Renovascular hypertension

Renovascular hypertension is the most prevalent form of curable hypertension. Despite some unanswered questions, there is a growing consensus about the need to identify patients with renovascular hypertension so that a specific therapy can be recommended. The renin-angiotensin system is the chief pathophysiologic mechanism responsible for hypertension in patients with renal ischemia but other, yet poorly defined, mechanisms may be operative. Most patients with renovascular hypertension do not present with typical or discriminative clinical features. Thus, many physicians do not perform work-up to uncover renovascular disease even if diagnosis is dictated by patients' clinical course. It is difficult to make the proper diagnosis unless there is a high index of suspicion and certain procedures are performed. How can we, then, select a few patients for the work-up from the vast sea of people with hypertension? The identification of such patients and the pursuit of a renovascular etiology is a matter of clinical judgment. Delineation of renovascular hypertension should be undertaken only after careful deliberation. When clinical clues suggestive of renovascular hypertension are present, appropriate diagnostic tests should be undertaken in patients who are candidates for PTRA or surgery. Captopril-stimulated PRA test is done first. If the test is positive (and in some clinically relevant circumstances even if it is not done or is negative), DSA should be obtained. IV-DSA is being steadily replaced by the superior IA-DSA. The need for renal vein renin determination varies from center to center, but when carefully performed, it yields meaningful information. Ultimately, a conventional arteriogram is done to define the extent of renal artery stenosis and to assess intrarenal vascular anatomy. For selected patients, the benefit-risk ratio clearly outweighs the cost considerations. The spectrum of renovascular hypertension is variable, further compounding the diagnostic indications and contraindications. At one end of this spectrum are those patients in whom surgical therapy is likely to be beneficial, and at the other end are the patients who have relative contraindications to surgery. In between lies the vast gray zone that constitutes a great judgmental challenge in clinical medicine. What is to be done with the patients who have mild to moderate renovascular hypertension whose BP is controlled on medical therapy? There are some patients who may benefit from renovascular repair despite the nonlateralization of renal vein renins. What is the mechanism underlying their hypertension?(ABSTRACT TRUNCATED AT 400 WORDS)     

Renovascular hypertension

Renovascular disease frequently escapes clinical diagnosis. Critical stenosis of the renal artery causes hypoperfusion of the kidney which in turn is the cause of renovascular hypertension and ischaemic nephropathy. Detection of renovascular disease in the population of hypertonic patients should be based on clinical symptoms. In a selected group one of the imaging methods can be used. The increasing number of patients with stenosis of the renal artery is indicated for percutaneous transluminal angioplasty or surgical revascularization as the function of the ischaemized kidney is a risk. Medicamentous treatment of hypertension, which is usually successful, is indicated in patients with atherosclerosis with a history of cardiovascular complications or a high risk of the latter. The contribution and risk of different therapeutic methods must be considered individually with regard to the clinical condition as well as the findings on the blood vessels. CONCLUSION: A unique contribution of angioplasty in stenosis of the renal artery or surgical revascularization is the possibility to improve renal haemodynamics and thus renal function. Prevention of ischaemic nephropathy calls for early diagnosis of renovascular disease.     

Renovascular hypertension in children

Renovascular disease is an uncommon but important cause of hypertension in children. It is usually diagnosed after a long delay because blood pressure is infrequently measured in children and high values are generally dismissed as inaccurate. Many children with renovascular disease have abnormalities of other blood vessels (aorta, cerebral, intestinal, or iliac). Individuals suspected of having the disorder can be investigated further with CT, MRI, or renal scintigraphy done before and after administration of an angiotensin-converting-enzyme inhibitor, but angiography is still the gold standard. Most children with renovascular disease will need interventional or surgical treatment. Endovascular treatment with or without stenting will cure or reduce high blood pressure in more than half of all affected children. Surgical intervention, if needed, should be delayed preferably until an age when the child is fully grown. Modern treatment provided by a multidisciplinary team of paediatric nephrologists, interventional radiologists, and vascular surgeons offers good long-term treatment results.     

