The impact of the number of stapler firings on anastomotic leakage in minimally invasive rectal surgery: risk factor or technical marker of complexity? A systematic review, meta‑analysis, and metaregression

BACKGROUND: Anastomotic leakage is a major complication after minimally invasive anterior resection for rectal cancer. The number of stapler firings for rectal transection has been suggested as a modifiable risk factor, but its independent role and optimal threshold remain unclear. OBJECTIVE: To evaluate the impact of the number of stapler firings on anastomotic leakage after rectal surgery and to assess the influence of surgical and patient-related variables. DATA SOURCES: A comprehensive search of PubMed, Cochrane Library, and Ovid MEDLINE was performed. STUDY SELECTION: Studies reporting anastomotic leakage rates stratified by stapler firing count (one, two, or three or more) were included. INTERVENTION(S): Rectal transection with one or more stapler firings during minimally invasive anterior resection for rectal cancer. MAIN OUTCOME MEASURES: Incidence of anastomotic leakage according to stapler firing (SF) count. RESULTS: Twenty two studies including 8,725 patients and 784 anastomotic leakage events were analyzed. A single stapler firing was associated with a significantly reduced risk of anastomotic leakage compared with two stapler firings (odds ratio 0.57, 95% confidence interval 0.39-0.83), three or more stapler firings (odds ratio 0.28, 95% confidence interval 0.16-0.51), and two or more stapler firings (odds ratio 0.46, 95% confidence interval 0.34-0.63). The risk of anastomotic leakage was lower with fewer than three stapler firings compared with three or more stapler firings (odds ratio 0.38, 95% confidence interval 0.30-0.48). Meta-regression identified low rectal transection and preoperative radiotherapy as significant effect modifiers. LIMITATIONS: All included studies were observational, introducing potential bias and increased heterogeneity and the certainty of evidence was low across all comparisons. CONCLUSIONS: Three or more stapler firings were consistently associated with a higher risk of anastomotic leakage. However, because the certainty of evidence was low and owing to exploratory meta-regression findings, stapler firing number appears to reflect operative complexity more than a definitively established independent causal risk factor.