Perioperative Probiotics or Synbiotics in Adults Undergoing Elective Abdominal Surgery

Systematic review and meta-analysis of 34 studies in adults undergoing elective abdominal surgery, including colorectal, upper gastrointestinal, transplant, and hepatopancreatobiliary procedures. Across the active intervention arms, 1354 participants received probiotics or synbiotics and 1369 participants were in control groups.

Perioperative probiotics or synbiotics were given around elective abdominal surgery. The reviewed interventions varied substantially in strain composition and formulation; probiotic dose, form, frequency, duration, and route were not standardized in the extracted data, while synbiotic regimens included 12 days preoperatively and 4 days postoperatively.

Perioperative probiotics and synbiotics reduced postoperative infectious complications overall, and synbiotics appeared more effective than probiotics alone. The pooled risk of postoperative infectious complications was RR 0.56 (95% CI 0.46-0.69; P < 0.00001; I2 = 42%), with subgroup effects of RR 0.46 for synbiotics (95% CI 0.33-0.66; P < 0.0001) and RR 0.65 for probiotics (95% CI 0.53-0.80; P < 0.0001). Length of hospital stay was also shorter overall (WMD -2.59 days, 95% CI -4.31 to -0.87; P = 0.003), driven by synbiotics (WMD -3.89 days, 95% CI -6.60 to -1.18; P = 0.005), while probiotics alone did not significantly reduce stay (WMD -0.65 days, 95% CI -2.03 to 0.72; P = 0.35). Mortality was unchanged (RR 0.98; 95% CI 0.54-1.80; P = 0.96), and adverse events were minimal with no significant safety signal.

The evidence is limited by substantial heterogeneity in probiotic and synbiotic formulations, dosing, and treatment duration, as well as variability in study design. Several outcomes showed high heterogeneity, especially length of stay (I2 = 88% overall and 91% for synbiotics), and mortality/noninfectious complications were not clearly improved. The review also reflects mixed surgical populations, which may limit direct applicability to any single procedure type.