Asian Cardiovasc Thorac Ann 1999;7:135-137
© 1999 Asia Publishing EXchange Pte Ltd
Traumatic Pseudoaneurysm of the Abdominal Aorta
Lim Chong Hee, MBBS, FRCS,
Jeremy Lim, MBBS1,,
Tan Yong Seng, MBBS, FRCS
Department of Cardiothoracic Surgery
National Heart Centre
Republic of Singapore
1 Ministry of Health
Republic of Singapore
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For reprint information contact: Lim Chong Hee, MBBS, FRCS Tel: 65 321 4029 Fax: 65 224 3632 Department of Cardiothoracic Surgery, National Heart Centre, Mistri Wing, 17 Third Hospital Avenue, Singapore 168752, Republic of Singapore.
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Abstract
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Delayed pseudoaneurysm of the abdominal aorta is an exceedingly rare but potentially fatal complication following blunt abdominal trauma. A 25-year-old male presented 3 months after a road traffic accident with central abdominal pain. A 4-cm pseudoaneurysm of the infrarenal aorta was detected by computed tomography. Successful surgical repair was performed with an interposition graft and reimplantation of the inferior mesenteric artery.
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Introduction
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Traumatic injury to the abdominal aorta is a rare but potentially fatal entity with a spectrum ranging from intimal flap to frank transection. We report a case of abdominal pseudoaneurysm following blunt abdominal trauma.
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Case Report
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A 25-year-old Chinese male was involved in an accident where he skidded and was flung off his motorcycle. He was unconscious for approximately 10 minutes and on arrival at the accident and emergency department, was noted to be restless with a left mandibular swelling and oxygen saturation of only 50%. There was also bruising around the umbilicus. Operative reduction and fixation was carried out for the open mandibular fracture. Chest radiography revealed a left pneumothorax for which tube thoracostomy was performed. A computed tomography (CT) scan of the head did not detect any intracranial injuries but a CT scan of the abdomen revealed bilateral perirenal hematomas and retroperitoneal hemorrhage (Figure 1
). No aortic injuries were noted at that time. Intravenous pyelography showed good contrast uptake by both kidneys and nonsurgical management was decided. The patient was observed carefully for a few days in the ward and after detecting no evidence of progressive disease, he was discharged.
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Figure 1. Computed tomography scan of the abdomen at initial presentation, showing a periaortic hematoma.
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The patient reported no complaints at follow-up one week later and an abdominal examination did not detect any normality. Three months later, he complained of abdominal pain, mainly in the umbilical region and left iliac fossa. There was no radiation to the back and the pain was described as dull and aching. He had no symptoms of claudication or neurological deficit in the lower limbs. He was hemodynamically stable and his abdomen was soft with no pulsatile mass or bruit. A repeat CT scan showed a focal pseudoaneurysm of the infrarenal aorta, approximately 4 cm long with the inferior extent 2 cm above the aortic bifurcation (Figure 2). The perirenal hematomas had resolved. Duplex scanning demonstrated high antegrade flow in the true lumen of the aorta with slow flow in the false lumen during diastole (Figure 3). Repair was performed via a midline laparotomy with a 30-cm length of 14-mm interposition graft (Unigraft; B. Braun, Melsungen, Germany) and reimplantation of the inferior mesenteric artery. As expected, we encountered dense adhesions in the periaortic area. The aortic cross-clamp time was 83 minutes. The postoperative period was uncomplicated and the patient was discharged on the 7th postoperative day.
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Discussion
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Traumatic pseudoaneurysm of the abdominal aorta is extremely rare and only 26 cases have been reported in the last 78 years.1 It is more common in males in the age range 4 to 75 years. The time lapse between the initial injury and diagnosis of pseudoaneurysm is variable and has been up to 28 years later. Blunt abdominal trauma causing aortic injury is most commonly due to a motor vehicle accident, especially when a seatbelt is used. This may explain the preponderance of males as they are more prone to traumatic injury. Injury can be inflicted by both direct and indirect mechanisms. Direct injury occurs because of the relatively fixed position of the aorta by the vertebral column and the lumbar vessels. Vascular damage can occur from pressure on the aorta or laceration due to thoracolumbar fractures. Indirect injury occurs by transmission of pressure from adjacent organs through the aortic wall to the blood column within, causing a sudden increase in intraluminal pressure and consequent tears. However, total rupture is uncommon and Bergquist and Takolander2 postulated that pressures of 1000 to 2500 mm Hg are required for complete rupture. Deceleration force also contributes to shearing but it is probably more relevant to the pathogenesis of thoracic injury.
