AUTHOR AND EDITOR INFORMATION

Section 1 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

INTRODUCTION

Section 2 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Background

Systemic hypertension is less common in children than in adults, but the incidence of hypertension in children is approximately 1-5%. The presence of hypertension in younger children is usually indicative of an underlying disease process (secondary hypertension). In children, approximately 5-25% of secondary hypertension is attributed to renovascular disease.

In 1934, Goldblatt et al demonstrated a relationship between hypertension and renal ischemia. They were able to consistently produce elevations in systolic blood pressure by producing renal ischemia with a constricting clamp. Removal of the clamp restored blood pressure to the reference range. Four years later, Leadbetter and Burkland applied this information by performing a nephrectomy of a unilateral ischemic kidney. This remained the method of surgical treatment until 1960 when Lambeth et al reported resolving hypertension by correction of renal artery stenosis. Nephrectomy is now reserved as a last resort in the treatment of renovascular hypertension. In the 1960s, the delineation of the renin-angiotensin system and its relation to hypertension also had a large impact on the medical therapy and diagnostic studies used in renovascular hypertension.

Pathophysiology

Often, the cause of renovascular disease is unknown. Most severe forms of renovascular hypertension seem to involve ischemic-related stimulation of the renin-angiotensin system. Blood flow in renal vessels is hindered by constriction or even complete reduction of the vessel diameter. With the decreased perfusion, renin release is stimulated. This results in vascular constriction and increased release of aldosterone. The additional aldosterone leads to the retention of sodium and water. This increases blood volume. Together, the increased constriction and blood volume increase blood pressure.

Some congenital lesions are related to renal hypoplasia. Tumors and other masses may impinge on the renal vasculature. Trauma, irradiation, vessel anastomosis in transplantation, and thrombosis all may lead to constriction of vessels and the resulting hypertension. The most common cause of renal hypertension in newborns is a thrombosis or embolization related to umbilical artery catheterization.

Fibromuscular dysplasia

Fibromuscular dysplasia (FMD) involves fibrous or muscular hypertrophy of the vessel tunica media with fibrous intimal hyperplasia. Some authors even refer to this disease as fibromuscular hyperplasia. Often, poststenotic dilatation is also present. The process may range from mild occlusion to complete occlusion of the vessel. On radiographs, FMD produces the classic string-of-beads appearance less often in children than in adults. Rather, FMD tends to show short discrete or longer tubular segments of stenosis.

The site of stenosis usually occurs at the orifice of the renal artery at its origin in the aortic wall. The next most common location is within the main renal artery, and the segmental arteries are the least common site of stenosis. Total occlusion most often occurs at the orifice of the renal artery. The disease may be unilateral or bilateral, but the inciting event for FMD is unknown. Some have suggested an autoimmune origin. In 1995, Stanley proposed that the lesion forms as a developmental disease in the muscular layer, which is followed by intimal hyperplasia from the abnormal flow through the constricted lumen.¹

Midaortic syndrome

Midaortic syndrome consists of more widespread vascular involvement than just the renal artery. Aortic narrowing exists that often extends from the aortic hiatus to just above the inferior mesenteric artery. One or both of the renal arteries are usually involved, and narrowing of the celiac and superior mesenteric arteries may exist. Midaortic syndrome is considered a variant of FMD and may result in total occlusion of the renal artery, with perfusion dependent on collateral circulation. Extensive collateralization from the inferior mesenteric artery and a Riolan arcade may exist. Renal artery stenosis is usually bilateral.

Neurofibromatosis

Hypertension in patients with neurofibromatosis is often essential, but some patients also present with renovascular hypertension. These children have a pattern of renal artery stenosis that is similar to that observed in FMD. However, involvement of the intrarenal arteries and arterioles may also exist. Neurofibromatosis usually involves the renal arteries of both kidneys.

