[Renal mechanisms of protective potassium effect in essential hypertension]

In experiments on nonlinear rats, the renal functions were investigated at aqueous diuresis induced by intragastric administration of sodium potassium, potassium hydrocarbonate (20 mM/kg), and potassium succinate (10 mM/kg). We have found that the load by potassium raised glomerular filtration rate and sharply increased excretion of not only K+ but also Na+ and Cl- with urine, that led to hyponatremia and hypochloremia following hyperkalemia. In addition, the intracellular concentration of K+ increased more than extracellular one, especially after administrating KHCO3 and potassium succinate. It promoted potassium efflux from cells by concentration gradient, hyperpolarization of cellular membrane and vascular smooth muscle relaxation. Thus, these data explain renal mechanisms of a known protective effect of potassium at essential hypertension.

[Effect of praeruptorum caumarin on cardiac mass, myocardial [Ca2+]i and Na+, K(+)-ATPase, Ca2+, Mg(2+)-ATPase activity in renovascular hypertensive rats]

AIM

To investigate the preventive and reversional effect of praeruptorum caumarin compound on left ventricular hypertrophy in renovascular hypertensive rats (RHR) and its mechanism.

METHODS

The two-kidney-one-clip (2K1C) RHR model was used. The blood pressure, wet weight of the left ventricle, surface area of myocardial cells, resting [Ca2+]i level and Na+, K(+)-ATPase, Ca2+, Mg(2+)-ATPase activity of myocardial membrane and mitochondria were measured.

RESULTS

Praeruptorum caumarin 30 mg.kg-1.d-1 was given ig for 9 weeks from the 6th or 9th week after operation in the preventive or regressive group. The blood pressure, left ventricle wet weight and area of myocardial cells of the preventive and regressive group were significantly reduced than that of the LVH group. The resting [Ca2+]i of the both praeruptorum caumarin treated groups (121 +/- 13, 133 +/- 9 nmol.L-1) were lower than that of the LVH group (158 +/- 7 nmol.L-1). The KCl-induced [Ca2+]i elevation was decreased more significantly in preventive and regressive group than that of the hypertrophic myocytes. The activity of Na+, K(+)-ATPase and Ca2+, Mg(2+)-ATPase increased by 40% and 93% in the preventive group, 28.4% and 48.8% in regressive group than that of the LVH group.

CONCLUSION

Praeruptorum caumarin was shown to prevent and reverse hypertrophy of LVH by lowering [Ca2+]i and increasing the ATPase activity.

Renal cortical remodelling by NO-synthesis blockers in rats is prevented by angiotensin-converting enzyme inhibitor and calcium channel blocker

The cortical remodelling was studied when chronically nitric oxide synthesis (NOs) blockade (L-NAME-induced) hypertensive rats are simultaneously treated, or not, with angiotensin-converting enzyme inhibitor or calcium channel blocker. Four groups of eight rats each were studied as follows: Control (C), L-NAME (L), L-NAME+Enalapril (L+E) and L-NAME+Verapamil (L+V). The systolic blood pressure (SBP) was weekly recorded. The cortex of the left kidneys was analysed according to the vertical section design. The volume-weighted mean glomerular volume (VWGV) was made through the "point-sampled intercepts" method. Enalapril and verapamil were efficient in reducing the SBP in rats submitted to NOs blockade. Glomeruli had considerable alterations in L group rats (glomerular hypertrophy or sclerosis) and tubular atrophy. The VWGV was 100% greater in L group rats than in the C group rats, while it was 30% smaller in L+E and L+V groups than in L group. The tubular volume was 30-50% greater, while the tubular length was 20-30% smaller in the L group than in the other groups. The renal cortical region showed glomerular sclerosis/hypertrophy and tubular remodelling in rats with NOs blockade that was efficiently prevented with the simultaneous treatment with enalapril or verapamil.

