Improved outcomes using laparoscopy for emergency colectomy after mitigating bias by negative control exposure analysis

Abstract

Background: Laparoscopy is superior to open surgery for elective colectomy, but its role in emergency colectomy remains unclear. Previous studies were small and limited by confounding because surgeons may have selected lower-risk patients for laparoscopy. We therefore studied the effect of attempting laparoscopy for emergency colectomies while adjusting for confounding using multiple techniques in a large, nationwide registry. Methods: Using National Surgical Quality Improvement Program data, we identified emergency colectomy cases from 2014 to 2018. We first compared outcomes between patients who underwent laparoscopic versus open surgery, while adjusting for baseline variables using both propensity scores and regression. Next, we performed a negative control exposure analysis. By assuming that the group that converted to open did not benefit from the attempt at laparoscopy, we used the observed benefit to bound the effect of unmeasured confounding. Results: Of 21,453 patients meeting criteria, 3,867 underwent laparoscopy, of which 1,375 converted to open. In both inverse probability of treatment weighting and regression analyses, attempting laparoscopy was associated with improved 30-day mortality, overall morbidity, anastomotic leak, surgical site infection, postoperative septic shock, and length of hospital stay compared with open surgery. These effects were consistent with the lower bounds computed from the converted group. Conclusion: Laparoscopic surgery for colorectal emergencies appears to improve outcomes compared with open surgery. The benefit is observed even after adjusting for both measured and unmeasured confounding using multiple statistical approaches, thus suggesting a benefit not attributable to patient selection.