A pseudoaneurysm results from local full-thickness disruption of the arterial wall with hemorrhage that is contained by tamponading from surrounding structures. If the defect is large enough, it allows communication between the aortic lumen and the hematoma. In time, the blood is resorbed and a fibrous capsule develops. Symptoms are due to local compressive effects, thrombus formation or embolic phenomena, and even frank rupture. Patients most commonly present with pain or a pulsatile mass. However, some have presented with malignant hypertension secondary to renovascular hypertension, recurrent thromboembolism to the mesenteric vessels, and even biliary obstruction.3–5 In spite of the fact that most aortic injuries resulting from blunt abdominal trauma are infrarenal, pseudoaneurysm is most commonly suprarenal (postulated to be due to the better protection afforded to the suprarenal aorta by the lower end of the thoracic cage). Paradoxically, it is the density and relative rigidity of the structures around the suprarenal aorta, particularly the crura, that result in more successful tamponade than the loose fatty tissue of the lower retroperitoneum, and hence the higher incidence of pseudoaneurysm formation. In a review by Miller and colleagues1, 12 pseudoaneurysms were suprarenal, 5 were juxta-renal, and 9 were infrarenal.
The gold standard for investigating aortic injury is angiography although a recent study of thoracic aorta injuries demonstrated helical CT to be more sensitive but less specific than aortography for all forms of aortic injury.6 CT and duplex Doppler ultrasonography are very useful initial noninvasive modalities of imaging. CT shows the hematoma and the surrounding fibrous capsule well but may not demonstrate a communication. Duplex Doppler ultrasonography confirmed the diagnosis of pseudoaneurysm in a recent case report.7 The Doppler signs consist of a high-speed flow from the aorta to the pseudoaneurysm during systole with a slower flow out of the pseudoaneurysm during diastole. It is important to recognize this to-and-fro pattern within the neck of the pseudoaneurysm to differentiate it from other lesions with vascular flow such as hematomas or true aneurysms.
Surgical management is indicated for all pseudoaneurysms because of the risk of rupture and the consequent high mortality. However, in the acute stage, there is a case to be made for nonoperative management of minor intimal tears with serial angiography in a dedicated unit because small lesions may heal without the need for surgery.8 Early diagnosis requires a high index of suspicion and appropriate imaging studies. Because of the possibility of delayed presentation, all cases of suspected abdominal aortic injury should be followed up with serial imaging or at least a repeat CT scan if the first was not conclusively negative for aortic injury.
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References
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Bergquist D, Takolander R. Aortic occlusion following blunt trauma of the abdomen. J Trauma 1981;21:319–22.[Medline]
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Smith RB, Perdue GD, Walker LG Jr, et al. Post-traumatic aneurysm of the abdominal aorta with recurrent emboli to the superior mesenteric artery: a case report. Surgery 1968;64:736–42.[Medline]
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Chan CM, Leyman TS. Traumatic abdominal pseudoaneurysm causing biliary obstruction: a case report and review of the literature. J Vasc Surg 1997;25:936–40.[Medline]
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Fabian TC, Davis KA, Gavant ML, Croce MA, Melton SM, Patton JH, et al. Prospective study of blunt aortic injury: helical CT is diagnostic and antihypertensive therapy reduces rupture. Ann Surg 1998;227:666–77.[Medline]
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Llorente JG, Gallego MG, Arnaiz AM. Chronic post-traumatic pseudoaneurysm of the abdominal aorta diagnosed by duplex Doppler ultrasonography: a case report. Acta Radiologica 1997;38:121–3.[Medline]
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Lock JS, Huffman AD, Johnson RC. Blunt trauma to the abdominal aorta. J Trauma 1987;27:674.[Medline]
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Abstract
Introduction
