The human body is composed of countless blood vessels, and blood vessels are the most important conduits and structures in the body. Blood vessels are very prone to dilate under the impact of high speed and high pressure blood flow for a long time, and aneurysms are formed after dilating to a certain extent, the most common of which is abdominal aortic aneurysm.
1.What is abdominal aortic aneurysm?
The abdominal aorta is a main blood vessel located deep in the abdominal cavity and at the front edge of the spine. The body perfuses the abdominal organs and lower limb vessels through the abdominal aorta. Normally, the abdominal aorta is straight and generally less than 1.8 cm in diameter. In the presence of atherosclerosis, smoking, inflammation, infection, etc., the strength of the vascular wall of the abdominal aorta is weakened and the impact of blood flow causes it to dilate, which is called an abdominal aortic aneurysm when the diameter expands by more than 50% of its original size. The dilated area is usually between the bifurcation of the renal artery and the iliac artery, and some patients may have dilatation of the iliac artery as well. Because of the word “aneurysm”, many people may mistakenly think that abdominal aortic aneurysm is a malignant tumor. In fact, the essence of abdominal aortic aneurysm is the dilatation of blood vessels without the presence of any tumor cells.
2. What are the causes of abdominal aortic aneurysm?
The causes of abdominal aortic aneurysm include both endogenous and exogenous causes. The endogenous causes lead to the deterioration of the texture and strength of the abdominal aortic vessel wall. The most common cause is atherosclerosis, in which atherosclerosis of the artery results in a weakening of the middle elastic fibers, leading to a weak wall. Patients with congenital diseases such as Marfan syndrome and Edu syndrome are born with reduced structural strength of the vessel wall due to mutations in genes encoding important components of the vasculature. Both specific syphilis infections and nonspecific bacterial infections can erode blood vessels and cause changes in their texture. Inflammatory diseases such as aortitis and leukoaraiosis can cause inflammatory cell infiltration of the vessels, and the components secreted by the inflammatory cells can destroy the vessel structure, again leading to reduced strength. Common external causes are mainly trauma and medical external exposure, which can directly damage the vessel wall, leading to aneurysmal dilatation. Hypertension is an important long-term external factor. Elevated blood pressure leads to an increased pressure load on the vessel wall, and when the vessel wall itself is poorly textured, localized dilatation can occur due to the inability to tolerate the pressure of blood flow within the aorta.
3.What are the dangers of abdominal aortic aneurysm?
Although abdominal aortic aneurysms are not tumors, they are no less dangerous than malignant tumors. Its main danger is the rupture of the aneurysm after expansion, which leads to hemorrhage and death. As the aneurysm expands, the wall becomes progressively thinner and continues to decrease in strength. According to the theorem of physics, the pressure on the wall is proportional to the square of the tumor’s diameter. In other words, the strength of the wall decreases as the diameter of the aneurysm increases, while the pressure on the wall increases geometrically with the diameter of the aneurysm, and eventually the pressure on the wall exceeds the strength of the wall and the aneurysm ruptures. Once the abdominal aortic aneurysm ruptures, the high velocity and high volume of blood flow will surge out like the Yangtze River and the Yellow River breaking its banks, and the patient can die within minutes due to massive blood loss. Figuratively speaking, abdominal aortic aneurysm is like a time bomb in the stomach, which may explode at any time. Compression of the surrounding organs as the aneurysm grows can result in related compression symptoms. The dislodgement of the blood-attached embolus in the aneurysm cavity may cause arterial embolism in the lower limbs.
4.What are the clinical manifestations of abdominal aortic aneurysm?
Abdominal aortic aneurysms may be asymptomatic when the aneurysm is small, but as the aneurysm increases in size, symptoms may gradually appear. The most common symptoms are a pulsating mass in the abdomen, consistent with the heartbeat; back pain when the aneurysm compresses the spine; intestinal obstruction when the aneurysm compresses the duodenum; and significant abdominal pain before and when the aneurysm ruptures. Lower limb pain, pale skin and lowered skin temperature can be seen when the thrombus is dislodged and leads to lower limb artery embolism.
5.How is the diagnosis of abdominal aortic aneurysm made? Is it easy to diagnose?
The diagnosis of abdominal aortic aneurysm is not difficult. The easiest way to detect an abdominal aortic aneurysm is to palpate oneself around the navel. Once a periodically pulsating mass that follows the heartbeat is palpated, the initial diagnosis of abdominal aortic aneurysm can be made. However, it is often difficult to palpate a significant mass in fat individuals. Ultrasound is an excellent screening and confirmation method that is inexpensive, convenient and non-invasive. When the ultrasound indicates a large tumor, a CT or MRI (CTA or MRA) is needed to determine whether surgery is indicated, to understand the anatomical pattern of the tumor, and to develop a treatment plan accordingly.
6.What are the treatment options? What is the effect?
Surgery is the only solution to the explosion of this time bomb. There are no drugs that can reverse abdominal aortic aneurysm. Surgical treatment is required when one of the following 3 conditions is met.
(1) The diameter of the aneurysm is greater than 4.5 cm.
(2) The rate of enlargement exceeds 0.5 cm every 6 months.
(3) The presence of symptoms: such as compression symptoms, arterial embolism in the lower extremities, and pain.
If the patient does not present any of the above 3 conditions, surgical treatment is not required, but close follow-up is required, such as ultrasound or CTA every six months, to observe whether the tumor diameter has increased.
Surgical treatment includes both traditional open surgery and intracavitary minimally invasive repair. The traditional open surgery is abdominal aortic aneurysm resection + artificial vessel replacement. The advantages are that the surgery does not require high anatomical conditions such as vascular morphology, the total cost may be slightly less than that of endoluminal repair, and the requirement for postoperative follow-up is relatively low. The disadvantages are that the procedure is highly invasive, with a high complication rate and a long postoperative recovery time. Minimally invasive endoluminal repair treatment involves implanting a stent with an artificial vascular membrane inside the aneurysm through the femoral artery route and fixing it at the normal vessels at both ends; in this way, blood flow flows through the lumen of the stent to the distal end of the aneurysm, and the blood flow is confined within the stent and no longer acts on the aneurysm wall; the blood flow inside the aneurysm lumen and outside the stent gradually coagulates to form a thrombus, and the aneurysm wall no longer enlarges and ruptures due to the absence of blood flow. Endoluminal repair is an epoch-making advance in the history of abdominal aortic aneurysm treatment. Compared to traditional aneurysm resection with artificial vessel replacement, endoluminal repair is minimally invasive, less invasive, and faster to recover, especially for patients who are elderly, have many comorbidities, and are afraid of traditional surgery.
In recent years, due to the continuous development and application of new endoluminal devices, the requirements of endoluminal repair for aneurysm anatomy have been reduced and the indications for surgery have been broadened, allowing more patients to benefit from it. Previously, minimally invasive surgery required a small incision in the groin, but today the use of vascular closures has made it possible to perform endoluminal repair through a completely transdermal puncture without any incision and under local anesthesia, resulting in a shorter and less invasive operation.
Although dangerous, abdominal aortic aneurysm is not a terminal disease. With a comprehensive understanding of it and the selection of an appropriate treatment plan, excellent results can be obtained.