What is Crohn's Disease? (Part I)

Crohn's disease (also known as granuomatous colitis and regional enteritis ) is an inflammatory disease of the intestines that may affect any part of the gastrointestinal tract from the mouth to the anus and causes a wide variety of symptoms. It primarily causes abdominal pain, diarrhea (which might be bloody), vomiting, or weight loss¹ . Additionally, it may also cause complications outside of the gastrointestinal tract such as skin rashes, arthritis, and inflammation of the eye(s).

Crohn's disease is an autoimmune disease meaning that the body's immune system attacks the gastrointestinal tract, resulting in inflammation; it is classified as a type of inflammatory bowel disease (IBD). Research has shown evidence of a genetic link to Crohn's, placing individuals with siblings affected by the disease at a higher risk to contract the disease. In addition, it's also recognized to have a large environmental component as evidenced by a higher number of cases in western industrialized nations. From the standpoint of gender, the occurrence in males and females are affected at about the same rate. Currently, there is no known pharmaceutical or surgical cure for Crohn's disease. Treatment options are, therefore, restricted to controlling symptoms, maintaining remission, and preventing relapse.

The incidence of the disease has been ascertained from population studies in both the United States and Norway and is similar at 6 to 7.1 per 100,000 people. Studies have shown that it's more common in northern countries and has a higher preponderance in the northern part of those countries. The incidence of Crohn's is thought to be similar in Europe, but lower in both Asia and Africa.

How is Crohn's disease classified?

Crohn's is generally classified as a autoimmune disease and invariably affects the gastrointestinal track. Due to this fact, most gastroenterologists categorize the presenting disease by the affected areas. Il eocolic Crohn's disease , which affects both the ileum (the final part of the small intestine that connects to the large intestine) and the large intestine, accounts for fifty percent (50%) of cases. Crohn's ileitis , which affects only the ileum, accounts for thirty percent (30%). Crohn's colitis , which affects the large intestines, accounts for the remaining twenty percent (20%) of cases and may be particularly difficult to distinguish from ulcerative colitis. Crohn's can affect any part of the digestive tract, from the mouth to the anus.

Crohn's can also be categorized by the behavior of the disease as it progresses. This determination was formalized in the Vienna classification of Crohn's disease² . There are three (3) categories of disease presentation: stricturing, penetrating, and inflammatory. Stricturing disease causes a narrowing of the bowel which may lead to a bowel obstruction or changes in the caliber of feces. Penetrating disease creates abnormal passageways (fistulae - pictured above left) between the bowel and other structures.Inflammatory disease (or non-stricturing, non-penetrating disease) causes inflammation without causing strictures or fistulae.

What are the symptoms and possible complications from Crohn's disease?

Gastrointestinal symptoms -

Abdominal pain could be the initial symptom of Crohn's disease and is often accompanied by diarrhea - especially in persons who have had surgery. In person's who have had surgery (or multiple surgeries), may end up with a condition known as "short bowel syndrome" of the gastrointestinal tract. The nature of diarrhea associated with the disease depends on the part of the small intestine or colon involved. For example, in a person with Ileitis, stools might be large volume with watery feces. Comparatively, a person with Colitis might have a smaller volume of feces that occur at a higher frequency. Generally visible bleeding in feces is less common in Crohn's disease than it is in ulcerative colitis, however, it may be present with Crohn's colitis. With the latter, bloody bowel movements are typically intermittent and can be either bright or dark red in color.

Symptoms caused by intestinal stenosis are also common with Crohn's Disease. Abdominal pain is often most severe in the area of the bowel with stenosis. In severe cases, vomiting and nausea may indicate the beginning of a small bowel obstruction. Crohn's Disease may also be associated with primary sclerosing cholangitis - an inflammation of the bile ducts.

Perianal discomfort may also be present with Crohn's Disease. Itchiness or pain in the area of the anus might be suggestive of inflammation, fistulization or abscess around the anal area or anal fissure. Perianal skin tags are also common with Crohn's Disease. At the opposite end of the gastrointestinal tract, the mouth may be affected by non-healing sores ( aphithous ulcers ); rarely the esophagus and stomach might also be involved. This can result in difficulty swallowing, upper abdominal pain, and vomiting.

Systemic symptoms -

Crohn's disease - like many other inflammatory diseases - can cause a variety of systemic symptoms . . . that is, symptoms that affect the entire body. Among children with Crohn's, one of the most common systemic symptoms is growth failure. It is estimated that, if Crohn's manifest itself during the growth spurt that occurs in puberty, that approximately thirty percent (30%) of children will experience a retardation of growth³ . Fever may also be present, however, fevers higher than 101.3 F (38.5 C) are uncommon unless there is a complication such as an abscess (pictured above). In older individuals, it may manifest as weight loss. This is usually related to decreased food intake, such individuals with intestinal symptoms from Crohn's often feel better when they do not eat. People with extensive small intestine disease may also suffer from malabsorption of lipids and carbohydrates.

