Crohn’s Disease or Terminal Ileitis: Classification & Types, Epidemiology, Causes, Risk Factors, Symptoms, Signs, Treatment, Investigations, Tests

Crohn’s disease is chronic inflammatory disease in the gastrointestinal tract, which typically involves distal part of ileum. It primarily causes breaks in lining of the two intestines, large and small, but can also affect the complete digestive tract, anywhere from mouth to anus. This is mainly characterized by cramping and diarrhea.

This disease also is given name of granulomatous enteritis or terminal ileitis among others.

Crohn’s disease does not have a medical cure. Once it starts, it tends to fluctuate between periods of activity and inactivity.

There Are Five Types of Crohn’s Disease Based On Their Symptoms:

• Ileocolitis: This is the most common type of this disease mainly affecting the ileum or small intestine and the colon. The general symptoms of ileocolitis are diarrhea, considerable weight loss and cramping or pain in the middle or lower right part of the abdomen.
• Ileitis: This mainly affects the ileum. Symptoms are the same that of diarrhea, considerable weight loss and cramping or pain in the middle or lower right part of the abdomen, but in addition inflammatory abscesses or fistulas may form in the lower right part of the abdomen.
• Gastroduodenal Crohn’s Disease: This type Crohn’s disease affects the stomach and duodenum or the starting point of small intestine. General symptoms are weight loss, loss of appetite and nausea and also vomitings if the narrow segments of bowels get obstructed.
• Jejunoileitis: This type affects the jejunum causing areas of inflammation mainly in the upper half of small intestine. Common symptoms are cramps after meals, diarrhea, abdominal pain and formation of fistulas that can later become intense.
• Granulomatous Colitis: This type affects only the colon. Symptoms include diarrhea, rectal bleeding, formation of ulcers, fistulas, abscess formation around the anus, skin lesions, and joint pains.

There is a likelihood that a person may have multiple areas of the digestive tract affected leading to overlap between the types mentioned above.

In the United States, the number of new cases and prevalence number of people who have the disease have increased steadily during the last 50 years.

• About 7 of every 100,000 people are affected with Crohn’s disease. These are among the highest in the world. The incidence is about 1 to 3 per 100,000 in Australia, Southern Europe, and South Africa, and is less than 1 per 100,000, in South America and Asia.
• Crohn’s disease is more prevalent in the Whites than in the Asians and African Americans.
• Crohn’s disease is slightly more common among men.
• Prevalence is generally higher in urban areas than in rural areas and also higher in higher socioeconomic classes.
• Most people newly diagnosed with Crohn’s disease are aged between 15 to 30 years, but it can occur at any age. Sometimes it is newly diagnosed in people aged between 60 to 80 years.
• Crohn’s disease can be quite debilitating. However, with medical treatment and other measures that are used to minimize the discomfort of flares, most people learn to cope up with it. Almost every individual with Crohn’s disease can lead a normal life.

Current theories regarding its pathophysiology indicates role for infectious, dietary, environmental, and immunological factors in a person who is genetically and immunologically vulnerable.

It starts as inflammatory infiltrates around intestinal crypts and subsequently develops into ulceration of superficial mucosa. This inflammation gradually progresses to involve deeper layers and forms non-caseating granuloma. This granuloma involves mesentery and all layers of intestinal wall and regional lymph nodes. The detection of granulomas is highly suggestive of this disease but even if they are not present it does not rule out its diagnosis.

Endoscopic findings during the initial stages include hyperemia and edema of inflamed mucosa, which further develops into discrete deep superficial ulcers present transversely and longitudinally giving it a cobblestone appearance. These ulcerations or lesions are separated by healthy areas known as skip lesions.

The acute transmural inflammation leads to bowel obstruction caused by mucosal edema associated with spasm. This inflammation makes the bowel wall thick leading to luminal narrowing, formation of strictures, and scarring. This subsequently leads to formation of fistula, perforation, and/or abscess formation. This inflammation also damages intestinal mucosa resulting in decreased ability for absorption, which can lead to malnutrition, dehydration, and vitamin deficiencies. Involvement of terminal ileum can cause decreased bile acid absorption leading to fat-soluble vitamin deficiency or gallstone formation. Excessive fat in stool binds to calcium and increases oxalate absorption predisposing to oxalate kidney stones.

In addition to manifestations related to gastrointestinal tract, Crohn’s disease also involves multiple other organs and systems to include eyes, mouth, liver, bile ducts and skin. Some of these disorders carry autoimmune mechanisms.

There are no proven theories as to its cause, although many theories exist. However, it may be helpful to understand the possible causes and how they interact with one another. This can give better understanding of the symptoms, diagnosis, and treatment.

• Immune system problems.
• Genetics.
• Environmental factors.

Immune System Problems: Immune system problems have been linked to inflammatory bowel disease (IBD), including Crohn’s. Immune system defends the body from harmful microbes i.e., bacteria, viruses, fungi, and other foreign substances that have entered the body. The body usually does not respond to all the microbes, however, and also many microbes are helpful especially in digestion. Hence the immune system leaves them untouched.

