Crohn’s Disease: Causes, Symptoms, and Treatment

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While the disease occurs most commonly in the small intestine and colon, it can affect any part of the GI tract between the mouth and the anus. This range from affecting just the large intestine to affecting the whole GI tract. The disease is appearing more often in newly industrialized countries. When it comes to gender, there is an equal chance of men and women developing the disease, but some studies suggest that men are more likely to suffer the more severe complications of Crohn’s disease. The risk of developing Crohn’s disease is highest for people between the ages of 20 and 30. However, the disease can occur at any age.

Extensive research has been conducted and continues to be discovered by researchers for perhaps one of the most perplexing and complex health conditions, Crohn’s disease. This is because not all that much is known on the causes of the disease and there is no known cure to date. Probably the most substantial finding on Crohn’s disease is that it is a type of IBD (Inflammatory Bowel Disease). This is a general term that refers to chronic swelling/inflammation of all or part of the digestive tract. Crohn’s disease is chronic, with periods of acute symptoms, and periods of symptom-free remission. The course of the disease varies greatly among patients. Crohn’s disease can be both debilitating and life-threatening and can affect quality of life.

What is Crohn’s Disease?

Crohn’s disease is a severe, lifelong disease that affects the bowel. It is a type of inflammatory bowel disease (IBD). The cause of Crohn’s disease is unknown. Crohn’s disease can affect any part of the gastrointestinal tract, from the mouth to the back passage, but most often occurs in the small intestine and colon. Crohn’s disease appears to run in some families and certain communities, which suggests that the disease might have a genetic cause. People with a close relative who has (or had) Crohn’s disease are more likely to develop the disease. A gene known as NOD2 has been found to be linked to a higher likelihood of developing Crohn’s disease. Up to one in four people with Crohn’s disease has or had a relative with the disease. NOD2 is a gene that helps the body to fight off bacterial infections. There are many theories about what causes Crohn’s disease, but none have been proven. Some researchers believe it could be caused by an infection, while others suggest that diet and stress play a role. Because the specific cause is not known and it is few people who get the disease, it is not considered to be a true result of unhealthy eating or stress. Because Crohn’s disease is an autoimmune disease, there is a lot of research currently being done on how the immune system can be curbed to prevent it from attacking the body.

Prevalence and Risk Factors

Those of Jewish heritage have close to a five times greater risk of developing Crohn’s, and the disease is especially prevalent among Ashkenazi Jews. African Americans also have a higher risk of developing Crohn’s than the general population, although their risk is still lower than that of Jewish people. Crohn’s is most prevalent among individuals of northern European descent. Although the reasons for these ethnic discrepancies are not entirely understood, it is believed that they are due to genetic factors. Children of parents with IBD are three to five times more likely to develop Crohn’s or UC than the general population, and the more closely related the family member with IBD, the greater the risk. Twin studies have shown that if one twin has IBD, the other twin is at least 50% more likely to have it than a non-twin sibling. These findings indicate that there is indeed a genetic susceptibility to IBD, although a specific “IBD gene” has yet to be identified.

The prevalence of Crohn’s disease is relatively higher in developed countries. It is a lifelong chronic condition that afflicts individuals of all ages, but it becomes more common between the ages of 15 and 30. At present, there are estimated to be at least 115,000 people with Crohn’s disease in the United Kingdom. In Canada, there are over 170,000 Canadians living with Crohn’s and colitis. In the United States of America, between 400,000 and 600,000 people are affected. Canadians have amongst the highest rates of inflammatory bowel disease (IBD) in the world. The number of new cases of Crohn’s disease has been steadily rising over the last decade, and it is thought to be more common than ulcerative colitis. It affects both men and women, but there are some differences in the location and behavior of the disease among both genders. For example, women are more likely to have involvement of the perianal area, while men are more likely to have disease in the upper gastrointestinal tract. Both are equally likely to have disease in the small bowel and colon.

Impact on Quality of Life

Overall, the primary goal in the treatment of Crohn’s disease is to eliminate symptoms, which is done by induction and maintenance of remission. However, the ultimate goal for both patients and healthcare providers is to normalize or near-normalize HRQOL. A recent study by Feagan et al. has demonstrated that the drug infliximab is effective in achieving clinical remission and also effective in mucosal healing and ultimately achieving deep remission. The benefit of this deep remission is that it is associated with a decreased risk of hospitalization or surgery and an increased likelihood of corticosteroid-free remission. This, of course, all leads to a better HRQOL for the patient. Infliximab is effective in both initiating and maintaining remission and is now used as a first-line agent in patients with moderate to severe Crohn’s disease. The efficacy in achieving deep and sustained remission in these patients has changed the treatment algorithm of Crohn’s disease and has shifted the focus to aggressive therapy early in the prescriptive course. This should result in an improved prognosis and HRQOL for these patients.

