Crohn's Disease (Inflammatory Bowel Disease)

What is Crohn's Disease?

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Crohn's disease is a chronic and relapsing inflammatory disorder that can affect any part of the gastrointestinal tract, from the mouth to the anus, as well as other organs of the body. Crohn's disease is a type of inflammatory bowel disease. Ulcerative colitis is also part of this category and shares some similar clinical features as Crohn's disease. However, ulcerative colitis only affects the large intestine. Crohn's disease involves all three layers of the bowel wall (inner lining, muscular layer and outer lining). To contrast, ulcerative colitis only involves the mucosa (inner lining). The patterns of intestinal involvement in Crohn's disease are divided into large bowel alone (colonic) (25%), small and large bowel (ileocolic) (40%), and small bowel alone (30%). The duodenum is rarely involved (only 2%). The main pathological features of Crohn's disease are ulcers (shallow and deep), connection of the bowel lumen with surrounding structures (fistulae) and scar tissue leading to narrowing of the bowel lumen (strictures causing lumen obstruction). The extra-intestinal structures involved in Crohn's disease can be local or systemic. Local involvement can occur when fistulae are present, such as between the bowel and the vagina or the bladder. Systemic extra-intestinal manifestations include:

Skin
Mucous membranes: shallow ulcers of the mouth and vagina
Eyes: inflammation of the iris (iritis)
Joints: painful and inflamed large joints (arthralgia and arthritis).
Liver/gallbladder: chronic active liver inflammation (hepatitis) and scar tissue damage with liver dysfunction (cirrhosis), gallstones.

Statistics on Crohn's Disease?

Crohn's disease is an important cause of morbidity in Australia and affects approximately 50 people per 100 000 of the population. The incidence is set to increase even further in future years. The disease is most common in adolescents and young adults with up to 60% of patients being diagnosed before 25 years of age. However, Crohn's disease can occur at any age. Females are affected slightly more than males.

Risk Factors for Crohn's Disease

The cause of this disease is unknown but various genetic and environmental factors are thought to have a role. There is evidence for a genetic component, in that siblings of Crohn's patients are 20-35 times more likely to develop Crohn's. Smoking, as well as a higher sugar content in the diet may increase the risk. An elemental diet improves symptoms. Crohn's disease is more common in Western societies and more common in Caucasians compared to black-skinned populations. Infection with a type of bacteria or virus has been proposed but largely unproven in clinical trials.

Progression of Crohn's Disease

The disease usually manifests between 20 and 40 years of age, being rare before 10 or after 60. Crohn's disease typically follows a chronic and recurrent course. However, many patients remain well and have an almost normal lifestyle. If you have extensive disease you will have more frequent exacerbations and require multiple hospital admissions. Inflammation of the lining of the gut causes symptoms of diarrhoea which may be streaked with blood or mucus if the colon is involved. It is usually an episode of severe abdominal pain which will cause you to present to hospital. Involvement of the small intestine disrupts its normal functions of breaking down and absorbing food. This means the body may have trouble absorbing all the nutrients it needs. With time, Crohn's disease can lead to malnutrition and iron deficiency anaemia. In children in particular this can lead to growth retardation and even delays in puberty. Extension of the inflammation throughout the thickness of the bowel wall can lead to a number of other complications as the bowel becomes stuck down to nearby organs. This can cause:

Adhesions- These are fibrous thickenings or scarring which can make future surgery in the abdomen difficult.
Perforation (rupture of the bowel wall) and abscess formation.
Fistulae- Connections can develop between diseased bowel and other hollow organs such as the stomach, rectum, bladder, uterus, vagina or even skin. This can cause additional complications such as faecal vomiting, passage of faeces via the vagina or severe urinary tract infection.

Chronic and extensive Crohn's disease is associated with an increased risk of adenocarcinoma of the colon.

Symptoms of Crohn's Disease

The presentation of Crohn's disease varies between patients depending on the site and severity of disease. Typical symptoms include:

Diarrhoea (80%).
Abdominal pain.
Weight loss.