Frequency

United States

As mentioned above, the incidence of hypertension in children is reported to be 1-5%. In adolescents, it may be as high as 10%. Unlike in adults, 70-80% of hypertension in children may be due to secondary hypertension, which is often correctable. Of those children with secondary hypertension, 5-25% have elevated blood pressure with a renovascular etiology. Renovascular hypertension is common in children and is second only to coarctation of the aorta as a surgically correctable cause of hypertension. With improved screening for coarctation in younger children, renovascular hypertension may be the most common cause of surgically correctable hypertension.

International

Geographic differences in the overall prevalence of renovascular hypertension have not been reported, although the etiology of renovascular hypertension does appear to vary geographically. In the western hemisphere, FMD is the most common cause of pediatric renovascular hypertension. Reports from Asia identify arteritis, either aortoarteritis or Takayasu arteritis, as the most common cause of renovascular hypertension in children. One study in south Asia found that 87% of the patients presenting with renovascular hypertension had arteritis.² A report from South Africa also indicated that Takayasu arteritis was the most important cause of renovascular hypertension in nonwhite children.

Mortality/Morbidity

Renovascular hypertension can develop into chronic hypertension, and patients usually present with malignant hypertension. If left untreated, this can produce serious consequences, including coma and death.

• The actual mortality rate of untreated renovascular hypertension has not been reported, in part because effective treatments are available.
• Chronic hypertension can damage blood vessels, leading to such pathology as plaques, aneurysms, claudication, and dissection.
• The main comorbidity of renovascular hypertension is directly related to its effects in end-organ damage.
• Neurologic manifestations are often the presenting symptoms because severe hypertension can lead to retinopathy, headaches, dizziness, confusion, seizures, and stroke.
• The heart is frequently affected because increased afterload leads to congestive heart failure and ventricular hypertrophy.
• Renovascular hypertension may also damage the kidneys, especially when significant stenosis of the perfusing vessels is present.
• Although they are rare, oliguric renal failure and ischemic kidneys have been reported with renovascular disease.
• Finally, renovascular hypertension is often associated with failure to thrive in young children.

Race

Blood pressure has been shown to be higher in black children than in white children, but the difference has not been deemed clinically significant. When adjusted for height, much of this difference is eliminated. Renovascular hypertension is less common among older black children than among adolescent whites, but the prevalence is actually higher in young black children.

Sex

Multiple studies have demonstrated that no clear sex difference occurs in childhood renovascular hypertension.

Age

In children, the prevalence of renovascular disease as the cause of hypertension is inversely related to age. In other words, younger children are more likely to have hypertension that is due to renovascular disease. In children younger than 5 years, the incidence of potentially surgically correctable hypertension is close to 80%. This incidence drops to 40-45% in children aged 6-10 years. In children aged 11-20 years, a 20% incidence of surgically correctable hypertension is observed.

CLINICAL

Section 3 of 11  

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History

• Patients may be asymptomatic, and hypertension may be discovered during routine examination or preparation for surgical treatment of another problem.
• In most studies, more than one half of children who were hypertensive were also asymptomatic or their hypertension was discovered during a routine examination.
• When present, symptoms are nonspecific and are often related to the organ systems most affected by hypertension.
• • The most common symptom of renovascular hypertension seems to be headache.
  • Other neurologic symptoms of renovascular hypertension include changes in mental status, vision changes, vomiting, seizures, coma, encephalopathy, hyperexcitability, and hyperirritability.
  • Symptoms of resulting congestive heart failure may also be present, such as decreased energy, edema, and shortness of breath.
  • In patients with abdominal aortic narrowing, claudication may be present.
  • Some children have anorexia, and infants or young children often present with failure to thrive.
  • Occasionally, patients have oliguric renal failure.

Physical

• Upon physical examination, patients have a blood pressure elevation above the 95th percentile for their age, sex, and height. Generally, children with blood pressures greater than 140/100 mm Hg are thought to be more likely to have secondary hypertension, and renovascular hypertension is more likely in children with higher blood pressure.
• Eye examination may reveal retinopathy and retinal hemorrhages.
• Patients with heart failure may present with tachypnea, cardiomegaly, and vasomotor instability leading to mottling and acrocyanosis.
• Lower extremity pulses may be diminished with aortic coarctation, whether thoracic or abdominal.
• An enlarged liver may be palpated, and an abdominal bruit may be auscultated.
• Patients with tumors impinging on renal vasculature may present with an abdominal mass in the area of the kidney.
• Rarely, signs or symptoms of visceral artery involvement are present because of the extensive collateralization that occurs.
• Café au lait macules are classic in the presentation of neurofibromatosis. Patients with neurofibromatosis may also have macrocephaly, neurofibromas, dermal neurofibromas, and axillary freckling.