Garrity et al. have recently published a study assessing health-related quality of life (HRQOL) in patients with Crohn’s disease treated at tertiary medical centers. This investigation is noteworthy as it demonstrates that high-quality medical care does not necessarily confer a high HRQOL. In fact, in certain aspects, the concern and energy of medical care can result in impairment of HRQOL. Garrity et al. identified that patients with Crohn’s disease have a diminished HRQOL compared with the normal population, and it is diminished further in patients with more severe disease and those with complications. Despite the importance of work as a contributor to social status, there was no association of employment with HRQOL. This study highlights the importance of the ability to work, showing that unemployment does not affect HRQOL in employed patients but is significantly associated with diminished physical HRQOL in those who are unable to work. This investigation is important as it identifies various prognostic factors and suggests areas to improve HRQOL in patients with Crohn’s disease. The improvement of HRQOL should be an important tool to measure the efficacy of treatment in Crohn’s disease, and studies that identify how to achieve this have the potential to greatly influence patient outcomes.

As previously mentioned, the primary symptoms of Crohn’s disease are abdominal pain, diarrhea (with or without blood), fever, weight loss, and loss of appetite. A considerable proportion of patients with Crohn’s disease require surgery, either to alleviate symptoms that do not respond to drug therapy or to correct complications that have arisen in the course of the disease. Both surgery for Crohn’s disease and the disease itself, which does not respond to medical or surgical therapy, can severely affect the well-being of patients with this condition. Surgery is particularly associated with a diminution in quality of life, mostly because the disease often recurs in the same or a different site in the bowel. A major issue for patients with Crohn’s disease is the unpredictability and variability of their symptoms. This may interfere with all aspects of their daily lives and, for those who are students, may result in difficulties in academic attainment.

Causes and Pathophysiology

The concordance rate of Crohn’s disease in identical twins is 50%, indicating a strong genetic predisposition. Both twin and family studies have demonstrated that relatives of patients with Crohn’s disease have a higher risk of developing the disease. Genetic polymorphisms associated with Crohn’s disease have been found in NOD2 (nucleotide-binding oligomerization domain 2). NOD2 is associated with intracellular recognition of bacterial lipopolysaccharides and is linked to regulation of the innate immune response to bacterial agents. Carriage of NOD2 mutations increases the risk of developing Crohn’s disease by 2 to 4 fold. Other genes associated with Crohn’s disease are those involved in regulating immune function and the inflammatory response.

Crohn’s disease is an idiopathic inflammatory disorder that has been linked with genetic and environmental factors. It is a chronic, relapsing condition that can affect any part of the gastrointestinal tract; however, there is often healthy bowel between sites of disease involvement. A characteristic feature of Crohn’s disease is transmural inflammation, which means it involves all layers of the bowel. Ulceration and fistulae are complications that can also occur.

Genetic Factors

Another method to study genetic components in IBD is through looking at monogenic disorders that cause IBD-like symptoms. These are caused by mutations in one gene and provide a specific target to give clear cause and effect evidence. Although the rate at which these disorders are identified is low and its applicability to standard IBD is still uncertain, it may be valuable research in the future.

GWAS studies depend on large groups of volunteer subjects. They compare the genomes of those with a certain disease with a group without the disease. The SNPs (single nucleotide polymorphisms) from the genomes of the disease group are analyzed to find any trends that suggest specific genetic factors related to the disease. The results of GWAS studies provide a strong hand of evidence with which to obtain research grants and close in on further detailed research into the function of these genes and how they translate to the development of IBD.

The genetic basis for the development of Crohn’s disease is well supported, and it is known to run in families, with 20% of sufferers having a close relative also with some form of IBD. With the rise of Genome-Wide Association Studies, significant progress has been made in understanding the genetic components in Crohn’s disease and ulcerative colitis. To date, over 30 genes have been associated with Crohn’s disease and the number is rising. These genes mainly regulate innate immunity and the function of immune cells, while the IL23R gene has been shown to have potential protective effects. These findings are significant as they atomize the beginning of the disease with overactive immune responses to microbial antigens.

