Repeated abdomen ultrasound examination revealed oval, heteroechogenic structure, with dimensions of 125 mm × 100 mm × 100 mm, localized on the right abdominal flank, between the lower surface of the liver and right kidney. The presence of perirenal hematoma in retroperitoneal space has been suspected. In CT scan the collection of fluid with 11–58 Hounsfield units density under the right renal capsule has been described (Fig. 2). In the arterial phase of contrast-enhanced CT examination there was no extravasation of contrast, and
in delayed imaging the leakage of contrasted urine to the space limited by the right kidney capsula SB203580 nmr was noticed. On the next day the small calcium oxalate-monohydrate stone was found in the urine container. Ultrasound examinations performed on consecutive days suggested progressive increase in diameter of the fluid structure up to 162 mm × 71 mm. Due to high risk Buparlisib mw of urinoma rupture, the decision of the surgical evacuation of the undercapsular fluid was made, despite the patient’s stable condition and lack of any complaints. The percutaneous catheter was inserted on the 39th day, resulting in drainage of 700 ml of bloody fluid. During the following days the volume
of the evacuated fluid was gradually reduced. Finally, at the 48th day of hospitalization the catheter was removed with no recurrence of urinoma and the patient was discharged from hospital. The urinary collecting system disruptions are usually caused by renal injury, pelvic mass, posterior urethral valves, or different bladder outlet obstruction, pregnancy, retroperitoneal
fibrosis and transmitted back pressure due to obstruction of the urinary system by a ureteral stone ,  and . It is also the result of iatrogenic injury, most often during extracorporeal shock wave lithotripsy (ESWL) . According to Friedenberg et al. urinoma occurs if four risk factors coexist: preserved renal function, chronic partial distal obstruction which primarily interferes with high volume flow, renal calyces or fornices capable of extravasation during increased pelvic pressure and renal hilus that allows urine to extravasate outside of the kidney . In our patient severe bilateral nephrolithiasis was present with staghorn stones in pelvises and multiple fine concrements (Fig. 3). The intravenous Sclareol fluid therapy and diuretics used in the treatment of prerenal AKI, in the presence of the stone partially closing the outlet from the right kidney pelvis, could lead to increased pressure in the pelvico–calyceal system. However, the stone casts might have weakend the place of least resistance – the calyceal fornix, leading to its rupture and urinoma formation. Several additional risk factors of urine stone formation due to secondary hypercalciuria could be found in our patient. The calcium excretion with urine examined during hospitalization remained within the normal range. However we cannot exclude former hypercalciuria.