An Unusual Presentation of Acute Appendicitis Mimicking Sigmoid Diverticulitis: A Case Report.

Acute appendicitis typically causes right lower quadrant pain, but in elderly patients with comorbidities, it can present atypically, complicating diagnosis. This case highlights a rare presentation, mimicking sigmoid diverticulitis. A 70-year-old man with chronic heart failure, arrhythmia, and renal failure presented with two days of left lower quadrant pain. Examination showed tenderness, rebound, and guarding. Laboratory tests revealed a white blood cell count of 12,000/µL and creatinine of 2.5 mg/dL. C-reactive protein was elevated at 25 mg/L. Computed tomography revealed an inflamed appendix with an appendicolith and localized inflammation near the sigmoid colon, but no diverticulitis. An appendectomy confirmed a perforated appendix in contact with the sigmoid colon. In elderly patients, acute appendicitis may present atypically with left-sided pain, risking misdiagnosis. Careful evaluation and imaging are essential for accurate diagnosis and management in those with comorbidities.