Renovascular hypertension

Bilateral Renal Artery Stenosis with Abdominal Aorta Coarctation in a Child with Severe Hypertension

This report describes the clinical course, diagnostic evaluation, and management of a 12-year-old child with bilateral renal artery stenosis (RAS) and concurrent narrowing of the abdominal aorta. The child was presented with a 2-day history of headache, vomiting, seizures, and right hemiparesis with normal findings from fundoscopic examination. There were no clinical or laboratory features suggesting the etiology of hypertension, nor had there been any diagnostic procedures in screening for hypertension due to bilateral RAS. Abdominal aortography confirmed the diagnosis of bilateral RAS and abdominal aorta coarctation. The hypertension was severe and resistant to combination of several antihypertensive agents. Aortobilateral renal bypass with autogenous saphenous grafts and midaortic angioplasty with polytetrafluoroethylene (PTFE) was performed. Histopathologic studies revealed subintimal fibrosis.

Angioplasty for renovascular hypertension in 78 children

OBJECTIVES

To evaluate the outcome of percutaneous transluminal angioplasty (PTA) in children with renovascular hypertension (RVH) treated at a single centre over 29 years.

METHODS

A retrospective study of the medical charts of all children with RVH who underwent PTA between 1984 and 2012. The primary outcome measurement was blood pressure (BP) achieved after the procedure. The BP before the procedure was compared with that at last available follow-up, 6 (range 0.6-16) years after the initial procedure.

RESULTS

Seventy-eight children with median (range) age of 6.5 (0.5-17) years were studied. Twenty-three (29.5%) had an underlying syndrome, 35 (44.9%) children had bilateral renal artery stenosis (RAS), 18 (23%) intrarenal disease and 11(14%) showed bilateral RAS and intrarenal disease. Twenty (25.6%) children had mid-aortic syndrome and 14 (17.9%) cerebrovascular disease. One hundred and fourteen PTA procedures were carried out including 31 stent insertions. Following PTA, BP was improved in 49 (62.8%) children and of those 18 (23.1%) were cured. Children with involvement of only the main renal arteries showed improved BP control in 79.9% of the children with cure in 39.5%. BP was intentionally maintained above the 95th centile for age and height in four children with coexistent cerebrovascular disease. No change in BP was seen in 18 children despite observed technical success of the PTA, and in seven children due to technical failure of the procedure.

CONCLUSIONS

PTA provided a clinical benefit in 62.8% of children with RVH.

Captopril-enhanced renal scintigraphy in the diagnosis of pediatric hypertension

Hypertension in childhood is no longer a rare condition mainly secondary to renal, or renovascular diseases, as a growing proportion of children are obese and hypertensive, with the phenotype of metabolic syndrome. Thus, we need to reconsider our practice in the examination of the hypertensive child and redefine the place of non-invasive methods for screening of renovascular hypertension, and specifically, to evaluate the value of captopril-enhanced renal scintigraphy at the two ends of the palette: the obese child with hypertension and the severely hypertensive prepubertal child. Renal artery stenosis in children is mainly due to fibromuscular dysplasia and stenoses associated with syndromes involving single or multiple smaller branch vessels. This explains the low specificity and sensitivity of the color-Doppler ultrasound method and captopril renal scintigraphy. Even the more sophisticated computed tomography (CT) and magnetic resonance imaging (MRI) angiographic techniques are, at present, not sensitive enough to exclude stenoses of the small branches definitely. Thus, children in whom there is a strong suggestion of renovascular hypertension should undergo angiography with a view to endovascular treatment, as non-invasive imaging has no significant benefit and might lead to a delay in treatment. In the cases when the probability of renovascular disease is moderate a basic assessment of renal function and structure is sufficient. In the neonate, catheter-associated thromboembolic disease is among the most common causes hypertension. It should be controlled medically until the patient is old enough to undergo angiography and angioplasty successfully. Thus, in this age group, there is a place for functional imaging with renal sonography and angiotensin-converting enzyme inhibitor (ACEI) renography to detect hemodynamically significant renovascular disease, with the limitations mentioned above. However, the rapid technical evolution of non-invasive methods requires periodic re-consideration of the actual standpoints.

Angioplasty for renovascular hypertension in children: 20-year experience

OBJECTIVE

Our aim was to evaluate the clinical outcomes, safety, and efficacy of percutaneous transluminal angioplasty for renovascular hypertension in children.