Regression of renal vascular fibrosis by endothelin receptor antagonism

In previous studies, we have observed that endothelin participates in the progression of renal vascular and glomerular fibrosis during hypertension by activating collagen I gene synthesis. The present study investigated whether administration of endothelin receptor antagonists leads to the regression of renal sclerotic lesions. Experiments were performed in transgenic mice harboring the luciferase gene under the control of the collagen I-alpha2 chain promoter. Hypertension was induced by long-term inhibition of nitric oxide synthesis by N(G)-nitro-L-arginine methyl ester (L-NAME); systolic pressure gradually increased, reaching a plateau of 165 mm Hg after 10 weeks of hypertensive treatment. At the same time, collagen I gene expression was increased 2- and 5-fold compared with control animals in afferent arterioles and glomeruli, respectively (P<0.01). This increase was accompanied by the appearance of sclerotic lesions within the renal vasculature. When renal vascular lesions had been established (20 weeks of L-NAME), animals were divided into 2 subgroups: the one continued to receive L-NAME, whereas in the other, bosentan, a dual endothelin antagonist, was coadministered with L-NAME for an additional period of 10 weeks. Bosentan coadministration did not alter the increased systolic pressure at 30 weeks; in contrast, collagen I gene activity returned almost to control levels in renal vessels and glomeruli. In this subgroup of animals, renal vascular lesions (collagen and/or extracellular matrix deposition) and mortality rates were substantially reduced compared with untreated mice. These data indicate that endothelin participates in the mechanism(s) of renal vascular fibrosis by activating collagen I gene. Treatment with an endothelin antagonist normalizes expression of collagen I gene and leads to the regression of renal vascular fibrosis and to the improvement of survival, thus providing a complementary curative approach against renal fibrotic complications associated with hypertension.

Cardiorenal protection in diabetes

Diabetes is twice as common in hypertensive patients than in the general population, and is a major cause of cardiovascular morbidity. Diabetes is the most common cause of end-stage renal disease in the United States, and is primarily responsible for the 9% increase in prevalence of end-stage renal disease during the past 10 years. However, there is evidence that tight blood-pressure control can reduce the vascular complications of diabetes. This reduction was demonstrated in the United Kingdom Prospective Diabetes Study, in which patients who were randomized to a tight blood-pressure control group had 24% fewer vascular complications (including strokes and diabetic retinopathy) than patients in usual-care groups. Thus, the target goal for blood pressure in patients with diabetes is 130/85 mmHg. Microalbuminuria is an early marker of diabetic nephropathy, and is most pronounced in patients whose 24-hour blood pressure shows a nondipping pattern (failure of the blood pressure to fall at night). The prevalence of nondipping blood pressure is increased in patients with diabetes and in patients with renal disease due to other causes. Further, there is evidence that patients with nondipping blood pressure show more rapid deterioration of renal function than patients with dipping blood pressure. High nocturnal pressure in patients with nondipping blood pressure may accelerate glomerular damage. For example, studies of animals with diabetes have shown that the afferent glomerular arteriole is dilated when compared with the efferent arteriole, thereby exposing the glomerulus to the systemic arterial pressure. Numerous studies have shown that angiotensin-converting enzyme (ACE) inhibitors are superior to some antihypertensive agents (particularly beta blockers and diuretics) in the prevention of renal damage. This observation is based on results of a metaanalysis that demonstrated a 9%/year glomerular filtration rate decrease in patients taking beta blockers or diuretics, but only a 1%/year decrease in patients taking ACE inhibitors. The role of calcium channel blockers is more controversial, but there is evidence to suggest that nondihydropyridine calcium channel blockers may confer the same benefit as ACE inhibitors. Alpha blockers and angiotensin-receptor blockers show promise, but have been less widely studied.

