Renin-dependent hypertension in children with reflux nephropathy

Hypertension in infancy

Hypertension in infants is rare and requires a thorough evaluation. The incidence of hypertension in infancy has risen in recent years, reflecting both better monitoring methods and increasingly successful salvage of smaller and smaller newborns. Overall mortality and morbidity rates for uncontrolled hypertension in infants are unknown. With appropriate treatment, the prognosis for resolution of hypertension is good. In most cases, hypertension is short-lived and blood pressures return to normal even when medication is discontinued. Recent experience with improved antihypertensive agents in infancy has meant that nephrectomy for renovascular hypertension is rarely required. There is still much to learn about the indications for treatment of elevated blood pressures in infancy and the potential adverse effects of therapy. Infants with a history of neonatal hypertension should be followed closely because the long-term prognosis is not known and recurrence of hypertension remains a possibility. Because hypertension can develop in high-risk newborns following discharge from the nursery, these infants deserve routine blood pressure measurements as part of their outpatient follow-up.

Captopril test in children with reflux nephropathy

We studied the plasma renin activity (PRA) and blood pressure (BP) responses to a single oral dose of captopril in children with renal scarring due to vesicoureteral reflux. The test was performed on 19 children, of whom 13 were normotensive and 6 hypertensive. Basal PRA was within the normal range for age for all except 1 patient. Mean basal PRA values for normotensive and hypertensive patients were not significantly different. At 90 min post captopril, the mean PRA increase was 3.61 ng/l per second (SD = 7.07) in the normotensive group but only 0.77 ng/l per second (SD = 0.83) in the hypertensive group. In 11 patients the average systolic BP 60-90 min post captopril was 0.9%-12.4% lower than the basal value. Diastolic BP decreased after captopril administration in 10 patients and increased in 9. The changes in mean arterial pressure and PRA between 0 and 90 min post captopril were inversely correlated (r = 0.605, P less than 0.01). Because of the PRA responsiveness in the normotensive patients with renal scarring, we suggest that there was activation of the renin-angiotensin axis in this group. However, it is not apparent whether such patients are more at risk of developing hypertension at a later time.

Management of children with hypertension from reflux or obstructive nephropathy

During a ten-year period, 35 children presenting with vesicoureteral reflux, ureteropelvic junction obstruction, or a "small kidney" were found to be hypertensive. Of these, 15 subsequently underwent surgical procedures for relief of hypertension. Seven were "cured," six were "improved," and two were "unchanged." The severity of hypertension could not be correlated with the degree of reflux nor with the degree of obstructive uropathy. However, all children with reflux in our study who were hypertensive had some degree of calicectasis noted preoperatively on intravenous pyelogram. Also it was noted that hypertension may occur several years after successful anti-reflux surgery. Children with vesicoureteral reflux, ureteropelvic junction obstruction, or a small kidney need to have blood pressure determinations at regular intervals, even if all previous readings had been in the normotensive range and whether or not they were followed up medically or post surgically. We suggest that blood pressure determinations be made every three months for the first year after diagnosis of reflux or ureteropelvic junction obstruction, and at least once a year thereafter.

Blood pressure regulation, peripheral renin activity and aldosterone in patients with pyelonephritic renal scarring

Patients with renal scarring due to previous upper urinary tract infections (UTI) are at risk of developing hypertension and renal insufficiency. In this study glomerular filtration rate (GFR), systolic (SBP) and diastolic (DBP) blood pressure, peripheral renin activity (PRA), plasma (p-Aldo) and urine aldosterone (u-Aldo), the urinary excretion of sodium (UNa) and potassium (UK) and the fractional sodium (CNa/CIn) and potassium (CK/CIn) excretion were determined in 22 female patients with verified renal scarring and a history of febrile UTI and in nine age-matched healthy women with normal i.v. urograms. The patients had significantly lower GFR, higher SBP, higher PRA and higher CK/CIn than the healthy controls. A significant correlation between CNa/CIn and SBP (r = 0.51, P less than 0.05), DBP (r = 0.50, P less than 0.05) and PRA (r = -0.47, P less than 0.05) was found. The ratio of UK/UNa was significantly correlated to SBP (r = -0.43, P less than 0.05), DBP (r = -0.44, P less than 0.05), PRA (r = 0.65, P less than 0.01) and p-Aldo (r = 0.68, P less than 0.01). It is concluded that the renin-aldosterone system probably is involved in the pathogenesis of hypertension in patients with pyelonephritic renal scarring and that screening determinations of UNa and UK may prove useful for detection of individuals with increased PRA and p-Aldo.

