Uriniferous perirenal pseudocyst: new observations.

The chronic encapsulated extravasation of urine, most accurately designated as uriniferous perirenal pseudocyst, causes urine to collect within a characteristic complex of radiographic findings including an elliptical soft-tissue mass in the cone of renal fascia. This results in the flank oriented inferomedially with upward and lateral displacement of the lower renal pole, medial displacement of the ureter, obstructive hydronephrosis, and perhaps evidence of extravasation into the mass. Since the clinical recognition of the mass is typically delayed several weeks following the original traumatic episode, prompt radiological diagnosis is essential before irreparable damage to the kidney occurs.