Utility of coaxial technique for renal angioplasty in patients with a difficult-to-cross stenosis

The aim of this study was to evaluate the feasibility of coaxial approach in difficult-to-cross lesions in patients with failed percutaneous transluminal renal angioplasty by conventional over-the-wire exchange technique. Twelve stenoses in 10 patients (six women and four men; age range 19 +/- 7 years) with uncontrolled hypertension were treated by this method. The stenosis was caused by nonspecific aortoarteritis in 8 patients and fibromuscular dysplasia in 2 patients. It was ostial in seven and post-ostial in five vessels. Conventional exchange technique was unsuccessful in all of them. All procedures were done by femoral route. Technical success was seen in 11 (92%), without complication. The stenosis improved from 90 +/- 2.1% (range 80-100%) to 6 +/- 7% (range 0-20%), blood pressure decreased from 198 +/- 12.3 mm Hg (range 180-220 mm Hg)/130 +/- 6.7 mm Hg (range 120-140 mm Hg) to 119 +/- 5.7 mm Hg (range 110-130 mm Hg)/83 +/- 3.9 mm Hg (range 80-90 mm Hg), and number of drug treatments for hypertension fell from 3.6 +/- 0.52 (range 3-4) to 1 +/- 0.94 (range 0-3; p < 0.01). Percutaneous transluminal renal angioplasty resulted in "cure" in 3 patients and "improvement" in 7 patients. Follow-up period was 3-21 months (mean 6.4 months). No restenosis was detected. Coaxial approach is safe and effective in treating difficult-to-cross lesions in which renal angioplasty by conventional exchange technique is unsuccessful.

L-arginine restores the effect of ouabain on baroreceptor activity and prevents hypertension

In spontaneously hypertensive rats, ouabain exerts an excitatory effect on baroreceptor nerve activity (BNA). The aim of this study was to determine the effects of ouabain on BNA in other experimental models of hypertension and its interaction with nitric oxide. Rats were made hypertensive using the procedures for N(omega)-nitro-L-arginine methyl ester (L-NAME), deoxycorticosterone acetate (DOCA) salt, and 2-kidney, 1 clip (2K1C) hypertension models. In these groups, systolic arterial pressure was 195+/-7, 149+/-6, and 148+/-4 mm Hg, respectively, compared with 110+/-4 mm Hg in normotensive rats. Acute ouabain administration had an excitatory effect on BNA in normotensive rats (37+/-4%), an inhibitory effect in L-NAME hypertensive rats (-60+/-7%), and no effect in DOCA-salt and 2K1C hypertensive rats. The effects of ouabain were not related to arterial pressure levels, and no excitatory effect on BNA was observed in prehypertensive DOCA-salt rats. Long-term administration of L-arginine (3 g x kg(-1) x day(-1)) prevented DOCA-salt (121+/-8 mm Hg) and 2K1C (104+/-4 mm Hg) hypertension, markedly attenuated L-NAME (130+/-9 mm Hg) hypertension, and restored the excitatory effect of ouabain on BNA in these groups to levels similar to the normotensive rats and their respective control groups. We conclude that ouabain has a diverse effect on BNA in experimental models of hypertension, and it can be normalized by L-arginine. The data also indicate that nitric oxide may play a pivotal role in mediating the excitatory effect of ouabain on BNA, and we speculate that a therapeutic combination of ouabain and L-arginine may be beneficial in secondary hypertension.

Stents for atherosclerotic renovascular disease

There is extensive documentation of excellent clinical results with renal stents in patients who have technically failed angioplasty and who would have been expected to otherwise have a high incidence of clinical failure. In addition, the technical success of renal stents is vastly superior to that of conventional angioplasty in atherosclerotic renovascular disease, and stents have been a major factor in making the endovascular treatment of ASRVD both practical and reliable in experienced hands. Restenosis rates appear roughly equivalent or lower for stents versus PTA as far as can be determined without good comparative studies. Restenosis appears to be decreasing to 15%-20% in more recent series, perhaps because of the accumulation of knowledge regarding patient selection and techniques. It is, therefore, clear that the use of stents to treat technical failures of angioplasty will result in overall improved patency in the treated population; however, it remains to be determined whether stents should be routinely placed with the intention of inhibiting restenosis, in the presence of technically successful angioplasty with minimal residual stenosis or pressure gradient. Such a determination may require comparative study that is more complicated than a simple randomized comparison of angioplasty versus stents.

