Abdominal aortic aneurysm: symptoms, causes, and treatment

What are Abdominal aortic aneurysms(AAAs)?

Abdominal aortic aneurysms are considered to be the most common form of vascular disease, affecting more than 15 million people worldwide. They are enlargements in the wall of the abdominal aorta (the main blood vessel carrying blood away from the heart) causing it to weaken and giving it an hourglass appearance on CT scan. 


They usually appear as painless, rising, or pulsating masses that can grow large enough to rupture with life-threatening consequences. Aneurysms are related to increasing age (>50-60 years), male sex, and smoking. Aneurysm formation has also been associated with hypertension, atherosclerosis, ischemic heart disease, and patent foramen ovale (P.F.O).


Aneurysms can be asymptomatic or associated with abdominal pain or both and may produce back leg, or stomach aches. The most important complication is rupture and death due to exsanguination (bleeding out). Rupture of an AAA is a medical emergency and if diagnosed early enough the mortality rate for elective surgery can be reduced from 50-60% to less than 10%.


A ruptured AAA causes about 30,000 deaths per year in the USA as it represents the third most common cause of cardiovascular hospital admission. Most aneurysms are confined within the abdomen but they can occasionally extend into surrounding organs such as the bowel, colon, bladder, etc.


Abdominal aortic aneurysms
AAA


What are the causes of Abdominal aortic aneurysms(AAAs)?

there are a number of causes of AAA. Some of those include :

the most common cause of AAA is atherosclerosis or artery disease. The risk of developing aneurysms increases with age and with diseases such as high blood pressure and diabetes. 65% of all AAAs occur in men over age 65. The aneurysm can also develop in association with pregnancy, coarctation of the aorta (narrowing), bicuspid aortic valve (an inherited defect involving two leaflets in place of three), and connective tissue disorders such as Marfan syndrome and Ehler-Danlos syndrome.


What are the symptoms?

if you have an AAA, you may not notice it for many years because there often aren't any symptoms in the early stages. When symptoms appear, they may include:


  • Abdominal or back pain that becomes severe when you breathe in; the pain goes away when you breathe out. - this is a sign of aneurysm rupture. The first symptoms of rupture are often sudden and very painful. If the tear is large enough, blood may pour into your abdomen or chest cavity. This can cause life-threatening bleeding that needs emergency surgery to stop it. 

  • A pulsing sensation over the aneurysm (felt through the skin)  - this occurs as blood surges against the weakened artery wall with each heartbeat 

  • Swelling around the middle of your body is caused by fluid buildup (ascites). You might also see swelling in your feet or ankles. - the wall of the aneurysm may tear, causing blood to leak into the surrounding tissue and creating a collection of fluid (hematoma). This causes pain and more rapid enlargement of the aneurysm. The hematoma can also block off the artery that supplies blood to nearby organs, causing problems with those organs.

  • Aneurysms are usually painless. But if the aneurysm grows quickly or ruptures, you may develop: 
  • Abdominal pain and shortness of breath 
  • Sudden and intense pain in your abdomen or chest that doesn't go away 
  • The wall of the aneurysm may tear, causing blood to leak into the surrounding tissue and creating a collection of fluid (hematoma). This causes pain and more rapid enlargement of the aneurysm. 


Can it rupture?

Yes, AAA can rupture if they are not detected in time. If you have an AAA, see your doctor regularly so your doctor can monitor it for changes in size. Rupture is often fatal because there is usually substantial bleeding before the diagnosis is made. Surgery follows soon after diagnosis to prevent potentially fatal complications from blood loss.


What are the treatments? 

investigations, such as abdominal ultrasonography and CT scans, may be used to determine if an AAA is present and how big it is. Ultrasound uses high-frequency sound waves like sonar to make images of structures in your body. A probe (transducer) placed on the abdomen sends sound waves through your skin and tissues into the blood vessels and develops a picture of their size and structure on a computer screen or special paper. 

CT scans use X-rays in combination with computer technology to create sharp, detailed images of your internal organs and other anatomic structures. If a coronary angiogram shows that you need surgical repair, open or endovascular stent graft repair is usually very successful in maintaining an active lifestyle.

If you're having open surgery, your doctor may choose to remove the aneurysm at the same time. There are two main types of surgery to repair AAA: 

Open surgery 

this involves making a large incision (cut) in your abdomen or chest and using surgical instruments to fix the aneurysm with sutures (stitches) or metal staples. Sometimes part of your intestine must be moved aside so the surgeon has room to work. The blood vessels supplying or draining your organs are also reattached so there is no interruption in blood flow during the operation. 


Endovascular stent-graft

An endovascular stent graft can be used to repair AAA rather than open surgery. A hollow tube is threaded up through your arteries to the site of the aneurysm. The stent-graft is placed across the aneurysm, using X-rays to see where it goes. Once in place, it expands and presses against the inside of your artery to support the weakened area of your artery wall.

Japanese researchers have developed a new device that can be inserted into blood vessels to treat abdominal aortic aneurysms (AAA). It is designed to be installed by endoluminal access. 


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Risk Factors for AAAs


Tobacco Smoking

Smoking is one of the major risk factors involved in AAAs formation. It increases the levels of nicotine and carbon monoxide in the blood and can lead to the narrowing of arteries, which increases the risk for aneurysm formation.


Family History 

Having a first-degree relative with an abdominal aortic aneurysm (AAA) is associated with an increased risk of abdominal aortic aneurysm (AAA) formation.


High Blood Pressure 

Persons with high blood pressure are at higher risk of abdominal aortic aneurysms (AAA). Hypertension may cause weakening and bulging of arterial walls, leading to AAA formation. High blood pressure may also increase strain on weakened artery walls.


The prevalence

The current prevalence data on AAA describes that approximately 0.5 percent of men and 0.1 percent of women in the United States between 65 and 74 years old have AAA. The prevalence increases to 9.0 percent in men and 2.7 % in women older than 85 years old.


Atherosclerosis 

Atherosclerosis increases the risk for abdominal aortic aneurysm formation because it decreases blood flow through the artery wall and speeds up the process of arterial damage, which weakens walls over time. Atherosclerosis results in the formation of fatty streaks or atheromas, which are accumulations of cells, lipids, and extracellular matrix. This process is accelerated by smoking and high blood pressure.


Genetic factors 

Abdominal aortic aneurysm (AAA) may be caused by mutations in genes involved in cell proliferation, apoptosis regulation, and extracellular matrix production that play key roles in both physiological developmental stages and disease pathogenesis. 

Several genetic studies have identified risk factors for abdominal aortic aneurysm including "TGF-β" gene polymorphisms associated with increased susceptibility to AAA formation. It has been shown that the composition of extracellular matrix in regions adjacent to developing AAAs is different compared with normal areas of elastin-containing tissue, thus suggesting that the differentiation stage of medial cells may influence the development of an aneurysm.