Crohn's disease

Question 1

Definition

Answer 1

Chronic, relapsing-remitting, non-infectious inflammatory disease of GI tract

Question 2

Inflammation

Answer 2

o Anywhere from mouth to anus
o Skip lesions – normal areas between areas of inflammation
o Full thickness of intestinal wall i.e. transmural
o Terminal ileum in 45%, colon 32%, ileocolon 19%, upper GIT 4%

Question 3

How common?

Answer 3

Prevalence: 10 per 100,000

Less common than UC

Question 4

Who’s affected?

Answer 4

Most commonly presents in adolescence and early adulthood but can occur at any age
20-30% present before 20, median age diagnosis = 30yrs
M=F
Smokers
Worldwide but more in northern Europe, UK &North America, increased likelihood in Hispanic, Asians, Jewish races

Question 5

Cause

Answer 5

Thought to be immune mediated caused by environmental triggering events in genetically susceptible people

Strong genetic association - CARD15(NOD2) gene on chromosome 16 confer susceptibility

Question 6

Risk factors

Answer 6

• FHx: 20% have first degree relative with it
• Smoking: 2 fold increased risk
• Infectious gastroenteritis: risk increased 4x following episode but overall risk low
• Early after appendicectomy
• NSAIDs, OCP – overall risk low
• Stress/depression may precipitate relapses

Question 7

Pathology

Answer 7

Affects: all GI tract – especially terminal ileum and ascending colon, rectum involved in 50% of cases, lesions are patchy (unaffected areas between areas of disease)

Macroscopic: small bowel thickened, deep ulcers and fissures in mucosa, cobblestone appearance, fistulae and abscesses in colon, aphthoid ulceration is an early features

Microscopic: granulomas present in 50-60% non-caseating epithelioid cell aggregates with Langhans’ giant cells

Inflammation: transmural/deep

Strictures: common

Crypt Abscesses: uncommon

Goblet Cells: present

Question 8

Symptoms (GI)

Answer 8

Depends on regions of GI tract affected 
•	Persistent diarrhoea
•	Abdominal pain/discomfort 
•	Blood in stools 
•	Fatigue
•	Weight loss
•	oral aphthous ulcers

Colonic: diarrhoea, blood/mucus in stool, pain related to defecation, faecal urgency, tenesmus
Perianal: anal tags, fissures, fistulae on abscess formation

Question 9

Symptoms (extraintestinal)

Answer 9

Occurs in 6%, more common if Crohn’s colitis

MSK – arthritis (commonly sacroiliac or other large joints), clubbing, osteopenia/osteoporosis/ osteomalacia

Skin – erythema nodosum, pyoderma gangrenosum, psoriasis

Eyes – episcleritis, uveitis, conjunctivitis

Liver/biliary - primary sclerosing cholangitis (more associated with UC), cholangiocarcinoma (due to association with PSC), autoimmune hepatitis, cirrhosis, gallstone, fatty liver

RARE: bronchiectasis, bronchitis, pancreatitis, hyperhomocysteinemia, renal stones, VTE

Question 10

Signs

Answer 10

• Pallor
• aphthous mouth ulcers
• signs of systemic illness: anorexia, fatigue, malaise, fever, clubbing
• abdominal pain/tenderness or mass – usually in lower right quadrant
• perianal pain or tenderness
• anal/perianal skin tag, fissure, fistula or abscess
• signs of malnutrition and malabsorption – weight loss, faltering growth, delayed puberty
• signs of extraintestinal manifestations

Question 11

Differentials

Answer 11

• UC
• Infective colitis
• IBS
• Coeliac disease
• Diverticulitis
• Endometriosis
• Intestinal ischaemia
• Others include pseudomembranous colitis (C. diff infection), microscopic colitis, acute appendicitis, anal fissure, malignancy, laxative misuse

Question 12

Investigations

Answer 12

BLOODS: FBC (anaemia, raised WCC), U&Es, LFTs, raised inflammatory markers (CRP and ESR FAECAL CALPROTECTIN: good sensitivity for IBD
STOOL MICROSCOPY AND CULTURE: rule out infective cause

COLONOSCOPY + BIOPSY – gold standard for diagnosis, shows disease extent, biopsy differentiates between UC and Crohn’s. May consider upper intestinal endoscopy
CT abdo/pelvis
MRI

Question 13

management - inducing remission

Answer 13

1st LINE: corticosteroids e.g. prednisolone (induce remission only)
2nd LINE: immunosuppressant agents - thiopurines (e.g. azathioprine, mercaptopurine) or methotrexate (induce and maintain remission)
3rd LINE: biologic therapy e.g. infliximab, adalimumab (induce and maintain remission)

Question 14

Management - maintaining remission

Answer 14

1st LINE: azathioprine

Question 15

Surgical management

Answer 15

80% require surgery at some point but should avoid if possible (if unavoidable take bowel saving approach to prevent short gut syndrome) – recurrence 15% per year

Indicated if medical management failed or severe complications

May involve ileocaecal resection, small or large bowel resection, surgery for perianal disease, stricturoplasty

Question 16

Other general management

Answer 16

• Lifestyle: smoking cessation, nutrition
• Screening for CRC
• Symptom management
• Pain – analgesics, paracetamol preferred

Question 17

Prognosis

Answer 17

Lifelong, periods of relapse and remission which are unpredictable and vary
Higher mortality than general population

Question 18

Complications

Answer 18

FISTULAE – perianal (54%), entero-enteric (24%), recto-vaginal (9%), enterocutaneous, enterovesciular

STRICTURES

GI MALIGNANCY - 3% CRC risk, small bowel cancer 30x more common

Malabsorption 
Osteoporosis (steroid use)
Gallstones 
Renal stones 
Psychosocial impact 
Intestinal complications: stricture, fistula (25%), perianal disease, acute dilation & perforation of GI tract, haemorrhage 
Toxic megacolon 
Anaemia –iron deficiency, vit B12/folate deficiency or anaemia of chronic disease