Understanding and Managing Diarrhoea in Adults


Published: 12 April 2021

What is Diarrhoea?

diarrhoea bristol stool chart
Generally, the stools passed by someone experiencing diarrhoea are between Type 5 and Type 7 on the Bristol Stool Chart.

Diarrhoea is when more than three loose, watery stools are passed within one day (Healthdirect 2019a).

Generally, the stools passed by someone experiencing diarrhoea are between Type 5 and Type 7 on the Bristol Stool Chart (Continence Foundation of Australia 2020).

Diarrhoea may be either:

  • Acute, lasting for up to two weeks (but generally resolving on its own within 1 to 2 days), or
  • Chronic, lasting for over four weeks.

(Better Health Channel 2015)

Diarrhoea is a common condition that generally doesn’t indicate a serious underlying issue. However, it can be an uncomfortable and unpleasant experience (NHS Inform 2020).

It is common for adults to experience one episode of acute diarrhoea every year (MedlinePlus 2016).

The Physiology of Diarrhoea

During the digestion process, the small and large intestines absorb nutrients and fluid from food that has been consumed (Bladder & Bowel Community 2021). The remaining substance then becomes waste (faeces) and is excreted. Generally, stools are between 60 and 90% water (Gotfried 2020).

Diarrhoea occurs when less fluid than usual is absorbed from the waste, or there is an increased fluid secretion from the intestines (Gotfried 2020).

Causes of Diarrhoea

Acute Diarrhoea

Most cases of acute diarrhoea are caused by infections such as gastroenteritis (Nemeth & Pfleghaar 2020). Potential pathogens include:

  • Viruses (e.g. norovirus, rotavirus, cytomegalovirus, viral hepatitis)
  • Bacteria (e.g. Campylobacter, Clostridium difficile (C. difficile), Escherichia coli (E. coli))
  • Parasites (e.g. Giardia lamblia, cryptosporidium).

(Healthdirect 2019b)

It is estimated that one-fifth of all infectious diarrhoea cases are caused by norovirus (Bladder & Bowel Community 2021).

Other causes of acute diarrhoea include:

  • Contaminated food or water from overseas (known as ‘traveller’s diarrhoea’)
  • Food poisoning
  • Anxiety or distress
  • Excess alcohol
  • Excess coffee
  • Food allergies
  • Appendicitis
  • Certain medicines (e.g. antibiotics, non-steroidal anti-inflammatory drugs (NSAIDs), selective serotonin reuptake inhibitors (SSRIs))
  • Damage to the intestinal epithelium (e.g. from radiotherapy or medicines)
  • Damage to the intestines due to decreased blood supply (e.g. from a hernia).

(Healthdirect 2019b)

diarrhoea norovirus
It is estimated that one-fifth of all infectious diarrhoea cases are caused by norovirus.

Chronic Diarrhoea

Chronic diarrhoea may be caused by:

  • Lactose intolerance
  • Irritable bowel syndrome (IBS)
  • Coeliac disease
  • Crohn’s disease
  • Cystic fibrosis
  • Diabetes
  • Diverticular disease
  • Microscopic colitis
  • Chronic pancreatitis
  • Ulcerative colitis
  • Bowel cancer
  • Bile acid malabsorption
  • Having a gastrectomy
  • Having bowel surgery
  • As a side effect from chemotherapy.

(Healthdirect 2019b; NHS Inform 2020)

Types of Diarrhoea

Diarrhoea can be classified into different categories depending on the reason why excess fluid is present in the stool. These include:

Type of Diarrhoea Description Causes
Rapid passage of stool Occurs when the stool exits the large intestine too early, causing a watery consistency
  • Overactive thyroid (e.g. hyperthyroidism)
  • Certain surgical procedures (e.g. removal of part of the stomach, small intestine or large intestine)
  • Inflammatory bowel disease
  • Caffeine
  • Certain medicines (e.g. laxatives)
  • Food high in sugar
  • Food intolerance
  • Anxiety and stress
Osmotic diarrhoea Occurs when a substance cannot be absorbed and remains in the intestine, creating excess fluid
  • Certain food (e.g. some fruits and beans)
  • Sugar substitutes
  • Lollies and chewing gum
  • Lactose intolerance
  • Antibiotics
Secretory diarrhoea Occurs when fluid and salts are secreted into the stool by the intestines
  • Infection
  • Certain laxatives
  • Certain rare tumours
  • Certain polyps
Inflammatory diarrhoea Caused by inflammation of the epithelium in the large intestine, which results in proteins, blood, mucus and other fluids being released into the stool
  • Ulcerative colitis
  • Crohn’s disease
  • Tuberculosis
  • Certain cancers (e.g. lymphoma)
Malabsorption Occurs when oil or grease is present in the stool due to inadequate absorption of nutrients
  • Certain disorders (e.g. Coeliac disease, Crohn’s disease)
  • Removal of part of the small intestine

(Gotfried 2020; Ruiz Jr 2021)

Symptoms of Diarrhoea

Diarrhoea may be associated with other symptoms including:

  • Nausea and vomiting
  • Abdominal pain
  • Fever
  • Headache
  • Decreased appetite
  • Abdominal bloating
  • Faecal urgency
  • Fatigue.

(Healthdirect 2019a)

Complications of Diarrhoea

Seek medical advice if a client is experiencing:

  • Bright red blood or mucus in stools
  • Dark, tar-like and smelly stools (may indicate internal bleeding)
  • Pale or greasy stools that have a foul smell and are difficult to flush
  • Fever that does not respond to paracetamol
  • A large volume of watery stools
  • Dehydration symptoms
  • Persistent vomiting
  • Difficulty keeping anything down
  • Medicine-related diarrhoea
  • Severe abdominal pain
  • Weight loss
  • Comorbidity (e.g. diabetes).

(Healthdirect 2019a; NHS Inform 2020)

Diarrhoea can cause excess fluid loss, which may result in dehydration (NHS Inform 2020). This has the potential to be serious, particularly in older adults (Healthdirect 2019a).

Symptoms that indicate dehydration include:

  • Reduced urine output
  • Dark urine
  • Sunken eyes
  • Dry mouth and tongue
  • Fatigue
  • Headache
  • Confusion
  • Rapid heartbeat
  • Cool peripheries/extremities
  • Low blood pressure
  • Irregular heartbeat
  • Muscle cramping
  • Delirium or a change in cognition.

(Healthdirect 2021; NHS Inform 2020; VIC DoH 2018)

Treating Diarrhoea

diarrhoea treatment hydration
Ensure that clients experiencing diarrhoea stay hydrated.

In most cases, acute diarrhoea will resolve on its own without treatment, especially if it is infection-related (NHS Inform 2020).

While the client recovers, you will need to manage their symptoms. You should:

  • Encourage the client to get plenty of rest
  • Maintain effective hygiene practices (if the diarrhoea is infection-related) to ensure that the infection does not spread
  • Ensure the client stays hydrated. Consider giving water or oral rehydration fluids
  • Administer medicines if clinically appropriate
  • Encourage the client to eat small, light meals as soon as they feel able to
  • Avoid giving fatty or spicy foods
  • Make short-term dietary adjustments as their intestines recover:
    • Avoid giving alcohol and fatty, sweet or spicy foods
    • Encourage consumption of starchy foods and yoghurt
  • Treat any underlying causes (e.g. IBS, coeliac disease).

(Healthdirect 2019a; NHS Inform 2020; Better Health Channel 2015)

If the client is severely dehydrated, they may require intravenous fluid therapy (NHS Inform 2020).

If diarrhoea is a long-term issue for the client, you may need to consider dietary changes. Consult a dietician for advice and investigate any underlying causes (Continence Foundation of Australia 2020).

Preventing Diarrhoea

The best way to prevent diarrhoea is to maintain effective hygiene practices, as this will reduce the risk of spreading infections that cause these symptoms (Healthdirect 2019a).

Refer to the following articles for comprehensive information on maintaining effective hygiene:

Additional Resources


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