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Crohn's disease

 
Medical Encyclopedia: Crohn's Disease
 

Definition

Crohn's disease is a type of inflammatory bowel disease (IBD), resulting in swelling and dysfunction of the intestinal tract.

Description

Crohn's disease involves inflammation of the intestine, especially the small intestine. Inflammation refers to swelling, redness, and loss of normal function. There is evidence that the inflammation is caused by various products of the immune system that attack the body itself instead of helpfully attacking a foreign invader (a virus or bacteria, for example). The inflammation of Crohn's disease most commonly affects the last part of the ileum (a section of the small intestine), and often includes the large intestine (the colon). However, inflammation may also occur in other areas of the gastrointestinal tract, affecting the mouth, esophagus, or stomach. Crohn's disease differs from ulcerative colitis, the other major type of IBD, in two important ways:

  • The inflammation of Crohn's disease may be discontinuous, meaning that areas of involvement in the intestine may be separated by normal, unaffected segments of intestine. The affected areas are called "regional enteritis," while the normal areas are called "skip areas."
  • The inflammation of Crohn's disease affects all the layers of the intestinal wall, while ulcerative colitis affects only the lining of the intestine.

Also, ulcerative colitis does not usually involve the small intestine; in rare cases it involves the terminal ileum (so-called "backwash" ileitis).

In addition to inflammation, Crohn's disease causes ulcerations, or irritated pits in the intestinal wall. These pits occur because the inflammation has made areas of tissue shed.

Crohn's disease may be diagnosed at any age, although most diagnoses are made between the ages of 15–35. About 0.02–0.04% of the population suffers from this disorder, with men and women having an equal chance of being stricken. Whites are more frequently affected than other racial groups, and people of Jewish origin are between three and six times more likely to suffer from IBD. IBD runs in families; an IBD patient has a 20% chance of having other relatives who are fellow sufferers.

Crohn's disease is a chronic disorder. While the symptoms can be improved, a patient will not be completely cured of the underlying disease.

— Rosalyn S. Carson-DeWitt



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Dictionary: Crohn's disease   (krōnz) pronunciation
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n.

Ileitis involving the terminal portion of the ileum and characterized by abdominal pain, ulceration, and fibrous tissue buildup.

[After Burrill Bernard Crohn (1884–1983), American physician.]


 
Food and Nutrition: Crohn's disease
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Chronic inflammatory disease of the bowel, of unknown origin, treated with antibiotics to prevent infection and with anti-inflammatory agents. Sufferers may be malnourished as a result of both loss of appetite due to illness and also malabsorption. Also known as regional enteritis, since only some regions of the gut are affected. See also gastro-intestinal tract.

 

Definition

Crohn's disease is a type of inflammatory bowel disease (IBD), resulting in swelling and dysfunction of the intestinal tract.

Description

Crohn's disease involves swelling, redness, and loss of function of the intestine, especially the small intestine. There is evidence that this inflammation is caused by a misfire of the immune system, which attacks the body itself instead of attacking foreign invaders, such as viruses or bacteria. The inflammation of Crohn's disease most commonly occurs in the last part of the ileum (a section of the small intestine), and often includes the large intestine (the colon). However, inflammation may also occur in other areas of the gastrointestinal tract, including the mouth, esophagus, or stomach. Crohn's disease differs from ulcerative colitis, the other major type of IBD, in two important ways:

  • The inflammation of Crohn's disease may be discontinuous, meaning that areas of involvement in the intestine may be separated by normal, unaffected segments of intestine. The affected areas are called "regional enteritis," while the normal areas are called "skip areas."
  • The inflammation of Crohn's disease affects all the layers of the intestinal wall, while ulcerative colitis affects only the lining of the intestine.

Also, ulcerative colitis does not usually involve the small intestine; in rare cases it involves the terminal ileum (so-called "backwash" ileitis).

In addition to inflammation, Crohn's disease causes ulcerations, or irritated pits, in the intestinal wall. These pits occur because the inflammation has made areas of tissue shed away.

While Crohn's disease and ulcerative colitis are similar, they are also very different. Although it can be difficult to determine whether a patient has Crohn's disease or ulcerative colitis, it is important to make every effort to distinguish between these two diseases. Because the long-term complications of the diseases are different, treatment will depend on careful diagnosis of the specific IBD present.

Crohn's disease may be diagnosed at any age, although most diagnoses are made between the ages of 15–35. About 20–40 people out of 10,000 suffer from this disorder, with men and women having an equal chance of being stricken. Caucasians are more frequently affected than other racial groups, and people of Jewish origin appear three to six times more likely to suffer from IBD. IBD runs in families; an IBD patient has a 20% chance of having other relatives who are fellow sufferers.

Crohn's disease is a chronic disorder. While the symptoms can be improved, there is no known cure for the underlying disease.

Causes & Symptoms

The cause of Crohn's disease is unknown. No infectious agent (virus, bacteria, or fungi) has been identified as the etiologic agent. Still, some researchers have theorized that some type of infection may have originally been responsible for triggering the immune system, resulting in the continuing and out-of-control cycle of inflammation that occurs in Crohn's disease. Other evidence for a disorder of the immune system includes the high incidence of other immune disorders that may occur along with Crohn's disease.

The first symptoms of Crohn's disease may include diarrhea, fever, abdominal pain, inability to eat, weight loss, and fatigue. Some patients experience severe pain that mimics appendicitis. It is rare, however, for patients to notice blood in their bowel movements. Because Crohn's disease severely limits the ability of the affected intestine to absorb the nutrients from food, a patient with Crohn's disease can have signs of malnutrition, depending on the amount of intestine affected and the duration of the disease.

The combination of severe inflammation, ulceration, and scarring that occurs in Crohn's disease can result in serious complications, including obstruction, abscess formation, and fistula formation.

