What is one cause of normal-anion-gap acidosis?

Normal-anion-gap acidosis, also known as hyperchloremic acidosis, typically occurs when there is a reduction in bicarbonate levels without a corresponding change in the anion gap. One common cause of this condition is diarrhea.

During diarrhea, there is a significant loss of bicarbonate through the gastrointestinal tract. The body tries to compensate for this loss by retaining chloride ions, which helps maintain electrical neutrality in the plasma. As bicarbonate levels drop due to the loss, the anion gap remains normal because the decrease in bicarbonate is offset by an increase in chloride. This mechanism explains why diarrhea is associated with normal-anion-gap acidosis, as the overall balance of unmeasured anions does not change.

Other potential causes such as starvation, lactic acidosis, and renal failure are generally associated with changes in the anion gap due to the production of other acids or impaired renal function, leading to an increased accumulation of unmeasured anions. However, with diarrhea specifically, the primary issue is the loss of bicarbonate and an increase in chloride, maintaining a normal anion gap.