Renovascular hypertension: Surgical treatment

Renovascular occlusive disease is a common form of surgically remediable secondary hypertension. Operative options include: Bypass grafts, ex vivo reconstructions, endarterectomy, and transluminal dilation. Primary nephrectomy is undertaken only for irreparably diseased ischemic kidneys. Excellent results of surgical treatment reflect accurate identification of operative candidates and performance of appropriate operative procedures. Surgical benefits are more likely in pediatric patients and adults with fibrodysplastic or focal arteriosclerotic renovascular disease than in patients with clinically overt generalized arteriosclerosis. A review of 1631 renovascular hypertensive patients treated operatively documented a salutary outcome in 85–90% of patients.     

Renovascular hypertension: Etiology and pathophysiology

Evidence from animal studies demonstrates that the renin-angiotensin (ANG II) system and sodium retention play major roles in experimental renovascular hypertension (RVH). Two basic models have been described. In the first, one-clip two-kidney Goldblatt hypertension, the ischemic kidney secretes renin, which leads to increased ANG II formation and hence elevation of blood pressure (BP). As BP rises, sodium excretion by the intact contralateral kidney increases (pressure natriuresis); therefore, there is no sodium retention. In the second, one-clip one-kidney Goldblatt hypertension, the contralateral kidney is removed. In this case the pressure natriuresis can no longer occur, and sodium retention occurs. The ensuing expansion of plasma volume inhibits renin secretion, so that in this model the renin level is normal or low. Following the clipping of the renal artery, renal blood flow and pressure are maintained distal to the stenosis by an ANG II-mediated vasoconstriction. This acts preferentially on the efferent glomerular arterioles, so that the ratio of preglomerular to postglomerular resistance is reduced, which helps to maintain glomerular filtration despite the reduced renal perfusion pressure. In the contralateral kidney the afferent arteriolar resistance is increased, probably as a direct result of exposure to the higher intrarenal arterial pressure. ANG II constricts the efferent arterioles in the same way as in the ischemic kidney, so that the ratio of preglomerular to postglomerular resistance is unchanged. When an angiotensin converting enzyme (ACE) inhibitor is given, the efferent arterioles vasodilate. In the ischemic kidney this may produce a reduction of glomerular filtration rate (GFR), which is not seen in the contralateral kidney. Unilateral RVH in humans corresponds closely to the animal model of one-clip two-kidney hypertension. Plasma renin activity is usually high, and converting enzyme inhibitors lower BP effectively. The increased renin is due exclusively to increased secretion of renin by the ischemic kidney, and is completely suppressed in the contralateral kidney. It is not clear whether bilateral RVH corresponds to the one-clip one-kidney model, but there is circumstantial evidence to suggest that both renin and volume factors may be involved. The majority of cases of human RVH are caused by atheroma, which is commonly bilateral, or by fibromuscular dysplasia. The former tends to be associated with atheroma elsewhere in the arterial tree, and often progresses to complete occlusion and renal failure. The latter occurs in younger patients, and almost never progresses to complete occlusion.     

Renovascular hypertension. Diagnosis and intervention

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.     

Renovascular hypertension. Radiographic methods.

In recent years the choice of radiographic methods available in the investigation of renovascular hypertension has increased significantly. It can be difficult for the clinician to decide which patients will benefit from screening and which modality to choose. This article seeks to address some of these issues. The role of the plain radiograph and intravenous urogram are briefly mentioned. Doppler ultrasound, MR, CT and conventional arteriography are discussed in detail. Their advantages and pitfalls are reviewed. In our institution ultrasound to document renal size and gadolinium-enhanced 3-D MRA are our recommended first-line investigations unless MRA is contraindicated. Digital subtraction arteriography is reserved for the small subgroup in which MRA fails to obtain an answer, for whatever reason.     

Renovascular hypertension: nuclear medicine techniques.

