Urinoma is an acute complication that occurs following an injury to the kidney or upper urinary tract. Urine extravasation as a result of renal trauma is common, but development of urinoma may only occur in a few cases [1]. Urine may leak into the perirenal tissues resulting in liquefaction and formation of fibrous tissues which forms the perirenal pseudocyst [8]. The conditions for formation of urinoma include impairment of the renal collecting system, urinary extravasation, and ureteral obstruction [9, 10].
Spontaneous extravasation of urine to the perinephric space and development of a maternal urinoma is an uncommon complication during pregnancy [5,6,7, 11]. Common etiological factors for urinoma development in pregnant women include renal injury or urinary tract obstruction are [12]. In pregnant women, cases of spontaneous rupture of the kidneys and renal tract rupture have been reported, but development of urinomas as a result of these is very rare [13, 14].
Renal rupture may occur in the kidney parenchyma or in the renal collecting system. Spontaneous or traumatic rupture of the kidney may occur, primarily in kidneys with underlying anatomic abnormalities since those kidneys are susceptible to minimal traumatic insults [15,16,17]. Patients who have renal tract ruptures have been treated with double-J tube placements, which can provide sufficient drainage of the urine [18, 19]. During pregnancy, common causes of renal parenchymal rupture are renal aneurysms and trauma. Tubular calculi and obstruction of the lower urinary tract are common causes of rupture of the renal collecting system [12]. In patients with renal parenchymal rupture, the main concern is to stabilize hemodynamic status in the patient because both the mother and fetus may be in danger [20].
An important cause of temporary urinary tract obstruction during pregnancy may be due to increased uterine compression or increased ureteral pressure. This condition may occur when renal pelvis pressure exceeds a critical level between 70 and 75 mmHg due to ureteral or renal compression [21]. Urinoma in the left flank is more rare than in the right, because the uterus exerts greater pressure on the right ureter unless the gravid uterus is rotated more towards the left side [22, 23]. In the current patient, a spontaneous left renal parenchymal rupture occurred following a period of observation during her third trimester of pregnancy when the pressure increased within the urinary system and caused urine leakage into the perinephric space.
Diagnosis of this condition depends primarily on imaging studies with ultrasound used as the primary test [3, 24]. Abnormal ultrasound images may include: 1) discontinuity of the renal parenchymal or urinary tract; 2) fluid and dark areas surrounding the affected kidney; 3) a section of the ruptured kidney capsule floating in the surrounding fluid areas. In spite of its usefulness, the ultrasound has some limits on detecting or locating small ruptures. Following the abnormal findings using ultrasound, further tests including, CT, MRI or intravenous urography (IVU) are also recommended [25, 26]. Compared with the results using ultrasound, these other methods can be used to locate the rupture site, and more accurately estimate the size of the urinoma. These other methods can also delineate more clearly the relationship between the urinoma and surrounding tissues. Utilizing these methods facilitates making the diagnosis and planning the treatment protocol. Misdiagnosis of a urinoma could delay treatment and healing of the renal rupture, which may lead to development of severe complications. Hypertension, urinary peritonitis, renal atrophy and kidney failure are possible in patients with misdiagnosed urinomas [27, 28]. For this reason, awareness and monitoring of this condition during pregnancy should be noted.
In conclusion, pregnant women who experience renal rupture, an ultrasound examination should be administered every two to 4 weeks following the initial examination that reveals possible rupture, or renal contusion and laceration. In patients who develop a perinephric cyst, assessment of the kidney on the affected side should be carefully monitored. If a urinoma occurs in these patients, double-J tube insertion is suggested as the initial treatment prior to any other treatment interventions. This tube insertion into the urinoma will provide better and faster drainage of the fluid, and reduce pressure on the kidney. Following stabilization of the hemodynamics of the patient, a period of percutaneous drainage with a nephrostomy tube is then recommended after initial treatment of the urinoma.