Causes

Renovascular hypertension implies the cause of the elevated blood pressure is decreased arterial inflow to the kidneys. This results in activation of the renin-angiotensin system, with the development of systemic hypertension. Some congenital disorders may lead to renovascular hypertension, including arterial hypoplasia (as observed in multicystic renal dysplasia), neurofibromatosis, and Williams syndrome. The focus of this article is on the disease processes that most commonly cause renovascular hypertension in children.

• More commonly, renovascular disease in children is considered an acquired disease. FMD is the most common form of acquired renovascular hypertension. Its incidence varies geographically, but in the United States, it is the most common cause of secondary hypertension in children.
• Other forms of acquired renovascular hypertension include subisthmic coarctation, Moyamoya disease, Takayasu arteritis, Kawasaki disease, vasculitis, vascular trauma, renal artery thrombosis, tumors, midaortic syndrome, or anastomotic stenosis (such as posttransplantation).
• • Trauma or kidney transplantation can lead to scarring or anastomotic lesions that produce renovascular constriction.
  • Although Takayasu arteritis and Kawasaki disease occasionally lead to FMD, the cause of FMD is not always known.
• Often, the cause of renovascular disease is unknown. Umbilical catheters in newborns, especially those born prematurely, may result in embolization of the renal vasculature. Radiation therapy of tumors in the renal area may lead to renovascular hypertension.
• Multicystic renal dysplasia is commonly encountered in newborns. Prenatal detection by screening ultrasonography is common. These lesions are rarely bilateral and are usually associated with ipsilateral ureteral atresia. Hypertension and recurrent infections can result from this condition. As previously mentioned, multicystic dysplastic kidneys are not discussed in this article.

DIFFERENTIALS

Section 4 of 11  

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Other Problems to be Considered

Adrenal tumor
Aldosteronoma
Aortic insufficiency
Arterial hypoplasia
Stroke
Cushing disease
Cushing syndrome
Essential hypertension
Fibromuscular dysplasia
Increased intracranial pressure
Intracranial mass
Irradiation
Moyamoya disease
Renal cyst
Renal failure
Renal hypoplasia
Renal parenchymal disease
Renovascular hypertension
Retinopathy
Thrombosis
Umbilical catheter embolism

WORKUP

Section 5 of 11  

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Lab Studies

• Basic diagnostic tests for pediatric renovascular hypertension should accomplish 2 things.
• • Because the most common medical cause of hypertension in children is renal disease, the aim in initial testing should be the detection of unsuspected renal parenchymal disease.
  • Secondly, tests should identify the presence of end-organ damage due to the hypertension.
• The 1987 Report of the Second Task Force on blood pressure control in childhood recommends a fasting lipid profile in patients with findings suggestive of essential hypertension to evaluate atherosclerotic cardiovascular disease.³ The report also recommends the following initial tests in children with hypertension:
• • CBC count
  • Urinalysis
  • Urine culture (all girls, selected boys)
  • Serum electrolyte levels (sodium, potassium, chloride, and total carbon dioxide)
  • BUN levels
  • Serum creatinine levels
• Remember that the renal function test results are frequently normal in children with renovascular disease, even when the lesions are bilateral.
• Findings on a 24-hour urine study should also be within the reference range in renovascular hypertension.
• CBC count, serum electrolyte levels, BUN levels, and serum creatinine levels should indicate whether a pattern of renal function impairment or a pattern of aldosteronoma is present.
• Measure a 24-hour urine sample for electrolytes, creatinine, vanillylmandelic acid, catecholamines, 17-hydroxy steroids, and 17-keto steroids. Results should rule out the possibility of a medullary or cortical tumor.
• The erythrocyte sedimentation rate is a good indicator of active arteritis.
• Elevation of peripheral or renal vein plasma renin activity has been used to diagnose unilateral renal disease and predict surgical curability. However, an elevated level does not establish the cause of hypertension, and plasma renin levels that are within the reference range do not rule out renovascular disease.
• • Renal vein renin ratios compare the effluent activity of each kidney. Ratios greater than 1.5 are suggestive of functionally important renovascular disease. Volume depletion exaggerates reduced renal perfusion and may increase the ratio of renal vein renins in asymmetric disease.
  • One study found that nearly 90% of renal artery disease was detected when pretreated with furosemide. However, these findings can also be misleading, especially in bilateral disease.

