Background
Bowel anastomoses are a complex and important component of colorectal surgeries to restore bowel continuity.
Numerous anastomosis techniques have been described, with great variation between different techniques. Bowel anastomoses can generally be performed with variation in configuration (end-to-end, end-to-side, side-to-side), construction (stapled, handsewn), location (intracorporeal, extracorporeal). Many studies have examined the various factors in anastomosis construction in an attempt to standardise anastomosis techniques.
Despite this, there has been little discussion on the effect of anastomotic direction (isoperistaltic, antiperistaltic) on outcomes of anastomosis.

Objectives
This review aims to compare the short and long term outcomes of iso-peristaltic and anti-peristaltic configuration for side to side bowel anastomosis in colo-colic, ileo-ileal and ileal-colic anastomosis.

Methods
The study protocol was registered in the International Prospective Register of Systematic Reviews – University of York (PROSPERO) (CRD42023417762).
A total of 489 studies were identified from EMBASE, Medline (via PubMed) and The Cochrane library. Full text review was conducted for 99 studies and 8 were included in final analyses. Analyses was conducted with Cochrane Review Manager (RevMan web).

Results
Mean difference of intraoperative blood loss was -1.4 millilitres (95% CI, -3.33 to -0.67, p = 0.01) for antiperistaltic anastomosis compared to isoperistaltic anastomosis. Mean difference of operative time was 5.20 minutes (95% CI, 3.05 to 7.36, p = <0.0001 ) for antiperistaltic anastomosis compared to isoperistaltic anastomosis. Subgroup analysis of STC showed a mean difference of -2.62 minutes (95% CI, -6.70 to 1.45, p = 0.21) , -16.28 minutes (95% CI, -27.17 to -5.38, p = 0.003) for CD and 9.65 minutes (95% CI, 7.04 to 12.26, p = <0.00001) for colon cancer. Differences in post-operative outcomes (Length of Stay, Complications, Readmission and GIQLI-10 score) between antiperistaltic or isoperistaltic anastomosis were minor and not statistically significant.

Conclusions
Our analyses suggests that peristaltic direction of anastomoses does not have significant impact on the outcomes after a surgery. The analyses is hampered by the lack of high quality data that controls for all other factors except anastomosis direction. However, our findings are in line with individual RCTs and cohort studies that have compared peristaltic directions. There is uniform consensus in the concluding remarks that both peristaltic directions are appropriate with no clear benefit of one over the other. Where present, the magnitude of difference in outcomes may not be significant in practice. In the context of other factors that affect outcomes of anastomoses and surgery, the direction of the anastomoses is likely of little clinical significance.

Jia Lin Ng

Appearances