Treatment of infrarenal abdominal aortic dissection concomitant with an aneurysm

Aortic dissection occurs when layers of the aortic walls are separated by the blood flow through an intimal tear. Dissection of the aorta most frequently originates in the ascending aorta (70%), followed by the descending aorta (22%), the aortic arch (7%) and the abdominal aorta (1/%).1 The dissection limited to the abdominal aorta is rare.2 An isolated abdominal aortic dissection (IAAD) concomitant with an abdominal aortic aneurysm (AAA) is uncommon. We present here one patient with IAAD and AAA treated by endovascular therapy. CASE REPORT The patient was a 50-year-old woman. She had had a palpable mass in the abdomen for 2 months before seeing a doctor. In local hospital, the patient was diagnosed as AAA by ultrasonography. She was then transferred to our hospital for further diagnosis and treatment. A mass about 5 cm×6 cm could be palpated above the umbilical region. No abdominal pain and tenderness to palpation were elicited. Peripheral pulses were normally present. The patient had a history of hypertension for 10 years. Blood pressure on the admission was 160/90 mmHg. Blood analysis, chest X-ray, and electrocardiogram were all normal. However, a thoracic abdominal contrast CT scan found a dissection was present above the superior border of the AAA (Fig). The dissection was mainly located in the infrarenal aorta and the two renal arteries were not involved. After careful preoperative evaluation and preparation, we decided to treat the patient with endovascular therapy. With the patient under general anaesthesia, two groin incisions were made to show corresponding common femoral arteries. The intraoperative angiography was consistent with the preoperative CTA findings. Through the Luderquiest super stiff, guide wire, the main body of the stent graft (Microport, China) was deployed in the abdominal aorta and the right common iliac artery. The contralateral limb was released from the main body to the left common iliac artery. Postoperative angiography and CTA demonstrated normal flow through the aorta and endograft without leak of contrast medium into the AAA sac or the false lumen of the dissection. The patient was discharged and returns to our hospital every 3 months. The CTA and colour Doppler ultrasonography 6 months and 12 months postoperatively both revealed that the false lumen was totally excluded without endoleak. The patient has not complained of any discomfortFig. A.: 3-D reconstruction demonstrates a dissection (arrow) is coexistent with an aneurysm in the abdominal aorta. B. Cross-sectional CT presents a septum of the dissection. C. Intraoperative angiography showed that the dissection and the aneurysm were totally excluded.DISCUSSION The reported incidences of AAA vary between 3.0 and 117.2 per 100 000 person per year.3,4 Aortic dissection isolated to the abdominal aorta is a rare disease. In a study of autopsies of 182 patients with spontaneous aortic dissection, only 1% had dissection limited to the abdominal aorta.1 However, IAAD superimposed on the existence of AAA is even rarer. As to this patient, the dissection was located in the infrarenal abdominal aortic artery. Most AAAs are asymptomatic. Occasionally, patients may describe a “pulse” in their abdomen or may palpate a pulsatile mass due to the rupture or acute expansion of the aneurysm.5 The reported symptoms of IAAD include acute abdominal pain (70%), acute lower limb ischemia (25%) and 5% are asymptomatic or presented abdominal pain of short duration, melaena and/or haematuria. The clinical findings are abdominal tenderness, pulsatile abdominal mass, abdominal bruit, hyposphygmia extremities and lower limb neuromuscular dysfunction.6 Diagnosis of such combined disease is not too difficult. Definitive diagnoses could be made mostly according to the findings of ultrasonography, CT scan, angiography and MRI. As to our experience, the initial examination is contrast enhanced spiral CT scan, which can not only help to establish the diagnosis but also provide essential additional details for the planning of the surgical course. The 3-dimensional reconstruction of the contrast enhanced CT scan could provide the most direct impression and necessary information. Conservative therapy includes antihypertensive medication and careful followup. β-adrenoreceptor blockers play an important role in the treatment of aortic dissection.2 Some studies showed that the beta blockers could reduce the expansion rate of the AAA.7, 8 Presence of IAAD with an associated AAA is an indication for aortic repair due to a significant high risk of aortic rupture. In the landmark article on the natural history of concomitant infrarenal aortic aneurysm and dissection, Cambria and his colleagues9 reported five patients with infrarenal AAA who had associated DeBakey type III dissection extending to or involved the infrarenal AAA. Four of these patients had aneurysm rupture and died. In three patients, rupture occurred at the junction of the dissection process and the aneurysm. Dissection weakens the integrity of the abdominal wall. Farber and his coworkers10 recommend that an aneurysm greater than 3 cm in diameter is the indication for surgical repair if the patient suffered IAAD as well. Since 1991 Parodi and his colleagues11 first reported the endovascular treatment of AAA by stent graft, it is accepted by increasing number of doctor and patient for its safety and minimal invasion. Dake et al12 applied this endovascular way to treat the aortic dissection in 1999. The endovascular treatment became the standard therapy as open surgery to treat aortic disease. The result of short term follow-up of this patient is satisfying. The efficacy of endovascular therapy in treating such complicated lesion should be tried in more cases and followed for a long period.