Imaging Studies

• When renovascular hypertension is suspected, the criterion standard for diagnosis is renal arteriography. Because this is a very invasive procedure, performing less specific tests to modify the physician's suspicion of renovascular disease is frequently necessary before submitting the patient to this test. The following studies are useful in the assessment of patients with suspected renovascular hypertension.
• • Ultrasonography: Most authors think that radiographic studies should begin with Doppler ultrasonography of the kidneys and abdomen. This is useful in identifying renal disease and abdominal masses. In renal artery stenosis, ultrasonography often reveals a slowing and dampening of systole distal to the stenosis. Renal ultrasonographic findings are insufficient to rule out the need for angiography.
  • Renal scanning: Intravenous pyelography may be useful in detecting unilateral lesions, but is often unhelpful when bilateral disease is present. Many think that intravenous pyelography is an unnecessary part of the evaluation because results are often inaccurate in children. Likewise, technetium-99m (^99mTc) scanning, diethylenetriamine pentaacetic acid (DTPA) renal scanning, and other radionuclide studies may be misleading in bilateral renovascular hypertension. However, some think that DTPA or ^99mTc dimercaptosuccinic acid (DMSA) scanning is helpful in identifying patients at increased risk for renovascular hypertension when performed before and after the administration of the ACE inhibitor, captopril. Decreased function after treatment with captopril indicates a high likelihood of renovascular stenosis. If the scan findings remain normal, renovascular disease is not ruled out.
  • Intravenous digital subtraction angiography (DSA): Intravenous DSA has also been suggested as a means of identifying renovascular disease. Unfortunately, this test is dependent on the skill of the individual interpreting the radiograph, and image quality is diminished by patient or intestinal motion, gas, overlying vessels, and poor cardiac output. The use of abdominal pressure and glucagon can reduce interference from gas and intestinal motion.
  • Renal arteriography: Selective renal arteriography is the only reliable means to document renal artery stenosis. This test is still considered the criterion standard for diagnosis of renovascular hypertension. Renal arteriography is necessary whenever surgery or percutaneous transluminal angioplasty is anticipated. Adding digital subtraction technology to renal arteriography requires one half the volume of dilute contrast medium of standard arteriography, with comparable results. Use abdominal pressure and glucagon to prevent bowel motion and gas from affecting the image quality.
  • Magnetic resonance angiography (MRA), CT angiography, and spiral angiography: MRA, CT angiography, and spiral angiography are newer studies that hold a lot of promise for diagnosis and evaluation of renovascular hypertension. Unfortunately, they have not yet been sufficiently investigated for use in children with renovascular disease. At present, interpretation of the images is technically difficult, and their usefulness appears limited to imaging of main vessels.
• Chest radiography and echocardiography may be helpful in differentiating left ventricular failure from chronic hypertension.

Other Tests

• ECG may be helpful in differentiating left ventricular failure from chronic hypertension.

Histologic Findings

• Because many of the lesions in FMD occur at the renal artery orifice, obtaining a good histologic sample is frequently difficult.
• Evaluation of stenotic lesions invariably reveals the characteristic FMD in the medial or perimedial muscular layers associated with varying degrees of intimal hyperplasia.

