Renal disease in Lebanese children and adolescents. Findings in 118 consecutive percutaneous renal biopsies.

One hundred and eighteen consecutive percutaneous renal biopsies performed on 104 Lebanese children and adolescents at the American University of Beirut Medical Center over a period of six years were reviewed retrospectively. These patients represent the great majority of renal biopsies performed on Lebanese children and adolescents during that period. The kidney was localized with the help of an IVP or ultrasound and the procedure was performed without direct guidance. Adequate renal tissue was obtained in 112 biopsies with a success rate of 95.0%. The procedure appears to be safe in children. The renal diseases identified and their incidence is comparable to those reported in the literature. Acute nephropathy was seen in 9.6% of the patients, primary nephrosis in 45.0% and secondary glomerular disease in 14.6%. Tubulointerstitial disease, metabolic and hereditary diseases and end-stage renal diseases were found in 7.7%, 6.7%, and 5.8% of patients respectively. Some previously unreported conditions were identified.

Extra-adrenal pheochromocytoma.

Extra-adrenal pheochromocytomas, or gangliomas, develop in the paraganglion chromaffin cells of the sympathetic nervous system. They account for 10% of all pheochromocytomas in adults and 30-40% in children. These tumors are usually larger than their adrenal counterpart. The most common site of extra-adrenal phenochromocytomas is the para-adrenal area, but they also occur at the aortic bifurcation, chest, inferior mesenteric and iliac arteries, bladder, heart and brain. In this report, we describe a 13-year-old girl with a pheochromocytoma along the course of the left ureter, a finding which to our knowledge was previously described only once. Clinical presentation, diagnosis, and treatment are similar to adrenal tumors. Patients should be closely monitored with serum and urine catecholamine determination and MIBG scan to detect any recurrence or distant metastasis. Prognosis is usually good if the tumor is detected early to avoid major complications related to catecholamine excess.

Evaluation of renal function during childhood.

There are several methods to evaluate renal function during childhood. The use of serum creatinine, either alone or in combination with the Schwartz formula, is reliable and quick, but requires knowledge of conceptual age. A plasma creatinine concentration of 88.4 mumol/L (1.0 mg/dL), for example, represents normal renal function in an adolescent but more than 50% loss of renal function in a 5-year-old child. A timed urine collection for creatinine clearance is another evaluative method, but the adequacy of the urine collection always should be determined first. Urea clearance rarely is used to measure GFR because of the complex factors that influence urea excretion. Measurement of the disappearance of radioactive-labeled substances in plasma can be used to determine GFR. Radionuclide renal scans also can be used and offer the advantage of estimating the GFR of each kidney. Although infants and newborns have an intact urine diluting ability, their concentrating ability is impaired. The maximal urinary concentration in the neonatal period is less than 700 mOsm/kg, but reaches adult values of 1200 mOsm/kg by 6 to 12 months of life. Similarly, the infant kidney has a limited capacity for salt regulation, predisposing the infant to salt disturbances.

In vitro production of angiotensin II by isolated glomeruli.

The glomerulus has several components of the renin-angiotensin system (RAS). The purpose of this study was to evaluate the ability of glomeruli isolated from adult Wistar-Kyoto rats to produce angiotensin II (ANG II). When isolated glomeruli were incubated in Krebs buffer, the peak concentration of immunoreactive angiotensin (ANG) in the incubation medium, representing simultaneous production and degradation, occurred after 15 min of incubation (3.98 +/- 0.34 pg.mg protein-1.15 min-1, of which 18% was ANG II. When 125I-labeled ANG II was incubated with isolated glomeruli, the half-life of ANG II was 6.06 min. Hence, we estimated ANG II production at 3.77 +/- 0.21 pg.mg protein-1.15 min-1. When angiotensinogen-rich serum was added to the incubation medium, ANG concentration at 15 min increased by 500-fold (1,978 +/- 44 pg.mg protein-1.15 min-1, P < 0.001). ANG concentration in the glomerular incubate responded to perturbations known to alter systemic RAS. Enalaprilat, chymostatin, propranolol, and renin antiserum decreased ANG concentration in glomerular incubate, whereas salt depletion increased this (P < 0.05). We conclude that the rat glomerulus can generate ANG II independent of neural, hormonal, or vascular control.

Glomerular losartan (DuP 753)-sensitive angiotensin II receptor density is increased in young spontaneously hypertensive rats.

There is increasing evidence that an activated intrarenal renin-angiotensin system (RAS) alters renal hemodynamics and fluid balance and that such events may lead to the development of hypertension. To examine the role of the glomerular RAS in the development of hypertension in the spontaneously hypertensive (SHR) rat, we studied angiotensin (ANG) II receptors in isolated glomeruli from young (4- to 5-wk-old) and adult (10- to 12-wk-old) SHR and from age-matched, normotensive Wistar-Kyoto (WKY) rats. Glomerular ANG II receptor density in young SHR is 3-fold higher than in age-matched WKY rats (2033 +/- 154 versus 742 +/- 151 receptors/microns2; p < 0.05) and 1.5-fold higher than in adult SHR and WKY rats (1128 +/- 85 and 1198 +/- 181 receptors/microns2, respectively; p < 0.05). Additional studies demonstrated that the differences in receptor density are not related to disparity in receptor occupancy and that they are also independent of systemic ANG levels. Suppression of RAS by ANG converting enzyme inhibitors resulted in a 3-fold increase in receptor density in young SHR rats and a 4.5-fold increase in young WKY rats; receptor density remained greater in young SHR rats (5915 +/- 318 versus 3358 +/- 234 receptors/microns2, p < 0.05). Furthermore, competitive binding experiments using the nonpeptide ANG II antagonists losartan (AT1) and PD 123319 (AT2) indicate that the greater ANG II receptor density in the young SHR rats represents an increase in the number of a single population of AT1 receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Application since 1980 of antihypertensive agents to treat pediatric disease.

Strategies for using antihypertensive agents have changed significantly since 1980. This paper reviews clinical studies devoted to the use of antihypertensive agents in children beyond the newborn period. The availability of converting enzyme inhibitors and calcium channel blockers has significantly improved BP control in children with secondary forms of hypertension. The role of antihypertensive agents to chronically treat primary hypertension in children remains unclear. Additionally, some treatment protocols used in adults that apply to the treatment of hypertensive children and that have been used in the treatment of nonhypertensive disease are discussed. Preliminary studies suggest that the rate of decline of renal function in some forms of progressive renal disease may be retarded by the use of converting enzyme inhibitors.