American Board of Internal Medicine (ABIM) Certification Practice Exam

Which type of diarrhea stops with fasting and is associated with bloating and gas?

1. Secretory diarrhea

2. Osmotic diarrhea

3. Steatorrhea

4. Motility-related diarrhea

The correct answer is: Osmotic diarrhea

The type of diarrhea that stops with fasting and is associated with bloating and gas is osmotic diarrhea. This occurs when the ingestion of certain substances leads to an accumulation of unabsorbed solutes in the intestinal lumen, which results in water being drawn into the intestines and subsequently increased stool output. Common causes of osmotic diarrhea include lactose intolerance, where the body cannot sufficiently digest lactose; ingestion of certain sugars like sorbitol or mannitol; and other malabsorptive conditions. When a person fasts, the intake of these poorly absorbed osmotic agents ceases, allowing the osmotic load to diminish and reducing the amount of water drawn into the intestine, thus stopping the diarrhea. The associated bloating and gas are a direct result of the fermentation of unabsorbed carbohydrates, which can lead to increased gas production. In contrast, secretory diarrhea continues even during fasting because it is caused by the active secretion of electrolytes and water into the intestinal lumen, often due to infections or specific toxins. Steatorrhea, characterized by the presence of excess fat in the stool, involves malabsorption of fats and does not necessarily resolve with fasting. Lastly, motility-related diarrhea is caused by abnormal intestinal motility leading to either rapid passage