TREATMENT

Section 6 of 11  

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• Follow-up
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Medical Care

• Treat all children with hypertension with antihypertensive medication. In children with severe hypertension, beginning medical treatment before a definitive diagnosis is obtained may be necessary.
• Renovascular hypertension is often refractory to medical treatment. In children with renovascular hypertension, the excellent results of renal artery dilation and surgical revascularization make these procedures the treatments of choice over life-long antihypertensive medication.
• However, attempt to control a patient's blood pressure in preparation for surgical intervention. Especially, defer surgery until manifestations of malignant hypertension are relieved.
• Adrenergic blockers often are an effective means of lowering blood pressure in patients with renovascular hypertension.
• Diuretics may be beneficial.
• Nitroprusside and phenoxybenzamine are useful in the short-term management of malignant hypertension prior to surgery.
• Patients with renovascular disease treated with ACE inhibitors are at risk of decreased renal function. Although this is usually reversible, their use is generally avoided until definitive therapy has been attempted. Certainly, any patients with renovascular hypertension who are treated with ACE inhibitors should have their serum creatinine levels monitored, and therapy should be discontinued if their creatinine levels significantly rise.

Surgical Care

The invasive and surgical options for treatment of renovascular hypertension include: (1) percutaneous angioplasty, (2) surgical revascularization, and (3) nephrectomy.

