An unusual cause of urinary retention: a primary retrovesical echinococcal cyst.

We present a patient with symptoms of frequency, a mild decrease in urinary stream, and urinary retention due to a huge hydatid cyst located in the retrovesical region. Chest radiography and abdominal computed tomography did not reveal any other site of hydatid disease involvement. Since the cyst was in intimate contact with the seminal vesicles and the vasa deferentia, part of the hydatid sac wall adherent to these structures was left behind during the surgical excision. The patient was free of voiding symptoms, and no other episode of urinary retention had occurred at 6 months of follow-up. Pelvic computed tomography did not reveal recurrence of hydatid disease at 6 months postoperatively.