1. What is an abdominal aortic aneurysm? An aneurysm is a permanent, limited dilatation of an artery. Although the diagnostic criteria for abdominal aortic aneurysms are not uniform, the vast majority of authors consider a limited dilatation of the artery greater than or equal to two times the normal diameter to be an aneurysm. The average CT measurement of the diameter of the infrarenal aorta in adult men is 2.3 cm, whereas in women the corresponding diameter is only 1.9 cm. Therefore, a diagnosis of abdominal aortic aneurysm should start at 4 cm. The size of the aneurysm is often expressed as the maximum external transverse diameter of the aorta (measured by ultrasound, CT, MRI or directly during surgery). 2. What kind of patients have abdominal aortic aneurysms? Abdominal aortic aneurysms are most common in older men, with a male to female ratio of approximately 4:1 and a prevalence of 2.5% in men over 60 years of age. The incidence of abdominal aortic aneurysms has been increasing year by year. Two reports from Mayo Hospital show that from 1951 to 1980, the incidence rate increased from 12,2/100,000 to 36,2/100,000, a threefold increase, and that the increasing age of the population has played a role in the increasing incidence. 3. Is there value in screening programs for abdominal aortic aneurysms? Screening for abdominal aortic aneurysms in the total population is not realistic, and most aneurysms identified by screening are small. Conversely, selective screening is feasible and has a particularly high incidence in patients with peripheral vascular disease, heavy smokers, and a family history of aneurysms. 4. What causes abdominal aortic aneurysms? Because most patients with aneurysms have atherosclerosis in the arterial wall, abdominal aortic aneurysms used to be called atherosclerotic aneurysms. Atherosclerosis is thought to be the cause of atheroma-like degeneration. Smoking and hypertension are common risk factors for abdominal aortic aneurysms and obstructive vascular disease, but it is uncommon for abdominal aortic aneurysms to be combined with obstruction of the main-iliac aorta; therefore, it is more appropriate to call atherosclerotic aneurysms degenerative and nonspecific aortic aneurysms. 5.Can abdominal aortic aneurysms be inherited? The high incidence of abdominal aortic aneurysms in members of some large families suggests that genetic factors are involved in the pathogenesis, with abnormalities in the long arm of chromosome 16 found in some familial aneurysms. aortic coarctation, which is caused by a mutation in the protofibrillin-Ⅰ gene on chromosome 15. In the 1980s, several studies showed a familial predisposition to abdominal aortic aneurysms, with at least 18% of patients with abdominal aortic aneurysms having close relatives involved. 6. What are the other causes of abdominal aortic aneurysms? Degenerative aneurysms account for 90% of infrarenal aortic aneurysms. Other causes include cystic mesangial necrosis, arteritis, injury, hereditary connective tissue disease, disruption of anatomical structures, and infection can also lead to abdominal aortic aneurysms. Infected aneurysms originate from local infection of the arterial wall. Most infected aneurysms develop from bacteraemia caused by distant lesions (e.g., endocarditis) and are the most common type of aortic aneurysm in children. 7.What are the clinical manifestations of abdominal aortic aneurysm? Aneurysms are often diagnosed during routine physical examinations when asymptomatic pulsatile masses are found in the upper abdomen, and patients often find such masses and seek medical consultation. 8. Do all patients with abdominal aortic aneurysms present with symptoms? The most common symptom of an abdominal aortic aneurysm is unspecified abdominal pain in the patient. Rapid expansion of the aneurysm may produce more widespread pain, probably due to straining of the peritoneum on the surface of the aneurysm. The typical pain is a persistent or throbbing pain confined to the upper abdomen. Aneurysm invasion of different adjacent structures may produce corresponding symptoms. Large aneurysms often erode the vertebral body and cause severe back pain; early gastrointestinal symptoms of anorexia, nausea, and weight loss indicate gastrointestinal tract compression; ureteral compression may result in hydronephrosis. Ureteral obstruction may produce pain radiating to the groin, occasionally accompanied by pyelonephritis. Attachment thrombus in the lining of the aneurysm may cause embolism and lead to acute lower extremity ischemia. Rare manifestations include thrombosis that worsens lower extremity ischemia, acute congestive heart failure due to aortic vena cava disease, and primary aortoenteric fistula due to aortic aneurysm erosion of the third segment of the duodenum. 9.Why should abdominal aortic aneurysm be treated surgically? Rupture of abdominal aortic aneurysm is the most dangerous complication. Most patients do not have aura symptoms until the aneurysm ruptures suddenly causing definite signs and symptoms. A ruptured aneurysm indicates advanced disease, and despite prompt surgery, the mortality rate is greater than 50%. 