• Percutaneous transluminal angioplasty (PTA): This is a therapeutic radiologic procedure involving expansion of a small balloon on a special vascular catheter to dilate narrow areas in a blood vessel. Balloon expansion to 10 atm of pressure is generally used, and more than one dilation of the balloon may be required to achieve the desired effect.
• • PTA has had mixed results in children. Long-term maintenance of blood pressure improvement ranges from 38-90%. In 1997, Guzetta et al and Tyagi et al found that approximately 25% of patients treated with PTA developed restenosis.^{4, 2} In 1995, Casalini et al reported on PTA in a selected group of 36 children with renovascular hypertension.⁵ Of these patients, 34 (94%) were normotensive 2 years after the procedure.
  • PTA is considered cheaper and less invasive than surgical revascularization. It can be performed at the time of angiography. When patients are refractory to treatment or in the event of restenosis, surgery can still be performed. PTA is most effective in mid vessel stenosis. Lesions involving segmental arteries or the ostium of renal arteries and patients with neurofibromatosis were especially refractory to balloon angioplasty. Complications include thrombosis, vascular or renal perforation, and tearing or dissection of the vessel wall. The field of interventional radiology and vascular surgery continues to grow, and improvements in the outcomes of such procedures for management of this problem are likely.
• Surgical revascularization: Reports have shown that more than 90% of patients are cured or have improvement of their hypertension with surgical revascularization. The goal of the surgery is correction of the hypertension with preservation of renal function. Preservation of a functional kidney is especially important because of the high rate of bilateral disease in children.
• • Operative approach: For unilateral renal artery stenosis, a transverse transperitoneal incision may be used. This allows direct approach to the renal artery. Little dissection of the kidney is performed to limit disruption of the collateral vessels. These collaterals provide some renal perfusion during occlusion of the renal artery for bypass of the lesion. Generally, generous operative exposure is required for optimal operative therapy. In 1995, Stanley et al recommended a supraumbilical transverse abdominal incision.¹ In small children, the incision may need to extend from the xiphoid to the pubis. Reflection of the colon and viscera to the opposite side permit complete control of the inferior vena cava and the renal vasculature. Small children may require evisceration of the intestines for sufficient exposure. Dissecting the renal vein completely free and retracting it upward is usually best.
  • Surgical management of the renal lesion: Dissect the proximal renal artery before approaching the more distal artery to prevent inadvertent injury to small vessels. The aorta is circumferentially dissected just below the renal arteries, and the aortorenal junction is freed when the lesion involves the renal artery ostium. Once everything is free and just prior to cross-clamping, 1 mg/kg of heparin and 0.17 g/kg of mannitol are administered. Broad spatulation of the end of the renal artery or graft creates a generous anastomotic patch for attachment. In small children, perform anastomoses by use of an interrupted monofilament suture to allow for growth. A continuous suture may be used in older patients with a larger anastomosis. When the reconstruction is complete, reversal of the heparin is accomplished with a slow intravenous administration of protamine sulfate 1.2 mg/100 U of previously administered heparin.
• Renal autotransplantation: This involves bypassing the stenotic lesion by reconnecting the renal artery to the aorta in an end-to-side fashion. This procedure has a high success rate but requires extensive mobilization of the kidney. This is the preferred procedure for renal artery stenosis, but use of this method depends on the length of the stenosis and how widespread the renovascular disease is.
• Aortorenal bypass: The most common procedure requires bypassing the lesion by interposition of a graft end-to-side into the aorta and end-to-end to the renal artery. Various techniques can be used, and no uniform agreement regarding the best graft material has been reached.
• • Synthetic graft: Using synthetic graft material or a prosthesis is not the preferred technique. Risk of infection is increased, and technical limitations are associated with the use of this material.
  • Hypogastric artery graft: Stanley et al and Guzetta et al prefer to use a segment of hypogastric artery.^{1, 6} Its size conforms to that of the renal artery in most instances; a low incidence of dilation is observed, and it is easily amenable to suturing. Problems with this graft include potential arteritis and the possibility of impotence in patients who had both hypogastric arteries harvested for bilateral reconstruction.
  • Saphenous vein graft: In 1994, O'Neill reported using the saphenous vein as graft material to avoid potential problems with the hypogastric artery graft.⁷ One problem with reversed saphenous vein grafts is the tendency of the graft to dilate. Development of aneurysms occurs in approximately 25% of these grafts, and these tend to occur within the first 2 years postoperatively. To prevent these aneurysms, O'Neill places a 4- to 6-mm Dacron net mandril around the graft. Using the Dacron, Berkowitz et al reported no aneurysmal dilatation in 19 grafts in 1989.⁸ Three of the 19 patients did develop restenosis. Whether this was directly related to the use of a mesh support is unknown. Although this has not been reported, using a synthetic support for the graft has the potential to increase the risk of infection.
  • Aortoaortic bypass: Children with midaortic syndrome or subisthmic coarctation require an aortoaortic bypass using an 8-mm to 12-mm woven Dacron or expanded polytetrafluoroethylene graft. In the classic approach, the bypass is connected to the low thoracic aorta and the bifurcation of the iliacs. Grafts can also extend from the upper abdominal aorta behind the esophagus to the aortic bifurcation. Use the appropriate length of graft material to allow for growth while avoiding kinking. Placing the graft behind the kidney may help to protect the graft. Renal artery bypass grafts may be attached to the aortoaortic bypass graft or to the low aorta. Attachment of the renal artery graft to the native aorta below the coarctation should theoretically result in less anastomotic neointimal hyperplasia.
• Nephrectomy: Use this option as a last resort in the treatment of renovascular hypertension. The goal of treatment in renovascular hypertension is to resolve systemic hypertension without compromising renal function.
• • Because renovascular disease is often bilateral, with the contralateral renal system occasionally not affected until years later, keeping both kidneys functioning when possible is best. However, removal of the kidney is the best form of treatment in severe renal hypoplasia that reduces the functional capacity to less than 10% of the total renal function.
  • Nephrectomy may be necessary if complications arise during revascularization surgery or if the disease is too widespread (especially in segmental arteries) to be effectively bypassed. Children whose hypertension is refractory to the above forms of treatment may also need nephrectomies to correct their high blood pressure. Modern surgical technique has allowed surgeons to perform nephrectomy using laparoscopic surgery (see Media files 6-7).

Consultations

The need for consultation depends on the degree of end-organ damage.

• If a patient has had chronic hypertension that has led to heart failure, consider referring the patient to a pediatric cardiologist.
• Likewise, a patient presenting with neurologic symptoms may need to see a neurologist or neurosurgeon before surgical treatment is started.
• Once a diagnosis of renovascular hypertension is made, prompt treatment of the disease is the best protection against further end-organ damage.

