Comparison of urine anion gap, urine osmolal gap and modified urine osmolal gap in assessing the urine ammonium in metabolic acidosis.

Twenty-four hour urine and spot urine samples from 29 patients with metabolic acidosis were collected for evaluation of urine ammonium in relation to urine anion gap, urine osmolal gap (OG) and modified urine osmolal gap (MOG). Their underlying diseases included SLE in 8, RTA in 7, CRF in 6, RPGN in 2 (one with SLE), Lowe syndrome in 2, on acetazolamide in 2, gastroenteritis in 2, and CAH in one. Twenty-three patients had normal serum anion gap (< 14 mmol/L). Their mean CO2 was 13.77 (9.4-17.9) mmol/L, net acid excretion (NAE) was 33.18 +/- 35.36 mmol/24 hour, NH+4 excretion was 29.16 +/- 31.97 mmol/24 hour. Neither the 24-hour urine nor spot urine anion gap correlated with corresponding urine NH+4 with or without adding urine HCO-3 in the calculation. Spot urine NH+4 correlated well with urine OG (r2 = 0.82, p < 0.001) and less with MOG (r2 = 0.339, p < 0.006). The urine osmolality was well correlated with the sum of 2 (Na+ + K+ + NH+4) + urea for both spot (r2 = 0.990, p < 0.001) and 24 hour urine (r2 = 0.907, p < 0.001) collection. Twenty-four hour urine NH+4 did not correlate with the OG or the MOG. There was no correlation between spot urine NH4/Cr ratio and 24 hour urine NH4/Cr ratio (r2 = 0.243, p = 0.53) nor between spot NAE/Cr ratio and 24 hour urine NAE/Cr ratio (r2 = 0.380, p = 0.014). Therefore in the presence of low urine NH+4 (< 100 mmol/L), urine osmolal gap may be used to determine urine NH+4 indirectly with good correlation. Twenty-four hour urine collection is still necessary to assess renal acidification.

Aciduria glutárica tipo I: una encefalopatía metabólica extrapiramidal / Type I glutaric aciduria: an extrapyramidal metabolic encephalopathy

Se describen tres niños, uno varón, de 4, 6 y 2 años de edad, afectados de aciduria glutárica tipo I. Su desarrollo fue normal hasta la segunda mitad del primer año de vida, cuando sufrieron alteración de conciencia y convulsiones, seguidas de pérdida de las habilidades adquiridas, distonía y movimientos anormales. La tomografía axial y resonancia nuclear magnética de cerebro mostraron atrofia frontotemporal y de los núcleos caudados y putámenes. Habíagran cantidad de ácidos glutárico, 3-hidroxiglutárico y glutacónico en orina y actividad disminuida de la enzima glutaril CoA deshidrogenasa en cultivos de fibroblastos de los tres niños, confirmándose así el diagnóstico de esta afección metabólica

Mechanism of hypercalciuria in experimental metabolic acidosis.

To study the mechanism of hypercalciuria in metabolic acidosis, ammonium chloride loading (long) test was performed in 68 stone formers and 50 controls. Administration of ammonium chloride in both stone formers and controls produced a significant increase in urinary volume, ammonium and calcium excretions, no change in plasma calcium and creatinine clearance and significant decrease in plasma bicarbonate. However, on the third day of ammonium chloride loading test, urinary ammonium excretion and plasma bicarbonate levels were significantly lower while urinary calcium excretion was significantly greater in stone formers than in controls. Thus calciuresis could be correlated with the degree of metabolic acidosis but not with the rate of urinary ammonium excretion.