Angiotensin converting enzyme inhibition (ACEI) renography is the only imaging examination that tests directly for the presence of renovascular hypertension (RVH); other imaging examinations test for the presence of renal artery stenosis (RAS). The goals of ACEI renography are two-fold: 1) to detect those patients with hypertension who have renal artery stenosis as the cause of their hypertension and who would benefit from revascularization, and 2) to determine which hypertensive patients do not have renovascular hypertension and obviate the expense and risk of angiography and, potentially, revascularization. This review summarizes general components of renal scintigraphy (pretest voiding, hydration, patient position, relative uptake, time to peak height of the renogram curve, 20 min/max ratio, postvoid images, quality control) as well as those components specific to ACEI renography (choice of radiopharmaceutical, choice of ACE inhibitor, angiotensin II receptor blockers, diuretics, parenchymal mean transit time, monitoring of blood pressure, 1 versus 2 day protocols and omission of the baseline study). ACEI renography is highly accurate in patients with suspected RVH who have normal or near normal renal function. In this patient population, the sensitivity and specificity of ACEI renography for renovascular hypertension exceed 90%; angiography as an initial approach is not cost effective. Data from 10 studies evaluating cure or improvement in blood pressure in 291 patients undergoing revascularization showed the mean positive predictive value of ACEI renography to be 92%. When azotemic patients present with suspected RVH, as many as 50% of patients may have an intermediate probability ACEI renogram and the sensitivity of detecting RVH falls to approximately 80% even when intermediate and high probability tests are combined.     

Midterm Outcomes of Angioplasty for Pediatric Renovascular Hypertension

PurposeTo evaluate the midterm outcomes of percutaneous transluminal renal angioplasty (PTRA) for pediatric renovascular hypertension (RVH).Materials and MethodsThe clinical data of patients who underwent PTRA for RVH in the authors’ hospital from 2012 to 2019 were retrospectively analyzed. Postprocedural blood pressure, glomerular filtration rate (GFR) of the affected kidney, restenosis, and complications were closely monitored.ResultsPTRA was performed in a total of 30 children (20 boys and 10 girls), with a mean age of 7.3 years ± 0.7 (range, 40 days to 13.9 years) and a mean weight of 25.0 kg ± 2.3 (range, 3.4–53 kg). The median follow-up period was 26.5 months (range, 1 month to 7.5 years). Technical success was achieved in 26 (86.7%) of the 30 patients. Restenosis developed in 3 patients (10.0%). Only 1 patient underwent stent implantation, and the stent fractured 8 months later, requiring further intervention. There were no other complications. In terms of clinical benefit of blood pressure control after the initial PTRA procedure, 15 patients (50%) were cured and 7 patients (23.3%) showed improvement. There was no significant difference in the etiology, lesion location, and lesion length between patients with clinical benefit and failure (P = .06, P = .202, and P = .06, respectively). GFR of the affected kidney was significantly improved from 19.9 mL/min ± 11.2 to 38.1 mL/min ± 11.9 at the 6-month follow-up after PTRA (P < .001).ConclusionsThe overall results of PTRA for pediatric RVH caused by different etiologies are promising. PTRA not only provided a clinical benefit of blood pressure control in 73.3% of the patients but also significantly improved the function of the affected kidney.     

Renovascular hypertension as a complication of umbilical arterial catheterization

Renovascular hypertension (RVH) in the neonatal period is frequently associated with thromboembolic complications of umbilical artery catheterization. Seven newborn infants with RVH were studied by angiography and/or radionuclide examination. Aortography and, in one case, selective angiography showed variable degrees of renal artery occlusion or attenuation. Thromboembolic defects were frequently present in other vessels. Radionuclide flow studies, renograms, and computer analysis of data (ADAC) demonstrated defects in renal function, indicative of renal ischemia. There was a high degree of correlation between angiographic and radionuclide studies. Successful medical management suggests a more conservative alternative to nephrectomy in the hypertensive newborn.     

肾动脉成形术治疗肾血管性高血压

评估DSA下的肾动脉成形术对治疗肾血管性高血压的作用。材料和方法：对6例不同病因所致的肾血管性高血压患者在DSA下作了球囊成形术治疗，包括大动脉炎和动脉粥样硬化各二例及纤维肌肉增生、及肾移植后所致的肾动脉狭窄各1例。结果：6例病人作球囊成形术均获得成功，术后血压有较为明显的下降。结论：DSA下的肾动脉成形术对治疗肾血管性高血压是一安全、有效的方法。     

Renovascular hypertension: quantitative renography as a screening test

The accuracy and reliability of quantitative gamma camera renography in screening for functionally significant renovascular hypertension was investigated. Renal perfusion, total and relative renal function, and parenchymal transit times were measured in 141 patients with recently diagnosed or severe hypertension. Renal angiography was performed in 13 of the 15 patients diagnosed as having evidence of renovascular hypertension. In all 13 either occlusion or significant stenosis of the renal artery was correctly predicted. Previous studies utilizing static images, playback buffers, and renograms have shown that these methods have excellent sensitivity, but relatively low specificity because of false-positive results. The addition of computer quantitation, including measurement of parenchymal transit times, has greatly improved the accuracy of this test. Quantitative renography can now be regarded as a reliable means of selecting patients for transluminal dilatation of stenosed renal arteries and for follow-up after this procedure.     