An obstruction is a blockage in the intestine. This obstruction prevents the intestinal contents from passing beyond the point of the blockage. The intestinal contents "back up," resulting in constipation, vomiting, and intense pain. Although rare in Crohn's disease (because of the increased thickness of the intestinal wall due to swelling and scarring), a severe bowel obstruction can result in an intestinal wall perforation (a hole in the intestine). Such a hole in the intestinal wall would allow the intestinal contents, usually containing bacteria, to enter the abdomen. This complication could result in a severe, life-threatening infection.

Abcess formation is the development of a walledoff pocket of infection. A patient with an abscess will have bouts of fever, increased abdominal pain, and may have a lump or mass that can be felt through the wall of the abdomen.

Fistula formation is the formation of abnormal channels between tissues. These channels may connect one area of the intestine to another neighboring section of intestine. Fistulas may join an area of the intestine to the vagina or bladder, or they may drain an area of the intestine through the skin. Abscesses and fistulas commonly affect the area around the anus and rectum (the very last portions of the colon allowing waste to leave the body). These abnormal connections allow the bacteria that normally live in the intestine to enter other areas of the body, causing potentially serious infections.

Patients suffering from Crohn's disease also have a significant chance of experiencing other disorders. Some of these may relate specifically to the intestinal disease, and others appear to have some relationship to the imbalanced immune system. The faulty absorption state of the bowel can result in gallstones and kidney stones. Inflamed areas in the abdomen may press on the tube that drains urine from the kidney to the bladder (the ureter). Ureter compression can make urine back up into the kidney, enlarge the ureter and kidney, and can potentially lead to kidney damage. Patients with Crohn's disease also frequently suffer from:

  • arthritis (inflammation of the joints)
  • spondylitis (inflammation of the vertebrae, the bones of the spine)
  • ulcers of the mouth and skin
  • painful, red bumps on the skin
  • inflammation of several eye areas
  • inflammation of the liver, gallbladder, and/or the channels (ducts) that carry bile between and within the liver, gallbladder, and intestine

The chance of developing cancer of the intestine is greater than normal among patients with Crohn's disease, although this chance is not as high as among those patients with ulcerative colitis.

Diagnosis

Diagnosis is first suspected based upon a patient's symptoms. Blood tests may reveal an increase in certain types of white blood cells, an indication that some type of inflammation or infection is occurring in the body. The blood tests may also reveal anemia and other signs of malnutrition due to malabsorption (low blood protein; variations in the amount of calcium, potassium, and magnesium present in the blood; changes in certain markers of liver function). Stool samples may be examined to make sure that no infectious agent is causing the diarrhea, and to see if the waste contains blood.

A colonoscopy may be performed to view the interior of the colon. During colonoscopy, a doctor passes a flexible tube with a tiny, fiber-optic camera device (an endoscope) through the rectum and into the colon. The doctor can then carefully examine the lining of the intestine for signs of inflammation and ulceration that might suggest Crohn's disease. A tissue sample (a biopsy) of the intestine can also be taken through the endoscope to examine under a microscope for evidence of Crohn's disease.

Both an upper and lower GI (gastrointestinal) x ray series can be helpful in determining how much of the intestine is involved in the disease. In the upper GI (also called a small bowel series), the patient drinks a chalky solution called barium, which acts as a contrast agent to illuminate the gastrointestinal tract on x-ray film. After the barium is ingested, x rays are taken at specific time intervals as the barium passes through the stomach and into and through the small intestine. The lower GI series provides an x-ray study of the large intestine. The patient is given an enema containing barium, and in some cases, air is also pumped into the rectum to provide a clearer view of the large intestine. This is called a double-contrast barium enema.

Treatment

Crohn's disease is a chronic, often progressive, illness. A correct diagnosis and appropriate treatment with anti-inflammatory medications is critical to controlling the disease.

Some Crohn's patients find that certain foods are hard to digest, including milk, large quantities of fiber, and spicy foods. Dietary adjustments are usually necessary to minimize pain, diarrhea, and other symptoms.

Acupuncture and guided imagery may be useful tools in treating any pain associated with Crohn's disease. Acupuncture involves the placement of thin needles into the skin at targeted locations on the body known as acupoints in order to harmonize the energy flow within the human body. To treat chronic pain, such as that involved with Crohn's disease, an acupuncturist will frequently place the acupuncture needles along what is known as the large intestine meridian.

Guided imagery involves creating a visual mental image of one's pain in one's mind. Once the pain can be visualized, the patient can adjust the image to make it more pleasing, and thus, more manageable.

Several herbal remedies are also available to lessen pain symptoms and promote relaxation and healing. These include peppermint oil, slippery elm (Ulmus rubra), marsh mallow (Althaea oficinalis), and Chinese herbs. However, Crohn's patients should consult with their healthcare professional before taking them. Depending on the preparation and the type of herb, these remedies may aggravate the digestive tract or interact with any prescription drugs that are being taken to control the inflammation of Crohn's disease.

Allopathic Treatment

Treatments for Crohn's disease try to reduce the underlying inflammation, the resulting malabsorption/malnutrition, the uncomfortable symptoms of crampy abdominal pain and diarrhea, and any possible complications (obstruction, abscesses, and fistulas).

Inflammation can be treated with a drug called sulfasalazine. Sulfasalazine is made up of two parts. One part is related to the sulfa antibiotics; the other part is a form of the anti-inflammatory chemical, salicylic acid. Sulfasalazine is not well-absorbed from the intestine, so it stays mostly within the intestine, where it is broken down into its components. It is believed that the salicylic acid component actively treats Crohn's disease by fighting inflammation. Some patients do not respond to sulfasalazine, particularly those with more severe disease. These patients require steroid medications (such as prednisone). Steroids, however, must be used carefully to avoid the complications of these drugs, including increased risk of infection and weakening of bones (osteoporosis)

In 2001, the Food and Drug Administration (FDA) approved use of budesonide capsules for mild and moderate cases of Crohn's disease involving the small and large intestines. Although a steroid, the makeup of budesonide allows the drug to release into the intestines, where it can be mostly metabolized. As a result, less of the drug enters the patient's system, meaning fewer undesirable side effects. Some potent immunosuppressive drugs that interfere with the products of the immune system and hopefully decrease inflammation may be used for those patients who do not improve on steroids.

