Background: Insurance impacts access to therapeutic options, yet little is known about how healthcare reform might change the pattern of surgical admissions., Objective: We compared rates of emergent admissions and outcomes after colectomy before and after reform in Massachusetts with a nationwide control group., Design: This study is a retrospective cohort analysis in a natural experiment. Prereform was defined as hospital discharge from 2002 through the second quarter of 2006 and postreform from the third quarter of 2006 through 2012. Categorical variables were compared by χ. Piecewise functions were used to test the effect of healthcare reform on the rate of emergent surgeries., Settings: The study included acute care hospitals in the Massachusetts Healthcare Cost and Utilization Project State Inpatient Database (2002-2012) and the Nationwide Inpatient Sample (2002-2011)., Patients: Patients aged 18 to 64 years with public or no insurance who underwent inpatient colectomy (via International Classification of Diseases, Ninth Revision, Clinical Modification procedural code) were included and patients with Medicare were excluded., Intervention: Massachusetts health care reform was the study intervention., Main Outcome Measures: We measured the rate of emergent colectomy, complications, and mortality., Results: The unadjusted rate of emergent colectomies was lower in Massachusetts after reform but did not change nationally over the same time period. For emergent surgeries in Massachusetts, a piecewise model with an inflection point (peak) in the third quarter of 2006, coinciding with implementation of healthcare reform in Massachusetts, had a lower mean squared error than a linear model. In comparison, the national rate of emergent surgeries demonstrated no change in pattern. Postreform, length of stay decreased by 1 day in Massachusetts; however, there were no significant improvements in other outcomes., Limitations: The study was limited by its retrospective design and unadjusted analysis., Conclusions: There was a unique and sustained decline in the rate of emergent colon resection among publically insured and uninsured patients after 2006 in Massachusetts, in contradistinction to the national pattern, suggesting improved access to care associated with health insurance expansion. The reasons for lack of improvement in outcomes are multifactorial.