Treatment of renovascular disease and of renovascular hypertension

ABSTRACT: Treatment of occlusive lesions of renal arteries, defined as renovascular disease (RVD), is aimed both at preventing ischemic renal disease (IRD) and rescuing renal function through revascularization procedures, such as PTRA, endovascular stenting and surgical revascularization, as well as curing or improving hypertension in the presence of renovascular hypertension (RVH), i.e. hypertension caused by these vascular lesions. Preventive treatment of IRD is still an individual decision making process based on the type of renal lesions, degree of renal stenosis and progressive loss of renal mass as well as on immediate and late technical success of revascularization procedures together with their rate of complications. Rescue of renal function and-or prediction of the outcome of renal function after successful revascularization depends not only on the possibility of clarifying whether the decrease in renal function is a functioning-reversible phenomenon linked to renal hypoperfusion but also on the potential risk that the revascularization procedure may induce irreversible kidney damage. The rationale for treating RVH through revascularization procedures derives from the possibility of establishing a pathogenetic link between the occlusive lesions and hypertension, mainly through renal vein renin measurement and captopril renography and possibly their combination. Finally, medical treatment of hypertension is needed in patients who cannot undergo or refuse revascularization and whose blood pressure is not normalized by these procedures.     

Problem cases in renovascular hypertension

The clinical course and response to therapy of 16 patients with various complex forms of renovascular hypertension were investigated. Reconstructive surgery and/or transluminal dilatation was either ineffective (n = 5) or could not be performed for technical reasons (n = 11). The group contained 7 patients with multilocular fibromuscular disease involving both renal arteries, two cases with multiple arteriosclerotic vascular occlusions, 3 patients with branch renal artery aneurysms, 3 with renal artery stenosis in a solitary kidney and one patient with renal artery stenosis and contraction of the contralateral kidney due to a non-vascular cause. With antihypertensive treatment, particularly with the angiotensin converting enzyme inhibitor captopril (n = 7), blood pressure could be reduced from 214 +/- 40/124 +/- 23 mm Hg to 145 +/- 23/88 +/- 9 mm Hg (P less than 0.001). In 11 of the 16 patients (69%) the values decreased to less than 160/95 mm Hg. These results suggest that, in complex forms of renovascular hypertension, antihypertensive treatment may be a potent therapeutic alternative if surgery and/or transluminal dilatation can not be performed or seem to have too high a risk.     

Diagnostic procedure in renovascular hypertension

Detection of a renal artery stenosis (RAS) as a cause of arterial hypertension is of great practical importance because dilatation of the stenosis frequently results in an improvement or cure of the hypertension. In recent years, a number of screening procedures aimed at diagnosing renovascular hypertension have been developed, e.g., duplex sonography of the renal arteries, determination of plasma renin activity, or renal scintigraphy following administration of captopril. The possibilities and limitations of these screening procedures are described here. The best method for detecting renal artery stenosis is angiography, which can now be performed on an outpatient basis, using thin catheters.     

Postradiation renovascular hypertension.

Radiation injury to arteries can represent a significant complication of therapeutic irradiation, even when the dosage used has not been excessive as judged by approved protocols. Children in whom therapeutic abdominal irradiation has been used should be monitored indefinitely for the development of hypertension. The presence of hypertension in such children with normal blood urea nitrogen (BUN) and creatinine, and without proteinuria, should prompt investigation for a renovascular lesion. Standard bypass procedures are usually effective, although the long-term success may be compromised by continuing changes in affected vessels.     

Advances in the medical management of renovascular hypertension

Although clinical reports have suggested that antihypertensive therapy can control blood pressure in patients with renovascular hypertension, adequate randomized studies comparing medical versus surgical management are lacking. It is well recognized that progressive deterioration in renal function can occur despite good blood pressure control. Recent experience suggests that higher-risk patients with atherosclerotic renovascular hypertension can benefit from an aggressive surgical approach, whereas newer medical therapies capable of specific inhibition of the renin-angiotensin system suggest greater potential benefits to other patients. Properly performed randomized trials comparing medical versus surgical therapy of renovascular hypertension are needed.     

Autorenal transplantation in the treatment of renovascular hypertension

Autorenal transplantation was performed on 32 renal units including three bilateral transplants, in 29 renovascular hypertensive patients. Aortoarteritis in 18, fibromuscular dysplasia in six, and atherosclerosis in five were the causative renal arterial lesions. Young patients with severe or uncontrolled hypertension but with functioning kidneys were selected for this procedure. Follow-up varied from one to seven years. Twenty-two patients were cured of hypertension, four showed improvement and in three the transplanted kidneys failed to function due to vascular thrombosis postoperatively. There was no death in the series.     

Surgical treatment of renovascular hypertension

The evaluation of patients with inadequate control of diastolic blood pressure for surgically correctable forms of hypertension led to the detection and surgical treatment of 56 patients. Detection was facilitated by the use of hypertensive intravenous pyelography and Hippuran renal Scanning. Aortography proved the presence of renal artery disease and renal vein renin assay established its significance in the etiology of the patients' hypertension. Renal artery reconstruction was performed in 50 patients, including 5 who also had reconstruction of major aortoiliac lesions. The extent of renal artery disease precluded arterial reconstruction in six patients, who required nephrectomy. Two postoperative deaths occurred, for a mortality rate of 3.6 per cent. Improvement in mean diastolic blood pressure for the total group of patients from 118 mm Hg preoperatively to 86 mm Hg postoperatively was achieved. Forty-six patients (85 per cent) have a diastolic blood pressure of 90 mm Hg or less; in 5 patients the diastolic blood pressure is 91 to 100 mm Hg but is at least 20 mm Hg lower than the preorative level.     

Surgical correction of renovascular hypertension

The role of surgical revascularization in the management of patients with renal artery disease has changed in recent years. This has occurred owing to the advent of transluminal angioplasty as an effective method of treatment for certain patients, improved results of surgical revascularization in older patients with atherosclerosis, an enhanced appreciation of advanced atherosclerotic renal artery disease as a correctable cause of renal failure, and the development of more effective surgical techniques for patients with severe aortic atherosclerosis and branch renal artery disease. Surgical revascularization is at present the treatment of choice for patients with branch renal artery disease, ostial atherosclerotic renal artery disease, a renal artery aneurysm, and patients in whom renal angioplasty has been unsuccessful. Excellent clinical results continue to be achieved with surgical revascularization in properly selected patients.     

Medical management of renovascular hypertension

Summary The preferred treatment for renovascular hypertension is revascularization of the ischemic kidney, which helps to preserve renal function as well as lower blood pressure. Medical management plays an important role, however, both as initial therapy for patients who are undergoing revascularization and as maintenance therapy when this cannot be undertaken or has been unsuccessful. The relative merits of the different types of treatment depend on a variety of factors such as the age of the patient, the etiology of the renal artery stenosis, and the presence or absence of concomitant disease.     

Pathophysiology of experimental renovascular hypertension

The genesis of renovascular hypertension follows a continuum from an acute to a chronic phase. Reduction in renal perfusion initiates renin release and angiotensin-mediated systemic vasoconstriction. Aldosterone secretion, sodium and water retention, and expansion of the extracellular volume ensue. Sustained hypertension is further maintained by interacting physiologic mechanisms including increased angiotensin II sensitivity, vasopressin, ouabain-like substance, the sympathetic nervous system, CNS mechanisms, autoregulation, and structural changes.