Serious cases of malabsorption/malnutrition may need to be treated by providing nutritional supplements. These supplements must be in a form that can be absorbed from the damaged, inflamed intestine. When patients are suffering from an obstruction, or during periods of time when symptoms of the disease are at their worst, they may need to drink specially formulated, high-calorie liquid supplements. Those patients who are severely ill may need to receive their nutrition through a needle inserted intravenously.

A number of medications are available to help decrease the cramping and pain associated with Crohn's disease. These include loperamide, tincture of opium, and codeine. Some fiber preparations (methylcellulose or psyllium) may be helpful, although some patients do not tolerate them well.

The first step in treating an obstruction involves general attempts to decrease inflammation with sulfasalazine, steroids, or immunosuppressive drugs. A patient with a severe obstruction will have to stop taking all food and drink by mouth, allowing the bowel to "rest." Abscesses and other infections will require antibiotics. Surgery may be required to repair an obstruction that does not resolve on its own, to remove an abscess, or to repair a fistula. Such surgery may involve the removal of a section of the small intestine. In extremely severe cases of Crohn's disease of the colon that do not respond to treatment, a patient may need to have the entire large intestine removed (an operation called a colectomy). In this case, a piece of the remaining small intestine is pulled through an opening in the abdomen. This bit of intestine is fashioned surgically to allow a special bag to be placed over it. This bag catches the body's waste, which no longer can be passed through the large intestine and out of the anus. This opening, which will remain in place for life, is called an ileostomy. However, as an alternative to ileostomy, small intestines are now often shaped into substitute rectal pouches, and the patient may not always need the ileostomy.

Expected Results

Crohn's disease is a lifelong illness. The severity of the disease can vary, and a patient can experience periods of time when the disease is not active and he or she is symptom free. However, the complications and risks of Crohn's disease tend to increase over time. Well over 60% of all patients with Crohn's disease will require surgery, and about half of these patients will require more than one operation over time. About 5–10% of all Crohn's patients will die of their disease, primarily due to massive infection.

Prevention

Crohn's disease is a chronic, lifelong disorder. However, a study published in the New England Journal of Medicine in June 2000 reported that methotrexate (a chemotherapy drug) was found to prevent relapse episodes in a clinical trial of Crohn's patients. The study also found that human growth hormone was useful in reducing symptoms of the disease.

Resources

Books

Glickman, Robert. "Inflammatory Bowel Disease: Ulcerative Colitis and Crohn's Disease." In Harrison's Principles of Internal Medicine. Anthony S. Fauci et al., eds. New York: McGraw-Hill, 1998.

Long, James W. The Essential Guide to Chronic Illness. New York: HarperPerennial, 1997.

Saibil, Fred. Crohn's Disease and Ulcerative Colitis. Buffalo, NY: Firefly Books, 1997.

Periodicals

Peppercorn, Mark A., and Susannah K. Gordon. "Making Sense of a Mystery Ailment: Inflammatory Bowel disease."Harvard Health Letter 22, no. 2 (December 1996): 4+.

Sachar, David. "Maintenance Strategies in Crohn's Disease." Hospital Practice 31, no. 1 (January 15, 1996): 99+.

Karpa, Kelly Dowhower. "Crohn's disease patients find new relief from old drug."Drug Topics 145, no. 21 (November 5, 2001): 16;.

Organizations

Crohn's & Colitis Foundation of America, Inc. 386 Park Avenue South, 17th Floor, New York, NY 10016-8804. (800) 932-2423.

[Article by: Paula Ford-Martin; Teresa G. Odle]

 
Veterinary Dictionary: Crohn's disease
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A regional, granulomatous enteritis of humans; equine granulomatous enteritis, histiocytic ulcerative colitis of Boxer dogs, johne's disease of cattle, and regional or terminal ileitis of pigs are similar diseases and all have been proposed as possible animal models.

 
Wikipedia: Crohn's disease
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Crohn's disease
Classification and external resources
The three most common sites of intestinal involvement in Crohn's disease are

ileal, ileocolic and colonic.[1]

ICD-10 K50.
ICD-9 555
OMIM 266600
DiseasesDB 3178
MedlinePlus 000249
eMedicine med/477  ped/507 radio/197
MeSH D003424

Crohn's disease (also known as granulomatous colitis and regional enteritis) is an inflammatory disease of the intestines that may affect any part of the gastrointestinal tract from anus to mouth, causing a wide variety of symptoms. It primarily causes abdominal pain, diarrhea (which may be bloody), vomiting, or weight loss,[1][2][3] but may also cause complications outside of the gastrointestinal tract such as skin rashes, arthritis and inflammation of the eye.[1]

Crohn's disease is an autoimmune disease, caused by the immune system's attacking the gastrointestinal tract and producing inflammation in the gastrointestinal tract; it is classified as a type of inflammatory bowel disease. There has been very little evidence of a genetic link to Crohn's disease, though individuals with siblings who have the disease are at higher risk. It is understood to have a large environmental component as evidenced by the higher number of cases in western industrialized nations. Males and females are equally affected. Smokers are three times more likely to develop Crohn's disease. [4] Crohn's disease affects between 400,000 and 600,000 people in North America.[5] Prevalence estimates for Northern Europe have ranged from 27–48 per 100,000.[6] Crohn's disease tends to present initially in the teens and twenties, with another peak incidence in the fifties to seventies, although the disease can occur at any age.[1][7]

There is no known drug or surgical cure for Crohn's disease;[8] treatment options are restricted to controlling symptoms, maintaining remission and preventing relapse.

