Renal Vein Renin

Selective venous sampling for secondary hypertension

Selective venous sampling (SVS), an invasive radiographic procedure that depends on contrast media, holds a unique role in diagnosing and guiding the treatment of certain types of secondary hypertension, particularly in patients who may be candidates for curative surgery. The adrenal venous sampling (AVS), in particular, is established as the gold standard for localizing and subtyping primary aldosteronism (PA). Throughout decades of clinical practice, AVS could be applied not only to PA but also to other endocrine diseases, such as adrenal Cushing syndrome (ACS) and Pheochromocytomas (PCCs). Notably, the application of AVS in ACS and PCCs remains less recognized compared to PA, with the low success rate of catheterization, the controversy of results interpretation, and the absence of a standardized protocol. Additionally, the AVS procedure necessitates enhancements to boost its success rate, with several helpful but imperfect methods emerging, yet continued exploration remains essential. We also observed renal venous sampling (RVS), an operation akin to AVS in principle, serves as an effective means of diagnosing renin-dependent hypertension, aiding in the identification of precise sources of renin excess and helping the selection of surgical candidates with renin angiotensin aldosterone system (RAAS) abnormal activation. Nonetheless, further basic and clinical research is needed. Selective venous sampling (SVS) can be used in identifying cases of secondary hypertension that are curable by surgical intervention. Adrenal venous sampling (AVS) and aldosterone measurement for classificatory diagnosis of primary aldosteronism (PA) are established worldwide. While its primary application is for PA, AVS also holds the potential for diagnosing other endocrine disorders, including adrenal Cushing's syndrome (ACS) and pheochromocytomas (PCCs) through the measurements of cortisol and catecholamine respectively. In addition, renal venous sampling and renin measurement can help to diagnose renovascular hypertension and reninoma.

Renovascular Hypertension

Hypertension constitutes a major health problem and the challenge is to identify patients having ‘surgically’ curable renal vascular disease among the majority with so-called essential hypertension. The best of unsatisfactory diagnostic tests are renography and plasma renin activity both before and during angiotensin II blockade. The necessity of better screening tests has increased because of the recent advances in surgical techniques and especially percutaneous transluminal renal angioplasty. The latter has definitely become the method of choice for correction of suspected hemodynamically significant artery stenoses whenever technically feasible. With improved angioplasty techniques the risk of treating renal artery stenosis without hemodynamic and clinical importance (so-called cosmetic repair) has increased. Unfortunately randomized trials including surgery versus angioplasty are not available. It should be kept in mind that only after correction of the stenosis is achieved and the blood pressure has become normal, can the diagnosis of renovascular hypertension be made with certainty.

Experience with percutaneous transluminal renal angioplasty in renovascular hypertension

Percutaneous transluminal renal angioplasty (PTRA) was attempted in 17 patients with a diastolic blood pressure greater than or equal to 95 mmHg in spite of treatment with two or three antihypertensive drugs in combination and unilateral or bilateral renal artery stenosis with a reduction of vessel diameter to less than 25%. PTRA resulted in a dilatation of the stenosis in 12 patients. After an observation period of at least 6 months 2 patients were cured, 7 improved and 3 unchanged. Renal vein renin ratio (RVRR) was determined in the last 9 of these patients but was unknown when PTRA was done. RVRR was higher than 1.5 in 5 patients of whom one was cured and 4 improved and less than 1.5 in 4 of whom one was improved and 3 unchanged. No persistent complications were observed after PTRA. It can be concluded that PTRA is an effective antihypertensive treatment in several patients with renovascular hypertension, and a RVRR greater than 1.5 suggests a favourable outcome with regard to blood pressure regulation.

