American journal of kidney diseases : the official journal of the National Kidney Foundation
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To investigate the clinical significance of urine anion gap and urine osmolal gap as indirect markers of urine acidification in chronic metabolic acidosis, we evaluated urine ammonium (NH4+), net acid excretion (NAE), urine anion gap (Na(+) + K(+) - Cl-), and urine osmolal gap (urine osmolality - [2(Na(+) + K(+)) + urea]) in 24 patients with chronic renal failure (CRF), eight patients with classic distal renal tubular acidosis (dRTA), and eight NH4Cl-loaded normal controls (NCs). Urine NH4+ excretion was lower (P < 0.001) in the CRF (5.4 +/- 0.6 mmol/d) and dRTA (19.2 +/- 2.7 mmol/d) patients than in the NCs (52.6 +/- 3.7 mmol/d); NAE was also lower (P < 0.001) in the CRF (9.8 +/- 1.6 mmol/d) and dRTA (16.7 +/- 4.7 mmol/d) patients than in the NCs (79.4 +/- 4.7 mmol/d). ⋯ When the data from all subjects were pooled, urine anion gap correlated inversely with urine NH4+ (r = -0.70, P < 0.001) and with NAE (r = -0.83, P < 0.001), and urine osmolal gap correlated positively with urine NH4+ (r = 0.69, P < 0.01) and with NAE (r = 0.71, P < 0.05). We conclude that impaired urine acidification in CRF and dRTA patients is associated with an increase in urine anion gap and a decrease in urine osmolal gap, and that both urine anion gap and urine osmolal gap correlate well with NAE as well as with urine NH4+.
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Case Reports
Acute renal failure associated with the retinoic acid syndrome in acute promyelocytic leukemia.
All-trans-retinoic acid is an effective agent to induce remission in patients with acute promyelocytic leukemia (APL). Unlike conventional chemotherapy, this drug exerts its effect by inducing differentiation of immature leukemic cells. ⋯ We describe a patient with APL in whom acute renal failure developed during treatment with all-trans-retinoic acid. Transient renal enlargement during a period of leukocytosis and a beneficial response to treatment with dexamethasone suggest that renal failure in this patient was probably related to the retinoic acid syndrome.
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Ethylene glycol poisoning classically presents as a metabolic acidosis with an increased anion gap. Metabolism of ethylene glycol to organic acids, and increased production of lactate, are responsible for the increased gap. We report the case of an alcohol user who consumed ethanol and ethylene glycol concurrently, and presented without acidosis, with a normal anion gap. ⋯ An increased osmolal gap, not accounted for by the serum ethanol level, proved to be an important clue to the diagnosis. In this patient, ingestion of ethanol inhibited the hepatic metabolism of ethylene glycol to organic acids, obscuring the diagnosis. In intoxicated alcohol users, even in the absence of metabolic acidosis, serum osmolality measurements and calculation of the osmolal gap may facilitate the rapid diagnosis of ethylene glycol poisoning.
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A variety of therapeutic approaches have been used both to prevent acute ischemic and nephrotoxic renal injury and to improve renal function and reduce mortality once acute renal failure (ARF) has developed. Unfortunately, there have been few rigorous assessments of the efficacy of these treatment interventions. The reasons for the lack of abundant critical data regarding treatment effects in ARF are several. ⋯ At best, the results are equivocal regarding the use of early and vigorous dialysis in ARF. However, there are recent impressive data indicating that the use of biocompatible membranes is efficacious in recovery and survival. There is no clear evidence that one form of nutritional therapy has advantages over others, but some level of amino acid supplementation in addition to basic energy replacement is supported by the overall data.
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With the increasing occurrence of adynamic bone disease, it is essential to determine the level of bone turnover in chronically dialyzed patients before instituting vitamin D therapy. To assess the value of serum parathyroid hormone (PTH) levels for prediction of bone turnover, we determined sensitivity, specificity, and predictive value positive of serum PTH, alone or in combination with other variables, in 79 patients who underwent one or two bone biopsies. Serum PTH levels were determined by a radioimmunometric assay and were obtained at the time of bone biopsies. ⋯ All hemodialysis patients younger than 45 years of age with serum PTH levels above 65 pg/mL (n = 15) had high bone turnover, and CAPD patients with low or normal bone turnover had higher serum ionized calcium. However, overall, bone turnover could not be predicted by serum PTH measurements in 30% of hemodialysis and 51.3% of CAPD patients. The data suggest that for patients with serum PTH levels between 65 and 450 pg/mL, bone biopsies are indicated to precisely assess bone turnover prior to initiation of vitamin D therapy.