Kim H Y, Han J S, Jeon U S, Joo K W, Earm J H, Ahn C, Kim S, Lee J S, Kim G H
Department of Internal Medicine, Chungbuk National University, South Korea.
Clin Nephrol. 2001 Jun;55(6):448-52.
The fractional excretion of anions has been proposed as a new index for the differential diagnosis of metabolic acidosis, identifying the properties of the conjugate base by examining the renal handling of the anion. Here, we investigated clinical significance of the fractional excretion of anions in pathophysiologic diagnosis of metabolic acidosis by measuring urine ammonium (NH4+) excretion, the ratio of A plasma anion gap/delta plasma HCO3- concentration (deltaAG/deltaHCO3-), and fractional excretion of anions in three different groups of metabolic acidosis: acid overproduction (8 patients with lactic acidosis, 8 with diabetic ketoacidosis, 3 with hippuric acidosis following glue sniffing), acid underexcretion (10 patients with chronic renal failure) and normal controls (10 normal volunteers who underwent 3-day NH4Cl loading). As expected, urine NH4+ excretion was higher in overproduction acidosis than in acid-loaded normal controls (88.1 +/- 12.3 vs. 54.0 +/- 3.7 mmol/day, p < 0.05), and it was lower in chronic renal failure than in acid-loaded normal controls (12.8 +/- 1.7 vs. 54.0 +/- 3.7 mmol/day, p < 0.05). The fractional excretion of anions had no difference between overproduction acidosis and chronic renal failure (41.2 +/- 42.8% vs. 41.0 +/- 8.1%). However, the fractional excretion of anions showed significant differences between the subgroups in acid overproduction (lactic acidosis, 4.7 +/- 0.3%; diabetic ketoacidosis, 45.8 +/- 3.1%; hippuric acidosis, 126.0 +/- 14.4%; p < 0.05). The ratio of plasma deltaAG/deltaHCO3- also exhibited significant differences between the subgroups in acid overproduction (lactic acidosis, 1.5 +/- 0.1; diabetic ketoacidosis, 1.0 +/- 0.1; hippuric acidosis, 0.3 +/- 0.1; p < 0.05). There was an inverse linear correlation between the fractional excretion of anions and the ratio of plasma deltaAG/deltaHCO3- (r2 =-0.89, p < 0.05). In conclusion, determination of the fractional excretion of anions may provide a useful clue to the differential diagnosis of metabolic acidosis caused by acid overproduction.
阴离子排泄分数已被提议作为代谢性酸中毒鉴别诊断的一项新指标，通过检查肾脏对阴离子的处理来确定共轭碱的性质。在此，我们通过测量三组不同类型代谢性酸中毒患者的尿铵（NH4+）排泄、血浆阴离子间隙/血浆碳酸氢根浓度变化比值（deltaAG/deltaHCO3-）以及阴离子排泄分数，来研究阴离子排泄分数在代谢性酸中毒病理生理诊断中的临床意义：酸生成过多（8例乳酸酸中毒患者、8例糖尿病酮症酸中毒患者、3例吸食胶水后导致马尿酸酸中毒患者）、酸排泄不足（10例慢性肾衰竭患者）以及正常对照组（10名接受3天氯化铵负荷试验的正常志愿者）。正如预期的那样，酸生成过多型酸中毒患者的尿NH4+排泄高于酸负荷正常对照组（88.1±12.3对54.0±3.7 mmol/天，p<0.05），而慢性肾衰竭患者的尿NH4+排泄低于酸负荷正常对照组（12.8±1.7对54.0±3.7 mmol/天，p<0.05）。酸生成过多型酸中毒与慢性肾衰竭患者的阴离子排泄分数无差异（41.2±42.8%对41.0±8.1%）。然而，酸生成过多型酸中毒各亚组之间的阴离子排泄分数存在显著差异（乳酸酸中毒，4.7±0.3%；糖尿病酮症酸中毒，45.8±3.1%；马尿酸酸中毒，126.0±14.4%；p<0.05）。酸生成过多型酸中毒各亚组之间的血浆deltaAG/deltaHCO3-比值也存在显著差异（乳酸酸中毒，1.5±0.1；糖尿病酮症酸中毒，1.0±0.1；马尿酸酸中毒，0.3±0.1；p<0.05）。阴离子排泄分数与血浆deltaAG/deltaHCO3-比值之间存在负线性相关（r2 = -0.89，p<0.05）。总之，测定阴离子排泄分数可能为酸生成过多所致代谢性酸中毒的鉴别诊断提供有用线索。
