to the kidneys. While extravasation of urine is common as a result a severe blunt trauma (2-18%), spontaneous resolution is typical, and urinoma formation develops only in few instances. Less common causes of urinoma development are ureteral obstructions due to cancer, calculus formation, pregnancy, or congenital causes. Urinomas tend to develop gradually. Symptoms depend on size and location of the lesion. Eventually local pain and pressure symptoms may become apparent. Biochemical testing of renal function is indicated. Imaging (IVP, ultrasonography, CT scan) will identify the lesion. Image-guided percutaneous needle aspiration is both diagnostic and therapeutic. If left untreated, complications may arise including abscess formation, peritonitis, sepsis, and damage to the urinary tract by fibrosis and granuloma formation. It is recommended, as a first step, to drain the lesion with ultrasound or CT guidance. If a patient has an underlying obstructive problem it needs to be addressed according to its cause.