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.

A review of captopril renal scintigraphy and its effect on patient management

Renal artery stenosis is an important and potentially curable cause of hypertension. Captopril renography is now recognized to have a high sensitivity and specificity in its diagnosis. Ultimately, however, the result is of little benefit if it does not lead to a change in patient management. To assess how patient management was changed following the result of a captopril renogram, we reviewed the notes of 95 patients who had undergone this test over a 5 year period to identify renal artery stenosis. Of these patients, significant renal artery stenosis was suggested in 16 (17%), of whom only 9 (56%) underwent a change in management (7 proceeding to angiography with or without angioplasty, 2 having alterations in medication). In the 67 patients who had a negative renogram, 16 (24%) had an alteration in management (13 angiography, 3 altered drug treatment). Finally, of the 12 patients who had a non-diagnostic renogram, 7 (60%) had a management change (3 angiography, 4 altered drug therapy). Our results suggest that, despite evidence from the literature that captopril renography is both sensitive and specific for renal artery stenosis, clinicians still rely on other factors when determining who has significant stenosis and, therefore, who should proceed to a further investigation or have a change in medication. Ultimately, this reduces the clinical value of the test at present.

[Screening and diagnosis for eliminating renovascular hypertension. Value of 24-hour blood pressure monitoring and color-coded duplex ultrasound diagnosis]

BACKGROUND

Direct renal angiography is still the method of choice for identification of renal artery stenosis. Newer non-invasive diagnostic methods include color coded duplex sonography and also ambulatory 24-h blood pressure monitoring, since in a large proportion of patients with secondary forms of hypertension the usual blood pressure fall during nighttime disappears.

PATIENTS AND METHODS

In a prospective in-hospital study we investigated 86 patients with suspected renovascular hypertension. Circadian blood pressure was measured oscillometrically and color coded duplex sonography was performed immediately before direct renal angiography.

RESULTS

Angiography revealed renal artery stenosis (> or = 50%) in 42 patients. This compared to a sensitivity of 92.9% and specificity of 91.7% for the use of sonography in those patients (70.4%) who could be adequately examined. Mean 24-h pressure values as well as standard deviations of blood pressure means as an indicator for blood pressure variability were not different in the 2 groups of patients, when all the data were analysed together and also when the data for nighttime and daytime were examined separately. The percent of blood pressure fall during nighttime was also not different in the 2 groups. In both groups 4 hypertensive patients had a blood pressure increase during nighttime. In 11 patients without renal artery stenosis a blood pressure fall of < 10% was observed, compared to 12 patients with renal artery stenosis. The circadian pattern of pulse rate was similar in both groups.

CONCLUSION

We conclude that ambulatory blood pressure monitoring has a considerably lower diagnostic value for renal artery stenosis compared to angiography and also to color duplex sonography. This method therefore does not appear to be an appropriate screening approach for this kind of secondary hypertension. The color coded duplex sonography, however, seems to be the best non-invasive diagnostic method in those patients, who can be adequately examined.

Suppression of sympathetic nervous system attenuates the development of two-kidney, one-clip Goldblatt hypertension

PURPOSE

This study tried to assess the possible contribution of the sympathetic nervous system to the onset of two-kidney, one-clip (2K-1C) Goldblatt hypertension.

MATERIALS AND METHODS

The effect of chlorisondamine administration with or without subsequent splanchnicotomy on the development of hypertension was examined in 2K-1C rats with special reference to norepinephrine synthesis.

RESULTS

The 2K-1C rats were treated either with chlorisondamine or chlorisondamine plus subsequent splanchnicotomy, so that the development of hypertension was effectively arrested for 4 weeks. An apparently high rate of release of norepinephrine in 2K-1C rats was reduced by treatment with chlorisondamine plus splanchnicotomy. A similar trend was also seen in plasma norepinephrine concentration and norepinephrine clearance, to a lesser extent. There were significant positive relationships between percent change of systolic blood pressure and apparent rate of release of norepinephrine, plasma norepinephrine concentration and norepinephrine clearance in 2K-1C rats and 2K-1C + chlorisondamine + splanchnicotomy rats. There were no significant relationships in these parameters in sham-treated rats.

