In neonates, an increased anion gap metabolic acidosis may be due to which condition?

• A. Bicarbonate loss
• B. Renal tubular acidosis
• C. Sepsis
• D. Dehydration

Answer: (C)

An increased anion gap metabolic acidosis reflects the accumulation of unmeasured anions, such as lactate, ketones, or other organic acids. In neonates, sepsis commonly causes tissue hypoperfusion and anaerobic metabolism, leading to elevated lactate and a higher anion gap. That makes sepsis the best fit among the options.

Bicarbonate loss leads to a normal anion gap (hyperchloremic) acidosis because chloride rises to balance the bicarbonate loss. Renal tubular acidosis also typically yields normal anion gap acidosis due to impaired bicarbonate handling. Dehydration can contribute to lactic acidosis with a high anion gap if perfusion is markedly reduced, but the classic and most direct cause in this scenario is sepsis with lactic acidosis.