Renovascular Hypertension is a type of secondary hypertension caused by abnormal changes in the regular blood flow to the kidneys. While renovascular hypertension is sometimes discovered right away in patients who are known to have kidney problems, it is more commonly diagnosed after a period of observation and testing. Because of how the kidneys work, renovascular hypertension usually gets worse if it isn't treated.
When the arteries that carry blood to your kidneys become narrow, less blood flows to the kidneys. The kidneys mistakenly respond as if your blood pressure is low and give off hormones that tell the body to hold on to more salt and water. This causes your blood pressure to rise.
Renal artery stenosis is a narrowing or blockage of the artery that supplies blood to the kidneys.
The most common cause of renal artery stenosis is hardening of the arteries (atherosclerosis) from high cholesterol.
- Atherosclerosis (hardening of the arteries) occurs when a sticky, fatty substance called plaque builds up on the inner lining of the arteries. The plaque may slowly narrow or even block the renal (kidney) aretery.
- Risk factors for atherosclerosis are: high blood pressure, smoking, diabetes, high cholesterol, heavy alcohol use, cocaine abuse, and increasing age.
Fibromuscular dysplasia is another cause of renal artery stenosis, particularly in women under age 50. It tends to run in families. Fibromuscular dysplasia is caused by abnormal growth or development of cells in the walls of the arteries leading to the kidneys. This also leads to narrowing or blockage of these arteries.
Usually, high blood pressure causes no symptoms. Occasionally you may have a mild headache. If your headache is severe, or if you have any of the symptoms below, see a doctor right away.
These may be a sign of malignant hypertension :
- Blood in urine
- Crushing, angina-like chest pain
- Ear noise or buzzing
- Irregular heartbeat
- Vision changes
Exams and Tests
People with renovascular hypertension usually have severe, difficult-to-control high blood pressure. They may have a history of high blood pressure that is hard to control or does not get better with medication.
Your doctor may hear a "whooshing" noise, called a bruit, when placing a stethoscope over your belly area.
Other signs of this disease include:
- Acute kidney failure occurs when starting blood pressure medicines called ACE-I or ARBs
- Episodes of heart failure
- Hypertension in an elderly patient whose blood pressure was previously well controlled
- Rapid progression of kidney failure
- Angioplasty sometimes with stent placement
- Rarely, bypass graft
Opening the obstructed renal artery using angioplasty with or without a stent usually relieves hypertension if the renal vein renin activity ratio is > 1.5:1. Even when the ratio is lower, revascularization or removal of the affected kidney often cures hypertension.
Percutaneous transluminal angioplasty (PTA) is recommended for most patients, including younger patients with fibromuscular dysplasia of the renal artery. Placement of a stent reduces the risk of restenosis; antiplatelet drugs
are given afterward. Saphenous vein bypass grafting is recommended only when extensive disease in the renal artery branches makes PTA technically unfeasible. Sometimes complete surgical revascularization requires microvascular techniques that can only be done ex vivo with autotransplantation of the kidney. Cure rate is 90% in appropriately selected patients; surgical mortality rate is < 1%. Medical treatment is always preferable to nephrectomy in young patients whose kidneys cannot be revascularized for technical reasons.
Atherosclerotic lesions respond less well to surgery and angioplasty than do lesions due to fibromuscular dysplasia, presumably because patients are older and vascular disease is more extensive. Hypertension may persist, and surgical complications are more common. Surgical mortality rate is higher than that in young patients with fibromuscular dysplasia. Restenosis occurs within 2 yr after PTA in up to 50% of patients with renovascular atherosclerosis, especially when the lesion is located at the ostium of the renal artery, and, with stenting, in about 25%.
Without treatment, the prognosis is similar to that for patients with untreated primary hypertension. Medical treatment is inadequate without intervention to alleviate the stenosis, but aggressive medical treatment in adherent patients usually ameliorates and sometimes controls hypertension.
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