The risk of colectomy and colorectal cancer after appendectomy in patients with ulcerative colitis: a systematic review and meta-analysis

Background: Appendectomy decreases the risk of developing ulcerative colitis (UC), and is suggested to have a beneficial effect on the clinical course of established UC. However, recent studies showed no significantly decreased colectomy rate, and moreover an apparently increased risk of colorectal cancer (CRC). We aimed to investigate the suggested correlation in a meta-analysis, and analyze possible confounding factors.

Methods: A systematic review and meta-analysis were performed using MEDLINE, EMBASE and the Cochrane library. Data from studies describing the influence of appendectomy on colectomy and CRC were extracted from published reports. Exclusion criteria were patients <18 years, non-UC, and animal studies.

Results: From 891 studies, 13 studies evaluating 73323 UC patients (appendectomy n=2859) were included. All studies, except one, were rated as poor quality. Overall, colectomy rate in appendectomized and non-appendectomized patients was not significantly different (OR 1.25, 95%CI 0.88-1.77, I2=53%). The proportion of colectomies undertaken for CRC or high grade dysplasia (HGD) was significantly higher after appendectomy (OR 2.85, 95%CI 1.40-5.78, I2=32%), with 50% of the colectomies indicated for CRC/HGD compared to 9.4% in non-appendectomized patients. Possible additional confounding factors were a longer UC disease duration, less medication use and a higher prevalence of PSC in appendectomized patients.

Conclusions: Appendectomy in established UC is associated with apparently higher rates of subsequent CRC/HGD, but this appears to be due to inequalities in at-risk exposure between groups, presumably secondary to positive clinical effects of appendectomy on disease symptoms. This finding emphasizes the importance of regular endoscopic surveillance in this patient group.