Patient Selection and the Apparent Laparoscopic Advantage in Rectal and Rectosigmoid Adenocarcinoma: A Single-Centre Propensity-Weighted Analysis of Confounding by Indication

Background and Objectives: Observational comparisons of laparoscopic and open colorectal resection are vulnerable to confounding by indication because fitter patients with earlier disease are preferentially offered the minimally invasive approach. Using a single-centre cohort as a worked example, we quantified how far the apparent laparoscopic advantage changed under progressively stricter control for measured confounding. Materials and Methods: In total, 89 adults undergoing elective resection for rectal or rectosigmoid adenocarcinoma were analysed by initiated approach (laparoscopic strategy, n = 61, of whom 19 were converted; planned open, n = 28) and, as a sensitivity analysis, by approach completed (laparoscopic, n = 42; open, n = 47). The primary outcome was major morbidity (Clavien–Dindo ≥ IIIa within 30 days); secondary outcomes were a 90-day textbook outcome and all-cause mortality, analysed with Kaplan–Meier and Cox methods (median follow-up 6 months, interquartile range 2–9). Approach effects were estimated as crude, Firth-penalised covariate-adjusted, stabilised inverse-probability-weighted, overlap-weighted, and doubly robust odds ratios, with balance quantified by standardised mean differences and sensitivity to unmeasured confounding by E-values.