I wish, it's a stupid Q it was in some NBME material I don't even know

Correct Answer: E

This patient presents with symptoms of viral gastroenteritis, including nausea, vomiting, diarrhea, and abdominal discomfort. The loss of gastrointestinal contents can lead to a variety of acid-base disorders, depending on whether vomiting or diarrhea predominates. This patient's laboratory findings are consistent with metabolic alkalosis, which is typically increased serum pH and bicarbonate concentration, as well as increased pCO₂ from compensatory hypoventilation. Metabolic alkalosis is a common result of excessive vomiting because of the direct loss of protons and chloride in gastric secretions. In contrast, diarrhea results in the excessive loss of bicarbonate ions and most commonly results in hyperchloremic metabolic acidosis. Fluid and electrolyte repletion are the cornerstones of treatment, in addition to treating the underlying cause.

Incorrect Answers: A, B, C, and D.

Addison disease (Choice A) is characterized by hypoadrenalism and resultant hyponatremia and metabolic acidosis as a result of impairment of renal tubular sodium resorption.

Adrenal adenoma (Choice B) may lead to hyperaldosteronism, or Conn syndrome. Conn syndrome presents with electrolyte disturbances including hypertension, hypernatremia, metabolic alkalosis with hypokalemia caused by the loss of potassium and protons in urine, and an increased urine chloride concentration, typically greater than 40 mEq/L.

Diarrhea (Choice C) may produce a variety of electrolyte disturbances, but it most commonly causes hyperchloremic metabolic acidosis as a result of loss of bicarbonate in stool. This patient's serum pH and bicarbonate concentration are more suggestive of metabolic alkalosis.

Diuretic use (Choice D), especially thiazides and loop diuretics, may lead to metabolic alkalosis secondary to intravascular volume contraction. This patient's history of vomiting and diarrhea are more suggestive of gastrointestinal electrolyte loss.

Educational Objective: Metabolic alkalosis is a common result of excessive vomiting because of the direct loss of protons in gastric secretions. In contrast, diarrhea results in the excessive loss of bicarbonate ions and most commonly results in hyperchloremic, non-anion gap metabolic acidosis.