A bowel movement is the end of the road, so to speak, for digestion. Stools - or feces - are the combination of whatever is left once your digestive system has finished absorbing nutrients and fluid from the foods and beverages you consume. While some people move their bowels daily, it is considered "regular" to do so anywhere between 3 times in one day to 3 times per week.

Changes to your stool or bowel movements may be harmless and temporary, requiring no intervention or medical attention. Here are a few changes you might notice:

Colour changes

The most common culprits of stool colour changes are foods and medications. Occasionally, a colour change is a signal of an underlying problem.

  • Black or tarry stool: If stool emerges dark or tarry, you may have an injury or disorder of your digestive tract. When stool is black, it is a sign that bleeding has occurred in the upper digestive tract. The digestive juices turn the blood the tarry colour. Bleeding could come from an ulcer or inflammation. Stool may also appear black if you have eaten black licorice or blueberries, consumed lead, or taken iron pills or medicines containing bismuth.
  • Red stool: Red stool could indicate blood from the lower gastrointestinal tract, like from the large bowel, or from the rectum or anus. Bleeding could be caused by hemorrhoids, by a pouch in the colon (diverticulosis), or more rarely by an intestinal tumour or abnormal blood vessels. A recent meal featuring beets, tomatoes, or red food colouring could also be to blame. Constipation can cause a bit of blood to appear in the stool. In children, a small amount of blood in the stool may be caused by a milk allergy. Report the symptom to your child's doctor.
  • Pale white or clay-coloured stool: The colour of healthy brown stool comes from bile, which is released by the liver. So, sallow, colourless stool usually means that something is amiss in the liver, or perhaps the pancreas or gall bladder. This could mean infection, blockage, cysts, gallstones, or tumours. Medications, including bismuth and other anti-diarrheal drugs, may also sap stool of colour.
  • Green stool: In adults, green stool may be caused by diarrhea or by eating deeply green-coloured foods, like leafy vegetables or foods featuring green food colouring. Also iron supplements could give stool a green tint. Persistently green stool could be a sign of an intestinal infection or condition.
  • A note about the colour of baby stool: Green or yellowish stool is more common among infants than adults. The very youngest of newborns pass stool called meconium, which is thick, dark green and made of amniotic fluid, mucus, and bile, as well as fine hair and shed skin cells. After a few days, infant stool takes on a more mustardy-yellow tinge. After the meconium, breast-fed infants may pass loose stool that appears yellow-brown. Stool from a formula-fed infant may be darker, with a paste-like consistency. As baby grows and begins eating solids, the stool will take on a darker brown colour. Also, the colour of a baby's stool will be affected by what he or she eats.

Composition changes

An occasional bout of diarrhea or constipation can cause the stool to become softer or harder. Other composition changes could point to infection or illness.

  • Narrow stool: Now and then, an individual stool may be narrow, which is usually not a problem. Thin stool could also be a symptom of irritable bowel syndrome. Pencil-thin stool may be due to an obstruction in the colon, possibly caused by colon cancer.
  • Dry, hard, or rough stool: Stool that takes a long time to transit the intestinal tract leads to constipation, characterized by hard stool. Dry, hard, or rough stool is a common symptom of constipation.
  • Watery stool: Stool passing too quickly through the large intestine may result in the loose, watery stool of diarrhea.
  • Floating stool: When stool is buoyant, excessive gas is often to blame. Track your symptoms and take note of what food may have caused the gas. Episodes of diarrhea or other gastrointestinal infections could increase the amount of gas produced by the bacteria in the intestines. Also, problems with food absorption prevent the body from properly digesting fat and nutrients, leading to "floaters."
  • Stool with mucus or pus: Small amounts of mucus are nothing to worry about. Infection, inflammation, or irritation of the gastrointestinal tract may cause larger amounts of mucus or pus in the stool. So might underlying digestive conditions, including Crohn's disease, ulcerative colitis, irritable bowel syndrome, and colon cancer.
  • Stool with undigested food: Most often, the undigested food matter is indigestible anyway, in the case of high-fibre vegetables.

Changes in odour

Due to the many bacteria in the intestinal tract, stools normally smell quite bad. You know your own odour, and if something smells amiss, you would notice it. Eating certain foods seems to lead to smellier bowel movements. An out-of-control odour could indicate an underlying condition, like celiac disease, Crohn's disease, or ulcerative colitis.

Seek immediate medical attention if bowel changes are accompanied by rectal bleeding or severe abdominal pain. Otherwise, see a doctor...

  • if you notice blood or changes to the colour of your stool
  • if changes in shape and/or size of stool persists beyond 2 weeks
  • if floating stools persist for longer than a couple of weeks or if accompanied by blood in the stool, fever, or dizziness
  • if stools are foul-smelling, especially if accompanied by other symptoms - black, tarry colour; mucus in stool; chills, fever; cramping; abdominal pain; weight loss
  • if you notice undigested food in your stool accompanied by diarrhea or weight loss

Amy Toffelmire