METHODS

A retrospective review of data for all children with renovascular hypertension who underwent percutaneous transluminal angioplasty at a single center between 1984 and 2003 was performed. Patients with renal transplants and inflammatory multisystem diseases were excluded.

RESULTS

Thirty-three children, 1.9 to 17.9 years of age (median: 10.3 years), underwent renal angioplasty and/or stenting. Underlying syndromes were present in 10. On angiograms, 16 had bilateral renal artery stenosis, 15 intrarenal disease, 8 aortic stenosis, and 7 cerebrovascular disease. Forty-eight percutaneous transluminal angioplasty procedures were performed, including 15 stenting procedures. There was a high rate of restenosis after stenting (7 of 19 cases, compared with 2 of 27 cases after balloon dilation). Outcomes were cured (ie, blood pressure normal without treatment) for 9 patients, improved blood pressure with same or reduced treatment for 7, blood pressure maintained in >95th percentile because of cerebrovascular disease for 2, no change in blood pressure despite technical success for 10, and technical failure for 5. Blood pressure control improved in 11 of 13 children who had main renal artery disease alone and in 6 of 20 with associated intrarenal disease or stenoses in other vascular beds. There was 1 procedure-related death and 5 minor complications.

CONCLUSIONS

Angioplasty produced clinically worthwhile improvement for approximately 50% of patients. High incidence rates of extrarenal involvement and intrarenal disease and a high restenosis rate after stenting accounted for poor blood pressure control in the rest.

A comparison of outcome criteria in the diagnosis of renovascular hypertension

The outcome criteria used for the diagnosis of renovascular hypertension (RVHT) following renal revascularization have not been validated. Differing criteria of indeterminate accuracy have yielded conflicting conclusions concerning the prevalence and efficacy of treatment of RVHT. We compared the accuracy of conventional outcome criteria used in the diagnosis of RVHT to that of novel, ordered outcome analysis to determine whether such an analysis might provide a more consistent means of diagnosing RVHT. Twenty-seven patients underwent intervention for treatment of presumed RVHT (group I), and 40 patients with presumed essential hypertension were treated with antihypertensive medication alone (group II). A standard dichotomized (improved or unimproved) outcome scheme and a five-level, ordered outcome scheme (ranging from definitely unimproved to definitely improved) were used to generate nominal outcomes of therapy for each patient. The resultant outcome groups were examined to determine the effect of such partitioning on blood pressure and medication requirements. To determine their diagnostic accuracy, the conventional and ordered outcome schemes were compared with a consensus outcome scheme derived from the use of numerous criteria. Significant correlations were observed between the ordered outcome score and posttreatment reductions in systolic blood pressure (r = 0.53, p = 0.007), diastolic blood pressure (r = 0.74, p = 0.0001), and medication score (r = 0.71, p = 0.0001). Overall diagnostic accuracy was estimated to be 91% for ordered criteria and 85% for dichotomized criteria. Correlation of the ordered and conventional schemes' assignments with the consensus scheme's assignments was 0.79 (p = 0.0001) and 0.63 (p = 0.0001), respectively. A simple, ordered outcome scheme compares favorably with the standard dichotomized scheme in assigning a diagnosis of RVHT to patients following renal revascularization or nephrectomy. The ordered scheme offers the advantages of simplicity and accuracy over current schemes.

Methods of renal blood flow measurement

Variations in regional renal blood flow have been implicated in a variety of disease states. Many techniques have been developed in an attempt to accurately assess these changes. The microsphere technique is the most widely used method at the present time. This technique allows focal measurements to be performed, but there is a conflict between the resolution of the method and the number of microspheres necessary in each sample. New imaging techniques such as tomography and autoradiography enable visual assessment of renal blood flow. Though there is no ideal method, these techniques have opened up new possibilities in the quantification of regional renal blood flow.

Regional renal blood flow in normal and disease states

Renal function is intimately dependent on renal blood flow. Alterations in either total or regional renal blood flow have major consequences for renal function. Through homeostatic mechanisms the kidneys are able to maintain relatively stable rates of flow over a wide range of perfusion pressures. A combination of neural, endocrine, exocrine and autocrine signals serve to regulate renal blood flow at both local and systemic levels. Alterations in the balance of these systems occur in the presence of certain pathophysiological conditions and an understanding of the subsequent changes in regional renal blood flow distribution aids in the understanding of the associated changes in renal function. The regulation and distribution of regional blood flow and the effects of surgical and pathophysiological conditions on these factors are reviewed.

