Osmotic diarrhea is when undigested material reduces how much water and electrolytes the bowels can absorb. It can occur when a person’s body has difficulty digesting certain foods, such as lactose.

Occasionally, a person may pass poops that are larger or longer than usual. Some causes of this may include constipation, IBS, and fecal incontinence. Poop, or stool, is undigested food and waste that ...