Individual medical records of the patients who underwent the above procedures were reviewed to determine the incidence of post-operative complications as defined by American College of Surgery National Surgical Quality Improvement Program (ACS NSQIP) within 30 days (any NSQIP 30-day morbidity). The ACS NSQIP complications that were noted included bleeding, superficial wound infection, deep wound infection, organ space infection, wound dehiscence, acute renal failure, progressive renal insufficiency, urinary tract infection, prolonged ileus, pneumonia, failure to wean from ventilator, unplanned intubation, pneumothorax, pulmonary embolus, cardiac arrest, exacerbation of heart failure, deep venous thrombosis, cerebrovascular accident, transient ischemic attack, sepsis, septic shock, and death (all-cause 30-day mortality). The severity of each complication was graded independently by two clinicians (JAB and RS) according to the recently validated Accordion Severity Grading System (Table
Next, a weighted postoperative morbidity index (PMI) was calculated as previously described [8 (link)] (i.e., to calculate the PMI for each operative procedure, the weights of all the complications for all patients who underwent the corresponding procedure were summed and divided by the total number of patients undergoing that procedure). A PMI of 0 would indicate that no patient having the procedure had any postoperative complications, while on the other hand, and a PMI of 1.000 would indicate that every patient having the procedure suffered postoperative death. In order to analyze complication severity, the sum of severity weights for all patients having any complication after a procedure were divided by the total number of patients with complications in the group (i.e., the denominator was the number of patients having a complication after the procedure, rather than the total number of patients having the procedure). Descriptive statistics were performed in Excel 2007 (Microsoft Corp).