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Biomedical subjects

A Vallo

Publications and source records attributed to A Vallo.

At least 37 records · Page 2Linked to original sources
PubMed1992

[Other indications for growth hormone treatment: chronic kidney failure and Turner's syndrome].

Recently, it has been demonstrated that treatment with growth hormone (GH) can accelerate height velocity in children with chronic renal insufficiency (CRI), after kidney transplantation and in Turner syndrome. The pathogenesis of growth retardation in CRI is complex. Possibly the most important factor involved is the presence of peripheral resistance to insulin-like growth factors. The administration of GH in high doses may restore catch-up growth, both in children with CRI and in kidney post-transplant patients. After 12 months of treatment height velocity increased from 4.3 to 6.6 cm/year in 4 children with CRI, and from 2.5 to 7.4 cm/year in 3 patients with kidney transplant. GH therapy alone, but even more in combination with oxandrolone increases the growth rate in Turner syndrome and may increase the final height, but the long-term results of this treatment are awaited. No undesirable collateral effects have been reported.

Body Height↗
PubMed1991

Neonatal citrullinaemia with satisfactory mental development.

In an infant with neonatal citrullinaemia therapy was instituted on day 1 of life with a low-protein diet and oral supplements of arginine, alpha-keto-acids, essential amino acids and carnitine. The latter may have contributed to the excellent clinical outcome, as evidenced by normal growth and satisfactory psychomotor development at 3 years of age.

Amino Acid Metabolism, Inborn Errors↗
PubMed1991

Renal potassium excretion is reduced in children with idiopathic hypercalciuria.

Increased luminal calcium decreases potassium secretion in microperfused rat distal tubule. To determine if such an effect is also present in vivo, we evaluated renal potassium excretion in 49 children with idiopathic hypercalciuria (urinary excretion of Ca = 5.5 +/- 1.3 mg/kg/day) and in 214 age-matched control children (urinary excretion of Ca = 1.9 +/- 0.3 mg/kg/day). In comparison to controls, hypercalciuric children had significantly increased levels of sodium excretion (fractional excretion of Na = 0.7 +/- 0.3 vs. 0.6 +/- 0.3%, respectively; p less than 0.001) and decreased levels of fractional potassium excretion (7.2 +/- 2.9 vs. 9.2 +/- 3.4%, respectively; p less than 0.001) and of the transtubular potassium concentration gradient (4.2 +/- 1.5 vs. 5.9 +/- 1.5, respectively; p less than 0.001). All indices of potassium excretion correlated significantly and inversely with urinary calcium excretion (p less than 0.001). After an oral calcium load, performed in 30 hypercalciuric children, the increased rates of urinary calcium excretion were accompanied by increased rates of urinary sodium excretion and by a significant decrease in the transtubular potassium concentration gradient. These results support the hypothesis that increased luminal calcium concentration also inhibits renal potassium secretion in man.

Administration, Oral↗
PubMed1990

Renal tubular acidosis.

The term renal tubular acidosis (RTA) is applied to a group of transport defects in the reabsorption of bicarbonate (HCO3-), the excretion of hydrogen ions, or both. On clinical and pathophysiological grounds, RTA can be separated into three main types: distal RTA (type 1), proximal RTA (type 2) and hyperkalaemic RTA (type 4). Some patients present combined types of proximal and distal RTA or of hyperkalaemic and distal RTA. Diagnosis of RTA should be suspected when a patient presents a normal plasma anion gap, and hyperchloraemic metabolic acidosis. A normal plasma anion gap (Na(+)-[Cl- + HCO3-] = 8-16 mEq/l) reflects loss of HCO3- from the extracellular fluid via the gastro-intestinal tract or the kidney, dilution of extracellular buffer or administration of hydrochloric acid (HCl) or its precursors. Distinction of RTA from other disorders is greatly facilitated by the study of the urine anion gap (Na+ + K+ - Cl-). This index estimates the urinary concentration of ammonium in a patient with hyperchloraemic metabolic acidosis. A negative urine anion gap (Cl- much greater than Na+ + K+) suggests the presence of gastro-intestinal or renal loss of HCO3-, while a positive urine anion gap (Cl- less than Na+ + K+) is indicative of a distal acidification defect. Determination of plasma potassium, of urine pH at low plasma HCO3- concentration, and of urine PCO2 and fractional excretion of HCO3- at normal plasma HCO3- concentration permits the differentiation between the various types of RTA.

Acidosis, Renal Tubular↗
PubMed1990

Transtubular potassium concentration gradient: a useful test to estimate renal aldosterone bio-activity in infants and children.

