An abdominal aortic aneurysm is a dilated bulge in the wall of the abdominal aorta. The aneurysm can grow in size and eventually rupture and bleed, leading to the patient’s death. Abdominal aortic aneurysms occur mainly in older people over 60 years of age, with a male to female ratio of 10:3. They are often associated with hypertensive disease and heart disease, but are occasionally seen in younger people as well. They are more common in men than in women. Other rare causes are congenital dysplasia of the aorta, syphilis, trauma, infection, aortitis, and Marfan syndrome. Most abdominal aortic aneurysms are caused by atherosclerosis and are usually located distal to the renal artery, extending to the bifurcation of the abdominal aorta, often involving the iliac artery, and occasionally above the renal artery. Some patients may be asymptomatic before rupture or near rupture. The common causes include atherosclerosis, cystic degeneration of the middle layer of the artery, syphilis, congenital, trauma, and infection. Among them, atherosclerosis is the most common cause. When atherosclerosis occurs in the artery, the middle elastic fibers break down and the wall becomes weak, so it cannot withstand the pressure of blood flow in the aorta and becomes locally enlarged, forming an aortic aneurysm. Due to the high pressure of blood flow in the aneurysm, the aneurysm gradually expands and can compress the adjacent organs, even erode the sternum and ribs or bulge out to the body surface, becoming a pulsating mass. In the enlarged aneurysm, blood flow is slowed down and vortexes are formed, which can produce attached wall thrombus. Patients can die due to severe compression of vital organs or self-rupture of the aneurysm, and cystic aneurysms are more likely to rupture than pyknotic ones. Clinical symptoms Rarely seen before the age of 50, most commonly in men between the ages of 60-80. 1. Most patients are asymptomatic and are often found incidentally on physical examination for other reasons. A typical abdominal aortic aneurysm is a swollen mass pulsating laterally and anteriorly and anteriorly, and is accompanied by vascular murmurs in about 50% of patients; 2. Pain: a common symptom before rupture, mostly located around the umbilicus and in the middle and upper abdomen. If the aneurysm invades the lumbar spine, there may be lumbosacral pain. If there is severe pain in the abdomen or lumbar region recently, it often indicates that the aneurysm is on the verge of rupture. Abdominal mass: The most important sign is a distending, pulsating mass around the umbilicus or in the upper and middle abdomen, which is usually palpable unless the patient is obese. Femoral or dorsalis pedis artery pulsation is weakened or absent; 3. Rupture: It can be the first symptom of fatal complications, most commonly rupture of the tumor, blood breaks from the tumor into the abdominal cavity, fortunately it is more common to break into the retroperitoneal cavity, the bleeding from this part is slow. Abdominal pain and shock from blood loss can last for hours or days, and the patient may seek medical attention. Occasionally, the bleeding is limited, and the patient may have abdominal pain, fever, mild to moderate blood loss, and often rupture again. It may also rupture into the inferior vena cava, producing an aorto-venous fistula with a continuous murmur, high cardiac output, and heart failure. Occasionally, it may enter the duodenum and cause gastrointestinal bleeding; 4. Other serious complications: acute thrombosis may occasionally form within the aneurysm. Abdominal aortic aneurysm thrombosis or atherosclerotic debris can cause lower limb embolism. Intestinal obstruction may occur by duodenal compression, and peripheral edema may be caused by inferior vena cava obstruction. Secondary bacterial infections are rare.