Table 6

Meta-analyses of studies that have investigated appendicectomy in UC or PSC

I: Appendicectomy rate in patient and control groups: meta-analysis of four studies
Study	PSC (n)	UC (n)	Control group (n)	Comments
(a) van Erpecum⁴⁰	59	130	197	Small groups, reported all appendicectomy—before and after diagnosis.
(b) Mitchell⁴¹	170	170	170	Did not find low App+ in UC.
(c) Selby²⁵	23	236	280	Small PSC group.
(d) Florin	90	294	1466	Disease specific control groups.
Meta-analysis (a–d)	342	830	2113
App+	61	62	424	App data missing for 166 controls and 1 PSC.
App−	280	768	1523	App data missing for 166 controls and 1 PSC.
p Value (App+: disease v controls)	0.12	<0.0001; OR 0.29 (CI 0.22 –0.38)		OR (CI) of App+ in UC relative to App+ in control group.

II: Appendicectomy v colorectal cancer: meta-analysis of two studies
PSC, primary sclerosing cholangitis; IBD, inflammatory bowel disease; UC, ulcerative colitis; OR, odds ratio; CI, confidence interval; App, appendicectomy; CRC, colorectal cancer.
Meta-analysis (c, d)	113	530	High grade dysplasia not analysed because these data not available in (c).
App+ (CRC)	26 (1)	28 (3)	Prior appendicectomy data missing for 1 PSC-IBD case.
App− (CRC)	86 (3)	502 (4)	Prior appendicectomy data missing for 1 PSC-IBD case.
p Value (CRC v App+)	1.0	0.004; OR 14.9 (CI 3.2–70)	OR (CI) of colorectal cancer in UC patients with prior appendicectomy relative to UC patients who have not undergone prior appendicectomy.