Fifteen independent studies (5,199 patients: 782 with FAP and 4,417 with UC) were included. There was one prospective non-randomised study (n=104) and one retrospective case-matched study (n=78); the rest were retrospective studies.
In 14 studies the groups were matched on one or more characteristics; nine matched for pouch design and method of pouch-anal anastomosis; and eight matched for use or omission of diverting-loop ileostomy. Eight studies scored 6 or more stars for validity.
Patients with UC were significantly more likely to develop post-operative fistulas (10.4% versus 4.8%; OR 2.31, 95% CI: 1.43, 3.73, p<0.001; 8 studies, n=1,766; no significant heterogeneity) and pouchitis (30.1% versus 5.5%; OR 6.44, 95% CI: 3.21, 12.93, p<0.001; 12 studies, n=2,843; significant heterogeneity was found, p=0.05) than patients with FAP. There was no statistically significant difference between patients with UC and FAP in post-operative mortality (7 studies, n=1,519), anastomic leak or stricture (5 studies, n=1,047), pelvic sepsis (8 studies, n=2,309), wound infection (4 studies,n=401), incisional hernia (4 studies, n=379), small bowel obstruction (6 studies, n=1,303), pouch failure, (9 studies, n=3,031), sexual dysfunction (3 studies, n=954) or post-operative urinary dysfunction (1 study, n=110).
Patients with FAP reported significantly lower stool frequency per 24 hours than patients with UC (WMD 0.99, 95% CI: 0.21, 1.76, p=0.01; 7 studies, n=1,274; significant heterogeneity was found, p<0.001). There were no statistically significant differences between patients with UC and FAP for other functional outcomes.
A funnel plot based on rates of pouchitis showed some evidence of publication bias.
Larger studies showed an increased rate of pouchitis in UC compared with FAP patients. Higher quality studies showed no statistically significant differences between patients with UC and FAP for stool frequency per 24 hours or rates of pouch failure, but showed significantly higher rates of fistula formation, pouchitis and anastomotic leak in UC patients. Recent studies showed no significant difference between UC and FAP patients in stool frequency, pouch failure and anastomotic leak. Studies that reported histologically confirmed pouchitis showed a statistically significant increase in pouchitis in UC compared with FAP patients.
The results of other subgroup analyses were also reported.