Extraintestinal symptoms -

In addition to systemic and gastrointestinal involvement, Crohn's disease can also affect many other organ systems. Inflammation of the interior portion of the eye, known as uveitis , can cause eye pain, especially when exposed to light (photophobia). The inflammation may also involved the which part of the eye - the sclera - with a condition known as episcleritis . Both the episcleritis and the uveitis can result in loss of vision if left untreated.

Crohn's disease is also associated with a type of rheumatologic disease known as seronegative spondyloarthropathy . These diseases are characterized by inflammation of one or more joints (arthritis), or muscle insertions (enthesitis⁴ ).The arthritis can affect larger joints such as the knee or shoulder or may exclusively involve the small joints of the hands and feet. It can also involve the spine, leading to ankylosing spondylitis if the entire spine is involved or simply sacroiliitis if it only involves the lower spine. The symptoms of arthritis painful joints which are usually warm and swollen as well as loss of joint mobility and/or function.

Crohn's disease can also involve the skin, blood, and endocrine system. One of the skin manifestations, erythema nodosum , presents as red nodules which usually appear on the shin(s). The condition results from inflammation of the underlying subcutaneous tissue and is typically characterized by septal panniculitis . Another skin lesion caused by Crohn's disease is pyoderma gangrenosum (pictured at left). This skin condition causes a painful ulcerated nodule. Persons with Crohn's disease have an increased risk of developing blood clots . In addition, persons with Crohn's may suffer from autoimmune hemolytic anemia - a condition that causes the body's immune system to attack the red blood cells. This causes fatigue, pallor, and other symptoms associated with anemia.

Possible complications

Crohn's disease can lead to several mechanical complications within the intestines including obstruction, fistulae, and abscesses (pictured at right). The obstructions typically result from strictures or adhesion which narrow the lumen which blocks the passage of intestinal content. Fistulae can develop between two loops of bowel, between the bowel and the bladder, between the bowel and the vagina, or between the bowel and the skin. An abscess is a walled-off collection of infection, which can occur either in the abdomen or the perianal area.

There is also an increased risk of cancer in the area(s) of inflammation. For example, if inflammation is present in the small bowel, that patient is at higher risk for developing cancer of the small intestine. In addition persons suffering from Crohn's colitis have a relative risk of 5.6% of developing colon cancer (pictured at left along with a colon polyp). Due to this increased risk, a colonoscopy is recommended for anyone who has had Crohn's for at least eight (8) years.

Individuals suffering from Crohn's are also at a higher risk of malnutrition - particularly due to decreased food intake as well as malabsorption. This risk increases following surgery to resection the small bowel. Most people suffering from moderate to severe Crohn's are often referred to a dietitian for assistance in nutrition.

What is the pathophysiology and causes of Crohn's disease?

In persons suspected of having Crohn's disease, a biopsy of the colon is taken in order to confirm the diagnosis. Additionally, there are certain characteristic features of the pathology (observed by a doctor) that point toward a diagnosis of Crohn's disease. Among these are a transmural pattern of inflammation - meaning that it may span the entire depth of the intestinal wall. Ulceration is also a commonly seen outcome if the disease is highly active and, usually, there is an abrupt transition between unaffected tissue and the ulcer or ulcers. Microscopic examination may also show mucosal inflammation.

According to the Tenth edition of Brunner and Suddarth's Textbook of Medical-Surgery Nursing , regional enteritis is a sub-acute and chronic inflammation that extends through the layers of the bowel wall from the intestinal mucosa. It is characterized by periods of exacerbation (flare-up) as well as periods of remission. The enteritis begins with edema and thickening of the mucosa. Ulcers then begin to form on the inflamed mucosa. These lesions are normally in continuous contact with one another and are separated by normal tissue. Fistulas, fissures, and abscesses form as the inflammation extends into the peritoneum. In advanced cases, the intestinal mucosa has a "cobblestone" appearance. As the disease progresses, the bowel wall thickens and becomes fibrotic and the intestinal lumen narrows. In some cases diseased bowel loops sometimes will adhere to other loops surrounding them.

1Baumgart, D.C., Sandborn, W.J. (2007) "Inflammatory bowel disease: clinical aspects and established and evolving therapies , " The Lancet, pp. 1641 - 1657

2Gasche, C, et. Al (2000) "A simple classification of Crohn's disease: report of the Working Party for the World Congress of Gastroenterology, Vienna 1988 ," Inflamm Bowel Dis pp 8 - 15

3Buller, H.A. (1997) "Problems in diagnosis of IBD in children", The Netherlands Journal of Medicine pp S8 - S11

4Enthesitis is an inflammation of the entheses, the site where tendons or ligaments insert into the bone.

Source: Wikipedia.com ( http://en.wikipedia.org/wiki/Enthesitis )