Crohn’s Disease

Following my last post on UC, today I met a 70 something year old lady who has had UC since she was 21, and what a story she had: UC, pan-colitis, colon cancer, total colectomy with an ileo-anal pouch, Primary Scelorosing Cholangitis, liver failure, liver transplant- in that order, with lots in between. All as a complication of her UC.

Crohn’s disease is a similar condition to UC, both making up IBD- inflammatory bowel disease.

Crohn’s Disease

Definition: chronic inflammatory GI disease characterised by transmural granulomatous inflammation affecting any part of the gut, from mouth to anus, and especially the terminal ileum (in ∼70%) and proximal colon.

Unlike UC, there are unaffected parts of bowel in between diseased areas – skip lesions.

UC + Crohn’s = IBD (Inflammatory Bowel Disease)

Aetiology/risk factors:

-Cause unknown

-Genetic association

-Altered cell-mediated immunity

-Smoking increases risk 3-4x (opposite of UC. In UC smoking suppresses disease)

-NSAIDs may exacerbate disease

Epidemiology:  Prevalence- 0.5-1/1000, Incidence- 5-10/100,000/yr. (Slightly less common than UC).

-presentation mostly at ∼20-40 yrs (Slightly older than UC)

-less prevalent in Asians


Diarrhoea/ urgency (May be bloody or steatorrhoea. Bloody diarrhoea is usually a feature of UC)

-Crampy abdominal pain

Weight loss/ failure to thrive

Fever, malaise, anorexia


-Aphthous ulceration

Image result for aphthous ulcers

-Abdominal tenderness/mass

-Weight loss

-Signs of anaemia: conjunctival pallor, koilonychia (spoon-shaped nails)

-Perianal abscess/fistulae (abnormal connection between two hollow spaces)/skin tags

Anal strictures (narrowing’s)



-skin, joint and eye problems similar to UC (erythema nodosum, pyoderma gangrenosum, sero -ve arthritis of big joints, spondyloarthropathy, ankylosing spondylitis, sacroiliitis, conjunctivitis, episcleritis, iritis)


Bloods: FBC (↓Hb ↑WCC), ↑ESR, CRP, U&Es, LFTs (↓albumin), INR, blood culture

 –Ferritin, Total Iron Binding Capacity (TIBC), B12, Folate (more nutritional deficiencies in Crohn’s than UC as it tends to affect the terminal ileum, where many nutrients are absorbed, and can affect other parts of the small bowel, whereas UC only affects the colon.)

Cross-match if severe blood loss.

Stool sample: MC+S (microscopy, culture and sensitivities)/CDT (C. difficile toxin)

 –Faecal calprotection = marker of intestinal inflammation, used as marker for disease severity

Want to exclude infectious causes of diarrhoea (infectious colitis).

Infectious causes of bloody diarrhoea = CHESS


Haemorrhagic E.coli

Entamoeba histolytica (parasite)



Abdominal x-ray


Image result for axr ulcerative colitis

Thumb printing sign = thick haustral folds = thickened inflamed bowel wall

-colonic dilatation (toxic megacolon, > 6cm, bowel wall thickening and loss of mucosal folds in colon, rare complication in Crohn’s, compared to UC)


Image result for toxic megacolon ulcerative colitis

Toxic megacolon


Erect chest x-ray- perforation as a complication = air under the diaphragm

Image result for erect cxr bowel perforation

Capsule Endoscopy-used to detect Crohn’s in small bowel. A small capsule transmits video via radio to pads on the skin and movies are stored in a device.

Image result for capsule endoscopy


Small bowel enema– detects ileal disease

Barium enema- rarely used. Never do during severe attacks. Colonoscopy and barium enema carry a risk of perforation during acute attacks.

