Mucocele of the Appendix

The above images are from a patient who presented to the emergency room with right lower quadrant pain and nausea. Acute appendicitis was suspected. CECT demonstrated a dilated, tubular, fluid filled structure arising from the cecal base. Its maximal diameter was 3 cm. No pericecal inflammatory changes were seen. The patient was taken to the operating room and found to have an appendiceal mucocele.

Mucocele of the appendix refers to a dilated, mucus-filled appendix. CECT findings depend on the histologic type of mucocele. Mucosal hyperplasia (simple mucocele) and mucinous cystadenoma (benign tumor) will appear as a well circumscribed cystic structure with water attenuation of its lumen. Peripheral calcifications are seen in approximately 50% of cases. Mucinous cystadenocarcinoma (malignant tumor with higher risk of perforation) appears as a large, irregular mass with nodular mural thickening, solid and cystic components, and calcifications.

Clinically, the presentation of appendiceal mucocele is identical to that of acute appendicitis. However, pre-operative diagnosis of the former is important since it changes the surgical management - rupture of a mucocele can cause free spillage of mucus into the peritoneal cavity resulting in pseudomyxoma peritonei. Discovery of a neoplastic cause for appendiceal mucocele usually warrants a right hemicolectomy.


REFERENCES
Bennett GL, Tanpitukpongse TP, Macari M, et al. CT diagnosis of mucocele of the appendix in patients with acute appendicitis. AJR Am J Roentgenol 2009;192(3):W103-10.
Pickhardt PJ, Levy AD, Rohrmann CA, et al. Primary neoplasms of the appendix manifesting as acute appendicitis: CT findings with pathologic comparison. Radiology 2002;224:775-81.