Renin-Dependent Hypertension Caused by Nonfocal Stenotic Aberrant Renal Arteries

We have identified 2 relatively young patients with significant hypertension, an elongated single aberrant renal artery supplying blood to a renal segment, and evidence for localization of the elevated plasma renin activity to the side and vein draining the affected kidney. Furosemide-induced diuresis and acute oral captopril stimulated the renal vein/contralateral renin ratios to 4.3:1 and 6.5:1 in patients 1 and 2, respectively. These renal vein ratios are significantly higher than normal (>3:1 under similar conditions). Partial resection of the portion of the kidney affected by the aberrant tortuous artery led to a marked reduction in blood pressure in patient 1. Patient 2, not an operative candidate, responded satisfactorily to use of a converting enzyme inhibitor, which helped to confirm the dependency of the blood pressure on the abnormal flow relationship existing within that aberrant artery and the kidney. We believe these 2 patients are representative of a small but distinct subgroup within the larger number of patients with elongated single or multiple renal aberrant arteries. Each aberrant artery had no focal stenosis, although a decrease in flow relative to the tissue perfusion demands was apparent from the marked activation of the renin-angiotensin system in the venous system draining that artery. The increased length of such vessels may contribute to their decreased flow, although their average diameter may reside just above such a critical value for a normal length vessel. This new syndrome, involving more than one component of the flow/resistance relationship, has been overlooked when renin-dependent forms of hypertension are considered.

Endothelin-1 urinary excretion, but not endothelin-1 plasma concentration, is increased in renovascular hypertension

Animal experiments have shown an increase in prepro-endothelin-1 (prepro-ET-1) mRNA expression in the clipped kidney but none in the aortic and mesenteric arteries in 2-kidney, 1-clip Goldblatt hypertensive rats. The present study was aimed at investigating whether plasma and renal endothelin-1 (ET-1) systems are differently activated in patients with renovascular hypertension (RH). The plasma concentration and urinary excretion of ET-1 were measured in 5 patients with RH (before and after successful renal angioplasty), in 7 patients with essential hypertension (EH), and in 8 normotensive control subjects. Immediately before renal angioplasty, plasma samples for ET-1 and plasma renin activity (PRA) measurements were withdrawn from the aorta and both renal veins. Unlike the PRA, the plasma ET-1 concentration did not significantly differ between the involved and the uninvolved sides. The urinary ET-1 excretion level (Fig 1) was markedly increased in patients with RH (30+/-4 ng/g urinary creatinine (UC) vs. 2.5+/-0.2 ng/g UC and 2.6+/-0.5 ng/g UC in control subjects and patients with EH, respectively; P<.001), whereas the plasma ET-1 concentration was normal (0.8+/-0.2 pg/mL vs. 0.65+/-0.3 pg/mL and 0.8+/-0.2 pg/mL in control subjects and EH, respectively, not significant). Renal angioplasty was followed in all patients by normalization of blood pressure and PRA. One week after angioplasty, urinary ET-1 decreased to one fourth of baseline (8.04+/-5.23 ng/g UC, P<.001 vs. values before angioplasty and P<.04 vs. control subjects) and normalized 1 month thereafter (3.13+/-1.62 ng/g UC, not significant vs. control subjects), whereas plasma ET-1 remained steady. The present findings clearly indicate that in patients with RH, urinary ET-1 excretion is increased, whereas plasma ET-1 concentration remains normal. Successful percutaneous transluminal renal angioplasty induced a notable reduction in ET-1 urinary excretion, whereas it did not affect ET-1 plasma concentration.

Secondary hypertension: evaluation and treatment

Most patients with hypertension in the United States have essential (primary) hypertension (95%), the cause of which is unknown. The remaining 5% of adults with hypertension have the secondary form of hypertension, the cause and pathophysiologic process of which are known. Internists and other primary care physicians refer to this as treatable or curable hypertension, because the hypertension can be managed or even controlled with medications. Similarly, the condition is called surgical hypertension by surgeons in the belief that once the cause is determined and identified, surgical intervention will result in cure of hypertension. Secondary causes of hypertension include renal parenchymal disease, renovascular diseases, coarctation of the aorta, Cushing's syndrome, primary hyperaldosteronism, pheochromocytoma, hyperthyroidism, and hyperparathyroidism. Occasionally included in this category are alcohol- and oral contraceptive-induced hypertension and hypothyroidism, but these conditions are not discussed herein. The evaluation of secondary hypertension is of interest and can bring together different facets of anatomy, physiology, pharmacology, and radiology in the medical and surgical treatment of these disorders. Despite enthusiasm that can be generated in the evaluation of these conditions, evaluation can be expensive and should not be conducted for all patients with hypertension. Features that aid in the diagnosis of secondary hypertension include the following: 1. Onset of hypertension before the age of 20 or after the age of 50 years. The presence of hypertension at a young age may suggest coarctation of the aorta, fibromuscular dysplasia, or an endocrine disorder. Hypertension found for the first time after the age of 50 years may suggest the presence of renovascular hypertension caused by atherosclerosis. 2. Markedly elevated blood pressure or hypertension with severe end-organ damage, as in grade III or IV retinopathy. These findings suggest the presence of renovascular hypertension or pheochromocytoma. 3. Specific body habitus and ancillary physical findings. For example, truncal obesity and purple striae occur with hypercortisolism, and exophthalmos is associated with hyperthyroidism. 4. Resistant or refractory hypertension (poor response to medical therapy usually necessitating use of more than three antihypertensive medications from three different classes). 5. Specific biochemical test that suggest the existence of certain disorders, such as hypercalcemia in hyperparathyroidism, hyperglycemia in Cushing's syndrome and pheochromocytoma, and unprovoked hypokalemia with renin-producing tumors, primary hyperaldosteronism, or renin-mediated renovascular hypertension. 6. Other characteristics that may suggest secondary hypertension such as abdominal diastolic bruits (renovascular hypertension), decreased femoral pulses (coarctation of the aorta), or bitemporal hemianopias (Cushing's disease). A combination of a good history and physical examination, astute observation, and accurate interpretation of available data usually are helpful in the diagnosis of a specific causation.

