[Rapidly deteriorating adult hydronephrosis due to an aberrant vessel: a case report].

Hydronephrosis due to ureteropelvic junction (UPJ) obstruction generally progresses gradually. We experienced a case of hydronephrosis due to UPJ obstruction deteriorating rapidly in an adult woman. In spite of percutaneous nephrostomy, 99mTc-DTPA renogram showed a non-functional pattern. A nephrectomy was done. Peri-operatively, the aberrant lower pole vessel was found to be obstructing the UPJ. The hydronephrosis deteriorated rapidly because the extrarenal pelvis dilated in the shape of box, became suspended from the aberrant vessel. Therefore, we believe that the box pelvis is one of the most important factors deteriorating hydronephrosis.