Causes of urinary retention in old men include benign prostatic hyperplasia, prostatitis, prostate cancer, Scarring of the urethra or bladder neck as a result of injury or surgery, use of certain medicines particularly NSAIDs and opioid analgesics, constipation and neurogenic bladder. When the above common causes are not quite obvious by clinical examination and relevant investigations, then it is necessary to think of other rare diseases. It is with the above in our mind that a case of bladder outflow obstruction due to a large primary retrovesical hydatid cyst is herein reported in a 58-year-old man. Ultrasonography (USG) and Contrast Enhanced Computed Tomography (CECT) scan of the abdomen and pelvis of the patient revealed a large, multilocular, nonenhancing, cystic lesion in the rectovesical pouch having typical cartwheel appearance without any other intraabdominal organ involvement. These typical radiological characteristics led us to suspect the presence of a hydatid cyst. He underwent exploratory laparotomy where cystopericycstectomy was done. Pre-operative and post-operative albendazole prophylaxis was also given. In conclusion, hydatid cyst should always be considered in the differential diagnosis of pelvic cystic masses, specially in endemic regions.
Keywords: Echinococcal infection; Lower urinary tract symptoms; Rectovesical pouch of douglas.