Abdominal Aortic Aneurysm

Abdominal aortic aneurysm (AAA) is a localized dilation or bulging of the abdominal portion of the aorta, which is the major blood vessel supplying blood to the abdominal organs, pelvis, and legs. It occurs when the wall of the aorta weakens and stretches, leading to an increase in size.  The main causes include atherosclerosis, smoking, hypertension, genetic factors, and connective tissue disorders. Often, AAAs are asymptomatic in the early stages, but as they grow larger or if they rupture, symptoms such as abdominal, back, or groin pain may occur. A rupture can cause life-threatening internal bleeding.  Small, asymptomatic AAAs are usually monitored with regular imaging, while larger or symptomatic aneurysms may require surgical repair—either through open surgery or endovascular aneurysm repair (EVAR). The most serious complication is rupture, which carries a high mortality rate. 

Anatomically, abdominal aortic aneurysms are primarily classified based on their location relative to the renal arteries and the aortic bifurcation. 

Infrarenal aneurysms

The most common, occurring below the origin of the renal arteries, and are located in the distal aorta. 

Juxtarenal aneurysms

Situated very close to the renal arteries, extending up to or just involving the origin of the renal arteries, but without involving them. 

Pararenal aneurysms 

Involve the area around the renal arteries, often extending into the segment of aorta that includes the renal arteries.

Suprarenal aneurysms

Located above the renal arteries, involving the section of the aorta that supplies the visceral arteries, including the superior mesenteric, celiac, and renal arteries. 

Most abdominal aortic aneurysms (AAA) are asymptomatic and are often discovered incidentally during imaging for other reasons. When symptoms do occur, they may include a pulsatile, painless abdominal mass, or localized abdominal, back, or groin pain. As the aneurysm enlarges, pain may become more intense and persistent. If it ruptures, it typically causes sudden, severe abdominal or back pain, often accompanied by signs of shock such as low blood pressure, rapid heartbeat, dizziness, or fainting. Rupture is a medical emergency and requires immediate treatment.

Pathologically, AAAs may be classified as degenerative, inflammatory, or infectious. Degenerative AAAs are the most common, characterized by destruction of the elastic fibers and media layer of the aortic wall, usually associated with atherosclerosis. Inflammatory AAAs involve an inflammatory process within the vessel wall, leading to fibrosis and thickening, often associated with systemic inflammatory diseases. Infectious AAAs, or mycotic aneurysms, result from bacterial or fungal infections of the aortic wall, and tend to be rapidly enlarging and prone to rupture.

For prevention, lifestyle modifications such as quit smoking and controlling blood pressure are recommended. Screening via ultrasound is advised for men over 65 who have ever smoked, to detect AAAs early and prevent rupture. Early detection and proper management are critical to improving outcomes and reducing the risk of fatal complications.