Perforated Diverticulitis Presenting as Acute Leg Pain and Inability to Bear Weight: An Atypical Manifestation of a Common Pathology.

Acute diverticulitis commonly presents with abdominal symptoms but can rarely lead to extra-abdominal complications such as lower extremity necrotizing myositis. While fistulas involving the bladder or vagina are well described, retroperitoneal spread with extension into the thigh remains exceedingly uncommon. We present the case of a 77-year-old female who arrived with acute left thigh pain, swelling, and inability to bear weight. Initial workup was negative for deep vein thrombosis, but further history revealed preceding abdominal and back pain. Computed tomography identified extraluminal gas tracking from a perforated sigmoid colon into the retroperitoneum and anterior thigh. Exploratory laparotomy confirmed perforated diverticulitis with retroperitoneal fistulization and abscess formation extending into the thigh musculature. Surgical management included Hartmann's procedure, retroperitoneal washout, and debridement of necrotic thigh tissue. The patient recovered successfully following an intervention. This case underscores a rare but critical complication of diverticulitis, emphasizing the importance of considering intra-abdominal sources when encountering unexplained gas in the thigh. Timely diagnosis and aggressive surgical management are essential for optimal patient outcomes.