Five year prospective study of plasma renin activity and blood pressure in patients with longstanding reflux nephropathy

Eight of 100 normotensive children who had pyelonephritic scarring secondary to urinary infection and vesicoureteric reflux were found in an earlier study to have increased plasma renin activity (PRA). Because the risk of these patients becoming hypertensive is between 10% and 20% and because renin activity may play a part in the pathogenesis of the hypertension, PRA and blood pressure were studied in 98 of the original group after five years of follow up. Two patients could not be traced, and other factors that might influence blood pressure or PRA led us to exclude 13 others, 10 of whom were girls taking oral hormonal contraceptives. Increased PRA was found in 11 of the remaining 85 patients but not in five of the eight patients with increased PRA in the first study. Of eight children identified as hypertensive in the follow up study, only three had had increased PRA five years previously. In normal children PRA decreases with age. In the initial study this tendency was less pronounced in children with renal scars, and in the follow up study it was reversed. This was also confirmed by PRA standard deviation scores, which showed a significant increase in PRA during the five years. PRA tends to rise in patients with pyelonephritic scars as they grow older. There was no direct correlation between blood pressure and PRA, plasma creatinine concentration, or degree of scarring. Analysis of blood pressure standard deviation scores, however, suggested an excessive rise in blood pressure during the five years.

Reflux nephropathy

The whole subject of reflux nephropathy, which may affect 1 in every 300 of the white female population, and is the second most common disease of the kidney in the young, is still bedevilled by a lack of information regarding many of its important aspects, and the absence of any coordinated action to obtain it. What is required above all else is a means of its early detection in very young children, so that it may be prevented, at least in its more severe forms. Its financial cost can only be surmised, but the treatment of its end-stages is likely to be in the region of a hundred million dollars a year. The cost in wastage involving, as it does, young people, particularly females, is incalculable.

Renin and blood-pressure in children with renal scarring and vesicoureteric reflux

Plasma-renin-activity (P.R.A.) was raised in 9 of 15 hypertensive children with pyelonephritic scarring secondary to urinary-tract infection and vesicoureteric reflux and also in 8 of 100 normotensive children with such scars. P.R.A. was much less likely to fall with age in normotensive children with renal scarring than in normal children. The identification of hyperreninaemic normotensive children with renal scarring is important, since P.R.A. may prove to be of value in early identification of children at risk of developing hypertension. A longitudinal follow-up is proposed to establish this hypothesis.

Nonrenovascular renal hypertension in children

Hypertension in children has been reported with increasing frequency because of increased awareness of its occurrence by clinicians. Renovascular lesions have been stressed in the past. However, in recent years, a number of nonrenovascular renal lesions have received attention and form the basis for this report. Unilateral chronic atrophic pyelonphritis, segmental unilateral pyelonephritis, the Ask-Upmark kidney, and unilateral renal hypoplasia have been associated with curable hypertension. The subject of juxtaglomerular cell hyperplasia, which has variably been reported in these cases, is reviewed. Ureteral obstruction, in the form of uretero-pelvic or ureterovesical junction obstruction, solitary renal cysts, the unilateral multicystic kidney, renal trauma, and renal tumors (Wilms' tumor and juxtaglomerular cell tumors) may also be associated with hypertension in children. Pheochromocytoma must be ruled out in all cases. Because of renewed interest, these nonrenovascular renal causes of hypertension are now likely to be diagnosed with increased frequency.

Pediatric hypertension as a delayed sequela of reflux-induced chronic pyelonephritis

Chronic pyelonephritis secondary to vesicoureteral reflux has been shown to cause occasionally systemic hypertension. The hypertension may occur in the presence or absence of bacterial urinary infection, is renin-mediated and may develop years after ureteral reimplantation. Surgical excision of a scarred atrophic renin-producing segment may result in amelioration of the hypertension or at least provide better medical control with less toxic antihypertensive agents. Surgical removal of renal tissue is not recommended in patients with depressed renal function unless the hypertension is malignant and uncontrolled.