Incidental discovery of a ‘mega‐appendix’

A 67-year-old female presented to hospital following a fall and with obstipation for 3 days. An abdominal computed tomography (CT) scan was performed to evaluate for potential complications and incidentally revealed a markedly distended appendix with peripheral curvilinear calcifications, consistent with an appendiceal mucocele (Figs 1 and 2). The patient denied any abdominal pain or change in bowel habit. There was no prior history of appendicitis. The patient subsequently underwent an outpatient colonoscopy, which was unremarkable, including a normal appearance of the appendiceal orifice. Given the radiological findings, she proceeded with an elective laparoscopic stapled caeco-appendicectomy. Intraoperatively, the appendix was noted to be markedly distended (Fig. 3) with a macroscopically normal caecum. There was no intraoperative spillage of mucin. The patient recovered without complication. Histopathological assessment revealed a 21 × 5cm appendix with features consistent with a low-grade appendiceal mucinous neoplasm. The proximal resection margin was clear of neoplastic change. In its normal state, the appendix measures 4–5 mm in diameter and 8–9 cm in length in adults.1-3 An appendiceal mucocele is a rare condition where occlusion of the appendiceal lumen results in progressive distention with mucinous material, potentially leading to a ‘mega-appendix’. The underlying pathology can be benign or malignant.3 The differential diagnosis includes retention cysts, serrated polyps of the appendix, low-grade or high-grade appendiceal mucinous neoplasm, and mucinous adenocarcinoma of the appendix.4, 5 This case of ‘mega-appendix’ represents a rare clinical phenomenon and is the first reported case from Australasia. A review of the literature suggests that there is no international consensus on the definition of a ‘mega-appendix’, however a ‘long’ appendix is defined as greater than 10 cm.6 We identified four cases of an appendix measuring greater than 20 cm in References 2, 7-9; with the largest documented being a 55 cm appendix in a 13-year-old male. Authors suggest that the term ‘mega-appendix’ be considered for an appendix measuring greater than 20 cm in length. Surgical resection is the standard management of an appendiceal mucocele. Pre-operative colonoscopy is recommended to evaluate the mucosal and to exclude intraluminal lesions, which could potentially alter the surgical approach. Perforation and subsequent spillage of mucin from a neoplastic appendiceal mucocele can result in pseudomyxoma peritonei.3 Therefore, every precaution must be taken to avoid mucin spillage. This can be achieved safely with laparoscopic surgery provided the appendix is handled carefully to prevent perforation. Typically, a laparoscopic stapler is used to staple across a normal caecum. If there is a suspected tumour at the caecum, or the caecum cannot be safely stapled without spillage of mucin or narrowing the terminal ileum, then a right hemicolectomy should be performed. The appendix should be placed in an extraction bag, and the extraction site should be made large enough to ensure there is no perforation during removal. This case represents a rare phenomenon of a ‘mega-appendix’ and demonstrates that laparoscopic resection can be performed safely in patients with an appendiceal mucocele. Nazley Lanuola Youssef: Conceptualization; writing – original draft; writing – review and editing. Binura Buwaneka Wijesinghe Lekamalage: Conceptualization; writing – review and editing. Lucinda Jane Duncan-Were: Conceptualization; writing – review and editing. Benjamin Ian Cribb: Conceptualization; supervision; writing – original draft; writing – review and editing.