Acute blockage of the renin system and differential renal vein renin determinations in the diagnosis of renovascular hypertension

For validation of differential renal vein renin determinations in the diagnosis of renovascular hypertension (RVH), we investigated 102 patients suspected of suffering from RVH before and 1 h after administration of 25 mg captopril. Sensitivity, specificity and posterior probability for renin ratio (RR) and renin secretion (RS) were calculated based on 44 patients with proven RVH and 58 patients with primary hypertension (PH) using discriminant analysis. There is good (> 95%) and identical specificity of both variables under all conditions, whereas sensitivity remains poor even after Captopril administration (RR 23% vs. 32%; RS 20% vs. 34%). The posterior probabilities obtained by discriminant analysis revealed a cut-off point of 2.5 for the renin ratio and of 1.9 for the renin secretion. No change is observed after ACE inhibition. We conclude that the acute blockade of the renin system by captopril in differential renin sampling yields no advantages in diagnosing RVH and that there is no difference between RR and RS in the diagnosis of RVH.

Renal vein renin analysis: limitations of its use in predicting benefit from percutaneous angioplasty

Two hundred forty-four consecutive patients (mean age 61 years), including 123 who had technically valid renal vein renin (RVR) analysis and 121 without RVR data, underwent technically successful percutaneous renal artery angioplasty (PTRA). They were retrospectively examined to evaluate the utility of RVR analysis in identifying renal hypertension (RVH), predicting benefit from PTRA, and determining if the lack of knowledge of renin levels significantly affected clinical outcome after PTRA. Abnormal RVR values were associated wtih clinical benefit after PTRA in 62 of 93 patients (67% sensitivity, 20% specificity, 72% positive predictive value). Clinical improvement following PTRA occurred in 31 of 37 patients with normal pre-PTRA RVR values (16% negative predictive value). RVR analysis correctly identified 86 of 117 patients with renovascular hypertension (74% sensitivity, 16% negative predictive value). Improved blood pressure (BP) control occurred in 72% with abnormal RVR analysis and 66% of the 121 patients without RVR data (p > 0.1). We conclude that the very low negative predictive value significantly limited the use of RVR analysis in this elderly (mean age 60 years) patient population with a high incidence of mild renal functional impairment (mean serum creatinine 1.4 mg/dl) and bilateral renal artery stenosis (38%). The lack of pre-PTRA renin data did not significantly affect clinical outcome. If RVR data were relied upon as the exclusive selection criterion in patients of this type, many would be prevented from having the benefit of cure or improvement by PTRA.

Renal imaging in children with persistent hypertension

The role that imaging plays in the evaluation of the child with hypertension depends in large part on the results of thorough historical, physical, and laboratory examinations. How aggressively one searches for an underlying renal parenchymal or renovascular disorder must be individualized in each child. An individualized approach to renal imaging in children with hypertension is presented.

Time of flight renal MR angiography: utility in patients with renal insufficiency

We studied the renal arteries prospectively in 16 patients with renal insufficiency using a combination of two-dimensional and three-dimensional time of flight magnetic resonance angiography (MRA). Results were compared with conventional angiography. All renal arteries were identified by MRA. Accuracy for classifying renal arteries into patent, moderately (30-70%) stenotic, severely (> 70%) stenotic, or occluded was 91%. With regard to the presence or absence of severe occlusive disease (> 70% stenosis or occlusion) the sensitivity was 100%, with a specificity of 93%.

