Fused Ischiorectal Phlegmon with Pre- and Retroperitoneal Extension: Case Report and Narrative Literature Review.

Background/Objectives: Anorectal and retroperitoneal abscesses, although differing in frequency and presentation, present significant diagnostic and therapeutic challenges, especially when interconnected through complex fascial planes. Rare cases such as horseshoe ischiorectal phlegmons with extraperitoneal spread are particularly difficult to manage due to limited literature and the absence of standardized protocols. This article presents a rare case alongside a narrative review of similar cases, aiming to highlight key diagnostic pitfalls and therapeutic strategies. Methods: We conducted a narrative literature review using PubMed, Embase, Scopus, and Web of Science to identify reports on horseshoe ischiorectal phlegmons with extraperitoneal or retroperitoneal extension. Relevant studies were compared with the present case. Results: We describe a 59-year-old male who presented with severe sepsis, diffuse abdominal pain, and hemodynamic instability. Imaging and surgery revealed extensive necrotizing spread to the anterior abdominal wall, peritoneum, and retroperitoneal space, despite absent local perianal signs. Emergency midline laparotomy, wide debridement, and drainage were performed. Despite intensive care, the patient suffered rapid clinical deterioration and died within six hours postoperatively. Conclusions: This case and literature review highlight how a clinically silent ischiorectal phlegmon can progress to extensive extraperitoneal involvement and fatal sepsis. This underscores the need for early recognition, advanced imaging, and aggressive multidisciplinary management. Further studies are needed to develop evidence-based guidelines for complex anorectal abscesses with deep fascial extension.