The disease was independently described in 1904 by Polish surgeon Antoni Leśniowski and in 1932 by American gastroenterologist Burrill Bernard Crohn, for whom the disease was named. Crohn, along with two colleagues, described a series of patients with inflammation of the terminal ileum, the area most commonly affected by the illness.[9] For this reason, the disease has also been called regional ileitis[9] or regional enteritis.

Contents

Classification

Distribution of gastrointestinal Crohn's disease. Based on data from American Gastroenterological Association.

Crohn's disease is generally classified as an autoimmune disease. It invariably affects the gastrointestinal tract, and most gastroenterologists categorize the presenting disease by the affected areas. Ileocolic Crohn's disease, which affects both the ileum (the last part of the small intestine that connects to the large intestine) and the large intestine, accounts for fifty percent of cases. Crohn's ileitis, affecting the ileum only, accounts for thirty percent of cases, and Crohn's colitis, affecting the large intestine, accounts for the remaining twenty percent of cases and may be particularly difficult to distinguish from ulcerative colitis. The disease can attack any part of the digestive tract, from mouth to anus. However, individuals affected by the disease rarely fall outside these three classifications, being affected in other parts of the gastrointestinal tract such as the stomach and esophagus.[1]

Crohn's disease may also be categorized by the behavior of disease as it progresses. This was formalized in the Vienna classification of Crohn's disease.[10] There are three categories of disease presentation in Crohn's disease: stricturing, penetrating, and inflammatory. Stricturing disease causes narrowing of the bowel which may lead to bowel obstruction or changes in the caliber of the feces. Penetrating disease creates abnormal passageways (fistulae) between the bowel and other structures such as the skin. Inflammatory disease (or non-stricturing, non-penetrating disease) causes inflammation without causing strictures or fistulae.[10][11]

Symptoms

Endoscopy image of colon showing serpiginous ulcer, a classic finding in Crohn's disease

Many people with Crohn's disease have symptoms for years prior to the diagnosis.[12] The usual onset is between 15 and 30 years of age but can occur at any age.[13] Because of the 'patchy' nature of the gastrointestinal disease and the depth of tissue involvement, initial symptoms can be more vague than with ulcerative colitis. People with Crohn's disease will go through periods of flare-ups and remission.

Gastrointestinal symptoms

Abdominal pain may be the initial symptom of Crohn's disease. It is often accompanied by diarrhea, especially in those who have had surgery. The diarrhea may or may not be bloody. People who have had surgery or multiple surgeries often end up with short bowel syndrome of the gastrointestinal tract. The nature of the diarrhea in Crohn's disease depends on the part of the small intestine or colon that is involved. Ileitis typically results in large-volume watery feces. Colitis may result in a smaller volume of feces of higher frequency. Fecal consistency may range from solid to watery. In severe cases, an individual may have more than 20 bowel movements per day and may need to awaken at night to defecate.[1][7][14][15] Visible bleeding in the feces is less common in Crohn's disease than in ulcerative colitis, but may be seen in the setting of Crohn's colitis.[1] Bloody bowel movements are typically intermittent, and may be bright or dark red in colour. In the setting of severe Crohn's colitis, bleeding may be copious.[7] Flatulence and bloating may also add to the intestinal discomfort.[7]

Symptoms caused by intestinal stenosis are also common in Crohn's disease. Abdominal pain is often most severe in areas of the bowel with stenoses. In the setting of severe stenosis, vomiting and nausea may indicate the beginnings of small bowel obstruction.[7] Crohn's disease may also be associated with primary sclerosing cholangitis, a type of inflammation of the bile ducts.[16]

Perianal discomfort may also be prominent in Crohn's disease. Itchiness or pain around the anus may be suggestive of inflammation, fistulization or abscess around the anal area[1] or anal fissure. Perianal skin tags are also common in Crohn's disease.[17] Fecal incontinence may accompany peri-anal Crohn's disease. At the opposite end of the gastrointestinal tract, the mouth may be affected by non-healing sores (aphthous ulcers). Rarely, the esophagus, and stomach may be involved in Crohn's disease. These can cause symptoms including difficulty swallowing (dysphagia), upper abdominal pain, and vomiting.[18]

Systemic symptoms

Crohn's disease, like many other chronic, inflammatory diseases, can cause a variety of systemic symptoms.[1] Among children, growth failure is common. Many children are first diagnosed with Crohn's disease based on inability to maintain growth.[19] As Crohn's disease may manifest at the time of the growth spurt in puberty, up to 30% of children with Crohn's disease may have retardation of growth.[20] Fever may also be present, though fevers greater than 38.5 ˚C (101.3 ˚F) are uncommon unless there is a complication such as an abscess[1] Among older individuals, Crohn's disease may manifest as weight loss. This is usually related to decreased food intake, since individuals with intestinal symptoms from Crohn's disease often feel better when they do not eat and might lose their appetite.[19] People with extensive small intestine disease may also have malabsorption of carbohydrates or lipids, which can further exacerbate weight loss.[21]

Extraintestinal symptoms

Erythema nodosum

In addition to systemic and gastrointestinal involvement, Crohn's disease can affect many other organ systems.[22] Inflammation of the interior portion of the eye, known as uveitis, can cause eye pain, especially when exposed to light (photophobia). Inflammation may also involve the white part of the eye (sclera), a condition called episcleritis. Both episcleritis and uveitis can lead to loss of vision if untreated.

