Diarrhoea is a common digestive disorder that virtually all people will suffer at some stage during their lives. The definition of diarrhoea varies but it can generally be taken to mean increased stool water causing an increase in stool frequency or the passage of soft stools. Passage of greater than 3 stools per day or a stool volume of greater than 200 mL suggests the diagnosis of diarrhoea.
Diarrhoea is called acute if lasts for less than two weeks or chronic if it lasts for greater than 4 weeks. Diarrhoea can occur in virtually any person regardless of their age and general health. Diarrhoea can range from a mild discomfort to a severe and life threatening illness due to the risks of dehydration. In fact diarrrhoeal diseases are one of the top causes of death worldwide and it bcomes particularly common in developing countires with poor food practices and hygiene.
Children and the elderly are particularly prone to dehydration secondary to diarrhoea. However, the great majority of cases of diarrhoea follow short courses which don’t really require specific diarrhoea treatment to resolve.

Mechanisms for the formation of diarrhoea

Diarrhoea basically develops when there is a defect in the absorptive mechanism working in the intestines. This may be due to damage to the mucosa (lining of the bowel) from infections or inflammation or excess secretion of fluid and electrolytes from particular toxins (e.g. cholera). Sometimes there may be too much sugary material in the lumen of the bowel which draws more fluid across the membranes. In other patients the bowel may just be overactive from hormone disorders which causes very frequent bowel motions but the overall volume should remin approximately the same.

Causes of diarrhoea

By far the most common cause of diarrhoea is infection. Most cases are just mild viral infections caused by rotavirus (which some people may refer to as the stomach flu). This can be easily spread through daycare cantres, schools or families. Bacteria such salmonella, campylobacter and shigella are other common causes of diarrhoea. These cases tend to be more severe than viral diarrhoea and are caused by eating food or drinking water contaminated with these bacteria.
Diarrhoea can sometimes be caused by parasites which are transmitted by similar mechanisms. Giardia lamblia and cryptosporidium are possible parasitic causes of diarrhoea. Chronic diarrhoea can be caused by a number of medical problems. Irritable bowel syndrome is relatively common and associated with alternating periods of diarrhoea, constipation and bloating.
Certain medications, particularly antibiotics and anti-cancer drugs can cause diarrhoea because they disrupt the normal healthy bugs in the intestines and inhibit mucosal cell regeneration respectively. Inflammatory bowel diseases which include Crohn’s disease and ulcerative colitis also cause recurrent attacks of diarrhoea often stained with blood and mucus. Colorectal cancer or any other defects in the intestines may also cause diarrhoea.

Signs and Symptoms of diarrhoea

The signs and symptoms of diarrhoea include:

  • Passage of frequent, loose and watery stools;
  • Abdominal cramps or pain;
  • Fever– Particularly if there is an infectious cause;
  • Bleeding- Bacteria and parasites often can produce bloody diarrhoea (dysentery). In addition inflammatory bowel disease, polyps and colorectal cancer cause blood and mucus in the stools;
  • Nausea and vomiting may also be present in the case of infection.

Important points in the history of diarrhoea

Your doctor will ask you lots of questions so they can try to determine the likely cause of your diarrhoea in order to treat it. These questions will include:

  • How long have you had diarrhoea?
  • What is the clour and consistency of your stool?
  • Any blood or mucus?
  • Any other symptoms or fever?
  • Do you have abdominal pain with the diarrhoea?
  • Anybody else in the family sick?
  • Have you recently been overseaes?
  • Which medications do you take?
  • Do you smoke? How much alcohol do you drink?
  • Are you on a special diet?

The doctor will then briefly examine you to to check for signs of anaemia and dehydration. Your abdomen will also be caefully examined.


The doctor will then order a number of tests to determine the likely cause. These will include:

  • Blood tests: Looking at blood counts and haemoglobin to determine any anaemia due to bleeding and to look for the possibility of infection;
  • Stool examination: Samples of stool will be examined under the microscope to see if there are any pathogens identifiable;
  • Sigmoidoscopy, colonoscopy or barium examination may be used to visualise the bowel to determine if inflammatory bowel disease, polyps or suspected malignancy (cancers) are present. Patients with chronic diarrhoea often have extensive tests to determine the most likely cause.

Management of diarrhoea

Most cases of diarrhoea are self-limiting so treatment of diarrhoea is primarily supportive. Many patients become dehydrated so may require fluid resuscitation. If you experience diarrhoea at home you should drink lots of water to avoid dehydration and minimise your intake of caffeine and alcohol (as these aggravate diarrhoea and dehydration). You can also help yourself by eating lots of semi-solid foods such as dry toast, rice and bananas and taking probiotics (e.g. yoghurt) to replenish the good bacteria in your bowel.
If you have severe symptoms, bloody stools, fever, vomiting or persistent diarrhoea it is advisable to consult a doctor. Other diarrhoea treatment largely depends on the cause of the diarrhoea. Some patients will be given certain diarrhoea medications to decrease movements of the bowel and reduce the volume of stool such as bismuth sulphate, loperamide or codeine phosphate. However, if you have an infection, it may be better not to inhibit your bowel motions because this is the way your body is attempting to clear the body of nasty bugs. If infection is present you may require antibiotic for the diarrhoea.

Diarrhoea prevention

  • Washing your hand thoroughly before all meals and when preparing food;
  • When travelling to developing countries- Drink bottled water, only drink well-cooked meals, avoid raw fruit and vegetables and milk products;
  • When taking antibiotics, try taking probiotics such as Lactobacillus acidophilus, as this helps to replenish the natural flora that antibiotics can destroy.

Note: Probiotics are not recommended for patients having chemotherapy or who are immunosuppressed as they may have harmful effects.

Dietary management of diarrhoea

  • Take anti-diarrhoeal medication only as prescribed by your doctor;
  • Drink plenty of fluids as your body may lose a lot of fluid while you have diarrhoea (e.g. water, diluted soft drinks and weak cordials);
  • Avoid highly spiced and fatty foods, very hot or cold food/drinks, and alcohol, and limit caffeine (coffee and strong tea) as these may make diarrhoea worse;
  • While you have diarrhoea, reduce your fibre intake by replacing wholemeal bread and cereals with white varieties. Avoid raw fruit and vegetables with skins, seeds, nuts and legumes (e.g. baked beans);
  • Sometimes diarrhoea can cause temporary lactose intolerance, where ordinary milk may make the diarrhoea worse. In such case it may be helpful to change to soy milk or low lactose milk until diarrhoea ceases. Cheese and yoghurt in small amounts are usually tolerated;
  • Speak with your dietitian about other dietary management strategies for diarrhoea.

Article kindly reviewed by:

The DAA WA Oncology Interest Group
Food4Health (Helen Baker Dietitian-APD)


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