The aorta is the larger artery that runs down the middle of one's body from the heart to the umbilicus, or belly button. It is comprised of four sections: root of the aorta, ascending aorta, descending aorta, and abdominal aorta. The abdominal aorta begins where the aorta passes through the diaphragm into the abdominal cavity. It is the main artery that feeds the body with oxygenated blood via many arterial branches. Occasionally, the walls of the aorta may become weakened, and an aneurysm, or bulge within the artery, may occur. Ultrasound is used to evaluate abdominal aortic aneurysms.
Preparation
The aorta runs along the back in front of the spine, and can be obscured by bowel. Ultrasound cannot see through bowel gas, so the patient must fast for eight hours prior to the exam so the bowel gas can subside. The patient may keep his or clothes on for the examination. He or she will be asked to lie on his or back, and the shirt will be pulled up to expose the belly. Towels are used to protect the patient's clothing from ultrasound gel.
Protocol
The aorta is imaged in lengthwise and crosswise sections. While the whole aorta is examined, images are obtained at three spots:
- at or near the level of the celiac trunk and superior mesenteric artery near the diaphragm
- at the level of the renal arteries, the site of infrarenal abdominal aortic aneurysm
- just above the aortic bifurcation at the umbilicus.
The aorta bifurcates, or branches, into the iliac arteries. These arteries are also imaged and measured just below the bifurcation. Aneurysms are most common near the bifurcation, usually just above it.
Aneurysm Risk Factors
Aortic aneurysms are more likely in people who are 60 years of age and older. Hypertension and cardiovascular disease can cause weakened arterial walls that can become aneurysms. Arterial walls that are arteriosclerotic are more likely to develop an aneurysm. Arteriosclerosis is the hardening of the arteries. Smoking is a cause for cardiovascular disease and hypertension. Diabetics are also at a greater risk.
Abdominal Aortic Aneurysm Treatment
If aortic aneurysm surgery is recommended, one of two procedures may be advised. Open abdominal surgery might be performed to replace the weakened section of aorta with a graft. Another solution is to place an endovascular stent graft into the weakened section as reinforcement. This is done by feeding catheters into the leg arteries to put the stent into place.
People with aortic aneurysms may have regular aortic ultrasounds at one-year intervals to follow the progress of an aneurysm. That rate at which an aneurysm grows and its size can be an indicator of whether or not a patient is at risk for a rupture of an aneurysm. Those who have had surgical repair may continue to have yearly follow-up ultrasounds.
Resources
Textbook of Diagnostic Ultrasonography; Sandra L. Hagen-Ansert
VascularWeb: Abdominal Aortic Aneurysm
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