Diet

• Placing all patients who are hypertensive on a low-salt diet is recommended. In renovascular hypertension, this is unlikely to correct the systemic hypertension but may assist in managing the hypertension until more definitive therapy can be performed. It certainly does not hurt patients.
• Also, avoid dehydration because this may lead to decreased renal perfusion or increased renin release.

MEDICATION

Section 7 of 11  

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Medical treatment may be necessary to control blood pressure until surgery can be performed. In fact, attempt to reduce the blood pressure prior to surgery to improve the likelihood of a good surgical outcome. After surgery, medical treatment is necessary 25-30% of the time to provide complete resolution of improved or refractory hypertension.

Adrenergic receptor blockers and diuretics are the preferred form of medication. Arterial dilators are also useful in the preoperative management of malignant hypertension. Calcium channel blockers do not seem to be as widely used, and ACE inhibitors are generally avoided because of the potential compromise to renal function.

Drug Category: Adrenergic blocking agents

Adrenergic blockers, those working at both alpha-receptors and beta-receptors, tend to be some of the most effective medicines for prolonged treatment of renovascular hypertension. At low doses, alpha-adrenergic receptor blockers may be used as monotherapy in the treatment of hypertension. At higher doses, they may cause sodium and fluid to accumulate. As a result, concurrent diuretic therapy may be required to maintain the hypotensive effects of the alpha-receptor blockers. Beta-blockers inhibit chronotropic, inotropic, and vasodilatory responses to beta-adrenergic stimulation.

Drug Category: Diuretics

These agents promote excretion of water and electrolytes by the kidneys. They are used to treat heart failure or hepatic, renal, or pulmonary disease when sodium and water retention has resulted in edema or ascites. They may be used as monotherapy or combination therapy to treat hypertension. Diuretics may be helpful in the medical treatment of renovascular hypertension. Thiazide diuretics are preferred.

Drug Category: Arterial vasodilators

Arterial vasodilators may be useful in the short-term management of renovascular hypertension prior to surgery. Nitroprusside is especially useful for this purpose.

Drug Category: Renin-angiotensin inhibiting agents

ACE inhibitors have been used by some in the control of renovascular hypertension. However, ACE inhibitors increase the risk of decreased renal function. Although this is usually reversible, their use is generally avoided until definitive therapy has been attempted. Renal blood flow is maintained as a balance of both angiotensin-II–induced vasoconstriction and prostaglandin-mediated vasodilation. With ACE inhibitor therapy, kidney perfusion is increased and renal vascular resistance is decreased. ACE inhibitors induce vasodilation in both afferent and efferent arterioles. Glomerular filtration rate (GFR) generally increases. However, in hypoperfusion states (eg, renal artery stenosis, aggressive diuresis, decompensated congestive heart failure), GFR is likely to fall because of unopposed prostaglandin vasodilation.

FOLLOW-UP

Section 8 of 11  

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• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Further Inpatient Care

• Preoperative care
• • Provide pharmacologic treatment for patients with renovascular hypertension before the operations in an attempt to control blood pressure.
  • Routine chest radiography, ECG, and, perhaps, echocardiography are important in evaluating the patient's cardiovascular stability under the stress of hypertension.
  • Abdominal aortography and arteriography are necessary, not only for diagnosis but also to determine the extent of disease and the approach to surgical intervention.
• Postoperative care
• • Carefully monitor patients' blood pressures because postoperative medical therapy may be necessary.
  • Renal scanning or arteriography is also important after surgery to identify possible thrombosis, stricture, or any failures in the graft or anastomosis.

Further Outpatient Care

• Because the long-term outcome has not yet been determined, monitor sequential blood pressure measurements indefinitely.
• • In unilateral disease, development of contralateral stenosis has been reported to occur years (as many as 14 y) later in some cases.
  • In addition, stenosis of the graft or thrombosis may occur as many as 2 years postoperatively.
• Approximately 25% of patients treated surgically still require some drug therapy to maintain blood pressure measurements within the reference range.

