A case of ectopic opening of vasa deferentia into müllerian duct cyst.

We report very rare case in which the vasa deferentia entered a large Müllerian duct cyst in a 4-month-old infant. The presenting findings were lower abdominal mass and the complaint of urinary retention. A computed tomography scan of the pelvis showed a monolocular cystic mass between the bladder and the rectum. Surgical removal of the cyst was done because the mass increased in size and both hydronephroses and hydroureters were getting worse despite the use of antibiotics. The patient has no urological difficulty after the operation. This case was characterized as follows: the cyst was located on the midline, the vasa entered the cyst directly, the size of the cyst was large, and it was not associated with other malformations of the genitourinary system.