Peripheral and renal vein renin activity in patients with renovascular hypertension due to nonspecific aortoarteritis

The diagnostic utility of peripheral and renal vein renin estimations in relation to angiographic findings was evaluated in 13 patients with renovascular hypertension and non-specific aortoarteritis (NSAA, Gr I), in comparison with 10 patients with renal artery stenosis due to other causes (Gr II). Plasma renin activity (PRA) was measured by radioimmunoassay. Blood samples were collected after angiography from the femoral vein and renal vein on the affected side followed by sampling from the less affected or unaffected side. Renal vein renin ratio (RVRR) was calculated from renal vein renin values. The effect of captopril (25 mg oral) on blood pressure, PRA, and RVRR was examined in 8 patients from each group. Normotensive volunteers (8) with moderately low salt intake were also included in the study for comparison of twenty-four-hour urinary sodium output, peripheral PRA, and response to captopril. The mean peripheral PRA was high in both groups as compared with normotensive controls; however, the values were lower in patients with NSAA. The rise in PRA in response to captopril was insignificant in Gr I (p greater than 0.05) and RVRR greater than 1.5 was observed in 5 of 13 patients in contrast to 9 of 10 in Gr II (p less than 0.05). A paradoxical ratio, ie, (high renal vein renin levels on the less stenotic side) was noticed in 3 patients of Gr I, whereas none of the patients of GR II showed such a ratio. An improvement in RVRR after captopril was observed in 50% of patients of Gr I as compared with a marked response in all patients of Gr II.(ABSTRACT TRUNCATED AT 250 WORDS)

The diagnostic dilemma: a clinician's viewpoint

The prevalence of renovascular hypertension appears to be increasing, particularly in older patients with generalized arteriosclerosis, hypertension and impaired renal function. While clinical clues remain extremely useful in identifying patients at increased risk, older screening tests have been largely abandoned in favor of angiographic methods that provide visual identification of renal artery lesions. Renal scintigraphic techniques, with or without angiotensin-converting enzyme (ACE) inhibition, offer the potential for providing accurate measurements of renal function, and may be particularly useful in identifying critical renal arterial stenosis. In assessing the future role of scintigraphy, careful clinical validation of these correlations will be necessary, as will determinations of their usefulness in patients with renal insufficiency and those with bilateral renal artery stenosis. The role of adrenal scintigraphy in the localization of adrenal tumors is also reviewed. Their cost-effectiveness, limitations in sensitivity and specificity compared to current diagnostic technologies, and potential applications are discussed.

Diagnosis of unilateral renovascular hypertension: comparative effect of intravenous enalaprilat and oral captopril

The effectiveness of 2 angiotensin converting enzyme inhibitors, intravenous enalaprilat and oral captopril, in stimulating renin secretion was compared in 47 hypertensive patients with suspected renovascular hypertension. Both inhibitors were more effective stimuli to renin secretion than head-up tilting of the patient. In patients with unilateral renovascular hypertension single doses of angiotensin converting enzyme inhibitors increased the renal venous renin ratio compared to the recumbent ratio. This therapy reduced the number of false negative studies more effectively than head-up tilting and was tolerated better. Contralateral suppression of renin in the unaffected kidney, an important ancillary diagnostic marker of unilateral renovascular hypertension, was preserved. No false positive studies owing to the use of angiotensin converting enzyme inhibitors acutely were apparent. Mean arterial pressure decreased by 5 minutes with intravenous enalaprilat and by 20 minutes with oral captopril, and it continued to decrease gradually for at least 2 hours. No significant syncopal symptoms were observed with either inhibitor. Plasma renin activity increased by 5 and 15 minutes with enalaprilat and captopril, respectively. Plasma aldosterone levels decreased by 10 minutes with enalaprilat and by 30 minutes with captopril, and these changes increased in magnitude during the 2 hours of observation. To achieve the maximum diagnostic effectiveness from the renal venous renin ratio, single dose angiotensin converting enzyme inhibitors warrant consideration for routine use. Intravenous enalaprilat may be preferable because of certain achievement of an effective blood level.

