Renal tubular acidosis affects chloride by causing:

• A. Hyperchloremia
• B. Hypochloremia
• C. Normal chloride
• D. Variable chloride

Answer: (A)

Renal tubular acidosis causes a metabolic acidosis with loss of bicarbonate in the urine. As bicarbonate is lost, serum bicarbonate levels fall, and to keep electrical neutrality, chloride ions are retained and accumulate. This yields a non-anion gap (hyperchloremic) metabolic acidosis, so chloride rises rather than falls. That’s why hyperchloremia is the typical finding. Hypochloremia or normal chloride would not fit the pattern of bicarbonate loss in RTA, and while chloride can vary with volume status, the classic expectation is an elevated chloride level.