Crohn's disease is associated with a type of rheumatologic disease known as seronegative spondyloarthropathy. This group of diseases is characterized by inflammation of one or more joints (arthritis) or muscle insertions (enthesitis). The arthritis can affect larger joints such as the knee or shoulder or may exclusively involve the small joints of the hand and feet. The arthritis may also involve the spine, leading to ankylosing spondylitis if the entire spine is involved or simply sacroiliitis if only the lower spine is involved. The symptoms of arthritis include painful, warm, swollen, stiff joints and loss of joint mobility or function.[citation needed]

Crohn's disease may also involve the skin, blood, and endocrine system. One type of skin manifestation, erythema nodosum, presents as red nodules usually appearing on the shins. Erythema nodosum is due to inflammation of the underlying subcutaneous tissue and is characterized by septal panniculitis. Another skin lesion, pyoderma gangrenosum, is typically a painful ulcerating nodule. Crohn's disease also increases the risk of blood clots; painful swelling of the lower legs can be a sign of deep venous thrombosis, while difficulty breathing may be a result of pulmonary embolism. Autoimmune hemolytic anemia, a condition in which the immune system attacks the red blood cells, is also more common in Crohn's disease and may cause fatigue, pallor, and other symptoms common in anemia. Clubbing, a deformity of the ends of the fingers, may also be a result of Crohn's disease. Finally, Crohn's disease may cause osteoporosis, or thinning of the bones. Individuals with osteoporosis are at increased risk of bone fractures.[6]

Crohn's disease can also cause neurological complications (reportedly in up to 15% of patients).[23] The most common of these are seizures, stroke, myopathy, peripheral neuropathy, headache and depression.[23]

Crohn's patients often also have issues with small bowel bacterial overgrowth syndrome, which has similar symptoms.[24]

Complications

Endoscopic image of colon cancer identified in the sigmoid colon on screening colonoscopy for Crohn's disease.

Crohn's disease can lead to several mechanical complications within the intestines, including obstruction, fistulae, and abscesses. Obstruction typically occurs from strictures or adhesions which narrow the lumen, blocking the passage of the intestinal contents. Fistulae can develop between two loops of bowel, between the bowel and bladder, between the bowel and vagina, and between the bowel and skin. Abscesses are walled off collections of infection, which can occur in the abdomen or in the perianal area in Crohn's disease sufferers.

Crohn's disease also increases the risk of cancer in the area of inflammation. For example, individuals with Crohn's disease involving the small bowel are at higher risk for small intestinal cancer. Similarly, people with Crohn's colitis have a relative risk of 5.6 for developing colon cancer.[25] Screening for colon cancer with colonoscopy is recommended for anyone who has had Crohn's colitis for at least eight years.[26] Some study suggest that there is a role for chimioprotection in the prevention of colorectal cancer in Crohn's involving the colon; two agents have been suggested, folate and mesalamine preparations.[27]

Individuals with Crohn's disease are at risk of malnutrition for many reasons, including decreased food intake and malabsorption. The risk increases following resection of the small bowel. Such individuals may require oral supplements to increase their caloric intake, or in severe cases, total parenteral nutrition (TPN). Most people with moderate or severe Crohn's disease are referred to a dietitian for assistance in nutrition.[28]

Crohn's disease can cause significant complications including bowel obstruction, abscesses, free perforation and hemorrhage.[29]

Crohn's disease can be problematic during pregnancy, and some medications can cause adverse outcomes for the fetus or mother. Consultation with an obstetrician and gastroenterologist about Crohn's disease and all medications allows preventative measures to be taken. In some cases, remission can occur during pregnancy. Certain medications can also impact sperm count or may otherwise adversely affect a man's ability to conceive.[30]

Cause

The exact cause of Crohn's disease is unknown. Environmental and genetic factors have been invoked in the pathogenesis of the disease.

Genetics

Schematic of NOD2 CARD15 gene, which is associated with certain disease patterns in Crohn's disease.

Some research has indicated that Crohn's disease may have a genetic link.[31] The disease runs in families and those with a sibling with the disease are 30 times more likely to develop it than the normal population. Ethnic background is also a risk factor.

Mutations in the CARD15 gene (also known as the NOD2 gene) are associated with Crohn's disease[32] and with susceptibility to certain phenotypes of disease location and activity.[33] In earlier studies, only two genes were linked to Crohn's, but scientists now believe there are over thirty genes that show genetics play a role in the disease, either directly through causation or indirectly as with a mediator variable. Anomalies in the XBP1 gene have recently been identified as a factor, pointing towards a role for the unfolded protein response pathway of the endoplasmatic reticulum in inflammatory bowel diseases.[34][35]

Environmental factors

Diet is believed to be linked to its higher prevalence in industrialized parts of the world. Smoking has been shown to increase the risk of the return of active disease, or "flares".[36] The introduction of hormonal contraception in the United States in the 1960s is linked with a dramatic increase in the incidence rate of Crohn's disease. Although a causal linkage has not been effectively shown, there remain fears that these drugs work on the digestive system in similar ways to smoking.[37]

Immune system

Abnormalities in the immune system have often been invoked as being causes of Crohn's disease. Crohn's disease is thought to be an autoimmune disease, with inflammation stimulated by an over-active Th1 cytokine response.[38] However, more recent evidence has shown that Th17 is of greater importance in the disease.[39] The most recent gene to be implicated in Crohn's disease is ATG16L1, which may reduce the effectiveness of autophagy, and hinder the body's ability to attack invasive bacteria.[40]

Contrary to the prevailing view that Crohn's disease is a primary T cell autoimmune disorder, there is an increasing body of evidence in favour of the hypothesis that Crohn's disease results from an impaired innate immunity.[41] The immunodeficiency, which has been shown to be due to (at least in part) impaired cytokine secretion by macrophages,[42] is thought to lead to a sustained microbial-induced inflammatory response, particularly in the colon where the bacterial load is especially high. [43]