3H-naloxone binding in brain regions of normotensive Wistar, spontaneously hypertensive and renal hypertensive rats

In order to study the role of opioid receptors in two models of experimental hypertension the binding of 3H-naloxone to membranes prepared from discrete brain regions and spinal cord was determined. Renal hypertensive rats (RHR) were found to have a greater density of 3H-naloxone binding sites in the hippocampus and hypothalamus when compared to spontaneously hypertensive rats (SHR) and normotensive Wistar rats (NR). The apparent dissociation constant (Kd) for 3H-naloxone binding did not differ between groups.

Spatial navigation learning in spontaneously hypertensive, renal hypertensive and normotensive Wistar rats

The relation between blood pressure and cognitive performance was assessed in the spatial navigation task. Spatial learning by rats with spontaneous hypertension (SHR) and Goldblatt renal hypertension (RHR) was compared with that of normotensive Wistar rats (NR). The task required the rats to escape from water by finding a submerged and hidden platform. It was found that SHR rats showed improved learning capacity in the maze task in acquisition compared to the RHR and NR groups already on Day 1 and Day 2. The performances of all tested groups reached almost similar asymptotic level on Day 4 and in the probe trial on Day 5. After a reversal training the SHR rats did not show preference to swim in the new platform position quadrant. The present results confirm earlier reports on different behavioural characteristics associated with hypertension.

Renal artery stenosis: current diagnosis and treatment

OBJECTIVE

To provide an overview of the current approaches to management of renovascular disease.

DATA SOURCES

A literature review was performed and key references are provided relating to diagnostic tests, particularly captopril renography and renal duplex scanning. Options for treatment are reviewed from published series to December 1991. We also draw on the experience of our own Unit.

STUDY SELECTION

Data and opinions from five general reviews of renovascular disease, 10 articles on diagnostic tests and five articles relating to therapeutic approaches are summarised.

CONCLUSION

There is no simple screening test for renovascular hypertension that can be applied to an unselected population of hypertensive subjects. The diagnosis depends on judicious use of non-invasive screening tests in those subjects in whom one suspects, on clinical grounds, that there may be an underlying renovascular lesion. Captopril renography and duplex scanning of renal arteries are the most reliable non-invasive screening tests. A team approach with collaboration of hypertension specialist/vascular physician, vascular surgeon and experienced interventional radiologist is important for rational management and we would emphasise the importance of audit procedures.

Enhanced disruptive spatial learning effect after sufentanil in renal hypertensive rats versus normotensive rats

The effects of the peripherally administered sufentanil citrate (S), a potent opioid agonist with high affinity for mu receptors on the spatial navigation task, were tested in normotensive Wistar (NR) and renal hypertensive rats (RHR). Rats were injected subcutaneously once daily in doses of 0.25 or 1 microgram/kg S before the water maze training. In NR rats, weak effects of 0.25 micrograms/kg S and impairments after 1 microgram/kg S were seen, whereas in RHR 0.25 and 1 microgram/kg S showed clearcut impairments. These data from the Morris water maze task support previous reports that RHR have an increased sensitivity for opioid agonists.

Renal revascularization: indications and results

Although the prevalence of renovascular hypertension is low, clinical criteria can select a population in which renovascular hypertension is significantly more common (prevalence of 15%). In these selected patients, it is appropriate to proceed to a screening modality to look for a significant renal artery stenosis. Choices of the noninvasive methods include captopril-enhanced renal scintigraphy, magnetic resonance (MR) angiography, and intravenous digital subtraction renal angiography (DSRA). Intraarterial DSRA or conventional arteriography may also be used to reliably detect renal artery stenosis, with the advantage that both the diagnostic and the interventional procedure can be performed at the same setting. A high percentage of a group of patients who are selected by means of clinical and arteriographic studies will benefit from revascularization. Thus, the renal artery angioplasty may be performed during the arteriogram in which the stenosis is confirmed.

