Diarrhea most commonly causes which acid-base disorder?

Diarrhea most commonly leads to hyperchloremic metabolic acidosis. This condition occurs due to the loss of bicarbonate ions from the gastrointestinal tract when diarrhea is present. As the body loses bicarbonate, there is a reduction in the base component of the bicarbonate buffer system, which results in a relative increase in hydrogen ions, thereby lowering the pH and creating acidosis.

In cases of diarrhea, particularly when there is a significant loss of fluid and electrolytes, the kidneys may retain chloride ions to compensate for the loss of bicarbonate, leading to the designation of "hyperchloremic." The primary issue here is the loss of buffer (bicarbonate) and the consequent retention of hydrogen ions, resulting in the acid-base imbalance characteristic of this condition.

Understanding the underlying mechanisms of diarrhea and fluid loss highlights why hyperchloremic metabolic acidosis is the most consistent acid-base disturbance seen in these patients, distinguishing it from other acid-base disorders that do not typically arise in this context.