Overview

The World Health Organisation defines diarrhoea as ‘the passage of 3 or more loose or liquid stools per day (or more frequent passage than is normal for the individual)’. Diarrhoea can be divided into:

  • Acute diarrhoea – lasting <14 days
  • Persistent diarrhoea – lasting >14 days
  • Chronic diarrhoea – lasting >4 weeks

Acute diarrhoea is most commonly caused by infection, particularly viruses including norovirus.

History Taking

History of presenting complaint

With all presenting complaints, the following should be asked:

  • When did it start?
  • How long has this been going on?
  • Did it come on suddenly or gradually?
  • Is it continuous or intermittent?
  • Has this ever happened before?

Questions more specific to diarrhoea include:

  • How often are they opening their bowels?
  • How much stool are they passing?
  • What is the consistency of their stool?
  • Do they pass oily stools that are difficult to flush away – suggests fat malabsorption (e.g. coeliac disease)
  • Are they passing any blood?
  • Are they passing any mucus?
  • Do their symptoms occur at night? – this makes an organic cause more likely

Associated symptoms

  • Is there any abdominal pain?
  • Use SOCRATES to assess this
  • Do they have a fever?
  • Is there any nausea or vomiting?

Past medical history

  • Do they have any other medical conditions?
  • Have they ever had any surgery?
  • Do they take any regular medications?
  • Have they been prescribed antibiotics recently?

Other questions

  • Has anyone else around them been ill?
  • Have they been exposed to any source of infection (e.g. eating a meal out or travelling abroad)?
  • What recent types of food have they eaten?
  • Do their symptoms change with what they eat?

Red flags

Physical Examination

  • Measurement of vital signs and hydration status – diarrhoea can cause dehydration
    • May reveal tachycardia, hypotension (orthostatic hypotension may be present), delayed capillary refill time, reduced skin turgor, dry mucous membranes, decreased urine output, or altered mental status
  • Abdominal examination:
    • May reveal pain, tenderness, distention, organomegaly or masses, or changes in bowel sounds
  • Consider a rectal examination to assess for:
    • Stool character and content, mucus, blood, or suspected malignancy

Investigations

Acute diarrhoea

Most patients do not require testing, however, stool specimens for culture and sensitivity should be arranged if any of the following apply:

  • Systemically unwell, immunocompromised, needs hospital admission, needs antibiotics
  • Has recently had antibiotics, proton pump inhibitors (PPIs), or been in hospital
  • Blood or pus is present in the stool
  • Diarrhoea occurs after foreign travel
  • Diarrhoea is persistent (2 weeks or more) or the cause is uncertain
  • There is a public health indication (e.g. suspected food poisoning, outbreaks of diarrhoea, contacts with certain organisms such as Clostridioides difficile

If infectious causes of acute diarrhoea have been ruled out, the acute diarrhoea may be due to a chronic cause, and investigations for chronic causes should be considered.

Chronic diarrhoea

The following tests should be arranged for all patients:

  • Full blood count (FBC) – may detect anaemia
  • Liver function tests and albumin (LFTs)
  • Thyroid function tests (TFTs)
  • Urea and electrolytes (U&Es)
  • Vitamin B12 and folate
  • Calcium
  • Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)
  • Coeliac disease screening – immunoglobulin A (IgA), and IgA tissue transglutaminase (tTG) or IgA endomysial antibody (EMA)

Further investigations to consider are:

  • CA-125 testing if ovarian cancer is suspected
  • HIV testing if immunodeficiency is suspected
  • Sending stool samples for microbiological investigation and examination if an infection is suspected
  • Faecal calprotectin if inflammatory bowel disease is suspected
    • This should not be used in patients where cancer needs to be ruled out as it may be elevated in cancer
  • Faecal blood tests – for those that do not meet the referral criteria for suspected cancer

Initial Management

Emergency hospital admission for acute diarrhoea

Emergency admission should be arranged if any of the following apply:

  • Vomiting and unable to retain oral fluids
  • Clinical features of severe dehydration

Other factors that may increase the need for admission depending on clinical judgement:

  • >60 years old – due to increased risk of complications
  • Support at home
  • Fever
  • Bloody diarrhoea
  • Abdominal pain and tenderness
  • Co-existing comorbidities and drugs used

Suspected cancer pathway referral

Refer for an appointment within 2 weeks for colorectal cancer if any of the following apply:

  • ≥40 years + unexplained weight loss + abdominal pain or
  • ≥50 years + unexplained rectal bleeding or
  • ≥60 years + IDA or changes in bowel habit or tests show occult blood in faeces

A suspected cancer pathway referral should be considered if any of the following apply:

  • Adults with a rectal/abdominal mass
  • <50 years + rectal bleeding and any one of the following unexplained features:
    • Abdominal pain
    • Changes in bowel habit
    • Weight loss
    • IDA

