Abdominal aortic mechanism of injury relates to the biomechanical direct and indirect forces incurred while it is tethered between the spinal column, the peritoneum, and abdominal viscera [5, 6]. The most frequent force causing an abdominal aorta injury is compressive, associated with deceleration [55]. Indirect forces occur when the aortic wall is directly stretched and compressed against a high-pressure column of blood leading to intimal tears, pseudoaneurysm, rupture, or thrombosis [56, 57]. Atherosclerotic changes of the aorta are associated with a weakening of the intima in addition to loss of elasticity and compliance and thus thought to increase the risk of aortic injury [58, 59]. These forces can occur during motor vehicle collisions when the aorta is compressed by the seat belt, thus termed “seat belt aorta” [60]. Other mechanisms include long-distance falls, direct compression of the aorta, and penetrating injuries.

The underlying pathologic lesion of BAAI is the disruption of the intima. Depending on the magnitude of the traumatic forces, BAAI presents as a spectrum of disease ranging from a minimal aortic injury (MAI) to free rupture of the aorta [61]. The increasing use of CT scanning with angiography to evaluate patients with blunt trauma has resulted in increasing numbers of MAI diagnosed [61]. These traumatic intimal tears can manifest as intimal flaps or dissection which can be uncomplicated or progress to thrombosis or acute arterial insufficiency [21, 22, 29, 56]. Injuries involving the adventitia lead to pseudoaneurysm formation (Fig. 16.1) or even rupture of the aortic wall. Rupture of the aortic wall can also be due to branch vessel avulsion [2].

The majority of the injuries occur inferior to the renal arteries. Aortic injuries are classified based on presence of aortic contour abnormality and presence of free rupture [5]. This classification is based on experience with blunt thoracic aortic injury [62]. Intimal tears/flaps are not associated with external aortic contour abnormality. A pseudoaneurysm presents as a contained rupture and is clearly associated with an aortic contour abnormality. The most common associated injuries are small bowel injuries (38 %) and thoracolumbar spine injuries (25 %). The most common anatomic findings since 1996 were intimal tears/flaps (41 %) followed by reports of pseudoaneurysms (29 %) [8, 10, 11, 15–47].

Management of aortic injury varies and risk of mortality rises with the severity of the pathologic lesion. In a recent review of the National Trauma Data Bank of 436 patients with BAAI from 180 centers from 2007 to 2009, 90 % were managed nonoperatively. Of those who underwent operative repair, 69 % underwent endovascular repair, with the remainder undergoing open aortic repair and two extra-anatomic bypasses [64]. In general, cases of BAAI with uncomplicated intimal flaps are managed nonoperatively with anti-impulse (β-blockers) and antiplatelet (aspirin) therapy and close follow-up. The natural history of intimal flaps is a decrease in size and complete resolution [9]. Cases of aortic pseudoaneurysms require operative repair to prevent rupture, but these can be managed on a semi-elective basis during the initial hospitalization. Cases complicated by thrombosis, acute arterial insufficiency, and free rupture require an operative or endovascular repair.

The timing of repair also depends on the patient’s associated injuries. Patients with pulse and neurologic deficits, an expanding hematoma and concomitant intra-abdominal injuries, require emergent exploration and immediate repair. Otherwise, treatment can be individualized in the hemodynamically normal trauma patient.

Initial management is determined by the hemodynamic state of the patient. Hypotensive patients are managed with an exploratory laparotomy. A midline laparotomy incision allows exposure of all zones of the abdomen. Initial inspection identifies areas of ongoing hemorrhage, contained hematoma, or evidence of bowel ischemia [3]. Operative management of aortic injury is guided by its associated Zone 1 hematoma which may be supramesocolic or inframesocolic. Common pitfalls and pearls regarding management of the patient with an aortic injury are discussed below.

Reports of endovascular stent placement in cases of aortic injuries have recently increased in frequency because these techniques are less invasive and an attractive alternative for patients with both isolated aortic injuries and multisystem injuries in a manner similar to that of blunt thoracic aortic injury (Fig. 16.4). The use of stent grafts is not widely adopted, and most of the literature is limited to case reports and small case series where endovascular stents, aortic extension cuffs, and limb extensions have all been used in cases of blunt and penetrating trauma [23, 24, 29, 31, 34, 35, 44, 66–69]. Indications include cases with associated gross contamination from hollow viscus injury that can jeopardize aortic grafts due to risk of infection or management of injuries difficult to expose by conventional means. Endovascular interventions can be used as a stabilizing measure for critically ill patients and a bridge to open definitive repair. From an endovascular perspective as it relates to trauma, abdominal aorta zones of injury can be classified [5] based on feasibility of endovascular approach as follows: Zone I injuries occur from diaphragmatic hiatus to the superior mesenteric artery (SMA). Zone II injuries include the SMA to renal arteries. Zone III injuries are inferior to the renal arteries to the aortic bifurcation (Fig. 16.5). Zone I and III injuries are amenable to endovascular repair, whereas Zone II lesions are not amenable to endovascular stenting without fenestration for the SMA and renal arteries. The timing of the repair is dependent on the patient’s hemodynamic status and the presence of acute limb ischemia. Endovascular repair can be used for injuries from the diaphragmatic hiatus to the superior mesenteric artery or for injuries below the renal arteries to the aortic bifurcation. Injuries that involve the aorta in the vicinity of the SMA and renal arteries are not easy to manage by an endovascular technique as this would require graft fenestration for the SMA and renal arteries

Injury to the abdominal aorta is highly lethal. Among those who survive the transport to the hospital mortality rates range from 32 to 78 % with hemorrhagic shock being the most common cause of associated mortality [2, 4–6, 10]. Outcomes in cases requiring a resuscitative thoracotomy remain poor [74, 75]. In BAAI, mortality varies by the type of aortic injury. When minimal aortic injuries, dissections of the aorta, and pseudoaneurysms are included, aggregate mortality is 11 % [5]. In cases treated by endovascular repair, the long-term durability of aortic endografts for abdominal aortic trauma is not well described. Clearly long-term follow-up will be required in these cases.