Certain cancers can affect digestion in ways that change stools, but these changes go beyond smell:
Pancreatic cancer: Tumors can reduce digestive enzymes, causing fats to pass into stool. This can make poop greasy, pale, and very foul-smelling, a condition called steatorrhea.
Gastrointestinal cancer: If tumors bleed into the gut, stools may turn dark or black and have a metallic or “rotten blood” scent. Persistent dark stools and smell changes warrant evaluation.
These scenarios involve more than just odor, look for consistency change, color change, and other symptoms.
Doctors focus less on smell alone and more on patterns of symptoms. If foul smell comes with any of the following, it’s worth seeking medical help:
Blood or black color in stool
Ongoing diarrhea or constipation
Oily, greasy stools that don’t flush
Unexplained weight loss
Abdominal pain or bloating
Medical evaluation may include stool tests or imaging to check for infection, malabsorption, inflammation, or more serious conditions.
