Critical values for body mass index related to morbidity in high-volume low-complexity general surgery: a systematic review and meta-analysis.

Introduction: The aim of this study was to investigate the effect of body mass index (BMI, kg/m²) on outcomes of high-volume low-complexity (HVLC) general surgery procedures and to determine critical values for BMI when selecting patients into HVLC programmes.

Methods: A systematic review was conducted of studies looking at patients in different BMI categories undergoing HVLC general surgery procedures (laparoscopic cholecystectomy, inguinal hernia repair and umbilical or paraumbilical hernia repair), in accordance with the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines. A comparison meta-analysis model was constructed to compare the outcomes using random-effects modelling. The QUIPS (Quality In Prognosis Studies) tool and GRADE (Grading of Recommendations Assessment, Development and Evaluation) system were used to assess bias.

Results: A total of 26 studies including 486,392 patients were examined. In laparoscopic cholecystectomy, BMI ≥40 was associated with higher conversion to open surgery (odds ratio [OR]: 1.33, p=0.040) but did not affect complications (OR: 0.69, p=0.400) or length of hospital stay (mean difference [MD]: -0.01 days, p=0.900). In inguinal hernia repair, BMI ≥35 was associated with longer operative time (MD: 18.00 minutes, p<0.00001), and higher risk of wound complications (OR: 3.01, p<0.00001) and hospital readmission (OR: 1.46, p=0.0008). In umbilical or paraumbilical hernia repair, BMI ≥30 was associated with higher risk of wound complications (OR: 6.45, p<0.0001) and hospital readmission (OR: 5.56, p<0.00001), and longer operative time (MD: 4.01 minutes, p=0.030).

Conclusions: Obesity was associated with longer operative time (up to 23 minutes) and higher risk of postoperative morbidity (up to 4-fold) in HVLC procedures. BMI <40 (moderate GRADE certainty - laparoscopic cholecystectomy) and BMI <35 (moderate GRADE certainty - inguinal hernia) appear to represent optimal critical values for perioperative safety metrics.