The urinary abnormalities are an important health problem. If they are not recognized in due time, they usually lead to the loss of the renal unit function. In many cases, the diagnosis is late and incidental.

Case presentation. We present the case of M.I., a 74-year-old male admitted in our surgical unit with diffuse left lumbar pain, low urinary tract symptoms and slow increase in abdomen volume in the past 4 years. Computer tomography scan and ecography showed a large left lumbar cyst like mass with a dilated supernumerary ureter with ectopic ureteral orifice in the prostatic urethra and apparently normal anatomic inferior renal unit.

The goal was the excision of the “cyst like” mass (superior left renal unit) but because of the anatomical particularities (extensive fibrosis and local topographical changes) total nephrectomy was performed.

Conclusions. Given a normal contralateral kidney, the discovery of a urinary abnormality can be a real challenge, their evolution being a silent one. This type of disease can be suspected only with the development of clinical symptoms.

The anatomic particularities (duplex kidney) together with the long evolution of the disease changed the local topography making the preservation of the inferior left renal unit a difficult, almost impossible task for the surgeon.