what causes very foul smelling stools
2. Black or tarry stools (Melena) - the passage of black, tarry and foul-smelling stools; can be an indication of digested blood in the stool. Other causes are, iron deficiency anemia, cirrhosis, colorectal cancer, disseminated intravascular coagulation, peptic ulcer, or stomach cancer.ossible causes for clay colored stool result from problems in the biliary system (the drainage system of the gallbladder, liver, and pancreas): Malabsorption problems can cause undigested fat in the stool (steatorrhea) which is characterized by foul smelling, light yellow to gray, greasy or frothy stools.