CONCLUSION

Increased sympathetic innervation appears to participate in the development of 2K-1C Goldblatt hypertension.

[Rational hypertension treatment]

The primary objective of antihypertensive treatment is to prevent the involvement of target-organs, including hypertensive vascular disease of the kidney or left ventricular hypertrophy. Antihypertensive treatment should not worsen other cardiovascular risk factors (e.g. lipids) or impair quality of life. Contemporary efforts to optimize antihypertensive therapy are focused on single-drug therapy and on individualizing treatment according to patients age, sex, race and the presence of concomitant illnesses and therapies, in order to improve compliance and reduce overall cardiovascular morbidity and mortality. Several antihypertensive drugs such as ACE-inhibitors, beta-adrenergic-receptor antagonists, calcium channel blockers, diuretics, alpha-adrenergic-receptor antagonists, and newer substances such as imidazoline-receptor antagonists and angiotensin-II antagonists are discussed.

Effect of primary balloon expandable renal artery stents on long-term patency, renal function, and blood pressure in hypertensive and renal insufficient patients with renal artery stenosis

Stents were deployed in 83 renal artery lesions of 63 subjects. All were hypertensive and 29 were renal insufficient (RI). Technical success was 99%. Long-term (11.3 +/- 3.8 months) patency was evaluated with ultrasound in 69 lesions (51 ostial). Technical success and long-term patency rates were not significantly different between ostial and non-ostial lesions. Ten lesions restenosed (14%). At most recent follow-up (10.2 +/- 4.5 months) hypertensive subjects were classified as cured (3.7%), improved (35.2%), unchanged (53.7%), or worse (7.4%). Systolic pressure was significantly improved throughout follow-up but diastolic pressure was only significantly lower at discharge. Based on serum creatinine, Rl subjects were classified as improved (36%), unchanged (46%), or worse (18%). Complications included transfusion (10), renal artery perforation (3), and renal failure (8). Eight transfused subjects also had retroperitoneal bleeds. Rl subjects were more likely to develop acute renal failure. Subjects who died (9) were more likely to have Rl at baseline and to suffer renal artery perforation during the procedure. Patient risk factors and procedural technique contributed to complications in this study, but for most patients stenting yielded excellent technical success and long-term patency for ostial and non-ostial lesions. The effect on blood pressure and renal function was favorable.

Renal effects of a high unsaturated fat diet in renal artery stenosis in rats

The renal effects of an unsaturated fat (UNSAT) diet in mild to moderate two-kidney, one-clip (2K1C) renovascular hypertension were evaluated. An UNSAT diet (37% by energy) prevented the development of hypertension compared to 2K1C rats fed a high saturated fat (SAT) (37% by energy) and a normal fat (CONTROL) (11% by energy) diet. Urinary sodium and fractional sodium excretion increased in 2K1C rats as compared to SHAM operated controls, regardless of the diet received. In the early weeks of the experiment (weeks 2-4 post-surgery to induce hypertension), an enhanced natriuresis occurred in the 2K1C UNSAT as compared to the 2K1C CONTROL and SAT diet groups. This resulted from an increase in the glomerular filtration rate (GFR in mls.min-1) as measured using the single-injection [51Cr] EDTA method (2K1C UNSAT; 1.99 +/- 0.18 versus 2K1C SAT; 1.27 +/- 0.09, p < 0.02; and versus SHAM CONTROL; 1.45 x 0.01; p < 0.02). The increased GFR was not associated with alterations in effective renal plasma flow (ERPF) as measured using the single-injection [125I] Na hippurate method. No differences in sodium excretion; GFR; ERPF or renal blood flow (microsphere technique) were noted between the 2K1C UNSAT and SAT diet groups at weeks 6-8 post-surgery, despite a continued antihypertensive effect of the UNSAT diet. Hence, the antihypertensive effect of an unsaturated fat diet in 2K1C renovascular hypertension in rats is associated with transient glomerular changes leading to an enhanced natriuresis.

