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- Title
The urine-blood PCO<sub>2</sub> gradient as a diagnostic index of H<sup>+</sup>-ATPase defect distal renal tubular acidosis.
- Authors
Sejoong Kim; Jay Wook Lee; Junghwan Park; Ki Young Na; Kwon Wook Joo; Ahn, Curie; Suhnggwon Kim; Jung Sang Lee; Gheun-Ho Kim; Jin Kim; Jin Suk Han
- Abstract
The urine-blood PCO2 gradient as a diagnostic index of H+-ATPase defect distal renal tubular acidosis. Background. Urine pH during acidemia and urine PCO2 upon alkalization both may be useful to indicate H+ secretion from collecting ducts. The urine anion gap has been used to detect urinary NH4+ for differential diagnosis of hyperchloremic metabolic acidosis. We have previously demonstrated that the lack of normal H+-ATPase may underlie secretory defect distal renal tubular acidosis (dRTA). In this study we evaluated the diagnostic value of the urine-blood (U-B) PCO2 in H+-ATPase defect dRTA, and compared it with that of urine pH and urine anion gap during acidemia. Methods. In H+-ATPase defect dRTA, the diagnostic values of three urinary parameters were evaluated: ( 1) urine pH measured after acid (NH4Cl) loading; ( 2) urine-to-blood carbon dioxide tension gradient (U-B PCO2) during alkali (NaHCO3) loading; and ( 3) urine anion gap during acidemia. Seventeen patients were diagnosed as having H+-ATPase defect dRTA based on reduced urinary NH4+ and an absolute decrease in H+-ATPase immunostaining in intercalated cells on renal biopsy. Eight patients with non-dRTA renal disease served as control patients. Results. Upon NaHCO3 loading, U-B PCO2 was ≤30 mm Hg in all 17 dRTA patients and >30 mm Hg in all 8 control patients. With NH4Cl loading, urine pH was >5.4 in 15 of 17 dRTA patients and ≤5.4 in 7 of 8 control patients, and the urine anion gap was >5 mmol/L in 13 of 17 dRTA patients and≤5 mmol/L in 6 of 8 control patients. Therefore, the sensitivity and specificity of U-B PCO2≤30 mm Hg during NaHCO3 loading were both 100%, whereas those of urine pH >5.4 or urine anion gap >5 mmol/L during NH4Cl loading were below 90%. In control patients, the U-B PCO2 was found to be well correlated with the urinary NH4+ ( r= 0.79, P < 0.05). Conclusion. The U-B PCO2 during NaHCO3 loading is an excellent diagnostic index of H+-ATPase defect dRTA.
- Subjects
URINE; ADENOSINE triphosphatase; RENAL tubular transport disorders; KIDNEY tubules; KIDNEY diseases; RENAL biopsy
- Publication
Kidney International, 2004, Vol 66, Issue 2, p761
- ISSN
0085-2538
- Publication type
Article
- DOI
10.1111/j.1523-1755.2004.00801.x