Renovascular hypertension in blacks

To define the clinical characteristics of renovascular hypertension (RVH) and determine the clinical usefulness of captopril stimulated peripheral renin and postcaptopril renography in blacks at risk for RVH, 79 clinically selected hypertensive blacks were evaluated. Unstimulated (U-PRA), captopril stimulated (S-PRA) peripheral renin, and postcaptopril renography (PC-RENO) were obtained. All subjects underwent conventional renal arteriography. Renal artery stenosis (RAS) was present in 14 of 79 (18%) patients. Renovascular hypertension (RVH) was found in 7 of 79 (9%) patients. S-PRA had a sensitivity and specificity of 38% and 86% respectively to detect RAS; and a sensitivity and a specificity of 17% and 85% respectively to detect RVH. PC-RENO had a sensitivity and a specificity of 64% and 58% respectively to detect RAS; and a sensitivity and a specificity of 67% and 58% respectively to detect RVH. This study suggests that RAS occurs in 18% of clinically selected hypertensive blacks. RVH was present in 9% of this population. Captopril stimulated peripheral renin and postcaptopril renography are not useful as screening tools for the diagnosis of renovascular disease in blacks. Blacks at high risk should be evaluated with angiography.     

Renovascular hypertension update

Hypertension detected in patients with renovascular disease poses a major clinical challenge. The rapid expansion of noninvasive imaging, effective antihypertensive drug therapy, and endovascular interventional procedures combine to make optimal management a moving target. Renal arterial disease accelerates the development of hypertension associated with activation of multiple pressor systems and accelerated target organ injury. Younger individuals with fibromuscular lesions often respond well to renal revascularization with minor associated risks. Care must be taken in cases of complex vascular anomalies, such as renal artery aneurysms. Atherosclerotic renal artery stenosis is detected more commonly than ever before and affects more than 85% of patients referred for revascularization. Most are older patients with long-standing hypertension, diabetes, and pre-existing complications of vascular disease. The benefits of extensive workup and intervention in this group of patients are controversial. Antihypertensive drug therapy is most effectively achieved with drugs that block the reninangiotensin system, but most require multiple agents. Selection of patients for renal revascularization in this group is far more controversial than with fibromuscular disease. Several small trials failed to identify major benefits with renal artery angioplasty as compared to closely monitored drug therapy, although crossover rates from medical to interventional arms were high. The Cardiovascular Outcomes in Renal Atherosclerotic Lesions (CORAL) seeks to randomly assign subjects with proven, high-grade renal artery lesions to optimal medical management with and without stenting. This important trial employs distal embolic protection to prevent deterioration of renal function. Understanding the optimal role for renal revascularization depends heavily upon the successful conduct of such trials.     

Renovascular hypertension. Studies of 16 cases with long-term follow-up

Surgical correction of renovascular hypertension was studied in 16 patients. In all the patients severe high blood pressure and stenosis of at least one renal artery was demonstrated; in 14 patients plasma renin activity (PRA) in renal veins and peripheral blood was measured. All cases were followed for 36 to 48 months after surgical treatment. Blood pressure was normalized after surgical treatment (2 aortorenal bypasses, 2 nephrectomies and 7 autotransplants) in 7 patients, all of them had hyperreninemia, hypersecretion from the stenotic kidney and suppression of the contralateral kidney. In one patient with stenosis of one renal artery, blood pressure was normalized after surgery, even though no alterations in renin secretion was demonstrated. Surgery (1 bypass, 2 nephrectomies, 1 autotransplant and 1 aortorenal anastomosis) induced a decrease in blood pressure in five patients, all had normal PRA in peripheral blood and hypersecretion from the stenotic kidney. Three patients remained hypertensive in spite of nephrectomy of the stenotic kidney all had hyperreninemia without lateralization. In two patients renal failure was evident from the time they entered the study; both had hyperreninemia, lateralization and suppression of the contralateral kidney, one improved with nephrectomy of stenotic kidney and hemi-nephrectomy of the contralateral and the other remained hypertensive after nephrectomy. The initial status of renin secretion has prognostic value for the response to surgical treatment of renovascular hypertension.     

Renovascular hypertension in elderly patients.

In elderly patients with uncontrolled hypertension or increasing azotemia caused by renovascular disease, hepatorenal or splenorenal bypass procedures are helpful alternatives. The presence of diffuse atherosclerosis makes aortorenal bypass technically difficult. Surgery of this type can be accomplished with acceptable morbidity and mortality, even in suitably screened elderly patients.     

Case 6: Renovascular hypertension

Renovascular hypertension is a progressive disorder that can result in serious complications without adequate treatment. Unfortunately, identification of patients with the condition is often difficult, and the optimal approach to management continues to be debated.