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, also known as thoracoabdominal aortic aneurysms. 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, traumatic, and infectious. 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. The typical abdominal aortic aneurysm is a swollen mass pulsating laterally and anteriorly and anteriorly, with a vascular murmur in about 50% of patients. 2. Pain: It is a common symptom before rupture and is 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 area 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. The femoral artery or dorsalis pedis artery pulsation is weakened or absent. Rupture: It can be the first symptom of fatal complications, most commonly rupture of the tumor, blood from the tumor into the peritoneal cavity, fortunately more commonly 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 be formed in the aneurysm. Abdominal aortic aneurysm thrombosis or atherosclerotic debris can cause lower limb embolism. Intestinal obstruction may occur due to duodenal compression, and peripheral edema may be caused by inferior vena cava obstruction. Secondary bacterial infections are rare. Differential diagnosis Abdominal pain, shock, and low back pain are the most common manifestations of ruptured abdominal aortic aneurysms, and naturally, most incorrect diagnoses are associated with them. One of the most commonly misdiagnosed diseases is renal colic, which can account for more than 20% of all misdiagnoses. In the absence of shock symptoms, manifestations such as severe back pain, pronounced percussion pain in the kidney area, and microscopic hematuria often misdirect the physician’s thinking to urinary tract stones and renal colic, without realizing that these appearances are due to irritation of the kidney or ureter immersed in large amounts of blood, or to rupture of the opening of the renal artery and its ripples. Symptoms such as abdominal pain are also often incorrectly attributed to abdominal diseases such as gastrointestinal bleeding and rupture, sigmoid diverticulitis, intestinal obstruction, cholecystitis, cholelithiasis, and pancreatitis. Ruptured abdominal aortic aneurysms producing symptoms similar to these diseases may be associated with factors such as abdominal aortic gastrointestinal fistula, dislodgement of intra-aneurysmal appendage thrombus, and acute ischemia of the inferior mesenteric artery. A ruptured abdominal aortic aneurysm is easily masked by an incarcerated inguinal hernia, resulting in a missed diagnosis. The combination of abdominal aortic aneurysm with inguinal hernia and/or emphysema and systemic connective tissue dysplasia and degeneration may be the common pathologic basis for both. When an abdominal aortic aneurysm ruptures, the massive retroperitoneal hematoma increases the pressure on the inguinal weakness, leading to impaction of the hernia contents and making it easy for the physician to be blinded by superficial phenomena and miss the abdominal aortic aneurysm. Other less common conditions requiring differential diagnosis include acute myocardial infarction (heart attack) and blunt abdominal trauma. Patients with aortic aneurysms are often combined with severe atherosclerosis that affects coronary blood supply, and myocardial ischemia and hypotension resulting in electrocardiographic changes are the main reasons for misdiagnosis of acute infarction. However, most patients with acute infarction have a history of recurrent angina pectoris, and the pain site is mostly behind the sternum or radiating to the neck or left arm, which can be relieved by nitrates and morphine; whereas the pain of ruptured abdominal aortic aneurysm has the characteristics of extensive sites and ineffective analgesics such as morphine. The ECG of acute infarction shows a series of infarct pattern evolution and a specific curve of elevated serum cardiac enzyme profile, which are the differentiating points with ruptured abdominal aortic aneurysm. Diagnostic tests There are currently six methods to detect abdominal aortic aneurysm and estimate its size and extent: 1. abdominal palpation, which is the least accurate. 2, abdominal X-ray: if there is a typical oval-shaped calcification shadow, the diagnosis can be established, but at least 1/4 of the patients do not have this sign. 3.Two-dimensional ultrasonography: It is valuable for the diagnosis of abdominal aortic aneurysm, easy to operate, highly accurate in detecting aneurysm, and can clearly show its shape and attached thrombus, which is the preferred diagnostic method. 4, abdominal aortography: accuracy is not high, because the width of the aneurysm can be obscured by translucent wall thrombus. However, the imaging results often provide valuable information, so it is still a necessary preoperative test. 5.DSA: The results are similar to those of abdominal aortography without the need for intra-arterial injection of contrast agent. 6.CT: Compared with two-dimensional ultrasonography, it can show abdominal aortic aneurysm and its relationship with surrounding tissue structures such as renal artery, retroperitoneum and spine, as well as retroperitoneal hematoma more clearly. However, the cost is higher and the operation time is longer. MRI: Its diagnostic value is similar to ultrasound and CT. The disadvantage is that it is expensive and time-consuming to operate, but the imaging time will be greatly reduced with the new generation products. Treatment options Abdominal aortic aneurysm without medical treatment may heal on its own, the most serious local consequences are rupture and bleeding to death, the aneurysm diameter ≥ 4cm, the proportion of rupture is obviously is increased, even if the expert aneurysm is smaller. The same possibility of acute rupture of the heart exists. Therefore, in principle, abdominal aortic aneurysms should be operated as elective desperate surgery. Those who do not tolerate surgery well should be treated actively to create conditions for surgery. If the aneurysm is small in diameter, it should be examined regularly by diagnostic imaging techniques (e.g., B-mode ultrasound), and if it tends to increase in size, a surgical treatment decision should be made. In cases of ruptured abdominal aortic aneurysms, prompt emergency surgery is required. Surgical options include atherectomy. Aneurysm patenting and aneurysm dissection with artificial vessel graft. The third procedure is currently the most commonly used. According to the relationship between aneurysm and renal artery, the basic principles of surgery are as follows: 1. For abdominal aortic aneurysm below the plane of renal artery, the abdominal aorta and bilateral iliac arteries under the renal artery are revealed through the abdominal or retroperitoneal route, the abdominal aorta and bilateral iliac arteries under the renal artery are freed from the upper edge of the aneurysm and bilateral common iliac arteries, and the aorta and bilateral iliac arteries are blocked after systemic administration of heparin; the aneurysm wall is cut and the lumbar artery is rapidly sutured. The thrombus and atheromatous debris are removed from the aneurysm lumen; a straight or Y-shaped artificial rehabilitation vessel is implanted according to the morphology and specification of the aneurysm; after completing the anastomosis, the artificial vessel is wrapped and sutured with the previously incised aneurysm wall. The inferior mesenteric artery can be sutured to the lateral wall of the artificial vessel or ligated, which should be determined according to the blood supply of the left colon. If the distal anastomosis is built distal to the plane of the common iliac artery bifurcation, the blood flow of at least one side of the internal iliac artery should be preserved. 2, Abdominal aortic aneurysms above the plane of renal artery need to be exposed and blocked through a combined thoracoabdominal incision; the same temporary steps as the above surgery, after implantation of the artificial vessel, the circumflex abdominal artery, superior mesenteric artery and renal artery must be rapidly anastomosed with the artificial vessel in turn to complete the anastomosis, so as to shorten the time of visceral ischemia as much as possible and reduce the damage caused by ischemia. 3. In the early 1930s, metal stents for artificial vessels have been developed. A special delivery device was used to deliver it into the aneurysm cavity via the femoral artery, and the stent was expanded with the help of a balloon catheter. The stent is secured to the arterial wall by the elasticity of the metal stent and the hook-like attachment at the head end. This method is known as abdominal aortic aneurysm endoluminal stent bypass, which has the advantages of less trauma and faster recovery, especially for high-risk patients who cannot tolerate surgery, but it is still in the clinical trial stage and needs to accumulate experience and verify long-term results.