To estimate the incidence and economic burden of circular anastomotic complications in left-sided colorectal resections using manual circular staplers. Patients aged ≥18y who underwent left-sided hemicolectomy, sigmoidectomy, or low anterior resection with ≥1 manual circular stapler between 1-October-2016—31-December-2018 were identified from the Premier Healthcare Database. Circular anastomotic complications were defined as a composite endpoint of multiple circular stapler use (proxy for stapler failure) or circular anastomotic complications (anastomotic leak, bleeding, device/surgical complications, infection, and transfusion). To further enhance our definition of anastomotic complications, we used machine learning techniques (regularized lasso regression; 75%/25% training/test set split) with frequency-based heuristic feature selection on a high-dimensional dataset comprising 4,916 covariates to identify additional diagnosis/procedure codes associated with multiple circular stapler use; these codes were reviewed for clinical relevance to stapler performance by a clinical subject matter expert. Multivariable analyses were used to model the associations between circular anastomotic complications and total hospital costs, length of stay, operating room time, and 30-, 60-, and 90-day readmission rates. A total of 13,167 patients met the study criteria, of whom 2,984 (22.7%) had circular anastomotic complications. An additional 6 clinically-relevant diagnosis/procedure codes were identified by the machine learning-based analysis (corresponding to peritoneal drainage, ostomy, and residual hemorrhoidal skin tags). Compared to those who did not, patients who suffered circular stapler-related complications had significantly higher adjusted total hospital costs ($26,924 vs. $18,748; p<0.0001), length of stay (7.79 vs. 4.99 days; p<0.0001), operating room time (280 vs. 239 minutes; p<0.0001), non-home discharge status (29.3% vs. 17.7%; p<0.0001), and all-cause readmission at 30 days (12.2% vs. 8.7%; p<0.0001), 60 days (16.0% vs. 11.6%; p<0.0001) and 90 days (18.5% vs. 13.4%; p<0.0001). In this analysis of patients undergoing left-sided colorectal resection using manual circular staplers, anastomotic complications were common and associated with substantial adverse clinical and economic consequences.