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Mixed Acidosis CKD — ESENeph MCQ

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HardAcid-BaseMixed Acidosis CKDESENeph

A patient with CKD G4 has pH 7.27, bicarbonate 14 mmol/L and anion gap 22 mmol/L. The fall in bicarbonate is substantially greater than the rise in anion gap. What acid-base interpretation is most likely?

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Correct answer: A — High-gap acidosis with concurrent normal-gap metabolic acidosis

The best answer is “High-gap acidosis with concurrent normal-gap metabolic acidosis”. Advanced CKD can combine retained unmeasured acids with impaired ammonium excretion and hyperchloraemic acidosis; delta-gap analysis identifies the mixed metabolic process. “Isolated high-anion-gap metabolic acidosis with appropriate respiratory compensation” is less appropriate because the disproportionate bicarbonate fall indicates an additional acidifying process “High-gap acidosis with concurrent chloride-responsive metabolic alkalosis” is less appropriate because that would make bicarbonate fall less than expected, not more “Primary respiratory acidosis with appropriate acute metabolic compensation” is less appropriate because the bicarbonate and anion-gap pattern demonstrates a metabolic process “Primary respiratory alkalosis with appropriate acute metabolic compensation” is less appropriate because this does not generate the elevated anion gap

Reference: KDIGO 2024 CKD guideline: https://kdigo.org/wp-content/uploads/2024/03/KDIGO-2024-CKD-Guideline.pdf