Green Stool

Green stool color is certainly not a normal finding as the usual color is brown. Green stool may involve a number of pathological conditions, particularly infections of digestive tract. In addition to color, it is necessary to take into account the stool consistency (solid or diarrheal) and the frequency (number of bowel movements per day).



Salmonellosis typically manifests by diarrhea, abdominal pain and green color of stool. The affected person may also suffer from fever. Usually it is not a problem to track down the infection source from medical history, often it is chicken meat, eggs and their products.

Other diarrheal disorders

When there is a rapid passage of stool through digestive tract, greenish stool may occur. It is due to fact that stool does not have enough time to get colored by bile pigments into normal brown tone. On the other hand, especially in nutrient malabsorption, appearance of feces may be influenced by non-digested fats. Such stool has diarrheal consistence, yellowish color greasy appearance and unpleasant odour.

Iron supplements

Most iron-containing supplements cause digestive problems as loss of appetite and constipation. They also typically change stool color to green or even black tone. This can sometimes even imitate melena and cause panic of an uninformed patient. If a planned colonoscopy shall be performed by a patient who takes iron supplements, the supplements must be withdrawn from medication at least one week before colonoscopy term.

Leaf vegetables and food color additives

Eating excessive amounts of leafy green vegetables can cause discoloration of stool; the same applies to food that is artificially greenly colored. In these cases, however, stool color rapidly returns to normal state.

Stool of newborns and infants

Newborns have first few days after birth green colored stool called meconium. By breastfed babies greenish color of stools often persists. This is completely normal.

Diagnostic approach

Change of stool color shall not be ignored. When a patient has this complaint, medical history should be done. It is advisable to find out information about eating habits, current medication and other symptoms related to digestive tract disorders (diarrhea, fever, weight loss, blood in stool, mucus in stool, etc.). Physical examination should always include digital rectal exam. Stool should be thoroughly examined. When infection is suspected, a stool sample can be examined in a microbiological laboratory to rule out bacteria presence, especially salmonella. If the condition persists and we can not find its cause, it is wise to perform endoscopic examination of digestive tract including gastroscopy and colonoscopy.

Jiri Stefanek, MD  Author of texts: Jiri Stefanek, MD
 Sources: basic text sources