10. At what time should repair of an abdominal aortic aneurysm be performed? The decision to operate should be made when the risk of death from abdominal aortic aneurysm outweighs the risk of surgery, which, according to Laplace’s law, is proportional to the tension of the arterial wall and the diameter of its lumen. In this way, rupture of larger aneurysms is more common than rupture of smaller aneurysms. Studies of the natural course of abdominal aortic aneurysms have found that rupture of small aneurysms can occur but is rare. Current data indicate that the 5-year incidence of rupture for 5-5 and 9-cm aneurysms is 25%. The 5-year incidence of rupture for 6-cm aneurysms is nearly 35%, and for 7-cm aneurysms or larger, the 5-year incidence is more than 75%. No additional information is available to accurately estimate the risk of rupture for aneurysms smaller than 5 cm. 11. What are the risks of elective aneurysm surgery? The risk of elective aneurysm surgery depends on the physiological status of the patient. Concomitant heart disease, recent infarction, atherosclerosis at other sites, hypertension, decreased renal function, and chronic obstructive pulmonary disease can significantly increase the risk of surgery. Actual age is not as important as physiological age when determining surgical risk, and 80- to 90-year-olds can be operated on safely. Currently, the mortality rate of elective surgery is 2% to 5%. 12. Do all aneurysms eventually dilate and rupture? Most studies report that abdominal aortic aneurysms grow at a rate of 0.2-0.8 cm/a, with a mean of about 0.4 cm/a. Larger aneurysms generally expand more rapidly. Some aneurysms may remain stable for a long time without growth, while others enlarge gradually. The only factor associated with aneurysm expansion and rupture is the size of the aneurysm. Other factors that can contribute to enlargement are hypertension, obstructive lung disease, and renal insufficiency. 13.How to make an accurate diagnosis of abdominal aortic aneurysm? The accuracy of physical examination is highly variable, and aneurysms are easily detected in lean individuals. Ultrasonography is the most recommended method for evaluating suspicious abdominal aortic aneurysms. CT scan and MRI can also clearly show aneurysms, but they are much more expensive. Arteriography may underestimate or miss aneurysms because of the attached thrombus within the aneurysm wall. 14. What preoperative tests are required for abdominal aortic aneurysm? Enhanced CT scan is the best preoperative diagnostic method for abdominal aortic aneurysms. It provides accurate information about the size and structure of the aneurysm and shows the relationship between the abdominal aortic aneurysm and the surrounding organs. Identification of major venous and renal abnormalities also provides a definitive diagnosis in at least 20% of patients with iliac aneurysms present. Some surgeons routinely use aortography, while others rely on aortography films to identify aneurysms only in exceptional cases. 15. What does the procedure involve? The abdominal aorta is temporarily blocked and an artificial vessel is implanted to replace the main abdominal and iliac arteries. In 90% of abdominal aortic aneurysms, the aorta is often blocked below the renal artery, and the artificial vessel is either woven polyester (Woven Dacron), knitted polyester (Knitted Dacron), or polytetrafluoroethylene expanded (PTFE). The anatomical location of the distal anastomosis such as the distal abdominal aorta, iliac artery, and femoral artery also needs to be determined. 16.What complications can occur after abdominal aortic aneurysm surgery? Although the mortality rate of elective abdominal aortic aneurysm surgery has been limited to less than 5%, major complications are still common. They include heart attack, congestive heart failure, renal insufficiency, and pulmonary insufficiency. ischemic colitis, limb ischemia, graft vessel thrombosis, wound infection, stroke, and paraplegia. 17.What are the late complications of aortic aneurysm surgery? Late complications occur in more than 10% of patients and include aneurysm at the anastomosis, aortoenteric fistula, graft vessel obstruction, and infection. 18.What is the surgical option for patients with high-risk abdominal aortic aneurysms? Prior to the development of modern surgical techniques, the results of aneurysm ligation, wrapping, and non-resectional procedures that attempt to attenuate aneurysm thrombosis were suboptimal. Smaller aneurysms in high-risk patients should be followed up with ultrasound and CT scans. Axillary a double femoral artery bridging, aneurysm neck or outflow tract ligation to induce aneurysm thrombosis all have poor success rates. 19.What is the future view of treatment for abdominal aortic aneurysm? Endoluminal graft vascularization for abdominal aortic aneurysms is in early clinical trials. The approach is to introduce the endoluminal graft vessel into the aorta through the femoral or external iliac artery for repair. At least seven different delivery systems are currently under development, and the principles of endoluminal repair include distending the graft inserted into the aneurysm through the femoral artery and securing the proximal end of the endoluminal graft to the infrarenal abdominal aorta with an expandable metal stent, with or without support for the distal end of the graft. To date, the long-term results of this approach are not certain.