Very smelly stool indicates that there may be problems with dietary factors, digestive ability, constipation, rectal or colon tumors, and so on. 1. Dietary factors: due to long-term consumption of spicy, high-fat, high-protein food, food decomposition in the intestines will produce more ammonia, resulting in smelly stools. 2. Indigestion: If patients suffer from indigestion and the intestinal environment is disturbed, the content of probiotics will decrease and harmful bacteria will increase, which will cause the intestinal decomposition to produce hydrogen sulfide, ammonia and other gases, which will also make the stools appear very smelly. 3. Constipation: Due to the blockage of ganglionic conduction in the intestines and autonomic dysfunction in the intestines, the peristalsis of the intestines slows down, the stools in the intestines are retained for a long time, and the absorption of water is too much, which leads to the propagation of bacterial breeding, resulting in the manifestation of dryness of the stool, which will lead to the smelly stools. 4. Rectal or colon tumor: If there is a tumor in the rectum or colon, it will lead to intestinal obstruction, which will cause the stool to stay in the intestinal tract for too long, resulting in the phenomenon of smelly stool. It is recommended that patients with persistent foul-smelling stools should go to the hospital in time to take targeted treatment under the doctor’s diagnosis.