Inflammatory Bowel Disease

last authored: Aug 09, David LaPierre

 

Introduction

Inflammatory bowel disease describes two distinct but related diseases - ulcerative colitis and Crohn's disease. In the US, incidence of IBD is 3-10 per 100,000 people, while the prevalence is about 30-100 per 100,000. Both sexes are equally affected. A bimodal age pf presentation exists, with an initial peak between 20-50 and another in the 60's.

 

 

The Case of Mrs Stuhl

Mrs Stuhl is a 40 year-old woman with a five year history of occasionally bloody diarrhea, abdominal pain, and weight loss. Her family doctor considers inflammatory bowel disease.

• Q: what is the difference between Crohn's disease and ulcerative colitis?
• Q: What are the signs and symptoms of each?

 

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Causes and Risk Factors

Although causes remain elusive, the main theory regarding IBD involves a dysregulation of the normal intestinal immune processes, most likely in response to bacteria, normal flora, or otherwise, or some other environmental component.

 

Genetics

IBD affects people from every ethnic group, but is more common in people from Northern European ancestry. Approximately 10% of people with IBD have a first degree relative with the disease.

A large number of susceptibility loci have been identified, supporting the idea of polygenic effects. The Nod2/CARD15 gene appears especially important.

 

Immunologic factors

In normal intestine, lymphoid tissue is constantly activated in response to antigenic substances which have crossed the epithelial barrier. A large network of different cell types exists to discriminate harmful from nonharmful stimuli, and regulatory cells are important in attenuating inappropriate responses. In IBD, it appears an over-activation response more than a downregulation of inhibition is involved.

 

Environmental Factors

Even though IBD is more common in industrialized countries, the role of the environment remains poorly understood. Many infectious agents, such as Mycobacterium paratuberculosis or measles virus, have been implicated in IBD, but links remain shady.

Smoking leads to a more aggressive Crohn's disease while is seemingly protective in ulcerative colitis. Elemental diets and diversion of the fecal stream can reduce inflammation, but no dietary triggers have yet been found to cause IBD.

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Pathophysiology

 

Ulcerative colitis

Ulcerative colitis is characterized by inflammatory changes affecting the colonic mucosa in a continuous superficial fashion, starting in the rectum and spreading proximally to the . Approximately 40-50% have proctitis or proctosigmoiditis, 30-40% have left-sided colitis extending to the splenic flexture, and the remaining 20-25% have pancolitis.

There is an association with primary sclerosing cholangitis.

 

Crohn's Disease

Crohn's disease can involve any segment of the GI tract, often in a discontinuous fashion to form skip lesions. Transmural chronic inflammation, involving IL-1, IL-2, IL-6, and TNFα, results thickening and eventual strictures. The mucosal surface can become cobblestoned, relating to edema with linear ulcerations. Fissures, localized perforations, and abscesses can form fistulas - to gut, bladder, vagina, or skin.

The most common form is ileocecal Crohn's, affecting 40% of patients. Thirty percent of patients have disease affecting the small intestine, while 25% of people have exclusive colonic involvement. Ulcers can be apthous or more linear.

 

Distinguishing UC from CD

Crohn's: small bowel involvement, rectal sparing, perinanal disease, skip lesions, fistulas, and granuloma

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Signs and Symptoms

Diagnosis of IBD is made by incorporating clinical, radiologic, endoscopic, and histologic information. It is often diagnosed during presumptive surgery for appendicitis.

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Investigations

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Differential Diagnosis

• irritable bowel syndrome (IBS)
• gastroenteritis
• parasitic infection

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Treatments

Cure is unfortunately not possible, and this should be communicated to patients to ensure their expectations are appropriate. Gastroenterologists, together with family doctors, provide primary care to people with IBD. Nurse practitioners play an important role, as do dietitians. Pharmacists are important in ensuring medications are taken properly. Surgeons provide care to people with progressive, advanced disease. The principle is to use the least toxic regimen possible. Answer three questions - what is it? where is it? how bad is it? - when determining treatment.

 

Lifestyle treatments

The most important step for patients with Crohn's is to quit smoking; with UC, however, continued smoking can prevent worsening.

Understanding irritable bowel disease triggers, symptoms, and treatments is important for patients, their families, and the community. While there is no clear link between IBD and specific foods, some foods are easily tolerated by one person but can cause discomfort in others. Following the Canada Food Guide is important to ensure adequate nutritional intake.

 

Medications

Antiinflammatory medications include:

• 5'-ASA - mild anti-inflammatories, good first line for ulcerative colitis, but not Crohn's disease. Can be given by suppository, enema, or orally
• steroids are useful for flareups, but with multiple serious side effects, not useful for long term
• immunosuppressants - azithioprine, methotrexate
• biologicals - infliximab, intimira (sp?) can be used to keep people in remission

 

Surgery

Surgery is used in complicated cases of Crohn's disease, such as perforation, obstruction, bleeding, fistulas, and cancer; with refractory disease, or with steroid dependence. Surgery is to control, not to cure, and the least amount of bowel required should be taken out. Recurrence is very common. Female fertility can be affected by colectomy.

 

Indications for UC includes failed medical management, obstruction, toxic megacolon, or longstanding disease causing increased risk of malignancy.

Curative UC surgery involves excision of the rectum and colon and re-anastamosis of the anus to the terminal ileum by forming a J-pouch, or pelvic pouch. In patients who are very sick, or who have co-morbidities, two operations are done. The first step is to staple off the rectum and form a temporary stoma as the tissues heal, and the second is to join the pouch to the anus.

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Consequences and Course

Crohn's carries a 3x risk of colorectal cancer, while colitis carries a 7-30x risk. Disease severity does not appear to correlate with risk. Increased screening should occur: after first decade, screen every 8 years. After second decade, every 3 years; after third decade, every 2 years. Anemia can result from bleeding and bone marrow suppression from the inflammatory condition.

Primary sclerosing cholangitis can occur, potentially leading to cancer, and be serious enough to warrant liver failure.

Obstruction, perforation, or bleeding can occur. Abscess formation can lead to a fistula.

 

Ulcerative Colitis

Toxic megacolon - gross dilation of the large bowel, associated with fever, pain, dehydration, tachycardia, and bloody diarrhea, can result in perforation and can require urgent surgical intervention. Strictures usually suggest malignancy.

 

Crohn's Colitis

Ileal Crohn's disease can result in vitamin B₁₂ deficiency, fat malabsorption (bile salts) and deficiency of fat-soluble vitamins A, D, E and K. Strictures, abscesses, fistulas, and perianal disease can occur with Crohn's.

Chronic fat malabsorption leads to fat binding to calcium and thereby oxalate to be absorbed. This can increase the risk for urinary oxalate stone formation. Small bowel obstructions can also occur.

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The Case of Mr. Casey

Mr. Casey is a 50 year-old man with a 20 year history of Crohn's, previously well-managed with 5-ASA. His flare-ups have become more frequent and severe, and he would like to meet with a surgeon to discuss his options.

• Q: How should his disease be investigated prior to deciding on surgery?
• Q: What are the indications for surgery?
• Q: Will surgery be curative?

 

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Additional Resources

 

• Crohn's and Colitis Foundation of Canada - many educational resources, community chapters, and volunteer opportunities.
• American Association of Crohn's and Colitis

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