The form of the stool depends on the time it spends in the colon.
The seven types of stool are:
1. Separate hard lumps, like nuts (hard to pass).
2. Sausage-shaped but lumpy.
3. Like a sausage but with cracks on its surface.
4. Like a sausage or snake, smooth and soft.
5. Soft blobs with clear cut edges (passed easily).
6. Fluffy pieces with ragged edges, a mushy stool.
7. Watery stool, entirely liquid.
Types 1 and 2 indicate constipation, with 3 and 4 being the "ideal stools" especially the latter, as they are the easiest to pass, and 5–7 being further tending towards diarrhea or urgency.
Color variations of feces
Human fecal matter varies significantly in appearance, depending on diet and health. Normally it is semisolid, with a mucus coating. It normally has a brown coloration, which results from a combination of bile and bilirubin that is derived from dead red blood cells.
YellowYellowing of feces can be caused by an infection known as Giardiasis, which derives its name from Giardia, an anaerobic flagellated protozoan parasite that can cause severe and communicable yellow diarrhea. Another cause of yellowing is a condition known as Gilbert's Syndrome. This condition is characterized by jaundice and hyperbilirubinemia when too much bilirubin is present in the circulating blood.
BlackFeces can be black due to the presence of red blood cells that have been in the intestines long enough to be broken down by digestive enzymes. This is known as melena, and is typically due to bleeding in the upper digestive tract, such as from a bleeding peptic ulcer. The same color change (albeit harmless) can be observed after consuming foods that contain substantial proportion of animal bloods, such as Black pudding or Tiết canh. The black color is caused by oxidation of the iron in the blood's hemoglobin. Black feces can also be caused by a number of medications, such as bismuth subsalicylate, and dietary iron supplements, or foods such as beetroot, black liquorice, or blueberries.
Hematochezia is similarly the passage of feces that are bright red due to the presence of undigested blood, either from lower in the digestive tract, or from a more active source in the upper digestive tract. Alcoholism can also provoke abnormalities in the path of blood throughout the body, including the passing of red-black stool.
BluePrussian blue, used in the treatment of radiation, cesium, and thallium poisoning, can turn the feces blue. Substantial consumption of products containing blue food dye, such as blue koolaid or grape soda, can have the same effect.
SilverA tarnished-silver or aluminum paint-like feces color characteristically results when biliary obstruction of any type (white stool) combines with gastrointestinal bleeding from any source (black stool). It can also suggest a carcinoma of the ampulla of Vater, which will result in gastrointestinal bleeding and biliary obstruction, resulting in silver stool.