What is the typical ABG finding in renal failure?

• A. Metabolic alkalosis with metabolic compensation
• B. Metabolic acidosis with high anion gap and variable compensation
• C. Respiratory alkalosis with compensatory metabolic changes
• D. Normal ABG

Answer: (B)

Renal failure disrupts the kidney’s ability to excrete acid and regenerate bicarbonate, so fixed acids build up and bicarbonate is lost, producing a metabolic acidosis. In ABG terms, you’d see a low pH and a low HCO3−. The lungs respond by blowing off CO2, so the pCO2 falls as a compensatory mechanism. Because kidneys retain unmeasured anions (like sulfate, phosphate, and organic acids), the overall anion gap is typically elevated, giving a high anion gap metabolic acidosis with appropriate respiratory compensation. This pattern best matches the description of metabolic acidosis with a high anion gap and compensatory low CO2.