If the diagnosis remains uncertain, refer to secondary care

Referral to secondary care for chronic diarrhoea

The following patients should be referred to secondary care if any of the history, examination, and blood tests suggest the following, or the following apply:

  • Inflammatory bowel disease
  • Coeliac disease
  • Bile acid malabsorption
  • Malabsorption
  • <40 years and does not have typical symptoms of IBS
  • The diagnosis is uncertain

Differential Diagnoses: Acute Diarrhoea

Infective gastroenteritis

  • See the Infectious Disease chapter for more information
  • See the Infectious Disease chapter for more information
  • There may be associated abdominal pain, nausea, and/or vomiting
  • Characteristic features of the underlying pathogen may be present (e.g. eating reheated rice and experiencing symptoms >6 hours)
  • There may be a history of travelling and carrying out activities that may predispose them to infection (e.g. eating street food or staying in places with unsanitary conditions)
  • Other family members may be affected
  • Patients may be dehydrated
  • FBC may show leukocytosis
  • Stool cultures may identify the underlying pathogen

Diverticulitis

  • Acute-onset colicky LLQ pain
  • Generally seen in older patients (>50 years)
  • Diarrhoea may be bloody
  • There may be a long history of constipation
  • Fever may be present
  • LLQ tenderness may be present
  • FBC may show leukocytosis

Antibiotic therapy

  • More commonly seen with broad-spectrum antibiotics such as clindamycin, cephalosporins, and tetracyclines

Appendicitis

  • Acute-onset constant, severe, central abdominal pain that classically moves to the right lower quadrant (RLQ)
  • Anorexia is commonly seen
  • More common in children and young adults
  • Fever and tachycardia may be present
  • Rovsing’s sign may be present – palpating the left lower quadrant (LLQ) elicits pain in the RLQ
  • FBC may show leukocytosis

Acute mesenteric ischaemia

  • Presents with acute-onset central abdominal pain
  • Patients classically have atrial fibrillation or other cardiovascular diseases
  • There may be a history of post-prandial abdominal pain (intestinal angina)
  • Pain is generally out of proportion to examination findings
  • Hypotension and tachycardia may be present
  • An abdominal x-ray may show free air, dilated bowel loops, or bowel wall thickening
  • A chest x-ray may show free air under the diaphragm
  • Serum lactate may be elevated, and an arterial blood gas may show metabolic acidosis

Differential Diagnoses: Chronic Diarrhoea and Other Causes

Irritable bowel syndrome

  • Consists of abdominal pain, bloating, and changes in bowel habits with no rectal bleeding or unintentional weight loss
  • Abdominal pain is often relieved by defecation
  • Symptoms do not correlate with gluten consumption
  • Investigations are unremarkable

Crohn’s disease

  • Patients are generally <50 years old
  • A history of chronic diarrhoea may be present
  • There may be associated fatigue, weight loss, and fever
  • An ileocaecal (right lower quadrant) mass may be present on exam
  • Oral ulcers and perianal disease (e.g. skin tags, fistulae, abscesses etc.) may be present
  • Anaemia may be seen
  • ESR/CRP may be elevated
  • Faecal calprotectin may be positive

Ulcerative colitis

  • Patients are generally <50 years old
  • A history of chronic diarrhoea may be present – more commonly bloody than in Crohn’s
  • disease
  • Faecal urgency and tenesmus may be present
  • Extra-intestinal features (e.g. joint pain) may be present
  • Anaemia may be seen
  • ESR/CRP may be elevated
  • Faecal calprotectin may be positive

Coeliac disease

  • Weight loss is also generally present
  • Symptoms tend to occur with gluten ingestion
  • Iron deficiency anaemia, low vitamin D, or hypocalcaemia may be seen, although many patients may have no abnormalities
  • Anti-TTG or anti-EMA antibodies may be positive

Overflow diarrhoea

  • There may be a longstanding history of constipation with intermittent diarrhoea
  • Patients report passing hard stools
  • Patients may use manual methods to remove faeces
  • An examination may reveal findings consistent with faecal impaction (e.g. hard stools)

Colorectal cancer

  • Constitutional symptoms such as unexplained weight loss may be seen
  • The referral criteria mentioned above may apply

Thyrotoxicosis

  • Associated features of hyperthyroidism may be present, such as weight loss, heat intolerance, sweating, and increased appetite
  • A fine tremor, goitre, or exophthalmos may be seen
  • Tachycardia or hypertension may be seen
  • TFTs show suppressed thyroid-stimulating hormone (TSH)

Drugs

Some drugs that may cause diarrhoea include:

  • Laxatives
  • Allopurinol
  • Angiotensin-II receptor blockers (ARBs)
  • Antibiotics
  • Metformin
  • NSAIDs
  • Proton pump inhibitors
  • Selective serotonin reuptake inhibitors (SSRIs) 

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