Progression of Metabolic Acidosis in Chronic Kidney Disease

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Background: Metabolic acidosis, which is classified into either high anion gap type (high-AGMA) or non-anion gap type (non-AGMA), is a common complication in chronic kidney disease (CKD), but its development in CKD is obscure. Methods: Records of venous blood gas at a general hospital (2015–2017) were assessed by the physiological approach. Excluding records of primary respiratory disturbances, parameters of high-AGMA and non-AGMA (∆AG and ΔΔ, respectively) were compared with the estimated glomerular filtration rate (eGFR). Results: ΔAG correlated with eGFR negatively (r = –0.397, p < 0.001), but ΔΔ did not correlate with eGFR (p = 0.51). Among the records grouped by the CKD stage (either G1–3, G4, or G5), ∆AG in G5 (0.9 ± 2.7) was higher than those in G1–3 (–2.2 ± 2.6, p < 0.001) and in G4 (–2.0 ± 2.1, p < 0.001). ∆∆ in G4 (4.0 ± 4.1) was higher than that in G1–3 (1.5 ± 3.7, p = 0.056). Between the subgroups in G5 (either G5a: eGFR 10–15, G5b: eGFR 5–10, or G5c: eGFR <5 mL/min/1.73 m2), ∆AG in G5c (3.8 ± 2.1) was higher than that in G5b (0.8 ± 2.4, p < 0.001), which was higher than that in G5a (–0.9 ± 1.8, p < 0.001). ΔΔ in G5a (5.6 ± 4.1) was higher than those in G4 (p = 0.041) and in G5b (3.2 ± 3.9, p = 0.001), which was higher than that in G5c (0.8 ± 3.8, p = 0.006). Conclusion: High-AGMA developed and progressed in CKD stage G5. Non-AGMA generally progressed before the early phase of CKD stage G5 and regressed thereafter.