Abdominal aortic stenosis (AAS) refers to abnormal narrowing of the aorta anywhere along its course in the abdomen. The aorta enters the abdomen through the thoracic hiatus at the level of the 12th thoracic vertebra in front of the spinal cord and terminates as the right and left iliac arteries. Stenosis can result from congenital or acquired lesions. AAS produces a bottleneck effect, where there is hypertension above the lesion and hypotension below and can often be diagnosed based on the difference in blood pressure between the upper and lower extremities. Symptoms can be divided into three categories based on the major groups of arteries supplied by the abdominal aorta.
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The renal arteries that supply blood to the kidneys are branches of the abdominal aorta. When narrowing of the abdominal aorta reduces renal blood flow, the kidneys respond by releasing a hormone called renin. Renin, in turn, activates a substance called angiotensin, which causes vessel walls to constrict in an effort to increase blood flow to the kidneys, and stimulates the release of a third hormone, aldosterone, which increases the resorption of water and salt from the kidneys, in an effort to increase blood volume.
When decreased blood flow is caused by AAS, these compensatory measures are ineffective. The kidney responds by trying harder, and blood pressure above the level of the lesion can become dangerously high. Common symptoms of high blood pressure include headache (especially morning headache), ringing in the ears, dizziness, confusion, fatigue, shortness of breath and changes in vision. Left untreated, hypertension may produce myocardial infarction, congestive heart failure or stroke.
The blood vessels of the digestive system are also supplied by the abdominal aorta. Mesenteric ischemia typically presents as severe pain in the middle or upper abdomen, which begins 15 to 60 minutes after eating. Pain lasts for 60 to 90 minutes and then disappears until the next time you eat. In addition to pain, some people with mesenteric ischemia also complain of weight loss, diarrhea, nausea and vomiting, flatulence or constipation. The types of symptoms are less important than the overall pattern and their association with eating.
Intermittent claudication refers to symptoms of muscle pain, cramps, numbness or fatigue that occur when the muscles are at work and which are relieved by rest. Normally, blood vessels dilate, increasing blood flow during exercise or work. In patients with AAS, supply cannot keep up with demand, and the affected individual needs to rest. Symptoms may be felt anywhere in the lower extremities, but calf pain is considered classic. Muscles in the upper extremities are supplied by the brachial arteries and are unaffected by AAS.