However sometimes there are no gastrointestinal symptoms at all. Some patients may also present with local anal and perianal disease that precedes the development of colon and small intestinal symptoms by many years. Crohn's disease also causes generalised symptoms including malaise, lethargy, anorexia, nausea and vomiting, and low grade intermittent fever. Symptoms of extra-intestinal manifestations affecting the eyes, skin and joints may also be present. Note that is some cases Crohn's disease can present acutely as an emergency. This is usually as acute right sided abdominal pain that can appear similar to acute appendicitis. This is caused by acute inflammation of theterminal ileum which is anatomically close to the appendix. Occasionally Crohn's disease can present as perforation (causing severe abdominal pain with a rigid abdomen exacerbated by movement) or toxic megacolon (dilation of the colon associated with severe pain and signs of distension.

Clinical Examination of Crohn's Disease

Crohn's disease can usually not be diagnosed by physical examination alone. Even in severe disease, the examination may be unremarkable other than weight loss and general ill health. Your doctor however will carefully examine you abdomen which may reveal tenderness in the right iliac fossa (right lower abdomen) or a palpable mass. Your doctor will also inspect the anal area and perform a digital rectal examination. This may detect anal tags, fissures or perianal abscesses. You may also have signs outside of the gastrointestinal system such as inflammation of the eyes, skin signs of erythema nodosum (tender red nodules on the skin), and joint swelling due to arthritis.

How is Crohn's Disease Diagnosed?

The diagnosis of Crohn's disease relies on a typical clinical history and examination, as well as investigations to confirm the diagnosis. Your doctor may perform the following investigations to help make a diagnosis of Crohn's disease:

Full blood count- This may reveal anaemia due to malabsorption of vitamin B12, blood loss, or the effect of inflammation on the bone marrow. You may also have an elevated white cell) count if your disease is currently active.
Serum inflammatory markers- ESR and CRP may be elevated in active disease.
Liver function tests (LFT)- Can be used to monitor disease activity, and detect systemic involvement of liver if it occurs.
Blood cultures if sepsis suspected.
Stool cultures- May be needed if the case of diarrhoea to exclude infective colitis.
Electrolytes- May be disturbed secondary to diarrhoea but are non-specific changes.
Sigmoidoscopy and colonoscopy- These are the main investigations used. These allow direct visualisation of the colon mucosa which may detect shallow ulcers or more widespread, deep ulcers producing a cobblestone appearance. Colonoscopy also allows the terminal ileum to be inspected which is a common site of Crohn's disease. A biopsy (tissue sample) is essential to confirm the diagnosis and exclude other causes of colitis.
Plain abdominal x-rays and barium studies are useful to detect narrowing of the lumen, ulcers and fistulas.
Abdominal CT scan is occasionally performed to identify abscesses and other complications.
You may also be investigated with newer methods such as radionuclide (isotope) scans or wireless capsule enteroscopy which allow examination of areas of the GIT not accessible by endoscopy. These techniques may not be available at all centres.

Prognosis of Crohn's Disease

Acute regional ileitis (disease confined to the final section of the small intestine) may be cured by right hemicolectomy (the right side of the colon and part of the small bowel removed). However, since Crohn's disease can affect any part of the alimentary tract surgery generally does not provide a cure. At least 50% of patients will undergo surgery at some time to manage complications of this disorder. The mortality rate from Crohn's disease is approximately 14% over 30 years. Crohn's disease increases your risk of colon cancer marginally, but this is not thought to influence management.

How is Crohn's Disease Treated?

