Eight RCTs (n=391) were included.
Only one study reported an a priori sample size calculation. Methods of randomisation with allocation concealment were reported in six of the included studies and one study had blinded assessors. Seven of the included studies clearly reported on pouch formation. One study did not use intention-to-treat principles.
Straight coloanal anastomosis was associated with a non significant increased risk of anastomotic leak compared with colonic J-pouch (RR 0.36, 95% CI: 0.12, 1.08). Four of the six studies measuring anastomotic leak rate found no incidence in either group and were not weighted in the analysis.
Colonic J-pouch was associated with a non significant increased risk of anastomotic stricture compared with straight coloanal anastomosis (RR 2.45, 95% CI: 0.79, 7.57). Only two studies measured anastomotic stricture. There was no evidence of heterogeneity (I-squared 0%).
Straight coloanal anastomosis was associated with a statistically significant increase in odds of experiencing faecal incontinence compared with colonic J-pouch (OR 0.23, 95% CI: 0.08, 0.68).
There was a statistically significant but non clinically significant difference in stool frequency favouring the J-pouch (WMD -1.21, 95% CI: -1.92, -0.49) in the two studies included in the analysis. There was evidence of considerable and statistically significant heterogeneity (I-squared 81.3%).