With the bowel movement, all that is excreted from the digestive tract, which the body no longer needs. But feces are more than just a waste product to the doctor. Appearance and odor, texture, quantity and composition can provide important clues to disease.
Feces – a useful substance
Stool consists of three-quarters water, in addition to which it contains indigestible food components, mucus and exfoliated cells of the intestinal mucosa, as well as bacteria and their products of fermentation and putrefaction. The urge to defecate arises as soon as the rectum reaches a certain state of fullness; defecation can be controlled voluntarily. The consistency of the feces and the frequency of defecation depend on the diet and are subject to individual variations. An average of 60-250 g of stool is emptied per day; less when fasting, more when eating a high-fiber diet. The normally homogeneous, pulpy-solid stool is softened by carbohydrates, and much protein makes it harder. It gets its brown color from a breakdown product of the bile pigments. Bowel movements: 13 questions and answers
What is examined?
One or more of the factors described above may be altered by pathological processes and thus help in the diagnosis. In addition, blood, pathogens, and worm eggs can be looked for. Enzymes, lipids, and breakdown products can be measured for certain metabolic and digestive disorders.
Stool changes and possible causes
- Color: Certain foods such as beet or medications such as iron and charcoal tablets cause temporary discoloration. Intestinal diseases, metabolic disorders and infections can also cause discoloration. For example, yellow or discolored stools indicate liver or gallbladder disease, greenish-yellowish stools indicate infection, and grayish stools indicate fat digestion disorders, e.g., pancreatic disease. In black stools (“tar stools”), there is an urgent suspicion of bleeding in the upper gastrointestinal tract, and red-brown stools – bleeding in the lower gastrointestinal tract.
- Quantity and odor: in lipid metabolism disorders often occur massive, pungent smelling “fatty stools”, putrefaction processes in the intestine cause a jaundiced odor.
- Texture (consistency): thin-mucous, frequent emptying is typical of diarrhea, thickened feces or large chunks of stool occur in constipation and intestinal obstruction. Alternating hard and soft stools are indicative of irritable bowel syndrome, polyps or carcinoma. Fatty stools are clay-like and sticky and usually shine ointment-like.
- Composition: accumulation of mucus or pus is often a sign of inflammatory bowel disease, undigested food chunks may be a result of intestinal infection. Bright red blood deposits can occur with hemorrhoids or anal fissures, but can also be a sign of colon cancer. With the naked eye are sometimes also parasites such as maggots or ringworms, their eggs or tapeworm parts visible.
Laboratory diagnostics
Further analysis in the laboratory is carried out depending on the findings and suspected diagnosis. In most cases, other tests such as blood tests are performed at the same time.
- Hidden (= occult) blood: the so-called hemoccult test can detect blood in the stool that is not visible to the naked eye. Since it is often an early symptom of colon cancer, this easy-to-perform test is also used from the age of 50 as part of preventive medical checkups. For this purpose, a small amount of stool is placed in the test field of the prefabricated stool letter on three consecutive days and the letter is sealed. If the stool contains blood pigment, the test field on the back discolored when dabbed with a certain solution.
- Stool sample to test for pathogens: the stool sample is immediately delivered to the laboratory in a special tube on three consecutive days. The pathogen detection is done under the microscope, in culture or indirectly by detecting bacterial toxins. Sometimes blood must be taken in parallel and from it also created a culture.
- Stool fat determination: in diarrhea, diseases of the pancreas.
- Enzyme detection: in diseases of the pancreas.
- Measurement of nutrient composition: used when metabolic disease is suspected as a cause of failure to thrive.
Understanding lab values: The most important abbreviations in check