For some unknown reason people affected with Crohn’s disease immune system reacts inappropriately. Generally the immune system stops once the harmful microbes are eliminated, but for some reason, the inflammatory response simply will not stop in people affected with Crohn’s disease and the inflammation continues. Over time, this chronic inflammation in the digestive system can result in ulcers and other injuries to the intestines.

Genetics: Brothers, sisters, children, and parents of people affected with inflammatory bowel disease including Crohn’s disease are more likely to develop the disease themselves. About 10% to 20% of people with Crohn’s disease have at least one other family member who also has the disease. The disease is more common in certain ethnic groups, such as Whites and people of Jewish descent.

Environmental Factors: Environmental factors also may help trigger Crohn’s disease. These environmental factors may include the following:

• Substances from something that has been consumed.
• Cigarette smoke.
• Microbes such as bacteria or viruses.
• Few other substances not yet known.

• They may trigger an immune system response that once started cannot stop.
• They may damage the lining of the intestines directly, which may cause Crohn’s disease to begin or to speed up.

Crohn’s disease is sporadic. This means that the inflammation occurs without any aura or warning and then goes away over a period of time. It is highly unpredictable and impossible to predict when the condition may flare up, how long the flare will last, and when it will flare up again. People feel pretty good when the disease is inactive.

• Abdominal pain.
• Diarrhea.
• Loss of appetite.
• Weight loss.
• Blood in stools, which is rare.
• Fever. A high fever may indicate a complication involving infection, such as an abscess.
• Anemia.
• Sores in the mouth.
• Nutritional deficiencies, such as lowered levels of folic acid, iron, vitamin B12, and fat-soluble vitamins.
• Bowel obstruction.
• Abnormal tunnels or openings known as fistulas that sometimes forms between parts of the intestine or between the intestine and another organ such as the skin, bladder, or vagina. A fistula may be the first sign of this disease.
• Pockets of infection known as abscess.
• Anal fissures that are small tears in the anus.
• Skin tags resembling hemorrhoids.

Because of involvement of the immune system, there may also be other symptoms outside the digestive tract such as eye problems, joint pain, a skin rash, or liver disease.

The aim of treatment for Crohn’s disease is to reduce the inflammation, which in turn relieves the symptoms, prevents complications, and maintains good nutrition.

Medications used in reducing inflammation include antiinflammatory drugs, corticosteroids, immunosuppressants, and antibiotics.

• Mesalamine to reduce the inflammation. Generally used in people with mild Crohn’s disease.
• Corticosteroids to reduce the inflammation and suppress the immune system. Corticosteroids are used in people with severe systemic symptoms and those who do not respond to anti-inflammatory agents. These can be used only for a short period.
• Antibiotics reduce inflammation by reducing infection.
• Immunosuppressants work by suppressing the immune system.

• Symptoms such as diarrhea, cramps, and bloating are usually treated successfully with medications. Antidiarrheal agents relieve mild to moderately severe symptoms.
• Dietary therapies such as high fiber diets, low fiber diets, or low fat diets are helpful in some individuals over a short period, but may not be helpful over the long term.
• Dietary supplements or vitamins after discussing with a health care provider.
• Avoidance of dairy products in individuals who are lactose intolerant.

When medications fail, alternative treatment is surgery. Fistulas that bypass a large amount of the intestine and causing very severe symptoms or do not improve with medical treatment may need to be repaired surgically.

Crohn’s disease is diagnosed with the help of medical history, physical exam, imaging studies, and laboratory tests.

Crohn’s disease may be tough to diagnose and may be undiagnosed for years because symptoms usually develop gradually and may affect different parts of the intestine at different periods. Also the fact that other diseases can also have the same symptoms leads to further confusion. Crohn’s disease tends to cause the intestine to have a cobblestone appearance, which is a key factor in helping with the diagnosis.

• Flexible sigmoidoscopy or colonoscopy. Colonoscopy is the preferred test in general because it can be used to examine the entire colon versus sigmoidoscopy, which reaches only the last part of the colon.
• Abdominal X-ray to locate possible obstruction in the abdomen.
• Upper gastrointestinal series with small-bowel follow through to examine the intestines with use of a barium swallow.
• Upper gastrointestinal endoscopy, which allows to take a look at the interior lining of the esophagus, stomach, and duodenum.
• Barium enema, a test that is used to examine the colon or the large intestine.
• Computed tomography (CT) scan, which uses x-rays to produce detailed pictures of structures inside the body.
• Magnetic resonance imaging (MRI).
• Standard blood tests and urine tests, which may be used to check for anemia, inflammation, or malnutrition.
• A biopsy of a sample of tissue from the lining of the intestine collected during sigmoidoscopy or colonoscopy. It can be used to confirm the diagnosis and sometimes even tumors or cancer.

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