Cobblestoning, ‘rose thorn’ ulcers +/- colon strictures

Image result for barium enema crohn's cobblestoning

Spot the cobblestones

Image result for barium enema crohn's cobblestoning

More cobblestones

Image result for barium enema rose thorn ulcers

Rose thorn ulcers = deep ulceration

Colonoscopy + Rectal Biopsycolonoscopy is preferred to barium enema, to assess disease extent and allows biopsy. Useful for differentiating CD from UC, and monitoring for malignancy and disease progression.

=mucosal oedema and ulceration, cobblestone mucosa, fistulae, abscesses

=transmural chronic inflammation with infiltration of macrophages, lymphocytes and plasma cells. Granulomas with epithelioid giant cells may be seen in blood vessels or lymphatics.

MRI- can assess pelvic disease (e.g. abscess) and fistulae. Small bowel MRI assesses disease activity and shows sites of strictures


optimize nutrition (diet/supplements)- enteral is preferred, total parenteral nutrition (TPN) should be last resort

assess severity, consider admission if Temp↑, pulse↑, ESR↑, WCC↑, CRP↑, albumin↓

-Drug options: aminosalicylates (5-ASA), steroids, immunosuppressants, TNF inhibitors (infliximab), antibiotics 

Mild attacks– symptomatic but systemically well:

PREDNISOLONE (30mg/d PO for 1week, then 20mg/d for 4 weeks. If symptoms resolve, reduce prednisolone by 5mg every 2-4 weeks. Stop steroids when parameters are normal.)

Severe Attacks- looks systemically unwell: (manage similar to severe UC attack)

-Admit for IV steroids, nil by mouth, and IV fluids.


-Treat rectal disease: PR steroids e.g. PR HYDROCORTISONE (100mg in 100ml 0.9% saline/12h)

IV/PO METRONIDAZOLE (antibiotic) helps, especially in peri-anal disease or infection (400mg IV/500mg PO/8h)

-Monitor temperature, pulse and BP, stool frequency/ character, FBC, ESR, CRP, U&Es, AXR.

-Consider blood transfusion e.g. if Hb <90-100g/L, and parenteral nutrition.

-If improving within 5 days, transfer to oral PREDNISOLONE (40mg/24h).

-If not improving, INFLIXIMAB (anti-TNF) and ADALIMUMAB (anti-TNF)

-Consider abdominal sepsis complicating Crohn’s, esp. if abdo pain. Seek surgical advice.

Perianal disease- occurs in 50%, e.g. fistulae, abscesses

-MRI + Examination Under Anaesthetic (EUA)

-Oral antibiotics, immunosuppressant therapy +/- infliximab

-Local surgery +/- seton insertion  (seton =silk or latex string into fistula to drain it)

Additional therapies (useful in 50%)

Azothioprine- can be used as steroid sparing agent

Sulfasalazine- 5-ASAs are the mainstay treatment of UC but unproven efficacy in Crohn’s

TNF-α inhibitors- infliximab, adalimumab


Nutrition- Elemental diets contain amino acids and can give remission. Low residue (low fibre) diets help control Crohn’s activity, but won’t on their own give remission.


IV Immunoglobulins (IVIG)

Surgery- surgery is not curative. Indicated in drug failure, complications such as perforation, strictures causing obstruction, fistulae and abscesses.

-Rest distal disease e.g. temporary ileostomy

-Resection of worst areas


-Small bowel obstruction

-Toxic dilatation toxic dilatation of colon (toxic megacolon- diameter > 6cm)- rarer than in UC

-Abscess formation (abdominal, pelvic or ischio-rectal)

-Fistulae (in ∼10%) e.g. colovesical (colon to bladder), colovaginal (colon to vagina), perianal, enterocutaneous (colon to skin)



-Colon cancer

-Fatty liver

-Primary Sclerosing Cholangitis (more in UC), cholangiocarcinoma

-Renal stones




Prognosis: chronic relapsing condition. 2/3 will require surgery at some stage and 2/3 of these > 1 surgical procedure.

-Poor prognosis if age < 30yrs, steroids needed at first presentation, perianal disease, diffuse small bowel disease

References: Cheese & Onion, Rapid Medicine

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