Incidence of and risk factors for bowel ischemia after abdominal aortic aneurysm repair

Abstract

Background: Bowel ischemia is a rare but devastating complication after abdominal aortic aneurysm (AAA) repair. Its rarity has prohibited extensive risk-factor analysis, particularly since the widespread adoption of endovascular AAA repair (EVAR); therefore, this study assessed the incidence of postoperative bowel ischemia after AAA repair in the endovascular era and identified risk factors for its occurrence.

Methods: All patients undergoing intact or ruptured AAA repair in the Vascular Study Group of New England (VSGNE) between January 2003 and November 2014 were included. Patients with and without postoperative bowel ischemia were compared 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: Included were 7312 patients, with 6668 intact (67.0% EVAR) and 644 ruptured AAA repairs (31.5% EVAR). The incidence of bowel ischemia after intact repair was 1.6% (open repair, 3.6%; EVAR, 0.6%) and 15.2% after ruptured repair (open repair, 19.3%; EVAR, 6.4%). Ruptured AAA was the most important determinant of postoperative bowel ischemia (odds ratio [OR], 6.4, 95% confidence interval [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-minute increase; 95% CI, 1.1-1.3), blood loss >1 L (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 intact (open repair: 20.5% vs 1.9%; P < .001; EVAR: 34.6% vs 0.9%; P < .001) as well as after ruptured AAA repair (open repair: 48.2% vs 25.6%; P < .001; EVAR: 30.8% vs 21.1%; P < .001).

Conclusions: This study underlines that although bowel ischemia after AAA repair is rare, the associated outcomes are very poor. The cause of postoperative bowel ischemia is multifactorial and can be attributed to patient factors and operative characteristics. These data should be considered during preoperative risk assessment and for optimization of both the patient and the procedure in an effort to reduce the risk of postoperative bowel ischemia.