Introduction
Bowel ischemia is a rare but devastating complication following abdominal aortic aneurysm (AAA) repair. Its rarity has prohibited extensive risk factor analysis, particularly since the widespread adoption of endovascular repair (EVAR). Therefore, the purpose of this study was to assess the incidence of postoperative bowel ischemia following AAA repair in the endovascular era, and identify risk factors for its occurrence.
Methods
All patients undergoing AAA repair, either intact or ruptured, in the Vascular Study Group of New England between January 2003 and November 2014 were included. We compared patients with postoperative bowel ischemia to those without, and stratified by indication (intact and ruptured) and treatment approach (open repair and EVAR). Criteria for diagnosis were endoscopic or clinical evidence of ischemia, including bloody stools in patients who died before diagnostic procedures were performed. Independent predictors of postoperative bowel ischemia were established using multivariable logistic regression analysis.
Results
A total of 7312 patients were included, with 6668 intact (67.0% EVAR), and 644 ruptured AAA repairs (31.5% EVAR). The incidence of bowel ischemia following intact repair was 1.6% (open repair: 3.6%, EVAR: 0.6%), and 15.2% following ruptured repair (open repair: 19.3%, EVAR: 6.4%). Ruptured AAA was the most important determinant of postoperative bowel ischemia (OR:6.4, 95%CI:4.5 – 9.0), followed by open repair (OR:2.9, 95%CI:1.8 – 4.7). Additional predictive patient factors were advanced age (OR:1.4 per 10 years, 95%CI:1.1 – 1.7), female gender (OR:1.6, 95%CI:1.1 – 2.2), hypertension (OR:1.8, 95%CI:1.1 – 3.0), heart failure (OR:1.8, 95%CI:1.2 – 2.8), and current smoking (OR:1.5, 95%CI:1.1 – 2.1). Other risk factors included unilateral interruption of the hypogastric artery (OR:1.7, 95%CI:1.0 – 2.8), prolonged operative time (OR:1.2 per 60 min. increase, 95%CI:1.1 – 1.3), blood loss >1L (OR:2.0, 95%CI:1.3 – 3.0), and a distal anastomosis to the femoral artery (OR:1.7, 95%CI:1.1 – 2.7). Bowel ischemia patients had a significantly higher perioperative mortality after both intact (open repair: 20.5% vs. 1.9%, P<.001; EVAR: 34.6% vs. 0.9%, P<.001), as well ruptured AAA repair (open repair: 48.2% vs. 25.6%, P<.001; EVAR: 30.8% vs. 21.1%, P<.001).
Conclusion
This study underlines that although bowel ischemia following AAA repair is rare, the associated outcomes are very poor. The cause of postoperative bowel ischemia is multifactorial in nature, and can be attributed to patient factors, as well as operative characteristics. These data should be considered during pre-operative risk assessment, and optimization of both patient and procedure in an effort to reduce the risk of postoperative bowel ischemia.