Plasma renin activity and oxygen content along the renal veins in hypertensive patients

Plasma renin activity (PRA) and oxygen content in three different locations in the renal veins were studied in 27 patients with suspected renin-dependent hypertension or during post-operative follow-up investigations after renal artery reconstruction. A significant decrease in PRA was found along the right renal vein but not along the left one. The oxygen content simultaneously measured was lower in the central parts of both renal veins than most peripherally, more on the right side than on the left one, indicating dilution of renal venous blood. An erroneous ratio between renal vein PRA of the affected and the contralateral kidney was found in two of 17 patients with unilateral renal artery stenosis when sampling from a central position in the renal vein. This indicates that a peripheral position of the catheter is important when sampling for renal vein PRA.

Renal artery stenosis in hypertensive diabetic patients

The prevalence of secondary forms of hypertension in diabetes is unknown. One hundred and five of 465 patients randomly selected from a diabetic clinic population were found to be hypertensive. Hypertensive patients aged less than 70 years were screened for renal artery stenosis using intravenous digital subtraction angiography. Two angiograms were technically unsatisfactory. All 18 insulin-dependent patients successfully screened had normal renal arteriograms. Five of 24 non-insulin-dependent patients had unilateral renal artery stenosis but functional tests did not clearly suggest that renal artery stenosis was causing the hypertension in these cases. No patient was referred for surgery or angioplasty. We conclude that renal artery stenosis is common in hypertensive non-insulin-dependent diabetics but may not, in many cases, be the cause of the hypertension. The criteria for investigating diabetic hypertensives for renal artery stenosis should be no different from those used in the general hypertensive population.

Renal angiography may be used primarily in the diagnosis of renovascular hypertension

Three hundred and twenty consecutive patients with hypertension were referred to examination with intravenous urography. Only 2 of the 320 urograms performed showed abnormalities possibly related to hypertension. Renal angiography was performed in 39 (12%) of the patients. Seventeen (7%) subjects had renal artery stenosis, of whom 8 (2.5%) were referred to surgery. Four became normotensive and the other 4 had a more treatable hypertension. Urography is an expensive and insensitive method for evaluation of patients with hypertension and should be abandoned. Proper treatment of renovascular hypertension demands the performance of renal angiography. We therefore suggest a program for primary use of renal angiography in the examination of patients with suspected renovascular hypertension.

Stimulus-response curve of the renal baroreceptor: effect of converting enzyme inhibition and changes in salt intake

We investigated the effect of converting enzyme inhibition (CEI) on the relationship between renal perfusion pressure (RPP) and steady-state plasma renin activity (PRA) in uninephrectomized conscious dogs on normal-salt (80 meq Na+/day) and low-salt (10 meq Na+/day) diets. Stimulus-response curves for the renal baroreceptor were determined by measuring the steady-state PRA while the RPP was lowered and then held constant by an inflatable cuff placed around the renal artery. On each diet the control stimulus-response curve can be described by two lines intersecting at a threshold pressure; in the higher pressure range PRA is relatively insensitive to changes in RPP, while in the lower pressure range PRA is very responsive to changes in RPP. On the normal-salt diet CEI significantly increases the sensitivity of PRA to RPP in the responsive range without affecting the threshold pressure itself or the values of PRA at pressures greater than the threshold pressure. On the low-salt diet CEI also increases the sensitivity of PRA to RPP significantly in the responsive range; we were unable to determine the effect of CEI on PRA at RPPs greater than the threshold pressure in the low-salt state because CEI causes a significant drop in blood pressure under these circumstances. The effect of CEI was significantly greater in the dogs on the low-salt diet than in the dogs on the normal-salt diet. Thus, CEI and salt depletion interact synergistically to increase the sensitivity of the renal baroreceptor only in the responsive range of the stimulus-response curve, i.e., at renal perfusion pressures below the threshold pressure.

The renin-angiotensin systems

The renin-angiotensin systems are important regulators of cardiovascular homeostasis and participate in a variety of pathological conditions. Recent advances have not only clarified the functioning of the systemic renin cascade but have also indicated the importance of the generation of angiotensin in tissues.

Clinical aspects of endocrine hypertension

Distinct hypertensive syndromes clearly related to overproduction of certain hormones are increasingly being recognized. The ability to recognize these disorders has come as a result of better understanding of their pathophysiology and the availability of sensitive and accurate diagnostic tools. The particular appeal of making the diagnosis centers around the potential curability of the hypertension with correction of the hormonal abnormality.