Routine diagnostic imaging for childhood urinary tract infections: a systematic overview

OBJECTIVE

To assess the quality of the evidence on which current recommendations for routine diagnostic imaging for childhood urinary tract infection are based.

METHODS

A systematic overview of the literature using the MEDLINE database (1966 to October 1994), article bibliographies, and a manual search of current publications using Current Contents, was undertaken. Preset criteria were used to categorize study sample and design, and interrater reliability was assessed with a random sample.

RESULTS

A total of 434 publications were evaluated, and 63 studies met the criteria for inclusion. There was 100% interrater agreement on inclusion eligibility and design classification. No controlled trials or analytic studies evaluating routine diagnostic imaging were found. All 63 studies were descriptive, and only 10 were prospective. None of the studies provided evidence of the impact of routine imaging on the development of renal scars and clinical outcomes in children with their first urinary tract infection.

CONCLUSION

Methodologically sound, prospective studies are needed to assess whether children with their first urinary tract infection who have routine diagnostic imaging are better off than children who have imaging for specific indications. We conclude that the current recommendations are not based on firm evidence.

Antihypertensive effect of sesamin. II. Protection against two-kidney, one-clip renal hypertension and cardiovascular hypertrophy

We investigated the antihypertensive effect of sesamin, a lignan from sesame oil, using two-kidney, one-clip (2K,1C) renal hypertensive rats. After clipping the left renal artery, animals were assigned to either a normal diet group (control group) or a sesamin-containing (1% (w/w)) diet group (sesamin group). The sham-operated rats (sham group) were fed a normal diet and tap water. The systolic blood pressure of the control group increased progressively in comparison with the sham group. This 2K,1C-induced hypertension was markedly reduced by feeding the sesamin-containing diet. The systolic blood pressure after 4 weeks was 123.60 +/- 4.01 mmHg in the sham group, 187.43 +/- 5.69 mmHg in the control group and 145.57 +/- 6.78 mmHg in the sesamin group, respectively. There were significant increases in left ventricle plus septum weight-body weight ratio in the control group compared with the sham group. This rise was also significantly reduced in the sesamin group. When the thoracic aorta was histochemically evaluated, the wall thickness and wall-to-lumen ratio in the control group were significantly increased, compared with the sham group, indicating that vascular hypertrophy had occurred in the control group. The sesamin diet tended to ameliorate this vascular hypertrophy, although its effect was not statistically significant. These findings suggest that sesamin is useful as prophylactic treatment to combat the development of renal hypertension and cardiac hypertrophy.

Stenoses of renal branch arteries in fibromuscular dysplasia: results of percutaneous transluminal angioplasty

PURPOSE

To evaluate percutaneous transluminal renal angioplasty (PTRA) in the treatment of renal branch artery stenoses caused by fibromuscular dysplasia.

MATERIALS AND METHODS

The authors retrospectively studied the files of 20 consecutive hypertensive patients with 25 branch artery stenoses associated with 10 main renal artery lesions. Results at clinical and angiographic follow-up were assessed by means of life-table analysis.

RESULTS

PTRA was technically successful in 21 of the 25 renal branch artery stenoses (84%). One of the technical failures was treated by means of selective embolization. Nine of the 10 associated main renal artery lesions were successfully dilated, and the 10th was improved. Immediately after PTRA, at 6-month follow-up, and at long-term follow-up, 70%, 76%, and 68% of the patients, respectively, were cured and 25%, 24%, and 16% were improved. Stenosis recurred in 9% of the branch arteries and was associated with clinical relapse; these arteries were redilated, and all patients were considered cured at the second 6-month follow-up.

CONCLUSION

PTRA should be considered the first-line treatment for hypertension due to renal branch artery stenosis in fibromuscular disease.

