A rare case report of an appendico-sigmoid fistula complicating untreated acute appendicitis: Unraveling complexity in diagnosis and treatment

Abstract

Introduction: Appendiculocolonic fistulas, often arising from benign conditions like abscess-forming appendicitis, manifest subtly. This case emphasizes their rarity, intraoperative discovery during acute appendicitis, and explores diagnostic intricacies, sensitive imaging, and distinctions in managing benign versus malignant cases.

Case presentation: A 23-year-old intellectually disabled patient, lacking regular medical follow-up and surgical history, presented to our emergency department with persistent right iliac fossa pain six months ago. Due to financial constraints, a CT scan was not performed despite an inflammatory syndrome, and the patient left against medical advice. Currently experiencing the same symptoms, investigations led to the diagnosis of acute appendicitis with a probable appendico-sigmoid fistula. Surgical exploration confirmed the appendico-sigmoid fistula and the presence of an uncomplicated Meckel's diverticulum. A conservative approach, including appendectomy, Meckel's diverticulum resection, and sigmoid fistula suturing, yielded favorable results.

Clinical discussion: Appendiculocolonic fistulas often arise from acute or chronic appendicitis with local abscess formation. Our case highlights the unusual progression of untreated acute appendicitis, evolving into an appendico-sigmoid fistula. While generally benign, documented cases of malignant causes, such as appendiceal cancer, exist. Diagnosis is intricate, requiring diverse methods, with abdominal CT as a sensitive imaging tool. Conservative approaches are generally recommended for benign cases.

Conclusion: Appendiculocolonic fistulas, though rare, pose a clinical challenge due to their elusive symptoms. Primarily associated with benign conditions, notably abscess-forming appendicitis, or, as in our case, untreated acute appendicitis. This case underscores the role of abdominal CT in precise diagnosis, guiding treatment decisions based on the lesion's nature.

Keywords: Acute appendicitis; Appendico-colonic fistula; Emergency; Imaging diagnosis; Meckel's diverticulum; Mesh.