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[Acute obstructive renal failure secondary to retroperitoneal mass].

The acute renal failure is a grave pathology, of rapid establishment and relatively frequent in the hospital environment. We can describe three etiological groupS, which are responsible for it, amongst which are emphasized the pre-renal reasons. The obstructive pathology, of minor incidence, increases with the age. It is described the case of a 67-yr-old patient who was admitted in the Nephrology Service because of abrupt decline of the renal function. Among the initial symptoms, he presented arterial hypertension (190/90) and preserved diuresis. Blood analysis: urea 199 mg/dl, creatinine 7.7 mg/dl, without proteinuria. Sonography reported a bilateral ureteral hydronephrosis with simple cyst of possible ischemic origin. In view of the absence of previous biochemical data of renal failure, we considered possible reasons which start with an acute pattern. In initial evaluation, pre-renal etiology was not seen (high blood pressure, right cardiac systole function). The absence of prostatic syndrome and sonography discovery did not justify a diagnosis of urinary tract obstruction. Finally, abdominal-pelvic scan showed a periaortic retroperitoneal mass which included both ureters and appeared to trigger the obstruction. Combined efforts were pursued with the Urology Service, which implanted a bilateral "double J" catheter and later operated surgically on the patient, carrying out an alternating ureterolysis of both ureters. The biopsy manifested a retroperitoneal fibrosis, and the renogram showed a residual renal function of 20% in the right kidney and 80% in the left kidney. Due to the failure of the previous measures and as a last therapeutic recourse when one year had passed from the diagnosis, a continuous regimen with tamoxifen (anti-estrogen drug) in dose of 20 mg/dl each 12 hours was started, which began a progressive remission in the size of the observed mass by scan (CT) and magnetic resonance (MR). The treatment was completed during 12 months and in this time, the levels of blood urea nitrogen and creatinine were reduced gradually too. Finally, at the end of the treatment, the magnetic resonance demonstrate the complete disappearance of the fibrosis.