A complication of a dropped appendicolith misdiagnosed as Crohn's disease

Appendicoliths are formed by calcium salts and faecal debris layered and lodged within the appendix. They are detected on unenhanced x-rays in less than 10% of patients with appendicitis. When an appendicolith is found extraluminally, it is pathognomonic for perforation of the appendix. Moreover, retained appendicoliths act as a nidus for infection and are likely to be the source of a postoperative intraperitoneal abscess. However, this is very rare with only 30 reported cases of intra-abdominal abscess secondary to an appendicolith in the literature over the past 40 years. Retained, or dropped, appendicoliths most commonly present as an area of high attenuation less than 1cm in diameter with an associated abscess close to the caecum or Morrison's pouch on computed tomography (CT). A study published in 2006 showed that although there is initial success with CT-guided drainage of abscesses secondary to faecaliths, all will recur and formal surgical drainage with removal of the appendicolith is required. This case report highlights not only an unusual complication of a retained appendicolith but also the importance of taking a thorough history and interpreting investigations in the context of the patient's past medical history so as to produce a differential diagnosis and prevent treatment of incorrect conditions.