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Crohn’s Disease

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Overview

Crohn’s disease (CD) is a type of inflammatory bowel disease (IBD) which can affect any part of the gastrointestinal (GI) tract from the mouth to the anus. The terminal ileum and colon are most commonly affected.

Its pathophysiology is not fully understood, however, genetic and environmental factors are implicated. Unlike ulcerative colitis (UC), inflammation is patchy and there are unaffected regions of bowel between areas of active disease (known as skip lesions). The inflammation is also transmural, affecting all layers of the GI tract, explaining why patients with CD are prone to fistulas, adhesions, and strictures.

For more regarding differentiating between CD and UC, see Inflammatory Bowel Disease.

Epidemiology

  • Prevalence in the UK is around 145 per 100,000
  • Its onset peaks between 15-30 years and 50-70 years, however, its incidence is rising in children

Risk Factors

  • Family history
  • Smoking
  • NSAID use

Presentation

Symptoms

Patients may present with:

  • Non-specific features:
  • Chronic and unexplained diarrhoea (for more than 4-6 weeks):
    • If the colon is affected (colitis), then diarrhoea may be bloody
  • Abdominal pain:
    • May be due to active inflammation adhesions, fistulas, strictures, or obstruction

Examination findings

  • Finger clubbing
  • Mouth ulcers
  • Pallor:
  • Signs of malnutrition and malabsorption:
  • Abdominal tenderness or a mass:
    • Often in the lower right quadrant suggesting terminal ileal inflammation
  • Signs of perianal disease:
    • Perianal pain or tenderness
    • Skin tags
    • Fissures
    • Fistulas
    • Abscesses
  • Signs of extraintestinal manifestations – see Inflammatory Bowel Disease: Complications for more

Investigations

Overview

  • Full blood count:
    • May show anaemia which can be due to chronic inflammation, blood loss, or iron/B12/folate malabsorption
    • Increased white cells suggest acute or chronic inflammation
    • Increased platelets suggest active inflammation
  • Iron studies:
    • To identify iron deficiency
  • Haematinics:
    • To assess serum B12 and folate:
  • C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR):
    • Elevated in inflammation and correlates with disease activity
  • Stool testing:
  • Faecal calprotectin:
    • A non-specific marker released from neutrophils in gastrointestinal tract inflammation
    • Can help with differentiating IBD from irritable bowel syndrome (IBS)
  • Colonoscopy with biopsies:
    • The diagnostic test
    • The presence of skip lesions, transmural inflammation, goblet cells, and granulomas suggest CD
  • Barium fluoroscopy, CT, or MRI:
    • May be used to assess the bowels in regions inaccessible by endoscopy
    • Pelvic MRIs can examine the extent and location of abscesses and fistulas

Management

Referral

The diagnosis of Crohn’s disease and initiation of treatment is initiated in secondary care. An urgent referral to a gastroenterologist should be made. If a patient is systemically unwell with features such as bloody diarrhoea, fever, tachycardia, or hypotension, emergency hospital admission should be arranged.

Inducing remission

Management involves initially inducing remission:

  • 1st-line: glucocorticoids (e.g. oral prednisolone or IV hydrocortisone) + taper
    • Budesonide may be used if glucocorticoids are contraindicated/not tolerated
    • In children where there are concerns regarding glucocorticoid side-effects or growth, enteral nutrition may be considered as an alternative
    • 5-aminosalicylate (5-ASA) drugs (e.g. mesalazine) may be considered as an alternative to glucocorticoids and budesonide, but are less effective
  • 2nd-line: add-on azathioprine or mercaptopurine:
    • Thiopurine methyltransferase (TPMT) activity must be checked before giving these. They should not be offered if TPMT activity is very low/absent
    • If azathioprine and mercaptopurine are inappropriate, methotrexate may be used instead
    • Do not offer azathioprine, mercaptopurine, or methotrexate as monotherapy
  • If the above measures fail or are not tolerated, infliximab or adalimumab may be considered 

Maintaining remission

Once remission is induced, management aims to maintain remission:

  • Patients should be advised to stop smoking as it can worsen CD
  • 1st-line: azathioprine or mercaptopurine
    • TPMT activity should be checked first
  • 2nd-line: methotrexate

Surgery

If there is a failure to respond to medical therapy/worsening symptoms, surgery may be indicated. Other scenarios requiring surgical approaches include:

  • Perianal fistulae:
    • If asymptomatic: treatment may not be needed
    • Oral metronidazole – to control infection
    • Surgery may be necessary
  • Perianal abscess:
    • IV antibiotics + incision and drainage
  • Strictures:
    • Balloon dilation if accessible by colonoscopy

Patient Advice

  • Patients should be advised to and be offered help to stop smoking:
    • Smoking can exacerbate CD
  • Patients should continue to eat a regular and balanced diet, as an improper diet may lead to malnutrition which can have serious consequences
  • NSAIDs and the combined oral contraceptive pill (COCP) should be avoided as they have been associated with worse outcomes in CD
  • Patients with any recurrence of symptoms should seek medical help urgently
  • Patients taking immunosuppressants with fevers, malaise, chills, sore throat, bruising, or mouth ulcers should seek medical help as they may be indicators of serious drug side effects (e.g. myelosuppression)

Complications

See Inflammatory Bowel Disease: Complications for more.

Prognosis

CD is a lifelong condition characterised by periods of relapse and remission.

  • Around 10% of patients may have prolonged clinical remission
  • Around 50% of patients may undergo surgery within 10 years of diagnosis
  • The location of the disease may tend to remain stable over time

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