Dysregulation of the Immune System

The autoimmune nature of Crohn’s disease suggests that the immune system of affected individuals is inappropriately activated, an event which can be triggered by environmental factors. The human immune system is comprised of two main components, the innate (non-specific) and adaptive (acquired) immune systems. The main functions of the immune system are to protect the host from invading pathogens such as bacteria, viruses, and fungi and to recognize and remove damaged and malignant host cells. To carry out these functions, a variety of different immune cells and mediators are used, the production of which is finely regulated. Cytokines are proteins that act as mediators and control the nature, location, and extent of an immune response. Evidence suggests that in Crohn’s disease, regulation of these cytokines is disturbed and is the root of both innate and adaptive immune system dysfunction seen in this condition. This, in turn, affects a loss of discrimination between harmful invaders and host cells and a chronic inflammatory response, both of which are seen in Crohn’s disease. By the beginning of this century, it was apparent that Crohn’s disease was associated with an overactive immune system. This was first suggested by the disease’s success in responding to treatment with immunosuppressive drugs – drugs that dampen immune system activity. More recently, it has been shown that the majority of inflammatory bowel disease (IBD) patients possess an abnormal immune response to enteric (gut) bacteria. This was confirmed by research showing that antibiotics or drugs targeting the immune response were successful in treating IBD. Furthermore, genetic studies have highlighted the importance of many different immune system pathways in causing IBD. Always there have been failed attempts to treat Crohn’s disease with drugs that target single cytokines, this is because upregulation of one cytokine pathway is compensated for by the overactivity of another. This complex immune system dysregulation is relatively specific to Crohn’s disease and is the reason why it has been difficult to treat.

Environmental Triggers

Like most diseases that are genetically determined, environmental triggers initiate the development of Crohn’s disease. These appear to be nonspecific, affecting most individuals only as transient alterations in their bowel function. Several acute infectious diseases of the intestine are associated with the development of chronic Crohn’s disease, including bacillary dysentery caused by Shigella species and salmonellosis. An increased prevalence of appendectomy has also been noted in Crohn’s disease, suggesting that appendectomy may hasten the clinical onset of disease in some individuals, although this association has not been consistently demonstrated. Cigarette smoking is the most well-established environmental factor associated with Crohn’s disease. It increases the risk of Crohn’s disease, particularly for involvement of the ileum and development of severe disease. Smokers who have developed the disease have a higher rate for reoperation and an increased risk for development of complications compared with nonsmokers. Prolonged use of nonsteroidal anti-inflammatory drugs is also associated with the development of inflammatory bowel diseases, particularly ulcerative colitis, although the data is less consistent for Crohn’s disease at this time. Various studies have suggested that intake of refined sugar is associated with the development of Crohn’s disease, as well as relapse of symptoms in persons with the disease, although more data is needed to confirm this finding. Diets high in animal protein and/or fat were positively associated with risk of inflammatory bowel disease in several case-control studies. The effects of fatty acid intake on risk for development of Crohn’s disease are less clear. In general, data supports that n-6 polyunsaturated fatty acids increase and fish oils decrease the production of inflammatory eicosanoids and cytokines. However, a recent study demonstrated increased risk of developing Crohn’s disease in persons consuming greater than 21 grams/day of total fat, and a fourfold increased risk with saturated fat intake in the highest quartile compared with the lowest quartile. There was no association between risk of developing Crohn’s disease and either n-3 or n-6 polyunsaturated fatty acid intake in this study. High consumption of caffeine has also been associated with increased risk of development of Crohn’s disease, particularly among ex-smokers. Although Crohn’s disease is more prevalent in developed countries, no conclusive data exists to implicate any specific dietary factor.

Symptoms and Diagnosis

Gastrointestinal Symptoms

Gastrointestinal symptoms of Crohn’s disease are highly varied but generally include the characteristic symptoms of pain in the abdomen and diarrhea. The main parts of the digestive system that can be affected are the small intestine and the colon. Pain in the abdomen is usually located in the lower right side and may be acute due to inflammation in the overlying peritoneum. Diarrhea in Crohn’s disease is typically non-bloody and occurs chronically. It can be associated with the consumption of food in patients with disease in the small intestine. In more serious cases, Crohn’s disease can lead to symptoms outside the GI tract. This occurs when the immune system is triggered and inflammation is sustained. An example is the condition aphthous stomatitis which involves repeated formation of mouth ulcers. Inflammation of the throat and esophagus can cause a sense of burning or narrowing of the throat. Inflammation of the perianal skin in the manifestation of skin tags, fissures, or abscesses can be highly discomforting and lead to social embarrassment.

Extraintestinal Manifestations

Extraintestinal manifestations are those that occur outside the intestine and are associated with IBD in general or one of its forms. The most common extraintestinal manifestations of Crohn’s disease are inflammatory conditions that affect the joints, skin, and eyes. In some cases, the joint inflammation may be mild and can be relieved with aspirin or other mild pain killers. More severe joint inflammation may require treatment with corticosteroids or another prescription medication. In some cases a patient may require more potent medications and occasionally a surgical procedure to alleviate symptoms. Skin problems range from mild to severe and can include erythema nodosum, a red swelling or lump, usually on the lower legs; and pyoderma gangrenosum, a skin ulcer. Eye conditions can be in the form of uveitis or iritis and can cause redness, pain or blurred vision. Involvement of the liver may occur as a primary condition or a complication of the use of certain medications. Patients with PSC have a higher likelihood of also having ulcerative colitis. Other conditions are not caused by the inflammation of Crohn’s disease and may need separate treatment.

