What organ isn't working when you have diarrhea?

When you have diarrhea, the primary organ affected is the intestines, particularly the large intestine (colon). The colon's role is to absorb water and electrolytes from waste, so when it isn't functioning properly, it leads to excessive fluid loss in the stool. This can result from infections, inflammation, or other gastrointestinal issues that disrupt normal absorption and motility.