The present investigation was designed to validate the usefulness of transtubular potassium (K) concentration gradient (TTKG) as an indicator of aldosterone bio-activity in infants and children. TTKG was calculated by the formula: [K]urine: (urine/plasma)osmolality/[K]venous blood. We compared this index with fractional K excretion (FEK) and urine K concentration to urine sodium (Na) concentration ratio (UK/UNa) in 473 normal children aged 1 month-15 years. Values of TTKG followed a non-gaussian distribution (median, 6.3; 3rd centile, 4.1; 97th centile, 13.4). TTKG in infants (n = 108; median, 7.8) was significantly higher than in children (n = 365; median, 6.0). TTKG correlated directly with FEK and UK/UNa. Indices of K excretion were also assessed in 13 patients with hypo- and pseudohypoaldosteronism. TTKG values varied between 1.6 and 4.1 and were all below the 3rd percentile established for the age of the subject. We conclude that calculation of TTKG is an easy and sensitive method for the evaluation of mineralocorticoid action in distal and collecting tubules.

Adolescent↗
PubMed1990

Autologous mixed lymphocyte reaction and T-cell suppressor activity in patients with Henoch-Schönlein purpura and IgA nephropathy.

To assess the existence of persistent abnormalities in the cellular mechanisms regulating the immunoglobulin (Ig) synthesis in Henoch-Schönlein purpura (HSP) and IgA nephropathy, we studied through a hemolytic plaque assay (PFC) the response to the autologous mixed lymphocyte reaction (AMLR) and the T-cell suppressor activity in 24 patients with IgA nephropathy, in 20 individuals with inactive HSP (IHSP) and in 18 normal controls. In the group with IgA nephropathy there was a significant increase in the number of IgA-secreting cells after AMLR (p less than 0.01), and 9 of the 15 patients tested had an impaired generation of T-cell suppressor activity. No such abnormalities were found in individuals with IHSP. These findings support the existence of persistent defect in the mechanisms regulating the Ig synthesis, limited only to the patients with IgA nephropathy.

Adolescent↗
PubMed1989

"Chloride-shunt" syndrome: an overlooked cause of renal hypercalciuria.

The case of a 7-year-old boy with the normotensive form of "chloride-shunt" syndrome is described. An unusual feature was the clinical presentation with lithiasis, caused by marked hypercalciuria of renal origin. The present studies were carried out to investigate the nature of the renal tubular defect. Indices for proximal and distal sodium chloride reabsorption were increased during hypotonic saline diuresis. Baseline sodium chloride excretion was low but increased above the range of control values after acute furosemide administration. Baseline potassium excretion was low, was not modified by the infusion of sodium chloride and increased significantly during infusions of sodium sulphate or sodium bicarbonate. Calcium excretion remained unchanged during sodium chloride, sodium sulphate or sodium bicarbonate infusions, but increased after furosemide administration. Nasal insufflation of 1-desamino-8-D-arginine-vasopressin induced both an increase in potassium excretion and a decrease in calcium and magnesium excretion. Plasma atrial natriuretic peptide was increased and was not significantly modified by infusion of hypertonic saline or acute administration of furosemide. These findings indicate that the primary renal abnormality appears to be an enhanced tubular reabsorption of sodium chloride, apparently present in the proximal tubule and the ascending loop of Henle. The associated presence of hypercalciuria also suggests a transport defect in the distal tubule. Decreased potassium excretion probably depends on a voltage-shunting defect in the cortical collecting tubule, which can be reversed by increasing the delivery of non-reabsorbable anions or by enhancing the conductance of the luminal membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrial Natriuretic Factor↗
PubMed1988

Renal tubular hyperkalaemia in childhood.

Potassium output from the body is regulated by renal excretion, which takes place predominantly in the late distal and cortical collecting tubules. The accepted model for potassium secretion implies the accumulation of potassium into the cell by the activity of basolateral Na-K-ATPase and its exit through voltage-dependent conductive channels. The factors regulating renal potassium secretion are potassium intake, distal urinary flow, systemic acid-base equilibrium, aldosterone, antidiuretic hormone and, probably, epinephrine. Renal handling of potassium is best studied by the response to the acute administration of furosemide. This loop diuretic not only increases sodium and chloride excretion but also enhances potassium and hydrogen ion excretion and stimulates the renin-aldosterone axis. The term "renal tubular hyperkalaemia" refers to a tubular dysfunction where the hyperkalaemia is disproportionate to any reduction in glomerular filtration rate (GFR) and not due primarily or solely to aldosterone deficiency or to drugs impairing either mineralocorticoid action or tubular transport. The syndromes of renal tubular hyperkalaemia mainly observed in childhood are "chloride shunt" syndrome, hyporeninaemic hypoaldosteronism and primary or secondary pseudohypoaldosteronism. Differential diagnosis between these conditions is easily made if attention is paid to the level of GFR, presence of sodium wasting, activity of the renin-aldosterone axis and renal response to acute administration of furosemide.

Child↗
PubMed1987

Hypomagnesaemia of hereditary renal origin.