Crohn's disease usually follows a relapsing and remitting course so treatment is targeted at managing acute attacks and preventing recurrences. It is likely that you will be managed with a combination of treatments including general supportive measures, medications, nutritional supplements and surgery in advanced cases. Medical treatment is usually the main treatment used. Steroids (such as Prednisolone) are used in exacerbations to control inflammation and are then tapered to a maintenance dose. Steroids can be given oral or locally (as enemas or slow release formulas) depending on the site of your disease. You may also be prescribed an aminosalicylate medication to prevent future attacks. Immunosuppressants (such as azathioprine or cyclosporine) may also be added to your treatment to reduce steroid requirements. Severe cases of Crohn's disease require admission to hospital for aggressive management including intravenous steroids, fluids, bowel rest with intravenous nutrition (to allow the bowel to recover), antibiotics, and correction of anaemia. A number of other medications can be used as adjunctive agents such as anti-diarrhoeals and bulk-forming agents (to help reduce fluid stools and urgency), antibiotics (to treat any infections) and iron, folate and other agents to control any anaemia. General measures: Your doctor will take time to educate you about your condition and help you become involved in your treatment. There are various support groups available to help you and your family help cope with the disease. It is also very important that you quit smoking as this increases the severity of your disease. Your doctor may be able to give you a medication called Zyban to help you achieve this. As your bowel is damaged by inflammation it can be difficult for your body to absorb all the vitamins and minerals it requires. You may require liquid protein, vitamin B12, folic acid, fat soluble vitamins and/or calcium supplements. Special elemental diets have also been found to be an appropriate treatment for Crohn's diseases. These diets cut out foods that you cannot tolerate which are associated with acute attacks. Surgery Most patients with Crohn's disease will require surgery at some stage in the course of their disease. Surgery is generally used for the following indications:

Strictures (narrowing) and intestinal obstruction, bleeding, perforation or fistulas.
Fulminant (very severe, life-threatening) colitis or acute presentations unresponsive to medical therapy.
Perianal disease- Local disease around the anus.
Persistent local ileal disease.

Surgery is usually either a resection (removal of a section of bowel) or stricturoplasty (relieving tightenings within the lumen of the bowel). Strictures can also be treated endoscopically using balloon dilation techniques. Whilst these techniques manage the local disease, they do not prevent recurrence elsewhere in the GIT. Surveillance As fore mentioned longstanding Crohn's disease is associated with an increased risk of colorectal carcinoma. If you have had Crohn's disease for longer than ten years it is recommended you have frequent colonoscopies to screen for the development of malignancy. The interval between examinations is yet to be agreed upon and will be dependent on the extent and severity of your disease. You should therefore discuss with your doctor how frequently you should be screened.

Children

Management of Crohn's disease follows similar principals in children. Dietary therapy is particularly important in the management of disease. Steroid treatments may be used for your child but they can have serious side effects on growth, bone mineral density (occasionally leading to osteoporosis and cosmetics. Budesonide (a new steroid drug) may reduce some of these systemic side effects as its effect tends to be localised to the small bowel. Aminisalicylates (either local or systemically) can be used for treatment of attacks and for maintenance therapy. The immunosuppressant agents used in adults may also be used in more severe cases. However, the experience of these drugs is more limited in children and some have serious side effects that are better avoided. Surgery may be required if your child has severe Crohn's disease which is impacting on their growth and not responding to medical and nutritional treatments. In this setting surgery for local disease can improve growth and pubertal development. Your doctor will be able to provide further information on the most suitable treatment for your child and their particular level of disease.

Crohn's Disease References

Burkitt, Quick. Essential Surgery. 3rd Edition.Churchill Livingstone. 2002.
Cotran, Kumar, Collins 6th edition. Robbins Pathologic Basis of Disease. WB Saunders Company. 1999.
Friedman S, Blumberg R. 'Inflammatory Bowel Disease,' in Braunwald, Fauci, Kasper, Hauser, Longo, Jameson. Harrison's Principles of Internal Medicine. 15th Edition. McGraw-Hill. 2001.
Knutson D, Greenberg G, Cronau H. Management of Crohn's Disease - A Practical Approach, Am Fam Physician 2003; 68:707-14,717-8. Available [online] at URL: http://www.aafp.org/afp/20030815/707.html
Kumar P, Clark M. Clinical Medicine, WB Saunders 2002.
Longmore M, Wilkinson I, Torok E. Oxford Handbook of Clinical Medicine, Oxford Universtiy Press, 2001.
Rampton D. Management of Crohn's disease [Clinical Review], BMJ 1999; 319:1480-1485.
Robinson M, Robertson D. (Ed.) Practical Paediatrics, 5th Edition, Churchill Livingstone, Sydney, 2003.
Selby W. Current issues in Crohn's disease, MJA 2003; 178 (11): 532-533. Available [online] at URL: http://www.mja.com.au/public/issues/178_11_020603/sel10204_fm-1.html