Angiotensin AT1 receptor blockade by specific antibody prevented two-kidney, one-clip renal hypertension in the rat

The effect of chronic angiotensin AT1 receptor blockade by a specific antibody on the development of two-kidney, one-clip renal hypertension was studied in Wistar rats. Renal artery constriction resulted in a fast and large increase in blood pressure in comparison with that of control rats. On the other hand, the pre-immunization of rats with a small part of the angiotensin AT1 receptor completely prevented the development of renal hypertension. We conclude that the development of two-kidney, one-clip renal hypertension can be blocked by a specific antibody raised against a part of the angiotensin AT1 receptor.

Use of the thoracic aorta for renal arterial reconstruction

PURPOSE

Thoracic aortorenal bypass is a new technique for surgical renal revascularization in patients with severe atherosclerosis of the abdominal aorta. In such cases, the thoracic aorta is often free of disease.

METHODS

From 1989 to 1992, thoracic aortorenal bypass was performed in 23 patients with hypertension, abdominal aortic atherosclerosis, and celiac artery stenosis; in 21 patients, renal artery stenosis was present bilaterally or in a solitary kidney.

RESULTS

There was one operative death. Among the remaining 22 patients, hypertension was cured or improved after operation in 19 (86%), and renal function was improved or stable in 21 (95%).

CONCLUSIONS

Thoracic aortorenal bypass has several advantages and is a useful alternative to abdominal aortic replacement in selected older patients who require renal arterial reconstruction.

Renal artery stenosis: analysis of Doppler waveform parameters and tardus-parvus pattern

PURPOSE

The utility of Doppler parameters and waveform contour analysis for diagnosis of renal artery stenosis was studied in a hypertensive population screened for renovascular hypertension.

MATERIALS AND METHODS

The Doppler results were compared with those obtained with angiography in a prospective double-blind study involving 118 kidneys in 46 patients with hypertension and 11 potential renal donors with normal blood pressure. Doppler parameters measured in the distal renal artery included systolic acceleration, acceleration time, peak systolic velocity, deceleration in late systole, pulsatility and resistivity indexes, and waveform features in early systole.

RESULTS

Angiograms demonstrated 28 stenotic renal arteries. There was no significant difference between stenotic (> 50% diameter narrowing) and nonstenotic renal arteries for any parameters studied. When stenosis was further categorized as moderate (50%-79%) or severe (80%-95%), significant (P < .05) differences for acceleration time and systolic acceleration were found between nonstenotic and severely stenotic arteries.

CONCLUSION

Doppler characterization of the tardus-parvus phenomenon in the distal renal artery is not an adequate screening method for detection of renal artery stenosis.

The usefulness of the captopril test as a simultaneous screening for primary aldosteronism and renovascular hypertension

The usefulness of the captopril test as a simultaneous screening method for primary aldosteronism (PA) and renovascular hypertension (RVH) was evaluated in 111 patients with essential hypertension, and in 79 patients with secondary hypertension, which included 16 patients with PA and 18 with RVH. Plasma renin activity (PRA, ng/mL/h) and plasma aldosterone concentration (PAC, ng/dL) were determined before and 90 min after administration of 50 mg of captopril in the supine position on a normal NaCl diet. A cutoff point or a discriminant function in the screening was determined by discriminant analysis. A quadratic discriminant function of PRA and PAC after the captopril test identified patients with PA with a false negative rate of 6.3% (1/16), and a false positive rate of 0.6% (1/174) which was significantly lower than that of 3.4% at the basal state (P < .05). In the screening for RVH, the criterion of a postcaptopril PRA of greater than 10.6 ng/mL/h had a false negative rate of 5.6% (1/18) and a false positive rate of 15.1% (26/172). This false positive rate was also significantly lower than that using a criterion for precaptopril PRA of 2.21 ng/mL/h (P < .05). Accordingly, the captopril test was a useful method in the simultaneous screening for PA and RVH, and it may be particularly applicable in specialized hypertension clinics.