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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pediatric nephrology 4 (1990), S. 268-275 
    ISSN: 1432-198X
    Keywords: Acid-base ; Metabolic acidosis ; Renal tubular acidosis ; Urine acidification ; Bicarbonate reabsorption ; Potassium ; Ammonium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The term renal tubular acidosis (RTA) is applied to a group of transport defects in the reabsorption of bicarbonate (HCO 3 − ), 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−≫Na++K+) suggests the presence of gastro-intestinal or renal loss of HCO3 −, while a positive urine anion gap (Cl−〈Na++K+) is indicative of a distal acidification defect. Determination of plasma potassium, of urine pH at low plasma HCO3 − concentration, and of urineP co 2 and fractional excretion of HCO3 − at normal plasma HCO3 − concentration permits the differentiation between the various types of RTA.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-198X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Pediatric nephrology 9 (1995), S. 423-427 
    ISSN: 1432-198X
    Keywords: Magnesium homeostasis ; Premature and full-term neonates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Renal handling of magnesium (Mg) has not been comprehensively studied in the newborn period due to the difficulty, until recently, of measuring the diffusible fraction of plasma Mg (UfMg). In the present study this methodology was used to assess Mg homeostasis in 84 newborn infants of different postconceptional age (26–42 weeks), weight (720–4,830 g) and postnatal age (1–72 days). Very premature infants (postconceptional age less than 35 weeks) had significantly higher values of plasma Mg than mature newborn infants. Plasma Mg related inversely to postconceptional age, weight, plasma total protein and plasma calcium, and directly to plasma potassium. Stepwise multiple regression analysis revealed that postconceptional age was the unique factor contributing to variations in plasma Mg. Plasma values of UfMg were the same in preterm as in term infants but, when expressed as a fraction of total plasma Mg (UfMg/Mg), they were significantly lower in very preterm infants. Fractional excretion of Mg and the ratio of urine Mg to urine creatinine did not vary as a function of postconceptional age. These results indicate that plasma UfMg is kept constant at different gestational ages despite variations in total plasma Mg; furthermore, no functional immaturity is present for renal tubular reabsorption of Mg, even in very low birth weight infants.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Pediatric nephrology 1 (1987), S. 465-472 
    ISSN: 1432-198X
    Keywords: Hypomagnesaemia ; Hypokalaemia ; Hypermagnesiuria ; Hypercalciuria ; Hypocalciuria ; Nephrocalcinosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 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 resessive 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.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-198X
    Keywords: Key words: Salt-losing nephropathy ; Renal sodium excretion ; Sodium ; Atrial natriuretic peptide ; Plasma renin-angiotensin system ; Vasopressin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. A state of normokalemic renal sodium wasting associated with an apparently inappropriate secretion of atrial natriuretic peptide (ANP) has not been previously recognized. We here report an 11-year-old boy who presented with a chronic “salt-losing” nephropathy manifested by normonatremic or mildly hyponatremic extracellular fluid volume depletion, hypodipsia, absence of salt appetite, normokalemic metabolic alkalosis, hyper-reninemic hyperaldosteronism, hypertrophy of the juxtaglomerular apparatus, and highly conserved capacities for concentrating diluting the urine. Plasma ANP values were paradoxically elevated (between 10 and 47 fmol/ml), despite the coexistence of intravascular volume depletion and increased plasma levels of renin and aldosterone. Although the patient had some clinical similarities to Bartter’s syndrome, fractional sodium chloride (NaCl) reabsorption during hypotonic saline diuresis was normal and no clinical amelioration was observed while on indomethacin therapy. Neither a tumor nor cardiac or cerebral abnormalities, which could be responsible for the increased ANP secretion, were detected. These clinical, biochemical, and histological features have not been previously described together and may represent a new clinical syndrome. The pathophysiology of this entity remains unknown, but an attractive, although unproven, hypothesis is that the renal defect in NaCl reabsorption in this patient could be related to an inappropriate and unregulated secretion of ANP.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Pediatric nephrology 2 (1988), S. 498-509 
    ISSN: 1432-198X
    Keywords: Potassium ; Hyperkalaemia ; Renal tubular acidosis ; Hypoaldosteronism ; Pseudohypoaldosteronism ; Furosemide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 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.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Pediatric nephrology 3 (1989), S. 113-121 
    ISSN: 1432-198X
    Keywords: Renal tubular disorders ; “Chlorideshunt” syndrome ; Hyperkalaemia ; Hypercalciuria ; Atrial natriuretic peptide ; Antidiuretic hormone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 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-reabsobable anions or by enhancing the conductance of the luminal membrane. Treatment with hydrochlorothiazide was successful in correcting most biochemical abnormalities but did not result in catch-up growth.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-198X
    Keywords: Potassium ; Renal potassium excretion ; Aldosterone ; Hypoaldosteronism ; Pseudohypoaldosteronism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 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: $$\frac{{[K]urine: (urine/plasma)osmolality}}{{[K]venous blood.}}$$ 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.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Pediatric nephrology 8 (1994), S. 262-262 
    ISSN: 1432-198X
    Keywords: Gitelman's syndrome ; Hypomagnesaemia ; Clearance studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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