Abstract
Posterior vaginal wall prolapse can represent a spectrum of underlying defects that are difficult to distinguish on physical examination alone. We present a case of a 47-year-old woman with symptomatic stage III posterior prolapse in whom magnetic resonance defecography revealed a rare cul-de-sac hernia containing a large peritoneal inclusion cyst. Preoperative identification of the hernia contents altered surgical planning, allowing for targeted vaginal drainage and repair. This case highlights the diagnostic value of magnetic resonance defecography in complex or atypical prolapse and its role in guiding management.