Renovascular hypertension
Renovascular hypertension: Excerpt from Professional Guide to Diseases (Eighth Edition)
Renovascular hypertension is a rise in systemic blood pressure resulting from stenosis of the major renal arteries or their branches or from intrarenal atherosclerosis. This narrowing or sclerosis may be partial or complete, and the resulting blood pressure elevation, benign or malignant.
Causes and incidence
Stenosis or occlusion of the renal artery stimulates the affected kidney to release the enzyme renin, which converts angiotensinogen — a plasma protein — to angiotensin I. As angiotensin I circulates through the lungs and liver, it converts to angiotensin II, which causes peripheral vasoconstriction, increased arterial pressure and aldosterone secretion and, eventually, hypertension.
Atherosclerosis (especially in older males) and fibromuscular diseases of the renal artery wall layers — such as medial fibroplasia and, less commonly, intimal and subadventitial fibroplasia — are the primary causes in 95% of all patients with renovascular hypertension. Other causes include arteritis, anomalies of the renal arteries, embolism, trauma, tumor, and dissecting aneurysm. Less than 5% of patients with high blood pressure display renovascular hypertension; it’s most common in persons younger than age 30 or older than age 50.
PEDIATRIC TIP Fibromuscular dysplasia is the most common cause of renovascular hypertension in children. The surgical cure rate is very high.
Signs and symptoms
In addition to elevated systemic blood pressure, renovascular hypertension usually produces symptoms common to hypertensive states, such as headache, palpitations, tachycardia, anxiety, light-headedness, decreased tolerance of temperature extremes, retinopathy, and mental sluggishness. Significant complications include heart failure, myocardial infarction, stroke and, occasionally, renal failure.
Diagnosis
Diagnosis is confirmed by the following tests:
CONFIRMING DIAGNOSIS Arterial digital subtraction angiography with assays of venous renin is the definitive diagnostic procedure. When stenosis is significant, transluminal angioplasty can be done during the same procedure.
❑ Gadolinium enhanced magnetic resonance angiography can identify turbulent blood flow indicative of renal stenosis.
❑ Duplex Doppler ultrasonography scans the renal artery and will reveal stenosis but results vary.
❑ Oral captopril renography is the simplest, noninvasive test for detection of renovascular hypertension but has a relatively high false-positive rate.
Treatment
Surgery, the treatment of choice, is performed to restore adequate circulation and to control severe hypertension or severely impaired renal function by renal artery bypass, endarterectomy, arterioplasty or, as a last resort, nephrectomy. Balloon catheter renal artery dilation is used in selected cases to correct renal artery stenosis without the risks and morbidity of surgery. Symptomatic measures include antihypertensives, diuretics, and a sodium-restricted diet.
Medications that may be used in an attempt to control blood pressure include diuretics, beta-adrenergic blockers, calcium channel blockers, angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, and alpha-adrenergic blockers. Diazoxide or nitroprusside may be given in the hospital if symptoms are acute. Response to medications is highly individual and the dosage or specific drug used may need frequent adjustment.
Lifestyle changes may be recommended, including weight, exercise, dietary adjustments, smoking cessation, and avoidance of alcohol. These habits add to the effects of hypertension in causing complications.
Special considerations
The care plan must emphasize helping the patient and his family understand renovascular hypertension and the importance of following the prescribed treatment.
❑ Accurately monitor intake and output and daily weight. Check blood pressure in both arms regularly, with the patient lying down and standing. A drop of 20 mm Hg or more on arising may necessitate an adjustment in antihypertensive medications. Assess renal function daily.
❑ Maintain fluid and sodium restrictions. Explain the purpose of a low-sodium diet.
❑ Explain the diagnostic tests, and prepare the patient appropriately; for example, adequately hydrate the patient before tests that use contrast media. Make sure the patient isn’t allergic to the dye used in diagnostic tests. After excretory urography or arteriography, watch for complications.
❑ If a nephrectomy is necessary, reassure the patient that the remaining kidney is adequate for renal function.
❑ Postoperatively, watch for bleeding and hypotension. If the sutures around the renal vessels slip, the patient can quickly go into shock because kidneys receive 25% of cardiac output.
❑ Provide a quiet, stress-free environment if possible. Urge the patient and his family members to have regular blood pressure screenings.
Book Source Details
- Book Title: Professional Guide to Diseases (Eighth Edition)
- Author(s): Springhouse
- Year of Publication: 2005
- Copyright Details: Professional Guide to Diseases (Eighth Edition), Copyright © 2005 Lippincott Williams & Wilkins.
More About Pheochromocytoma
More Medical Textbooks Online about Pheochromocytoma
Review other book chapters online related to Pheochromocytoma:
Medical Books Excerpts
- Hypertension
- "The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter" (2000)
- [ read ]
- Hypertension
- "The Diagnostic Approach to Symptoms and Signs in Pediatrics" (2006)
- [ read ]
Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
» Next page: Hypertension (Professional Guide to Diseases (Eighth Edition))
Rate This Website
What do you think about the features of this website?
Take our user survey and have your say:
Website User Survey
Medical Tools & Articles:
Next articles:
Tools & Services:
Medical Articles:
Forums & Message Boards
- Ask or answer a question at the Boards:
