Renin and hypertension in childhood

Pathologic characterization of a renin-secreting juxtaglomerular cell tumor in a child and review of the pediatric literature

We describe a rare case of renal hypertension in a 15-year-old caused by juxtaglomerular cell tumor and compare our findings with those of 20 children reported in the literature. These tumors are usually encapsulated and composed microscopically of polyhedral cells with bland nuclei separated by fibrovascular septa. Characteristic renin granules can be demonstrated by Bowie's stain or electron microscopy. These tumors are benign. Pathologists should recognize the morphologic characteristics of these tumors when dealing with renin-producing neoplasia.

Captopril in children with dilated cardiomyopathy: acute and long-term effects in a prospective study of hemodynamic and hormonal effects

Hemodynamic and hormonal effects of captopril were prospectively studied in 12 children (median age 5.8 years, range 4 weeks to 15 years) with dilated cardiomyopathy. A mean dose of 1.83 mg captopril/kg body weight was administered in three or four single doses depending on age. Left ventricular volume, ejection fraction (EF), cardiac index (CI), and systemic vascular resistance (SVR) were noninvasively determined by two-dimensional (2D) and Doppler echocardiography before and 2 days and 3 months after the onset of treatment. Blood pressure and heart rate were recorded as well. Additionally, on the day hemodynamic measurements were made, plasma renin activity (PRA), serum aldosterone, and plasma atrial natriuretic peptide (ANP) concentrations were determined. Plasma catecholamines were measured before and 2 days after captopril treatment. Concomitant medication was kept constant during the short-term phase of captopril treatment. During long-term therapy, diuretics were reduced according to the clinical status. Stroke volume (SVI) (-7%), end-systolic (ESVI) (-31%), and end-diastolic (EDVI) (-21%) volume indexes were significantly reduced (p less than 0.05) during short- and long-term therapy. The remaining hemodynamic parameters showed only minor, statistically not significant, changes. During short-term therapy, median serum aldosterone levels fell from 138-88.5 pg/ml (p less than 0.05), and plasma ANP decreased from 144-94 pg/ml (p less than 0.05). After 3 months these effects were less marked and statistically no longer significant. Changes in PRA and plasma catecholamines were not statistically significant at any time.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term follow-up of neonatal renovascular hypertension

Twelve neonates with hypertension have been followed for a mean of 5.75 years. At onset of hypertension, mean peak blood pressure was 159/99 mm Hg. Ten infants had umbilical artery catheters, 9 placed above the origin of the renal arteries. Radionuclide renal scan and/or angiography demonstrated renovascular disease, primarily renal artery thrombosis, in 11 infants. One-third of infants were asymptomatic, one-third had normal urinalyses and two-thirds had elevated peripheral plasma renin activities. Blood pressure normalized with medical therapy in all infants and remained normal when therapy was discontinued. Ten infants have normal creatinine clearances on follow-up but 5/11 have unilateral renal atrophy. Radionuclide scans have remained abnormal, even in infants without renal atrophy. In summary, neonatal renovascular hypertension is frequently secondary to renal artery thrombosis, associated with umbilical artery catheterization. Blood pressure usually normalizes with conservative medical management and remains normal off medications. Persistent abnormalities in renal size and function are common.

Impaired weight gain and renovascular hypertension

An eight month old infant was admitted to hospital because of poor weight gain. During the hospitalization she became unconscious and had convulsions. On these occasions a high blood pressure (205/120 mm Hg) was measured. In further evaluation of the hypertension, high plasma renin activity (32.8 ug/l/h) with a high serum aldosterone concentration (13000 pmol/l) was measured. Because of these findings renal angiography was performed: this revealed a stenosis of the left renal artery. A reconstruction of the renal artery was performed by a microsurgical technique and nine months after the operation the child was only mildly hypertensive but still required antihypertensive medication (propranolol 10 x 3, hydralazine 5 mg x 2): with this treatment her blood pressure was 110/80 mm Hg. After the operation her weight rose from below 2.5 percentile to the 10th percentile. The importance of blood pressure measurement in all children and infants admitted to hospital, regardless of their symptoms, is stressed.

Renin-angiotensin-aldosterone system

There is increased activity of the renin, angiotensin, aldosterone (RAA) system in infancy and childhood. An inverse relationship between plasma renin, aldosterone and age has been demonstrated. In childhood hypertension due to renovascular disease or pyelonephritic scarring peripheral plasma renin is increased. Renal vein renin measurements in children with renal hypertension have proved valuable in predicting surgical curability of the underlying lesion. The upper limit of normal for the renal venous renin ratio in normotensive children without renal disease is 1.5. Pharmacological blockade of the RAA system has a place in diagnosis and treatment of hypertensive children. The plasma renin aldosterone profile is diagnostically useful in the investigation of salt-wasting disease and can easily distinguish between aldosterone biosynthetic defects and pseudohypoaldosteronism.

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.

Plasma renin activity and aldosterone concentration in the human newborn

Twenty-one healthy newborn infants whose mothers had normal pregnancies and deliveries were studied. Plasma renin activity (PRA) and plasma aldosterone concentration (PAldo) were measured by semimicro methods in cord blood and on the 6th day of life. PRA and PAldo were increased in cord blood compared with values previously found in healthy infants between 1 month and 1 year of age. There was a twofold reduction in both values by the 6th day. PRA and PAldo were positively correlated when cord blood and 6th-day values were considered as a whole, but no significant correlations were found between either cord blood PRA or cord blood PAldo and their respective values on the 6th day. The PRA and PAldo findings were not related to birthweight, the infant's sex, weight change, 6th-day urinary sodium, or blood pressure measurements. The type of milk feed did not influence PRA but PAldo was slightly greater in bottle-fed babies on the 6 day. These observations confirmed that the inverse relationship between PRA, PAldo, and age extends into the neonatal period but they suggest that the balance of factors controlling these variables at birth is different to that operating at the age of 6 days.

Plasma renin activity and aldosterone concentration in children

Using semi-micro methods, plasma renin activity (PRA) and plasma aldosterone concentration (PA) were measured concurrently in 79 healthy children aged 1 month to 15 years to establish a reference range. PRA and PA varied inversely with age. Eleven children with renal hypertension had higher PRA and PA than age-matched controls. In contrast, PRA was much greater in 38 saline-depleted children. PA was not uniformly increased in this group and was within the normal range in children with adrenal diseases compared with the high values seen in other salt-wasting states. The findings emphasise the need to relate data from patients to age-matched control values before attempting interpretation and suggest that sodium depletion is a more potent stimulator of renin-aldosterone release than renovascular disease or renal scarring in children. Plasma renin-aldosterone profiles were also valuable in discriminating between renal and adrenal causes of salt loss in childhood.