Renal tubular acidosis is associated with abnormalities in which laboratory parameters?

• A. Creatinine and anion gap
• B. Calcium and phosphate
• C. Glucose and ketones
• D. Sodium and potassium

Answer: (A)

Renal tubular acidosis presents with a metabolic acidosis that is usually normal in the anion gap, reflecting a failure of acid secretion or bicarbonate reabsorption in the renal tubules rather than a systemic accumulation of unmeasured anions. The labs you look at to evaluate this condition center on kidney function and acid-base classification: creatinine gives a sense of glomerular filtration rate and overall renal function, while the anion gap helps distinguish whether the acidosis is high-gap (like lactic or ketoacidosis) or normal-gap (hyperchloremic acidosis seen in RTA). In pure RTA, you’d expect a normal anion gap and variable creatinine depending on whether there is concomitant CKD or tubular damage. The other lab pairs are less specific to RTA: calcium/phosphate can be affected in distal RTA but are not defining; glucose/ketones point to diabetes or ketosis; sodium/potassium are general electrolytes with many causes and are not as diagnostic for RTA.