Crohn's disease Flashcards
Define Crohn’s disease.
Chronic granulomatous inflammatory disease that can affect any part of the gastrointestinal tract from mouth to anus (esp. terminal ileum in ~70%).
Unlike in UC there is unaffected bowel between areas of actve disease (skip lesions). Transmural.
What are skip lesions?
Areas of unaffected bowel between areas of active disease (skip lesions) in Crohn’s.
How common is Crohn’s disease?
- Incidence ~10 per 100,000
- Typically presents between age 20-40yrs with a small peak at 50-60yrs
- M=F
- It is more common in white people and Ashkenazi Jews and smokers.
What are the risk factors for Crohn’s disease?
- White ethnicity - Ashkenazi Jews have a 2- to 4-fold increased risk of CD.
- Age 15-40 or 60-80yrs
- FH of Crohn’s
- Smoking - x2
Other:
- High refined sugar diet/processed foods
- Low fibre diet
- Oral contraceptive pill - x1.7
- Not breastfed - x3-4
- NSAIDS
What is the aetiology and pathophysiology of Crohn’s disease?
Cause is unknown but there is a strong genetic susceptibility. Combined with environmental factors may cause manifestation of the disease.
- Inflammation occurs in all layers, down to the serosa.
- Cobblestone appearance seen endoscopically separated by skip lesions of healthy areas
- Non-caseating granulomas (exclude TB and sarcoid)
- This makes Crohn’s patients prone to strictures, fistulas and adhesions
What is the prognosis with Crohn’s disease?
Approximately 50% of patients will require an intestinal resection within 5 years of diagnosis
What is the typical presentation of Crohn’s disease?
- Diarrhoea - bloody in colonic disease
- Weight loss and lethargy
- Crampy abdominal pain - caused by inflammation, fibrosis, or obstruction
- Perianal skin tags or ulcers
May present with RIF pain mimicking appendicitis - usually due to terminal iluem infection of Yersinia/TB.
What is shown?
Erythema nodosum
What is an important aspect of examination in Crohn’s?
- Oral inspection for ulcers
- Perineal inspection for perianal skin tags, fistulae, abscesses, and sinus tracts
- Digital rectal examination for occult blood and exclusion of a mass.
List some specific extraintestinal manifestations of Crohn’s disease.
- Signs of arthropathy - sero−ve arthritis of large or small joints, spondyloarthropathy, ankylosing spondylitis, sacroiliitis
- Cutaneous lesions e.g., erythema nodosum, pyoderma gangrenosum
- Ocular symptoms and signs e.g., of uveitis or episcleritis
What investigations would you do for Crohn’s disease?
Full panel of tests should be done to exclude other causes.
- Bloods:
- FBC - low Hb, high plt, high WCC- normocytic anaemia but sometimes megaloblastic if B12 deficiency
- ESR and CRP - raised
- Iron studies (normal or deficient), folate(deficiency)
- Comprehensive metabolic panel - hypoalbuminaemia/chol/calc
- LFTs may be abnormal
- Blood cultures - if suspect septicaemia
- Serological tests - for negagtive perinuclear ANCA (pANCA) and posistive ASCA
- Stool tests -
- MC&S - Check for C diff if diarrhoea, campylobacter, e.coli.
- Microscopy for parasites.
- Faecal calprotectin (good sensitivity), lactoferrin and raised active intestinal disease.
- Imaging - non-specific
- AXR - bowel loop distension and pneumoperiteoneum
- CT/MRI - skip lesions, bowel wall thickening, surrounding inflammation, abscesses, fistulae; exclude lymphadenopathy and malignancy
- Radionucleotide-labelled scans - better visualisation of fistulas and obstruction
- USS - for extramural complications
- Invasive:
- Endoscopy (OGD, colonoscopy)- may help differentiate between UC and CD, useful monitoring for malignancy and disease progression. Mucosal oedema and ulceration with cobblestone mucosa fistulae, abscesses.
- Biopsy - Transmural chronic inflammation with infiltration of macrophages, lymphocytes and plasma cells. Non-caseating granulomas wih epithelioid giant cells may be seen in blood vessels or lymphatics.
What are the features of Crohn’s on endoscopy and biopsy?
Endoscopy:
- aphthous ulcers
- hyperaemia
- oedema
- cobblestoning
- skip lesions
Biopsy -
- transmural chronic inflammation
- infiltration of macrophages, lymphocytes and plasma cells
- non-caseating granulomas with epithelioid giant cells
What are the consequences of malabsorption at the terminal ileum?
- Vitamin and nutrient deficiencies
- Less bile acid absoprtion –> fat soluble vitamins are lost, less fat absorption –> steatorrhoea
- Gallstone formation
- Excess fat in stool binds calcium, incerasing oxalate absorption and predisposing to oxalate kidney stones.
What is the non-surgical management of Crohn’s?
Conservative -
- STOP SMOKING
- Dietician advice
- Referral ito IBD nurse specialist
Medical:
INDUCE REMISSION
- 1st line: Glucocorticoids e.g. prednisolone - oral, topical OR IV
- 2nd line: 5-ASA drugs e.g. sulfasalazine, mesalazine, reduced relapses; not as effective as prednisolone
- +/- immunosuppression e.g. azathioprine, 6-mercaptopurine, methotrexate, to reduce relapses
- +/- anti-TNFa agents e.g. infliximab and adalimumab. - for refractory and fistulating disease
- +/- antibiotics e.g. metronidazole for peri-anal disease
MAINTAIN REMISSION
- 1st line: azathioprine or mercaptopurine (NB: check TPMT)
Surgery
- When medical treatment fails/failure to thrive/complications –> resection of bowel and stoma but still risk of recurrence
How do you manage Crohn’s disease acutely?
- Fluid resuscitation
- Remission inducing agents - IV/oral corticosteroids + 5-ASA analogues
- Analgesia
- Elemental diet +/- parenteral nutrition
- Monitor markers of activity (fluid balance, ESR, CRP, plt, stool frequency, Hb, albumin)
- Assess for complications
Consider need for blood transfusion if Hb<80mg/f
What are the extra-abdominal manifestations of Crohn’s?
- skin - pyoderma gangrenosum, erythema nodosum
- joints - arthritis is polyarticular, symmetric, clubbing, osteoporosis, sacroiliitis, ankylosing spondylitis
- mouth
- eyes - episcleritis (CD>UC) uveitis (CD< UC)
- liver
- bile ducts - PSC (CD < UC), gallstones
- renal - kidney stones,
- systemic - amyloidosis
What is the management of perineal fistulas in Crohn’s?
DIAGNOSIS:
- MRI is diagnostic - determines if SIMPLE (low fistula) or COMPLEX (high fistula that passes through or above muscle layers)
MANAGEMENT:
- Oral metronidazole
- Anti-TNF agents - may close perianal fistulas
- Surgery - draining seton placement
What do small bowel enema studies shown in Crohn’s?
- high sensitivity and specificity for examination of the terminal ileum
- strictures: ‘Kantor’s string sign’
- proximal bowel dilation
- ‘rose thorn’ ulcers
- fistulae