Secondary hypertension. A streamlined approach to diagnosis

Among the many potential causes of secondary hypertension are renal parenchymal disease, occlusive renal arterial disease, adrenocortical abnormalities, and pheochromocytoma. Renovascular hypertension can result from either renal parenchymal or occlusive renal arterial disease. Laboratory testing can help in identification and differentiation. Parenchymal diseases usually modify the urine substantially without producing urographic abnormalities, while occlusive arterial lesions produce urographic abnormalities but the urine remains normal. The diagnosis of renal occlusive arterial disease is best defined by arteriography. The only definite criterion for the existence of hypertension of renal origin is cure by either nephrectomy or renal revascularization. Adrenocortical causes of hypertension include enzymatic deficiencies, Cushing's syndrome, and primary aldosteronism. In enzymatic deficiencies, the physical findings provide the most important clues to the type of enzyme deficiency involved. In Cushing's syndrome, accurate determination of the cause of the hypercortisolism is important in terms of choice and success of treatment. The diagnosis of primary aldosteronism rests primarily on the demonstration of nonsuppressible aldosterone excretion rate during salt loading; the presence of inappropriate kaliuresis and/or suppressed plasma renin activity provides corroborative evidence of primary aldosteronism, but the absence of either or both does not preclude the diagnosis. Pheochromocytoma, although rare, is a serious and potentially fatal cause of hypertension. Definitive diagnosis depends on laboratory test results, and the tumor is usually localized by computed tomography.

Detection and investigation of renal artery stenosis

A retrospective analysis was done on 235 hypertensive patients undergoing renal arteriography. Of the 85 patients with renal artery stenosis 50 underwent 56 operations or angioplasties and have been followed up for at least a year. 41 (73%) of these procedures were curative or led to improved blood-pressure control. These results make it worthwhile identifying hypertensive patients with renal artery stenosis who may benefit from surgery or angioplasty. Vascular disease, epigastric bruit, and impaired renal function were commoner in the renal artery stenosis patients than in the 81 with normal arteriograms, but there were no features pathognomonic of stenosis. Intravenous urography had a sensitivity of 83% and a specificity of 69.5% in identifying renal artery stenosis; those for isotope renography were 90.5% and 38.5%, respectively. Divided renal vein renins did not predict the outcome of intervention. Arteriography should, if there are no contraindications to intervention, be the first and definitive investigation when renal artery stenosis is suspected--for instance, in hypertensive patients with accelerated or malignant hypertension, those whose blood pressure is poorly controlled by multiple therapy, and those who have had recent deterioration in blood-pressure control or renal function.

Evaluation and management of childhood hypertension

Hypertension in childhood is diagnosed according to age-adjusted values for each sex. It is more commonly diagnosed now than it was 2 decades ago because blood pressure is more frequently measured in children today. Surgically curable forms of hypertension are not common but usually present as moderate or severe hypertension (diastolic blood pressure greater than or equal to 110 mm Hg). Although many patients in this group are asymptomatic, some present with Bell's palsy, enlarged hearts, heart failure, encephalopathy, or stroke. Newer imaging techniques have proved particularly useful for localizing tumors, such as pheochromocytoma. Many antihypertensive drugs are now available, and therapy should be tailored to the patient's needs, with as few adverse or side effects as possible.

Indication for intervention in patients with renovascular hypertension

It is now possible to accurately identify patients with renovascular hypertension who need renal angioplasty or revascularization. Evaluation does not require hospitalization and begins with the determination of an ambulatory plasma renin activity (PRA) indexed against sodium excretion and a captopril test. Subsequently differential renal vein renins with matching inferior vena caval (IVC) renins are measured often with converting enzyme inhibition. Identifying criteria are as follows: (1) high PRA indexed against sodium excretion, (2) hypersecretion of renin following captopril administration, (3) absence of renin secretion from the contralateral kidney, and (4) an ipsilateral renal vein renin increment at least 50% greater than the matching IVC renin. Patients who meet the criteria are admitted for percutaneous transluminal renal angioplasty.

