The infrarenal aorta is a segment of the body’s largest artery, the aorta, located within the abdomen. This major blood vessel carries oxygen-rich blood from the heart to the lower body, including the legs and pelvis.
Anatomy and Function
The aorta originates from the left ventricle of the heart, descending through the chest into the abdomen. Below the diaphragm, it becomes the abdominal aorta. The infrarenal aorta is the portion of the abdominal aorta located below the renal arteries, which supply blood to the kidneys, extending to where the aorta divides into the common iliac arteries. This segment is particularly susceptible to certain conditions, despite the aorta’s strong walls designed to withstand pulsatile blood flow.
Common Conditions Affecting the Infrarenal Aorta
The most common condition affecting the infrarenal aorta is an abdominal aortic aneurysm (AAA), which is a localized weakening and ballooning or bulging of the arterial wall in this specific segment. These bulges can develop over time due to increased pressure within the aorta.
A common underlying factor contributing to AAA development is atherosclerosis. This condition involves the buildup of fatty plaques and other substances within the artery walls, which can weaken the vessel. As plaque accumulates and cells within the aortic wall die, the walls become weaker, leading to dilation and aneurysm formation. While atherosclerosis is frequently found in patients with AAAs, it may not always be the direct cause but rather a parallel process or a secondary development to the aneurysm’s expansion.
The primary danger of an infrarenal aortic aneurysm is the potential for rupture, which can lead to severe internal bleeding and is a life-threatening medical emergency. The risk of rupture increases significantly with aneurysm size. For example, aneurysms between 4.0-4.9 cm in diameter have an annual rupture risk of 1-3%, while those 5.0-5.9 cm have a 3-15% annual risk, and aneurysms 7.0 cm or larger carry a greater than 20% annual rupture risk. Other factors that increase rupture risk include continued smoking, high blood pressure, female sex, and a family history of AAA.
Symptoms and Diagnosis
Smaller infrarenal aortic aneurysms often cause no noticeable symptoms and are frequently discovered incidentally during other medical examinations. Regular screening for at-risk individuals is important.
When an aneurysm grows larger or begins to leak, symptoms may appear. These can include a deep, constant pain in the belly, back, or side, which may spread to the groin, buttocks, or legs. Some individuals may also experience a throbbing or pulsating sensation near the belly button. A ruptured aneurysm causes sudden, severe symptoms, including intense pain, dizziness, and rapid heart rate.
Diagnostic methods for infrarenal aortic conditions include various imaging techniques. Ultrasound is frequently used for screening and monitoring aneurysm size. Computed tomography (CT) scans offer detailed information about the aneurysm and surrounding anatomy. Magnetic resonance imaging (MRI) can also provide anatomical details of aneurysms and evaluate blood flow.
Management and Treatment Options
The management of infrarenal aortic aneurysms depends on factors such as the aneurysm’s size, growth rate, and whether it is causing symptoms. For smaller aneurysms, typically those less than 5.0 to 5.5 cm in diameter, conservative management is often recommended. This involves watchful waiting with regular monitoring through ultrasound or CT scans, often every 6 to 12 months, to track any changes in size. Risk factor modification is also a component of conservative management, including quitting smoking, controlling high blood pressure, and lowering cholesterol levels.
When an aneurysm reaches a certain size (generally 5.5 cm or larger in men, or 5.0 cm in women), is rapidly growing, or becomes symptomatic, surgical intervention is usually considered. Two primary surgical approaches are available: open repair and endovascular aneurysm repair (EVAR).
Open repair involves a larger incision in the abdomen to directly replace the weakened aortic segment with a synthetic graft. This method has been the traditional treatment for many years and offers excellent long-term outcomes.
Endovascular aneurysm repair (EVAR) is a less invasive option that involves smaller incisions, typically in the groin. Through these incisions, a flexible tube (catheter) is used to guide a stent-graft into the aorta, which is then expanded to reinforce the weakened area and divert blood flow away from the aneurysm.
EVAR generally results in shorter hospital stays and quicker recovery times compared to open repair. While EVAR is often preferred due to its less invasive nature and improved short-term morbidity and mortality outcomes, open repair remains a suitable option, particularly for younger patients or those with specific anatomical considerations.