The small intestine absorbs food nutrients. The waste is pushed into the large bowel where water is removed. The resulting faeces (poo or bowel motions) are temporarily stored in the rectum before being expelled from the body via the anus. The medical names for the expulsion of faeces include defecation and egestion.
Water makes up about three quarters of faecal content, while the rest is composed of solids, including undigested fibre, intestinal bacteria and dietary fats. Many illnesses and events can affect the colour and texture of faeces.
Always see your doctor if your bowel motions change and don’t resolve within a day or two. Seek urgent medical attention if you notice blood in them.
Normal adult bowel motions described
Characteristics of the normal, healthy bowel motion include:
- Bowel motions should be firm, moist and easy to pass.
- Regularity differs from one person to the next – the range of ‘normal’ includes once per week to several times every day, depending on the individual.
- The average adult produces between 100g and 180g of faeces every day.
- Bowel motions are brown because they contain bile pigments (stercobilin).
- Bacteria use chemical reactions to break down the faeces. These chemical reactions produce smelly compounds like hydrogen sulphide, which account for the characteristic odour.
Changes in colour
Healthy bowel motions are brown. If they change colour, seek medical attention immediately, as some of the causes may include serious illnesses. Common colour changes and their range of possible causes include:
- Red – blood smears on the toilet paper are usually caused by haemorrhoids or anal fissures. Bright red blood in the faeces (haemotochezia) usually means internal bleeding, and the causes could include bowel cancer.
- Black – one of the most common causes of black faeces is taking iron supplements. However, bleeding higher up in the digestive tract, such as from the oesophagus or stomach, can cause the faeces to appear black (melena). The cause could include bleeding from an ulcer.
- Maroon – blood is the usual cause of maroon-coloured faeces. Some of the causes can include bleeding from the bowel, often from diverticulosis, angiodysplasia (abnormal and leaky blood vessels in the intestinal lining) or bowel cancer.
- Cream or light coloured – light-coloured faeces usually means that bile salts are absent. This could be caused by a range of digestive diseases affecting the pancreas, gall bladder or liver. Hepatitis, for example, can make the faeces appear silver, white, grey or yellow.
Changes in texture
Healthy bowel motions are firm and moist. Common texture changes and their range of possible causes include:
- Watery – short bouts of diarrhoea can be caused by a range of factors, including food poisoning, gastroenteritis and anxiety. Chronic diarrhoea can be a symptom of more serious illnesses such as coeliac disease, inflammatory bowel disease, diverticulosis or bowel cancer. It can also be caused by medication, diet (high-fibre diets, coffee and diet soft drinks can cause diarrhoea) and, frequently, from irritable bowel syndrome. Lactose intolerance can also cause diarrhoea, often with cramping and wind.
- Hard and dry – when you are constipated, bowel motions tend to be hard, dry and uncomfortable to pass. Common causes of constipation include a low-fibre diet and some medications. Constipation can cause haemorrhoids to produce symptoms because of the straining involved to pass a hard, dry motion.
- Stringy – parasitic infections of the gut can cause bowel motions to become thin and stringy. For example, worms can affect the faeces in this way.
- Greasy – a high-fat meal can result in fatty, smelly faeces that tend to float in the toilet bowl. However, the constant passage of greasy stools could indicate a problem with fat digestion.
Bowel motions of newborns and young babies
Characteristics of normal, healthy bowel motions in newborns and young babies include:
- The first bowel motion passed by a newborn is a greenish-black, sticky and tar-like substance called meconium. The faeces lighten in colour when feeding starts.
- The breastfed baby’s bowel motions can range in colour from yellow to light green.
- The formula-fed baby’s bowel motions can range in colour from creamy-yellow to dark green.
- Regularity can range from several times per day to once weekly, depending on the baby.
Colour changes to bowel motions in babies
The bowel motions of a baby or young child can take on the colour of a recently eaten food, particularly if they have slight diarrhoea. However, consult with your doctor to rule out the possibility of more serious causes. Common dietary causes of colour changes to bowel motions in babies include:
- red – tomato soup, beetroot, red drinks such as cranberry juice
- black – liquorice, grape juice
- green – spinach, breast milk, formula milk.
Seek medical attention if your baby has diarrhoea
Babies can dehydrate very quickly. If your baby is passing frequent, watery bowel motions, give them plenty of extra fluids including cool water. See your doctor if the diarrhoea doesn’t pass, or if the child seems to be lethargic or otherwise unwell.
Diagnosis of bowel problems
Unusual changes to faecal colour or texture may be investigated using a number of tests including:
- medical history
- physical examination
- stool culture
- biopsy for coeliac disease or lactose intolerance
- colonoscopy or sigmoidoscopy
- blood tests.
Treatment depends on the underlying cause.
Where to get help
- Your doctor
Things to remember
- Water makes up about three quarters of faecal content, while the rest is composed of solids such as undigested fibre.
- Bowel motions should be firm, moist, easy to pass and coloured brown.
- Red, maroon or black faeces could indicate internal bleeding, so visit your doctor immediately.
This page has been produced in consultation with and approved by:
Canberra Hospital - Gastroenterology Unit
Page content currently being reviewed.
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