Percutaneous transluminal renal artery dilatation for fibromuscular dysplasia with special reference to the acute effects on the renin-angiotensin-aldosterone system and blood pressure

Twelve hypertensive patients (mean age 46.6 years, range 37-55 years) with fibromuscular dysplasia of the renal artery were treated with percutaneous transluminal renal angioplasty (PTRA) and the effects on the renin-angiotensin-aldosterone system and blood pressure were studied in the acute phase. The technical result of PTRA measured by angiography and reduction of PRA and aldosterone excretion was satisfactory in 11 patients. In spite of this only three patients were cured of their hypertension and two patients were improved at six months follow-up. During PTRA an immediate rise in plasma renin activity was noted in patients without beta-receptor blockade but not in patients treated with beta-receptor blocking agents suggesting a beta-receptor mediated release. This peak in renin release was not accompanied by any rise in systemic blood pressure. The blood pressure response in the acute phase did not show any regular pattern. We conclude that PTRA can serve as a model for studying effects of 'clamping' and 'declamping' of the renal artery in man.

Predictive value and changes of renin secretion in hypertensive patients with unilateral renovascular disease undergoing successful renal angioplasty

Peripheral and renal vein renin activity was measured in 46 hypertensive patients with arteriographically diagnosed unilateral renal artery stenosis before and six months after technically successful renal angioplasty. The renin-sodium profile was high in 80 percent before angioplasty, fell in all patients, and became normal or low in 85 percent after angioplasty. Renal vein renin activity, which initially showed lateralization of renin secretion to the ischemic kidney with contralateral suppression, became normal. Renal vein renin activity was more reliable for predicting the therapeutic response when expressed as the increment of renin for each renal vein over the infrarenal vena caval value (sensitivity 74 percent, specificity 100 percent) than as the ratio between the two renal veins (sensitivity 62 percent, specificity 60 percent). The predictive value of renal vein renin activity is poor when plasma renin activity is stimulated by long-term administration of captopril. These data support the usefulness and define the limitations of peripheral and renal vein renin measurements in selecting patients for treatment by renal angioplasty.

Curable hypertension. Usefulness of renal vein renin ratio

A case of severe hypertension in an adolescent male is presented. Initial evaluation of hypertension revealed a unilateral nonfunctioning kidney with no lateralization of renal vein renin ratio. Following 10 months of medical therapy, lateralization of renal vein renin was demonstrated, with subsequent cure of hypertension following nephrectomy.

Reversal of renovascular hypertension

The fall in blood pressure observed in both early and chronic phase Goldblatt 2-kidney 1-clip hypertension produced by removing or unclipping the ischaemic kidney is due to a profound fall in peripheral resistance. The two procedures have an equal effect upon peripheral resistance and the lesser efficacy of nephrectomy in lowering blood pressure is due to a greater rise in stroke volume perhaps associated with a greater degree of sodium retention. Neither changes in sodium balance, in the renin-angiotensin system nor in vascular reactivity explain the fall in blood pressure. A reduction in renal sympathetic afferent activity and a medullary based vasoactive humoral system may play a role although the nature and extent of that role remain to be defined.

Renal autotransplantation in the treatment of hypertensive disease associated with unilateral renal artery stenosis

Renal autotransplantation was performed on 15 subjects with renovascular hypertensive disease owing to unilateral renal artery stenosis. Kidney survival was achieved in 14 cases. Followup for a minimum of 6 months showed 50 per cent of the patients to be cured, 28 per cent improved and 22 per cent unchanged according to the criteria described herein. There was an 85 per cent cure rate among a subgroup of patients less than 35 years old, with less than 20 months of hypertension and non-atherosclerotic lesions. Plasma renin assay was not found to be a good prognostic indicator as reported previously. In our hands the method showed only a 70 per cent correlation with the final results. Non-atherosclerotic lesions had a better prognosis.

Frequent falsely negative renal vein renin tests in unilateral renal parenchymal disease

A retrospective analysis of 12 hypertensive patients with unilateral renal parenchymal disease was done to evaluate the roles of renal vein renin testing and an operation. The patients were considered to have renal parenchymal disease on the basis of radiographic and/or pathologic findings. Only 2 patients had positive renal vein renin studies. Both of these patients were improved after unilateral nephrectomy but 1 had subsequent progression of disease and renal failure. Of the 10 patients with negative studies 5 had unilateral nephrectomy: 4 of them, nevertheless, experienced substantial improvement in the hypertension. It is concluded that hypertensive patients with unilateral renal parenchymal disease often can benefit from an operation and that renal vein renin testing in such patients can be misleading.