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Renovascular Hypertension

Definition
Causes, incidence, and risk factors
Symptoms
Signs
Screening tests
Treatment
Prognosis
Prevention
Summary

Definition
Renovascular hypertension results from stenosis, or narrowing, of one or both renal arteries. Alternative names include renal hypertension; hypertension - renovascular

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Causes, incidence, and risk factors
The long term complications of poorly controlled hypertension include early death, coronary artery disease, myocardial infarction, congestive heart failure, peripheral arterial occlusive disease, renal failure, stroke, and loss of vision. While the most common cause of elevated blood pressure is "essential hypertension", renovascular hypertension is a form of secondary hypertension. It occurs in less than 5% of all patients with hypertension. Narrowing of the renal artery reduces blood flow to the kidney. Stenosis is most often related to atherosclerosis but may be caused by other maladies such as fibromuscular dysplasia (FMD).

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Symptoms
Symptoms are rare. Headache occurs occasionally. If hypertension is severe, symptoms may include: fatigue, confusion, visual disturbances, nausea and vomiting, chest pain, and/or congestive heart failure.

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Signs
Elevated blood pressure measurements, repeated over time, confirm hypertension. Renovascular hypertension is often severely high and difficult to treat. Diastolic blood pressure is often higher than 100. Renovascular hypertension is suspected when the onset of high blood pressure occurs at an advanced age or abruptly at an early age; stable hypertension suddenly becomes more difficult to treat; or when hypertension requires multiple medications for its satisfactory control.

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Screening tests
When the presence of renovascular hypertension is suspected, several screening tests are currently available. However, the advanced imaging technique of deep abdominal ultrasonography with Doppler evaluation has rapidly become the screening modality of choice for this disorder. This test allows visualization of the renal arteries and measurement of arterial velocities, resulting in assessment of renal artery stenosis. The test is highly accurate, but may be limited by body habitus and intestinal gas, and/or the presence of multiple renal arteries. It is also limited in its ability to evaluate the distal renal vasculature. CT and MR angiography are also excellent imaging techniques, but are more costly. Arteriography is invasive and should not be used as a screening test; it is a useful tool when performing interventional therapy or planning operative procedures (see below).

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Treatment
The obvious goal of treatment of renovascular hypertension is control of blood pressure, and prevention of the long-term sequelae of poorly controlled hypertension, including renal and cardiac failure. With the advent of medicines such as angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) control of blood pressure can almost uniformly be maintained. However, because these medications can alter renal blood flow and function, close monitoring of overall renal function is paramount. If control of blood pressure sacrifices renal function, direct renal artery intervention may be warranted. This may involve percutaneous intervention with a renal stent or an open surgery with a renal bypass or renal artery reconstruction. Lifestyle changes may be recommended, including weight loss, exercise, and dietary adjustments. Stop smoking. Stop drinking alcohol. These habits add to the effects of hypertension in causing complications.

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Prognosis
The overall prognosis of the patient with renovascular hypertension relates to their other medical conditions. If the renovascular hypertension has been present for a long time it may result in established organ dysfunction. In these cases, the long term benefit from aggressive medical, interventional, or surgical therapy may be limited. However, when early diagnosis and treatment of renovascular hypertension is accomplished, and strict blood pressure control is maintained, the long term prognosis of these patients is similar to age-matched controls. It must be remembered, however, that the disorder requires lifelong monitoring, and treatment may require frequent adjustments.

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Prevention
Preventing atherosclerosis may prevent the development of renal artery stenosis and subsequent development of renovascular hypertension. Lifestyle modifications such as diet, weight loss, and exercise may reduce the risk of hypertension. Smoking is perhaps the most critical, and certainly the most controllable, atherosclerotic risk factor. Albeit difficult, smoking cessation is paramount. Lipid lowering agents offer a relatively easy method of lowering cholesterol, but diet, too, has its place. Diabetes is the one atherosclerotic risk factor that is most difficult to control. While strict maintenance of serum glucose can be achieved in most patients with due diligence, this is no guarantee against the development of systemic atherosclerosis in the diabetic patient.

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Summary
Renovascular hypertension is a relatively rare cause of hypertension. The occurrence of severe hypertension of abrupt onset or in a previously well controlled hypertensive patient should raise concerns regarding the development of renovascular hypertension. Screening tests are non-invasive and relatively inexpensive. Treatment options include medical therapy alone, or in conjunction with percutaneous or surgical procedures. Regardless of treatment modality, long term follow up is mandatory. The best prevention is with life-style modification and control of atherosclerotic risk factors.

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