A Rare Case of Iliopsoas Abscess Extending to Scarpa's Triangle With Gluteal Fistulization.

Iliopsoas abscess (IPA) is a rare and potentially life-threatening condition, often presenting with nonspecific symptoms that delay diagnosis. Secondary IPA, typically resulting from contiguous spread of infection, can occasionally demonstrate atypical anatomical extension. We report the case of a 64-year-old female patient with a history of right nephrectomy, type 2 diabetes mellitus, and hypertension, presenting with a progressively enlarging mass in the right thigh. Imaging revealed a large multiloculated retroperitoneal abscess originating from the iliacus muscle and extending through the psoas to the right Scarpa's triangle and gluteal region, with potential active fistulization. The patient underwent extensive surgical drainage, debridement, fistulectomy, and dual-site drainage, followed by targeted antibiotic therapy. Postoperative recovery was favorable. This case highlights a rare and complex anatomical presentation of recurrent IPA. The extensive spread beyond classical retroperitoneal boundaries into Scarpa's triangle and the gluteal soft tissues underscores the importance of early imaging, surgical management, and multidisciplinary care in complex abscesses. A high index of suspicion, appropriate imaging, and individualized surgical intervention are essential for managing complex IPA. Atypical presentations such as this case warrant prompt recognition to prevent morbidity and ensure favorable outcomes.