Crohn's Disease

Question 1

Who is commonly affected by Crohn’s disease?

Answer 1

A bimodal peak age of presentation of between 15-30 years and then again at 60-80 years.

Question 2

Briefly describe the course of Crohn’s disease?

Answer 2

The disease typically follows a remitting and relapsing course. Severe exacerbations may be life- threatening, causing severe systemic upset, bowel perforation or obstruction.

Question 3

Briefly describe the pathophysiology of Crohn’s disease

Answer 3

Crohn’s disease can affect any part of the gastrointestinal tract (from mouth to anus), although commonly targets the distal ileum or proximal colon, however much of its aetiology remains unknown. Much like UC, Crohn’s disease appears to have a familial link, however unlike UC smoking increases your risk of developing the condition.

It is characterised by transmural inflammation (affecting all layers of the bowel) in the affected region of bowel, producing deep ulcers and fissures (a ‘cobblestone’ appearance’). The inflammation is not continuous, forming skip lesions throughout the bowel.

The microscopic appearance of Crohn’s disease is non-caseating granulomatous inflammation.

Question 4

Why are fistulas a common finding of Crohn’s disease? Where can these form?

Answer 4

Due to the transmural nature of the inflammation, fistula can form from affected bowel to adjacent structures, resulting in perianal fistula (54%), entero-enteric fistula (24%), recto-vaginal (9%), entero-cutaneous fistula, or entero-vesicalar fistula.

Question 5

Briefly differentiate between ulcerative colitis and Crohn’s disease

Note: site involvement, inflammation, macroscopic findings and microscopic findings

Answer 5

Question 6

What are the risk factors for Crohn’s disease?

Answer 6

The aetiology of Crohn’s disease is unknown, yet both environmental factors and genetic factors are thought to play a role. The main risk factors for CD include:

• Family history
  
  • 20% have first degree relative affected
• Smoking
  
  • Increases the risk of developing Crohn’s disease and risk of relapse
• White European descent (particularly Ashkenazi Jews)
• Appendicectomy
  
  • Increases the risk of developing CD directly after the surgery

Question 7

What are the clinical features of Crohn’s disease?

Note: signs and symptoms

Answer 7

Crohn’s disease typically presents with episodic abdominal pain and diarrhoea. The abdominal pain may be colicky in nature and will vary in site depending on the region of bowel involved. Diarrhoea is often chronic and may contain blood or mucus.

Systemic symptoms include malaise, anorexia and low-grade fever. It may also result in malabsorption and malnourishment if severe, albeit typically a late presenting feature (in children, this may initially present as a failure to grow or thrive).

As the disease affects the entire GI tract, both oral and perianal involvement are common:

• Oral aphthous ulcers (can be painful and recurring)
• Perianal disease (as skin tags, perianal abscesses, fistulae or bowel stenosis)

Question 8

What are the clincial features of Crohn’s disease?

Note: examination

Answer 8

Examination features include abdominal tenderness, mouth or perianal lesions, and signs of malabsorption or dehydration. Patients should also be examined for extra-intestinal features.

Question 9

What is shown in the image?

Answer 9

Aphthous oral ulcer in active Crohn’s disease.

Question 10

What other systems are commonly affected in Crohn’s disease?

Answer 10

1. MSK
2. Skin
3. Eyes
4. Hepatobiliary
5. Renal

Question 11

What are the extra-intestinal features of Crohn’s?

Note: MSK

Answer 11

• Enteropathic arthritis (typically affecting sacroiliac and other large joints) or nail clubbing
• Metabolic bone disease (secondary to malabsorption)

Question 12

What are the extra-intestinal features of Crohn’s?

Note: skin

Answer 12

• Erythema nodosum- tender red/purple subcutaneous nodules, typically found on the patient’s shins
• Pyoderma gangrenosum- erythematous papules/pustules that develop into deep ulcers and can occur anywhere (yet typically affect the shins)

Question 13

What are the extra-intestinal manifestations of Crohn’s?

Note: eyes

Answer 13

• Episcleritis
• Anterior uvetitis
• Iritis

Question 14

What are the extra-intestinal manifestations of Crohn’s?

Note: hepatobiliary

Answer 14

• Primary sclerosing cholangitis (more associated with UC)
• Cholangiocarcinoma (due to association with primary sclerosing cholangitis)
• Gallstones

Question 15

What are the extra-intestinal manifestations of Crohn’s?

Note: renal

Answer 15

• Renal stones

Question 16

What is shown in image A?

Answer 16

Extra-intestinal manifestation of Crohn’s disease: (A) Erythema nodosum

Question 17

What is shown in image B?

Answer 17

Extra-intestinal manifestation of Crohn’s disease: (B) Pyoderma gangrenosum

Question 18

What investigations should be ordered for Crohn’s disease?

Answer 18

Routine bloods are required to examine for anaemia, low albumin (secondary to malabsorption), and evidence of inflammation (raised CRP and WCC).

A faecal calprotectin test should be performed in all patents with recent onset lower gastrointestinal symptoms, with a good sensitivity for inflammatory bowel disease. A stool sample for any potential infective cause can also be considered.

Question 19

What imaging can be used to differentiate between Crohn’s and toxic megacolon or a bowel obstruction?