Complications

• The rate of PTA complications varies among physicians, but potential complications include thrombosis, vascular or renal perforation, and tearing or dissection of the vessel wall. Restenosis appears to occur approximately 25% of the time.
• Most authors have reported a 0% mortality rate because of surgery. Failure or complications in revascularization procedures lead to another operation approximately 27% of the time. Usually, the second operation is curative.
• • Reports in larger series indicate that graft stenosis may occur about 5% of the time, and thromboses have occurred in approximately 10% of revascularization operations. Specific complications of each graft material were delineated above under Surgical Care.
  • Take care to provide secure anastomoses. Likewise, implement a sufficient length of graft material to allow for growth in the child without kinking secondary to too much graft length.

Prognosis

• The prognosis in untreated renovascular hypertension is poor. The severity of the hypertension produces a lot of strain on target organs and can lead to death. Fortunately, most renovascular disease is correctable with surgical intervention.
• For 35% of patients, PTA produces normotensive blood pressures. Another one third of patients have decreased blood pressures. Unfortunately, a high rate of recurrence of hypertension and vascular stenosis appears to be observed in patients treated with PTA.
• Surgical revascularization provides a very good prognosis for patients with renovascular hypertension.
• • Approximately 70% of patients become normotensive without requiring additional pharmacologic treatment. Another 25% have reduced hypertension that can usually be resolved with the addition of medical therapy. Thus, fewer than 5% of patients appear refractory to revascularization. Some of the patients can experience resolution of their hypertension following nephrectomy.
  • Successful surgical intervention is expected to provide patients with a normal life span without complication. Children who undergo surgical revascularization appear to do well for at least 16 years postoperatively. They are able to participate in active sports and similar vigorous activities without problems. Further long-term follow-up is needed to determine the durability of these reconstructions and the actual life potential of these children.

MISCELLANEOUS

Section 9 of 11  

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• Follow-up
• Miscellaneous
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Medical/Legal Pitfalls

• The most important medicolegal pitfall is failure to recognize that hypertension in children must be carefully investigated.
• Until proven otherwise, children with hypertension have a surgically correctable condition.

MULTIMEDIA

Section 10 of 11  

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• Introduction
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• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

Media file 1:  Aortogram of a 4-year-old child with renovascular hypertension caused by stenosis of the left renal artery. Note that the left kidney has 2 renal arteries, and the artery to the superior pole has stenosis.
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Media type:  Radiograph

Media file 2:  Close-up view of the same arteriogram described in Media file 1. The stenotic lesion begins at the ostium of the left superior renal artery. This lesion was caused by fibromuscular dysplasia and did not respond well to balloon angioplasty.
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Media type:  Radiograph

Media file 3:  Operative photograph of the patient described in Media files1 and 2. The patient underwent aortorenal bypass using a reinforced saphenous vein graft. The inferior pole renal artery was preserved.
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Media type:  Photo

Media file 4:  Aortogram of an 8-year-old child with neurofibromatosis and renovascular hypertension caused by right renal artery stenosis.
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Media type:  Radiograph

Media file 5:  Operative photograph of the patient described in Media file 4. An aortorenal bypass was performed using saphenous vein graft reinforced with Dacron. The aorta is completely exposed as observed in this picture, and the graft is visible inferior to the native renal artery.
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Media type:  Photo

Media file 6:  Although nephrectomy is rarely indicated in the treatment of renovascular hypertension in children, it can be safely performed using modern pediatric surgical laparoscopy technique. This 3-month-old child with renal dysplasia and refractory hypertension underwent laparoscopic nephrectomy. The photograph illustrates the patient positioning and the placement of small trocars at the time of the nephrectomy. The dysplastic kidney was easily removed through a slightly enlarged umbilical incision.
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Media type:  Photo

Media file 7:  Same patient as described in Media file 6. The photograph was taken immediately after laparoscopic nephrectomy. This patient was discharged from the hospital 2 days after surgery. This approach eliminates the need for large incisions and facilitates recovery from surgery, minimizing pain and length of hospital stay.
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Media type:  Photo

REFERENCES

Section 11 of 11

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Miscellaneous
• Multimedia
• References

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