Microbes

A variety of pathogenic bacteria were initially suspected of being causative agents of Crohn's disease.[44] However, most health care professionals now believe that a variety of microorganisms are taking advantage of their host's weakened mucosal layer and inability to clear bacteria from the intestinal walls, both symptoms of the disease.[45] Some studies have suggested that Mycobacterium avium subsp. paratuberculosis plays a role in Crohn's disease, in part because it causes a very similar disease, Johne's disease, in cattle.[46] The mannose bearing antigens (mannins) from yeast may also elicit an antibody response.[47] Other studies have linked specific strains of enteroadherent E. coli to the disease.[48] Still, this relationship between specific types of bacteria and Crohn's disease remains unclear.[49][50]

Some studies have suggested that Crohn's disease, ulcerative colitis and irritable bowel syndrome have the same underlying cause. Biopsy samples taken from the colons of all three patient groups were found to produce elevated levels of a serine protease.[51] Experimental introduction of the serine protease into mice has been found to produce widespread pain associated with irritable bowel syndrome as well as colitis, which is associated with all three diseases.[52] The authors of that study were unable to identify the source of the protease, but a separate review noted that regional and temporal variations in those illnesses follow those associated with infection with a poorly understood protozoan, Blastocystis. [53]

A study in 2003 put forth the "cold-chain" hypothesis, that psychrotrophic bacteria such as Yersinia spp and Listeria spp contribute to the disease. A statistical correlation was found between the advent of the use of refrigeration in the United States and various parts of Europe and the rise of the disease.[54][55] Later studies have provided support for this hypothesis.[56]

Studies done at the University of Liverpool have offered ideas that would explain the apparent connection between Crohn's disease, Mycobacterium, other pathogenic bacteria, and genetic markers.[57][58]In many individuals genetic factors predispose individuals to Mycobacterium avium subsp. paratuberculosis infection. This bacteria then produce mannins which protect both itself and various bacteria from phagocytosis, which causes a variety of secondary infections.[59]Other mycobacterial diseases, such as leprosy and Tuberculosis could be considered similar in that they have strong genetic components, but are not genetic per se.

Pathophysiology

Section of colectomy showing transmural inflammation

During a colonoscopy, biopsies of the colon are often taken in order to confirm the diagnosis. There are certain characteristic features of the pathology seen that point toward Crohn's disease. Crohn's disease shows a transmural pattern of inflammation, meaning that the inflammation may span the entire depth of the intestinal wall.[1] Grossly, ulceration is an outcome seen in highly active disease. There is usually an abrupt transition between unaffected tissue and the ulcer. Under a microscope, biopsies of the affected colon may show mucosal inflammation. This inflammation is characterized by focal infiltration of neutrophils, a type of inflammatory cell, into the epithelium. This typically occurs in the area overlying lymphoid aggregates. These neutrophils, along with mononuclear cells, may infiltrate into the crypts leading to inflammation (crypititis) or abscess (crypt abscess). Granulomas, aggregates of macrophage derivatives known as giant cells, are found in 50% of cases and are most specific for Crohn's disease. The granulomas of Crohn's disease do not show "caseation", a cheese-like appearance on microscopic examination that is characteristic of granulomas associated with infections such as tuberculosis. Biopsies may also show chronic mucosal damage as evidenced by blunting of the intestinal villi, atypical branching of the crypts, and change in the tissue type (metaplasia). One example of such metaplasia, Paneth cell metaplasia, involves development of Paneth cells (typically found in the small intestine) in other parts of the gastrointestinal system.[60]

According to the volume 1 of the 10th Edition of Brunner and Suddarth’s Textbook of Medical-Surgical Nursing Regional enteritis is a subacute and chronic inflammation that extends through the layers (ie, transmural lesion) of the bowel wall from the intestinal mucosa. It is characterized by periods of remissions and exacerbations. The disease process begins with edema and thickening of the mucosa. Ulcers begin to appear on the inflamed mucosa. These lesions are not in continuous contact with one another and are separated by normal tissue. Fistulas, fissures, and abscesses form as the inflammation extends into the peritoneum. Granulomas occur in one half of patients. In advanced cases, the intestinal mucosa has a cobblestone appearance. As the disease advances, the bowel wall thickens and becomes fibrotic, and the intestinal lumen narrows. Diseased bowel loops sometimes adhere to other loops surrounding them.

Diagnosis

Endoscopic image of Crohn's colitis showing deep ulceration
CT scan showing Crohn's disease in the fundus of the stomach
Crohn's disease can mimic ulcerative colitis on endoscopy. This endoscopic image is of Crohn's colitis showing diffuse loss of mucosal architecture, friability of mucosa in sigmoid colon and exudate on wall, all of which can be found with ulcerative colitis.

The diagnosis of Crohn's disease can sometimes be challenging,[12] and a number of tests are often required to assist the physician in making the diagnosis.[7] Even with a full battery of tests it may not be possible to diagnose Crohn's with complete certainty; a colonoscopy is approximately 70% effective in diagnosing the disease with further tests being less effective. Disease in the small bowel is particularly difficult to diagnose as a traditional colonoscopy only allows access to the colon and lower portions of the small intestines; introduction of the Capsule endoscopy[61] aids in endoscopic diagnosis.

Endoscopy

A colonoscopy is the best test for making the diagnosis of Crohn's disease as it allows direct visualization of the colon and the terminal ileum, identifying the pattern of disease involvement. Occasionally, the colonoscope can travel past the terminal ileum but it varies from patient to patient. During the procedure, the gastroenterologist can also perform a biopsy, taking small samples of tissue for laboratory analysis which may help confirm a diagnosis. As 30% of Crohn's disease involves only the ileum,[1] cannulation of the terminal ileum is required in making the diagnosis. Finding a patchy distribution of disease, with involvement of the colon or ileum but not the rectum, is suggestive of Crohn's disease, as are other endoscopic stigmata.[62]The utility of capsule endoscopy for this, however, is still uncertain.[63]

Radiologic tests

A small bowel follow-through may suggest the diagnosis of Crohn's disease and is useful when the disease involves only the small intestine. Because colonoscopy and gastroscopy allow direct visualization of only the terminal ileum and beginning of the duodenum, they cannot be used to evaluate the remainder of the small intestine. As a result, a barium follow-through x-ray, wherein barium sulfate suspension is ingested and fluoroscopic images of the bowel are taken over time, is useful for looking for inflammation and narrowing of the small bowel.[62][64] Barium enemas, in which barium is inserted into the rectum and fluoroscopy used to image the bowel, are rarely used in the work-up of Crohn's disease due to the advent of colonoscopy. They remain useful for identifying anatomical abnormalities when strictures of the colon are too small for a colonoscope to pass through, or in the detection of colonic fistulae.[65]

CT and MRI scans are useful for evaluating the small bowel with enteroclysis protocols.[66]They are additionally useful for looking for intra-abdominal complications of Crohn's disease such as abscesses, small bowel obstruction, or fistulae.[67] Magnetic resonance imaging (MRI) are another option for imaging the small bowel as well as looking for complications, though it is more expensive and less readily available[68]

Blood tests

A complete blood count may reveal anemia, which may be caused either by blood loss or vitamin B12 deficiency. The latter may be seen with ileitis because vitamin B12 is absorbed in the ileum.[69] Erythrocyte sedimentation rate, or ESR, and C-reactive protein measurements can also be useful to gauge the degree of inflammation.[70] It is also true in patient with ilectomy done in response to the complication. Another cause of anaemia is anaemia of chronic disease, characterized by its microcytic and hypochromic anaemia. There can be various reasons for anaemia, including medication used in treatment of inflammatory bowel disease like azathioprine which can lead to cytopenia and sulfasalazine which can also result in folate malabsorption, etc. Testing for anti-Saccharomyces cerevisiae antibodies (ASCA) and anti-neutrophil cytoplasmic antibodies (ANCA) has been evaluated to identify inflammatory diseases of the intestine[71] and to differentiate Crohn's disease from ulcerative colitis.[72]

Feces

Calprotectin is a protein found in neutrophil cytosol. Neutrophils are integral to the inflammatory process caused by Crohn's disease. Faecal Calprotectin is a protein measured in a patient's feces. The fecal concentration correlates well with inflammation and disease activity. Normal fecal calprotectin level in a patient with active gastrointestinal symptoms excludes inflammatory bowel disease as a likely diagnosis and in many cases negates the need for colonoscopy or radio labelled white cell scanning[73].

Comparison with ulcerative colitis

The most common disease that mimics the symptoms of Crohn's disease is ulcerative colitis, as both are inflammatory bowel diseases that can affect the colon with similar symptoms. It is important to differentiate these diseases, since the course of the diseases and treatments may be different. In some cases, however, it may not be possible to tell the difference, in which case the disease is classified as indeterminate colitis.[1][7][14]

Comparisons of various factors in Crohn's disease and ulcerative colitis
Crohn's disease Ulcerative colitis
Terminal ileum involvement Commonly Seldom
Colon involvement Usually Always
Rectum involvement Seldom Usually[74]
Involvement around the anus Common[75] Seldom
Bile duct involvement No increase in rate of primary sclerosing cholangitis Higher rate[76]
Distribution of Disease Patchy areas of inflammation (Skip lesions) Continuous area of inflammation[74]
Endoscopy Deep geographic and serpiginous (snake-like) ulcers Continuous ulcer
Depth of inflammation May be transmural, deep into tissues[1][75] Shallow, mucosal
Fistulae Common[75] Seldom
Stenosis Common Seldom
Autoimmune disease Widely regarded as an autoimmune disease No consensus
Cytokine response Associated with Th17 [39] Vaguely associated with Th2
Granulomas on biopsy Can have granulomas[75] Granulomas not seen[74]
Surgical cure Often returns following removal of affected part Usually cured by removal of colon
Smoking Higher risk for smokers Lower risk for smokers[74]

Treatment

Currently there is no cure for Crohn's disease and remission may not be possible or prolonged if achieved.[77] In cases where remission is possible, relapse can be prevented and symptoms controlled with medication, lifestyle changes and in some cases, surgery. Adequately controlled, Crohn's disease may not significantly restrict daily living.[78] Treatment for Crohn's disease is only when symptoms are active and involve first treating the acute problem, then maintaining remission.

Medication

Acute treatment uses medications to treat any infection (normally antibiotics) and to reduce inflammation (normally aminosalicylate anti-inflammatory drugs and corticosteroids). When symptoms are in remission, treatment enters maintenance with a goal of avoiding the recurrence of symptoms. Prolonged use of corticosteroids has significant side-effects; as a result they are generally not used for long-term treatment. Alternatives include aminosalicylates alone, though only a minority are able to maintain the treatment, and many require immunosuppressive drugs.[75]

Medications used to treat the symptoms of Crohn's disease include 5-aminosalicylic acid (5-ASA) formulations, prednisone, immunomodulators such as azathioprine, mercaptopurine, methotrexate, infliximab, adalimumab[14] Cimzia[79] and natalizumab.[80][81] Hydrocortisone should be used in severe attacks of Crohn's disease.[82]

Lifestyle changes

Certain lifestyle changes can reduce symptoms, including dietary adjustments, proper hydration and smoking cessation. Eating small meals frequently instead of big meals may also help with a low appetite. To manage symptoms have a balanced diet with proper portion control. Fatigue can be helped with regular exercise, a healthy diet and enough sleep. A food diary may help with identifying foods that trigger symptoms. Some patients should follow a low fiber diet to control symptoms especially if fiberous foods cause symptoms.[78]

