Which of the following is a potential cause of metabolic acidosis in neonates?

Metabolic acidosis in neonates can occur due to the loss of bicarbonate, which is an essential component in maintaining the body's pH balance. Diarrhea is a significant cause of metabolic acidosis because it leads to the excessive loss of bicarbonate from the intestines. This loss can overwhelm the buffering capacity of the blood, resulting in a drop in pH and leading to acidosis.

It's important to note that while vomiting can result in metabolic alkalosis due to the loss of gastric acid (which is rich in hydrochloric acid), it does not typically contribute to metabolic acidosis. Cushing's syndrome, characterized by excess cortisol production, may disrupt various metabolic processes but is not a direct cause of metabolic acidosis in neonates. Dehydration, while potentially leading to various electrolyte imbalances and complications, is not specifically linked to causing metabolic acidosis. Thus, diarrhea stands out as the direct cause of bicarbonate loss, which is central to the development of metabolic acidosis in this population.