The retroperitoneal incision. An evaluation of postoperative flank 'bulge'

OBJECTIVES: To determine if intercostal nerve injury is related to postoperative flank "bulge" and to determine whether the extent of the retroperitoneal incision is related to the incidence of flank bulge following abdominal aortic aneurysm repair. DESIGN: Bilateral dissection of the 11th intercostal nerve on seven cadavers; neurophysiological evaluation of five patients, three with a flank bulge and two without; and retrospective analysis of the extent of retroperitoneal incision and incidence of postoperative flank bulge in 63 consecutive patients. SETTING: Urban academic medical center. PATIENTS: Sixty-three consecutive patients who underwent retroperitoneal repair of an abdominal aortic aneurysm and neurophysiological evaluation of five volunteer patients. INTERVENTIONS: Retroperitoneal repair of abdominal aortic aneurysms. MAIN OUTCOME MEASURE: Reduction of injury to the 11th intercostal nerve by avoiding extension of the retroperitoneal incision into the intercostal space. RESULTS: Of 14 dissections of 11th intercostal nerves, there were bifurcations of the main trunk within the intercostal space in four, at the tip of the 11th rib in seven, and at least 2 cm distal to the tip of the rib in three. Neurophysiological evaluation revealed iterative discharges, polyphasia, fibrillation potentials, and altered recruitment patterns compatible with intercostal nerve injury in patients with a bulge but not in the opposite abdominal wall musculature or in patients without a bulge. Seven (11.11%) of 63 patients had a bulge. Thirty-one of 63 patients had incisions into the 11th intercostal space in which a bulge developed in six (19.35%). Thirty-two patients had incisions that avoided extension into the intercostal space; a bulge developed in one (0.03%) (P = .53). CONCLUSIONS: Postoperative bulge is related to intercostal nerve injury with subsequent paralysis of abdominal wall musculature. Intercostal nerve injury can be reduced by avoiding extension of the incision into the 11th intercostal space.