Surgery

Crohn's cannot be cured by surgery, though it is used when partial or a full blockage of the intestine occurs. Surgery may also be required for complications such as obstructions, fistulas and/or abscesses, or if the disease does not respond to drugs. After the first surgery, Crohn's usually shows up at the site of the resection though it can appear in other locations. After a resection, scar tissue builds up which can cause strictures. A stricture is when the intestines become too small to allow excrement to pass through easily which can lead to a blockage. After the first resection, another resection may be necessary within five years.[83] For patients with an obstruction due to a stricture, two options for treatment are strictureplasty and resection of that portion of bowel. There is no statistical significance between strictureplasty alone versus strictureplasty and resection in cases of duodenal involvement. In these cases, re-operation rates were 31% and 27%, respectively, indicating that strictureplasty is a safe and effective treatment for selected patients with duodenal involvement.[84]

Short bowel syndrome (SBS, also short gut syndrome or simply short gut) can be caused by the surgical removal of the small intestines. It usually develops if a person has had half or more of their small intestines removed.[85] Diarrhea is the main symptom of short bowel syndrome though other symptoms may include cramping, bloating and heartburn. Short bowel syndrome is treated with changes in diet, intravenous feeding, vitamin and mineral supplements and treatment with medications. Another complication following surgery for Crohn's disease where the terminal ileum has been removed is the development of excessive watery diarrhea. This is due to an inability to reabsorb bile acids after resection of the terminal ileum.[citation needed]

In some cases of SBS, intestinal transplant surgery may be considered; though the number of transplant centres offering this procedure is quite small and it comes with a high risk due to the chance of infection and rejection of the transplanted intestine. [86]

Prospective treatments

Researchers at University College London have questioned the wisdom of suppressing the immune system in Crohn's, as the problem may be an under-active rather than an over-active immune system: their study found that Crohn's patients showed an abnormally low response to an introduced infection, marked by a poor flow of blood to the wound, and the response improved when the patients were given sildenafil.[87]

Recent studies using helminthic therapy or hookworms to treat Crohn's Disease and other (non-viral) auto-immune diseases seem to yield promising results.[88]

Complementary and alternative medicine

More than half of Crohn's disease sufferers have tried complementary or alternative therapy.[89] These include diets, probiotics, fish oil and other herbal and nutritional supplements. The benefit of these medications is uncertain.

  • Acupuncture is used to treat inflammatory bowel disease in China, and is being used more frequently in Western society.[90] There is evidence that acupuncture has benefits beyond the placebo effect, improving quality of life, general well-being and a small decrease in blood-bound inflammatory markers.[90]
  • Methotrexate is a folate anti-metabolite drug which is also used for chemotherapy. It is useful in maintenance of remission for those no longer taking corticosteroids.[91]
  • Metronidazole and ciprofloxacin are antibiotics which are used to treat Crohn's that have colonic or perianal involvement, although this use has not been approved by the Food and Drug Administration.[92] They are also used for treatment of complications, including abscesses and other infections accompanying Crohn's disease.[7]
  • Thalidomide has shown response in reversing endoscopic evidence of disease.[93]
  • Cannabis may be used to treat Crohn's Disease with its anti-inflammatory properties. Cannabis and cannabis-derived drugs may also help to heal the gut lining.[94]

Prognosis

Crohn's disease is a chronic condition for which there is currently no cure. It is characterised by periods of improvement followed by episodes when symptoms flare up. With treatment, most people achieve a healthy height and weight, and the mortality rate for the disease is relatively low. However, Crohn's disease is associated with an increased risk of small bowel and colorectal carcinoma, including bowel cancer.[95]

Epidemiology

The incidence of Crohn's disease has been ascertained from population studies in Norway and the United States and is similar at 6 to 7.1:100,000.[96][97] Crohn's disease is more common in northern countries, and shows a higher preponderance in northern areas of the same country.[98] The incidence of Crohn's disease is thought to be similar in Europe but lower in Asia and Africa.[96] It also has a higher incidence in Ashkenazi Jews.[14]

Crohn's disease has a bimodal distribution in incidence as a function of age: the disease tends to strike people in their teens and 20s, and people in their 50s through to their 70s, and ages in between due to not being diagnosed with Crohn's and being diagnosed instead with irritable bowel syndrome (IBS).[1][7] It is rarely diagnosed in early childhood. It usually strikes females who are pediatric patients more severely than males.[99] However, only slightly more women than men have Crohn's disease.[100] Parents, siblings or children of people with Crohn's disease are 3 to 20 times more likely to develop the disease.[101] Twin studies show a concordance of greater than 55% for Crohn's disease.[102]

History

Inflammatory bowel diseases were described by Giovanni Battista Morgagni (1682-1771), by Polish surgeon Antoni Leśniowski in 1904 (leading to the use of the eponym "Leśniowski-Crohn disease" in Poland) and by Scottish physician T. Kennedy Dalziel in 1913.[103]

Burrill Bernard Crohn, an American gastroenterologist at New York City's Mount Sinai Hospital, described fourteen cases in 1932, and submitted them to the American Medical Association under the rubric of "Terminal ileitis: A new clinical entity". Later that year, he, along with colleagues Leon Ginzburg and Gordon Oppenheimer published the case series as "Regional ileitis: a pathologic and clinical entity".[9]

See also

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External links

Crohn's disease at the Open Directory Project


 
Translations: Crohn
Top

Français (French)
idioms:

  • crohn's disease    la maladie de Crohn

Deutsch (German)
idioms:

  • crohn's disease    Crohnsche Krankheit

Español (Spanish)
idioms:

  • crohn's disease    Enfermedad o Mal de Crohn


 
 

 

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