Rectal duplications are rare congenital anomalies that represent 1%–6% of alimentary tract duplications. We report a case of a woman in her 50s who presented to our hospital with perianal pain and urinary retention. She had a history of imperforate anus repaired after birth and dynamic graciloplasty performed during her adulthood for faecal incontinence. Abdominal CT scan showed a fluid collection extending from the electrostimulator, placed in a subcutaneous pocket in the abdomen, to the rectouterine pouch. Infection related to the electrostimulator was assumed and, after a course of antibiotics without patient improvement, the electrostimulator was removed. The symptoms and the pelvic fluid collection persisted, and diagnostic laparoscopy was performed. Diagnosis of rectal duplication cyst was made intraoperatively, and the cyst was completely resected. Patient fully recovered after surgery. This is a rare case of a rectal duplication cyst presenting during adulthood and associated with imperforate anus.