原发性高血压及肾血管性高血压患者巯甲丙脯酸前后肾动态显像的初步观察

用ＣＳ－７型ｒ动态显像及分析研究１０例肾动脉狭窄（ＲＡＳ），１０例高血压病Ｉ期，２０例高血压病Ⅱ期及１６例Ⅲ期高血压病患者口服巯甲内脯酸（Ｃａｐ，５０ｍｇ）前后肾功能及肾血流灌注显像的变化，同时测定周围静脉血浆肾素。结果发现８例肾动脉狭窄＜９５％的ＲＡＳ患者Ｃａｐ试验均阳性，２例狭窄＞９５％的ＲＡＳ患者基础显像患肾呈低水平延长线型肾图，肾功能明显降低，口服Ｃａｐ后肾功无变化；高血压病Ｉ至Ⅲ期患者Ｃａｐ试验的阳性率分别为０％，５％和２５％，但均为双侧性。Ｃａｐ试验诊断ＲＡＳ的敏感性，特异性，准确性分别为８０％，８９％，８８％；基础显像＋Ｃａｐ试验的敏感性，特异性，准确性分别为１００％，８７％和８８％。１０例ＲＡＳ患者口服Ｃａｐ后周围静脉肾素均明显增高。这些资料表明：Ｃａｐ介入的￣（９９ｍ）Ｔｃ－ＤＴＰＡ肾动态显像对单侧ＲＡＳ具有较高的敏感性和特异性，但肾动脉严重狭窄时，亦可呈阴性结果，双侧性Ｃａｐ试验阳性应考虑重度高血压病。     

一肾一夹肾血管性高血压动物模型的制作

目的研究一肾一夹(1K1C)肾血管性高血压动物模型的制作。方法选用200~220 g体重的SD大鼠,制作1K1C高血压大鼠模型。随机分为正常对照组、单肾对照组(1K)、1K1C组、1K1C+BEA组。使用药物2-溴乙胺氢溴酸盐(BEA)破坏肾髓质。采用尾动脉袖套法测量各组大鼠血压的变化。结果1K组大鼠血压4周后有明显升高,与正常对照组比较,差异有统计学意义(P<0.05),但是1K组大鼠与正常对照组大鼠4周后血压远未达到肾血管性高血压入选标准;1K1C组大鼠血压在1周后开始升高,2周时已达到本实验高血压入选标准;1K1C+BEA组血压升高更明显,4周时血压与1K1C组比较,差异有统计学意义(P<0.05)。结论本方法制作肾血管性高血压模型简单易行,成功率约80%。     

Renovascular hypertension following radiotherapy and chemotherapy treated by transluminal angioplasty

A man aged 33 with poorly controlled hypertension who had been treated with radiotherapy and combination chemotherapy for testicular teratoma 8 years earlier was found on arteriography to have 75% stenosis of the left renal artery and occlusion of the right renal artery. The stenosis was dilated by transluminal angioplasty and the hypertension adequately controlled. Patients who develop high blood pressure after abdominal radiotherapy with or without chemotherapy should be investigated for renal artery stenosis.     

Partial Renal Embolization for Pediatric Renovascular Hypertension Secondary to Fibromuscular Dysplasia

We report a 7-year-old boy with renovascular hypertension showing multiple stenoses and microaneurysms of the dorsal branch of the left renal artery caused by fibromuscular dysplasia. Hypertension was successfully treated with transcatheter alcohol and gelatin sponge embolization of the dorsal branch and its distribution. The vertebral branch remained intact. No severe complication was encountered. Loss of renal function by renal scintigraphy was minimal. The patient remains asymptomatic at 1 year. Received: 0/00/00/Accepted: 0/00/00