What Is An Abdominal Aortic Aneurysm

Abdominal Aortic Aneurysm Definition

Abdominal Aortic Aneurysm is a localized dilatation of the abdominal aorta by more than 50 percent of the normal diameter. It is the most common form of aortic aneurysm.

Abdominal Aortic Aneurysm Causes

The most important cause for AAA (Abdominal Aortic Aneurysm) is atherosclerosis and atherosclerotic plaques.  Hypertension is also a contributory cause. Abnormal connective tissue turnover in media and adventitia of the vessel wall is also a known and interesting cause.

TIMPS and MMP

TIMPS is Tissue INACTIVATORS of METALLOPROTEINASES and MMP stands for METALLO MATRIX PROTEINASES. In a normal and healthy aorta , the TIMPS keeps a check on the MMP preventing if one could say the over digestion or turnover of the aortic connective tissue. Latest studies suggest that either the MMP is overactive or the TIMPS is underactive in those individuals who develop such aneurysms.

RISK FACTOR TRIAD

AAA develops more commonly in

MALES

OVER 50 YEARS OF AGE

SMOKERS

Abdominal Aortic Aneurysm Can Be INFLAMMATORY OR INFECTIOUS

In inflammatory pathology, the infiltrate of cells involves plasma cells, macrophages, lymphocytes and giant cells. These cells produce growth factors and can lead to peri aortic fibrosis.

It can be mycotic or infectious with salmonella being the most commonly found within the aorta wall.

Abdominal Aortic Aneurysm Diagnosis

On abdominal examination a pulsatile and expansile mass can be found

AAA can compress upon the ureters leading to hydronephrosis and upon the vertebral bodies leading to backache associated with vertebral erosions.

It can be an incidental finding on x rays with curvy linear calcium deposits

Diameter of abdominal aorta greater than 3 cm on ultrasound is diagnostic for AAA.

Abdominal Aortic Aneurysm Rupture

There is a good possibility of thrombus formation in the AAA and subsequent thromboembolism. Patients with AAA have a greater possibility of developing popliteal aneurysm and vice versa.

The AAA can compress upon the renal, superior and inferior mesenteric, iliac and vertebral arteries. The most disastrous complication is rupture of the aneurysm.

The posterior rupture is in the retroperitoneum and is not as deadly as the anterior.

The anterior rupture is the most dangerous and presents with sudden ,severe abdominal pain, backache and  shock due to hemorrhage.

Aneurysms with up to 5.8 cm can be observed and monitored via regular ultrasounds. Greater than 6 cm aneurysm should be repaired (stent / graft) electively as there is a significant possibility of rupture.

MORTALITY DIFFERENCE WITH RUPTURE

If AAA has not ruptured then mortality upon operating is near 5 %. If the aneurysm ruptures the emergency repair is associated with 50 % mortality.