Renovascular disease in childhood

Fifty-four children referred for investigation of hypertension had renovascular disease. In eight patients it was associated with neurofibromatosis, in three with idiopathic hypercalcemia of infancy, and in five cases it followed an arteritic illness. Fibromuscular dysplasia was the underlying abnormality in the majority of cases (46%). Twenty-six patients (48%) were first seen with accelerated hypertension; 38 children (70%) had bilateral renal arterial disease, and in 41 (76%), disease of the small intrarenal vessels was found. Renal vein renin ratios indicated unilateral disease in 31 cases; the results correlated with arteriography findings in 32 (62%) of 51 patients. Eleven children also had the middle aortic syndrome, and 9 of 16 patients, investigated by cerebral arteriography because of cranial bruits or focal neurologic signs, had cerebral vascular abnormalities. Twenty patients were treated surgically--10 by reconstructive procedures, 11 by nephrectomy or heminephrectomy, and 6 by transluminal angioplasty. Of these, 9 (45%) are normotensive with no treatment, 10 have a decreased requirement for antihypertensive drugs, and 1 had no improvement. Thirty-four patients were treated medically because of the extent of their disease; two patients have died of hypertensive complications. We conclude that renal vascular disease in children is often widespread, may be associated with intracerebral vascular disease, frequently affects both kidneys, including both intrarenal and extrarenal vessels, and is therefore not always amenable to surgical intervention and cure.

Morphological changes and alterations in regional intrarenal blood flow induced by graded renal ischemia

A model of renal ischemia was used to study morphological changes and alterations in intrarenal blood flow. Renal artery blood flow was reduced from 120 to 20 ml./minute (normal 172 +/- 14) for 3 weeks. Morphological changes were assessed histologically, and by electronmicroscopy. Intrarenal blood flow was determined using microspheres. Flow rates less than 80 ml./minute resulted in a progressive loss of renal volume with arterial thrombosis and renal infarction at 20 ml./minute. Histological changes included loss of glomerular volume, tubular dilatation (60 ml./minute), tubular cast formation (50 ml./minute) tubular atrophy, interstitial fibrosis, arteriolar thickening (40 ml./minute) and glomerular hyalinization (30 ml./minute). Electronmicroscopy changes at 60 ml./minute (loss of glomerular microvasculature, unfolding of glomerular vascular tuft, appearance of blind ending vessels) progressed to disruption of glomerular architecture noted at 30 ml./minute. Narrowing of medullary blood vessels (60 ml./minute) and neovascularisation (40 ml./minute) was observed. Progressive ischemia decreased medullary, inner cortical and outer cortical blood flow (5.9 to 2.1 ml./minute/gm.) p less than 0.01, with a compensatory increase to the opposite kidney.

Renin-producing renal cell carcinomas--clinical and experimental investigations on a special form of renal hypertension

The pathogenetic relationship between tumour and hypertension was investigated in 129 patients with renal cell carcinoma, of whom 41 (31.8%) were hypertensive. Of these 41 patients with renal tumours and hypertension, 6 (14.6%) were found to have primary reninism. In these patients the plasma renin activity in blood from the renal veins showed a tumour kidney to contralateral kidney ratio of between 4 and 7, and 2 patients also had secondary hyperaldosteronism. In the same 6 cases the renin content in the renal tumour tissue was significantly higher than that in tissue from the adjacent tumour-free renal cortex of the ipsilateral kidney. Immunohistochemical demonstration of renin in the tumour was only possible in these 6 cases. In 5 of these patients blood pressure returned to normal following nephrectomy; in the 6th case there was a drop in blood pressure after nephrectomy. In 3 renin-positive tumours examined, autonomous renin production was demonstrated in cell culture. Renin-producing renal cell carcinomas are an uncommon cause of renal hypertension. The differential diagnosis of hypertension should therefore also include renal tumour.

The natural history of atherosclerotic and fibrous renal artery disease

From 1969 to 1979, 169 patients with two or more renal angiograms for renovascular disease (85 atherosclerotic, 75 fibrous, 9 atherosclerotic and fibrous) were reviewed in an attempt to characterize progression of disease and to determine clinical markers of progression. Progression of renal artery atherosclerosis was observed in 37 patients (44 per cent); progression to complete occlusion was observed in 14 patients (16 per cent). In the 66 patients with medial fibroplasia, progression was observed in 22 patients (33 per cent). Serial serum creatinine measurements in conjunction with measurements of kidney size may be used as markers of progressive atherosclerotic renovascular disease. These clinical markers did not represent progressive disease for individuals with medial fibroplasia.