Renal tubular acidosis commonly shows abnormalities in which two laboratory values?

• A. Abnormalities in serum creatinine and anion gap
• B. Elevated alkaline phosphatase and low calcium
• C. Low creatinine and high potassium
• D. Normal creatinine and normal anion gap

Answer: (A)

Renal tubular acidosis involves a defect in the kidney’s ability to acidify urine, leading to a metabolic acidosis that is typically hyperchloremic and with a normal anion gap. Kidney function is usually preserved, so serum creatinine is often normal unless there is coexisting kidney disease or another process affecting GFR. In evaluating renal tubular disorders, clinicians monitor both kidney function (creatinine) and the type of acidosis (as reflected by the anion gap). In some patients, especially with concurrent nephron injury or mixed disturbances, abnormalities in creatinine and in the anion gap can be seen, making these two labs commonly considered in the broader assessment.

Thus abnormalities in serum creatinine and the anion gap are the two lab values most commonly considered in this context.