Incidence and odds ratio of appendicitis as first manifestation of colon cancer: a retrospective analysis of 1873 patients.

Background and Aim: Obstruction of the lumen of the appendix is the major cause of appendicitis. Tumors could obstruct this lumen and cause appendicitis in the elderly. The association between appendicitis and colon cancer has not been sufficiently investigated, and this study was designed to clarify this association.
Methods: This was a retrospective study. Patients diagnosed with acute appendicitis from January 1998 to December 2003 at the Taipei Veterans General Hospital were surveyed. Patients found to have colon cancers immediately or subsequently after appendectomy were included and analyzed.
Results: A total of 1873 patients were diagnosed as having appendicitis of whom 16 were found to have colon cancer. The incidence of appendicitis associated with colon cancer was 0.85%. The time from appendectomy to the recognition of colonic cancer was at a median delay of 5.8 months. From the Taiwan Cancer Research Annual Report, the incidence of colon cancer was 31.91/100,000 in the year 2000. The odds ratio of colon cancer incidence had a 38.5-fold increase among patients older than 40 with acute appendicitis.
Conclusions: In patients over 40 years who present with symptoms of acute appendicitis the possibility of a coexistent colonic neoplasm should always be kept in mind. These patients should undergo colonoscopy 6 weeks after surgery to exclude the possibility of a coexistent colorectal cancer.