Answer 19

In the acute situation, an abdominal radiograph (AXR) or CT imaging may be useful to exclude any potential toxic megacolon or bowel obstruction that may have occurred.

Question 20

What investigations should be ordered for Crohn’s disease?

Note: imaging

Answer 20

There are three main types of imaging that can be utilised in the diagnosis of Crohn’s disease:

• Colonoscopy with biopsy
• CT scan abdomen pelvis
• MRI scan

Question 21

What is the role of colonoscopy with biopsy in Crohn’s investigation?

Answer 21

The gold standard diagnostic investigation.

A characteristic macroscopic finding is cobblestoning of the bowel (fissures and ulcers separate islands of healthy mucosa), with non-caseating granulomatous inflammation on histology.

Question 22

What is the role of CT scan abdomen pelvis in Crohn’s investigation?

Answer 22

Usually warranted in severe Crohn’s disease, which may demonstrate bowel obstruction, perforation, collection formation or fistulae.

Question 23

What is the role of MRI scan in Crohn’s disease investigation?

Answer 23

Particularly useful for looking for enteric fistulae (MRI small bowel) and for peri-anal disease (MRI pelvis).

Question 24

When is examination under anaesthesia with proctosigmoidoscopy used in Crohn’s disease?

Answer 24

Examination under anaesthesia with proctosigmoidoscopy may also be considered to examine and treat perianal fistulae present.

Question 25

Why should anti-motility drugs, such as loperamide, should be avoided in acute attacks?

Answer 25

Anti-motility drugs, such as loperamide, should be avoided in acute attacks, as these can precipitate toxic megacolon.

Question 26

Briefly describe the medical management of Crohn’s disease: inducing remission

Answer 26

Any acute attacks will also warrant aggressive fluid resuscitation, nutritional support, and prophylactic heparin and anti-embolic stockings (due to the prothrombotic state of IBD flares).

The medical management to induce remission in Crohn’s Disease requires use of corticosteroid therapy and immunosuppresive agents, such as mesalazine or azathioprine. Biological agents, such as infliximab, can be trialled as rescue therapy if then needed.

Question 27

Briefly describe the medical management of Crohn’s disease: maintaining remission

Answer 27

Azathioprine is recommended as a monotherapy to maintain remission, mesalazine or methotrexate are alternatives that can be trialled or added in.

In recent years with the development of biological agents, patients can be started on infliximab, adalumimab, or rituximab if there has been a failure of treatment with other agents. These are often also used as rescue therapy during acute flares in those who have not responded to first line remission agents.

Smoking cessation is advised. Due to increased risk of colorectal malignancy, colonoscopic surveillance is offered to people who have had the disease for >10 years with >1 segment of bowel affected (follow-up time frame depends on risk stratification of disease following initial endoscopy).

Patients should be referred to IBD-nurse specialists and patient support groups. Enteral nutritional support should be considered in young patients with growth concerns, with close support from nutritional teams. Antibiotics are only offered to those with obvious concurrent infection or perianal disease (typically ciprofloxacin or metronidazole).

Question 28

How common is surgical management in Crohn’s?

Answer 28

Around 70-80% of Crohn’s patients require surgery at some point in their lifetime.

Question 29

When is surgical intervention used in Crohn’s disease?

Answer 29

Surgical intervention is indicated in those with:

• Failed medical management
• Severe complications (such as strictures or fistulas)
• Growth impairment in younger patients

Question 30

What are the common surgical operations used in Crohn’s disease?

Answer 30

Operations that are commonly required in patients with Crohn’s disease include:

• Ileocaecal resection (removal of terminal ileum and caecum with primary anastomosis)
• Surgery for peri-anal disease (e.g. abscess drainage, seton insertion or laying open of fistulae)
• Stricturoplasty (division of a stricture that is causing bowel obstruction)
• Small bowel or large bowel resections

Question 31

Why is a bowel sparing approach used in surgery in patients with Crohn’s disease?

Answer 31

In all proposed operations, a bowel-sparing approach must be taken to prevent short gut syndrome in later years.

Question 32

What are the GI complications of Crohn’s disease?

Answer 32

• Fistula
  
  • Including enterovesical, enterocutaneous, or rectovaginal fistula
• Stricture formation
  
  • Inflammation of the bowel can result in stricture formation, resulting in bowel obstruction
• Recurrent perianal abscesses/ fistulae
  
  • These are common and often difficult to treat, requiring multiple operations/ examinations under anaesthesia
• GI malignancy
  
  • Patient’s with Crohn’s disease have about a 3% risk of developing colorectal cancer over 10 years and small bowel cancer is about 30x more common in those with Crohn’s disease

Question 33

What are the extraintestinal manifestations of Crohn’s disease?

Answer 33

• Malabsorption
  
  • Including growth delay in children
• Osteoporosis
  
  • Particularly common if there is obstruction or fistula formation
  • Secondary to malabsorption or long-term steroid use
• Increased risk of gallstones
  
  • Due to reduced reabsorption of bile salts at inflamed terminal ileum
• Increased risk of renal stones
  
  • Due to malabsorption of fats in the small bowel which causes calcium to remain in the lumen; oxalate is then absorbed freely (as normally bound to calcium and excreted in stool), resulting in hyperoxaluria and formation of oxalate stones in the renal tract