Cases of hypomagnesaemia of hereditary renal origin represent at least three different congenital disorders of tubular reabsorption of magnesium (Mg). Isolated familial hypomagnesaemia has been reported in a heterogeneous group of patients and an autosomal dominant pattern of inheritance has often been found to be present. Familial hypokalaemia-hypomagnesaemia, inherited as an autosomal recessive trait, has been reported in 17 patients and we now describe 3 additional cases. Hypomagnesaemia is accompanied by hypokalaemia, metabolic alkalosis, hypocalciuria and moderate sodium chloride wasting. Titration of renal Mg reabsorption indicates the presence of a low threshold but a normal Tm. The inherited defect is probably situated at the level of the distal convoluted tubule and mimics the therapeutic effect of thiazides. This condition is frequently confused with Bartter's syndrome. Familial hypomagnesaemia-hypercalciuria, also inherited as an autosomal recessive trait, has been reported in at least 15 patients and we now add 3 new cases. Hypomagnesaemia is always accompanied by hypercalciuria and nephrocalcinosis. Ocular abnormalities such as myopia and horizontal nystagmus are often present. Hypermagnesiuria is of a greater degree than that observed in the previous entity and reflects a low Tm of Mg reabsorption. The defect must be situated at the level of the ascending limb of the loop of Henle and affects the transport of both calcium and Mg but not of sodium and chloride. This condition has not been clearly separated from hereditary distal renal tubular acidosis in the literature.

Humans↗
PubMed1987

[Supplementation of maternal milk with calcium and phosphorus for the feeding of premature neonates weighing 1500 g or less. How long should it be continued?].

Feeding four preterm infants weighing less than or equal to 1,500 g with human milk supplemented with calcium (160-200 mg/kg/day) and phosphorus (80-200 mg/kg/day) until term postmenstrual age was reached, and suitable levels of plasma calcium, phosphorus and alkaline phosphatase and urinary excretion index of calcium and phosphorus were attained. When such a supplementation was suppressed at 38-40 weeks of postmenstrual age a rapid onset of biochemical disturbances was observed: a rise of plasma calcium (p less than 0.025) and alkaline phosphatase (p less than 0.0025) with a decrease of plasma phosphorus (p less than 0.005) and of urinary phosphate excretion (p less than 0.002). Reincorporation to former supplemented regime results in quick recovery of these parameters. Authors can assert that the necessity of calcium and phosphorus supplementation of human milk for less than or equal to 1.500 g preterm infant feeding exceeds the term postmenstrual age if suitable calcium and phosphorus levels are to be obtained.

Alkaline Phosphatase↗
PubMed1986

Hyporeninemic hypoaldosteronism in children with chronic renal failure.

The syndrome of hyporeninemic hypoaldosteronism (SHH) is not infrequent in adults with chronic renal failure caused by chronic tubulointerstitial nephritis, but it has been reported rarely in children. We present a systematic study of the interrelation between renal excretion of potassium and the renin-aldosterone axis in 23 children with CRF of different and unselected causes. Twenty children with chronic renal failure never had hyperkalemia, and both renin and aldosterone were normally stimulated by intravenous administration of furosemide, whereas three patients had moderate hyperkalemia (serum potassium concentration between 5.3 and 5.6 mEq/L) and failed to raise plasma renin activity and aldosterone values in response to furosemide. There three patients with SHH had lower basal and stimulated values of fractional potassium excretion than did patients with normokalemic chronic renal failure. Fractional potassium excretion was curvilinearly related to glomerular filtration rate (GFR), but in all three patients with SHH it was lower than expected for the level of GFR present. Fractional sodium excretion was also related to GFR, but no abnormalities were found. Two patients had hyperchloremic metabolic acidosis. After furosemide administration, they excreted an acid urine with low ammonium content, features characteristic of type 4 or hyperkalemic renal tubular acidosis. Prostaglandin E2 excretion was also significantly related to GFR, and appeared appropriate in two patients with SHH. The identification of three patients with SHH among 23 with chronic renal failure of unselected causes suggests that this entity is not rare in childhood.

Child↗
PubMed1986

Hyperkalemic distal renal tubular acidosis in salt-losing congenital adrenal hyperplasia.

Functional indices of distal urinary acidification were assessed in two male infants, aged 1 and 3 months, with salt-losing congenital adrenal hyperplasia. In both cases the diagnosis was sustained by the presence of elevated plasma levels of 17-hydroxyprogesterone, hyponatremia, hyperkalemia, metabolic acidosis and increased plasma renin activity. Both patients were unable to lower urinary pH below 5.9 either during acute ammonium chloride-induced acidosis or after i.v. administration of furosemide. One patient also failed to decrease urine pH below 5.5 and to increase urinary potassium excretion during sodium sulfate infusion. Oral sodium bicarbonate loading was given to both patients but failed to induce a significant increase in the urine minus blood PCO2 gradient. This gradient remained low also after neutral phosphate administration. Repeated studies after acute administration of fludrocortisone in one case or after prolonged administration of hydrocortisone in the other resulted in complete normalization of all functional studies. We conclude that salt-losing congenital adrenal hyperplasia can lead to hyperkalemic distal renal tubular acidosis in early infancy. The defective renal secretion of hydrogen ion and potassium is probably related to the abolishment of the negative potential difference in the cortical collecting tubule induced by the impaired reabsorption of sodium.

Acidosis, Renal Tubular↗