Assuntos

RESUMO

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.

Assuntos

RESUMO

A syndrome of renal tubular resistance to aldosterone has been identified in infants with obstructive uropathy and urinary tract infection. Six infants (ages 9 days to 7 months) were seen with fever, vomiting, polyuria, dehydration, or failure to thrive. Urine cultures were positive for Escherichia coli. Radiologic studies demonstrated bilateral ureterohydronephrosis (four patients), left ureteral duplication with upper pole hydronephrosis (one), and left vesicoureteral reflux (one). The infants had hyponatremia, hyperkalemia, and metabolic acidosis. Plasma aldosterone concentration was markedly elevated, and plasma renin activity was similar to or higher than that reported in normal infants of comparable age. Fractional excretion of potassium was not significantly different from control values, both in absolute terms or when related to glomerular filtration rate, but fractional sodium excretion was significantly increased. The UK/UNa ratio was significantly lower in the patients. After medical or surgical therapy (when appropriate), all blood and urine determinations returned to normal, except for UK/UNa values, which although higher, remained significantly diminished. Our data indicate that a hyperkalemic salt-losing state can arise in infants with obstructive uropathy and urinary tract infection as a consequence of tubular unresponsiveness to aldosterone, and that the clinician should rule out such cause before establishing the diagnosis of primary pseudohypoaldosteronism.

Assuntos

RESUMO

The diagnosis in one infant of a severe state of chloride deficiency after ingesting a diet consisting exclusively of a modified cow milk formula containing only 0.5 mEq/100 kcal chloride ion led to the identification of 30 additional infants (age 2.6 +/- 0.7 months) fed the same commercial formula. The total absence of chloride in the urine was used as a biochemical index of subclinical dietary chloride deficiency. Serum and urine values were studied at diagnosis and 10 to 12 days after chloride replenishment, and compared statistically with the values obtained in a control group of 40 infants (age 2.8 +/- 1.2 months) fed exclusively a different modified formula containing an adequate chloride concentration. The outstanding laboratory abnormalities noted in the infants ingesting a low chloride formula were hypochloremia and metabolic alkalosis. Mean serum concentrations of potassium, urea, creatinine, and uric acid were in the normal range, but group values were statistically different from normal. A previously unreported finding was the demonstration of a significant elevation in the serum concentrations of calcium and phosphate and in the urinary excretions of calcium and magnesium, which persisted after almost complete recovery of the remaining biochemical disturbances. These results indicate the potential risk of nephrocalcinosis after dietary chloride deficiency.

Assuntos

RESUMO

Clinical and pathophysiologic studies were performed in five unrelated children with primary distal renal tubular acidosis who were diagnosed during infancy and followed for 3 to 9 1/2 years. All patients had permanent defects in hydrogen ion secretion, sodium reabsorption, and concentrating capacity. A transient, age-related, proximal tubular defect in sodium and bicarbonate reabsorption was also present. Renal bicarbonate wasting was mainly observed during the first years of life and progressively decreased with advancing age. Glomerular filtration rate remained within normal limits. Following sustained therapy with sodium and potassium bicarbonate, the patients had optimal growth, arrest of progression of nephrocalcinosis, and lack of other characteristic features of the disease with the exception of polyuria. Dosage of alkali was mainly determined by the magnitude of the renal bicarbonate loss and decreased progressively from a maximum of 3.9 to 10.0 mEq/kg/day during the first year of life to about 3 mEq/kg/day at or beyond 6 years of age. The total dosage of alkali required could be derived by the sum of the urinary excretion of bicarbonate plus 2 mEq/kg/day, which represents mean endogenous acid production. Although calciuria was normal when metabolic acidosis was corrected, patients with higher urinary sodium excretion had higher urinary excretion of calcium and thus were at greater risk of developing nephrocalcinosis if therapy was not carefully controlled.

Assuntos

Assuntos

RESUMO

Three unrelated infants with apparently distal RTA were investigated. Growth retardation, polyuria, nephrocalcinosis, inappropriately high urinary pH, and marked dependence of bicarbonate excretion on urinary flow were characteristic of the distal or classic form of RTA, but the urinary loss of bicarbonate at normal serum values exceeded that usually found in children or adults with this disorder. Renal tubular function was studied during hypotonic saline diuresis in the three patients and in seven healthy control infants of similar age. Fractional delivery of sodium to the distal nephron was significantly higher in the patients than in control subjects. Sodium transport at the diluting segment was not impaired. The results support the assumption that the bicarbonate wasting was the consequence of an increased delivery of this substance to an already impaired distal nephron and thus further inhibited the distal mechanisms of net acid excretion.

Assuntos

Assuntos