Causes

Acute (or brief) diarrhoea is usually caused by a bacterial (eg, salmonella), viral (eg, norovirus or rotavirus), or parasitic (eg, giardia) infection of the bowels. Diarrhoea caused by any of these infections is referred to as gastroenteritis.

Travel to places where the climate or sanitary practices differ form one’s home country may cause short-term gastroenteritis (eg from contaminated food or water) and is known as traveller’s diarrhoea.  Diarrhoea associated with jet lag will usually subside in a matter of days without treatment.

The most common causes of chronic diarrhoea are underlying diseases or conditions, including:

• Gluten intolerance (coeliac disease)
• Lactose intolerance (inability to properly digest lactose in dairy products)
• Irritable bowel syndrome
• Chronic bowel infection
• Inflammatory bowel diseases, such as Crohn’s disease and ulcerative colitis
• Bowel cancer.

You should see your doctor if you are concerned that you might have any of these conditions.

Chronic diarrhoea can also occur when taking certain medications, e.g. some antibiotics and cancer drugs.

Signs and symptoms

The main symptom of diarrhoea is loose, watery bowel motions (stools, faeces) three or more times a day.

Accompanying signs and symptoms may include:

• Urgent need to go to the toilet
• Abdominal pain and cramping
• Change in colour of your stools
• Mucous, pus, blood, or fat in your stools
• Vomiting
• General body weakness and tiredness.

Diagnosis

Diarrhoea is easily diagnosed by its symptoms.

If the diarrhoea lasts longer than two or three days, or is accompanied by symptoms such as fever or bloody stools, your doctor may perform diagnostic tests to determine the cause.

These diagnostic tests could include:

• Stool culture to test for infection
• Blood tests to rule out other diseases
• Fasting tests to reveal food intolerances
• Sigmoidoscopy or colonoscopy to look for signs of inflammatory bowel diseases (these tests involve using a device with thin flexible tube and a camera and light at one end to look inside the bowel).

You should see a doctor if you or your baby / child develop any of the following signs:

• Blood, pus, or mucous in stools
• A rash
• Diarrhoea lasting longer than one week or gets better and comes back
• New or worse symptoms.

Chronic or severe diarrhoea can lead to rapid dehydration, which is the excessive loss of fluids from the body. Dehydration is particularly dangerous in infants and children, the elderly, and people with weakened immune systems (e.g. people with HIV/AIDS or undergoing chemotherapy).

A doctor should also be seen if you, or a family member, becomes dehydrated. The signs and symptoms of dehydration include:

• Extreme thirst
• Little or no urine passed in the last eight hours
• Urine is dark in colour and smelly
• Reduced saliva in the mouth, dry lips, no tears, sunken cheeks or eyes
• Infants may have dry nappies (for longer than 4-6 hours) and/or have a sunken fontanelle (the soft spot on top of a baby’s head)
• Dizziness, lethargy, floppiness
• Rapid heart rate and breathing
• Cold hands and feet
• Skin that does not relax after being pinched.

Treatment

Because most cases of diarrhoea resolve on their own within a day or two, self-care to relieve symptoms is usually sufficient for treatment:

• Avoid caffeine, dairy products, and greasy, high fibre, or sugary foods
• Placing a hot water bottle or wheat pack on your stomach, or taking paracetamol (e.g. Panadol), may provide some relief from abdominal cramps
• Apply zinc and castor oil ointment or a barrier cream to affected areas if you, or your child, develops a rash (like nappy rash) from the diarrhoea
• Avoid taking non-steroidal anti-inflammatory drugs (NSAIDs), such as aspirin, ibuprofen, or diclofenac, for pain relief as these medications can cause diarrhoea
• Anti-diarrhoeal medications that slow diarrhoea (e.g. Imodium) should be avoided as these drugs prevent your body from getting rid of the bacteria or virus that may have caused the diarrhea.

To avoid dehydration, drink plenty of liquid every day, taking small, frequent sips. Ideal liquids are clear thin broths or soups, diluted non-caffeinated sports drinks (e.g. Powerade or Gatorade), and rehydration formulations (e.g. Gastrolyte) that are available without prescription from a pharmacy.

Prevention

Hand washing is one of the most effective ways of preventing the spread of viruses and bacteria that can cause diarrhoea. You should always wash your hands thoroughly after using the toilet, changing nappies, and before meals.

The following rules when preparing food can also help prevent diarrhoea:

• Always put foods that could spoil in the fridge
• Ensure that meat is cooked thoroughly
• Avoid eating raw meats, fish, and shellfish unless you are sure that they have been freshly prepared and are from a reliable source
• Never place cooked meat on surfaces or plates that have held raw meat
• Disinfect bench tops, stove tops, and chopping boards with a diluted bleach solution.

A vaccine for rotavirus is available.  The oral vaccine – Rotarix – is given in two doses at the six-week and three-month immunisation visits to reduce the incidence or severity of rotavirus infection. Rotavirus is a common cause of diarrhoea in infants and young children.