Diagnostic Procedures

No single test can diagnose Crohn’s disease. For this reason, a combination of tests is usually necessary to confirm the diagnosis or to help rule out the disease. If a doctor suspects an individual has Crohn’s disease, they may begin by checking blood for anemia, which could indicate bleeding in the intestines. A stool sample may also be taken to look for blood or infection in the intestines. After lab work is evaluated, the doctor can perform a series of tests which may include one or more of the following: upper GI series, small bowel series, colonoscopy, or flexible sigmoidoscopy. While the colonoscopy and flexible sigmoidoscopy are two separate tests, they are similar in nature and examine the large bowel, or colon, to look for inflamed tissue. These tests involve the use of a colonoscope, which is a long, flexible lighted tube with a camera on the end. A sample of tissue from the lining of the intestines can also be viewed under a microscope to check for inflammation, which can aid in diagnosis. An individual may be given special instructions to prepare the bowel for these tests, and a cleansing routine is necessary to clear the colon of waste. Following a clear liquid diet for 1-3 days prior to the tests and taking a laxative or an enema the night before are common ways the bowels are cleared.

Crohn’s disease is an ongoing disorder that causes inflammation of the digestive tract, which is also referred to as the gastrointestinal (GI) tract. The disease, which is a type of inflammatory bowel disease (IBD), can affect anywhere along the GI tract, from the mouth to the anus, but it is more commonly found in the small intestine and colon. It is important to diagnose Crohn’s disease as early as possible, even before the onset of symptoms, so that treatment can begin. Having a diagnosis enables an individual to gain a better understanding of what is causing their symptoms and allows them to take a more active role in their treatment.

Treatment and Management

The aim of treatment is to induce remission initially and then to try to maintain the sufferer in remission for as long as possible. The severity and pattern of the illness determines which treatment will be most suitable. Treatments include drug therapy, nutrition supplements, surgery, and new emerging therapies and the effectiveness of the treatment is regularly evaluated by the sufferer’s clinical team. Each kind of treatment has its own risks and benefits. Before starting the treatment for Crohn’s, the clinical team will explain the nature of the treatment, its aims and possible risks and side effects. Treatments to induce remission for a person with Crohn’s Disease: This usually involves taking one or more different types of medication. To get a better understanding of the experiences these people have had with treatment, take a look at the Treatment Diaries.


Medications used to treat Crohn’s are designed to suppress the inflammation of the intestines and to prevent further flare-ups. It has been found that if the disease is left untreated, it has a natural tendency to worsen and the inflammation spreads to a larger area of the intestines. Corticosteroids such as Prednisone have been very effective in the treatment of Crohn’s. These drugs are usually taken by mouth but are sometimes administered by intravenous infusion in the hospital. While corticosteroids can almost always induce a remission, it has been found that they are not very effective in maintaining a remission and should be withdrawn as rapidly as possible. This is due to the fact that corticosteroids can cause a variety of side effects especially with long-term use. These include a rounding of the face, increased body fat in the abdomen, and thinning of the arms and legs. High blood pressure, diabetes, cataracts, glaucoma, and osteoporosis are some of the other hazards of long-term corticosteroid treatment.

Lifestyle Modifications

Exercise is an important aspect of overall health, and any form of mild to moderate exercise is generally good for people with Crohn’s disease. Exercise can reduce stress, and aerobic exercise can improve your overall cardiovascular health. If you’re recovering from a flare-up or surgery, you may need to start with a low-intensity exercise program and slowly work up to a more vigorous routine. There may be times when high-intensity or high-impact exercise could worsen your symptoms, so it is important to recognize how your body is responding to different forms of exercise.

Maintaining good nutritional health is another key to managing Crohn’s symptoms. Not all foods affect people the same way, so it is important to know how different foods affect you. If you find certain foods worsen your symptoms, you may want to avoid them. Consider consulting a dietitian, who can help guide you in creating a diet plan that provides the necessary nutrients for good health and incorporates the foods that don’t adversely affect you. Drinking plenty of water is also important, especially in times of diarrhea, to avoid becoming dehydrated.

Stress can’t cause Crohn’s disease, but it can make your symptoms worse and can sometimes trigger a flare-up. Many people find that learning to relax and reduce stress in their lives can be beneficial. Techniques such as deep breathing, meditation, listening to music, or just taking time out to relax may help.

Lifestyle modifications are an important part of living well with Crohn’s disease. By reducing stress and making changes to your diet and exercise routine, you may be able to reduce the number of flare-ups that you have.

Surgical Interventions

One of the most effective methods for managing Crohn’s disease is surgery. If the disease does not respond to medications or is so severe that medication treatment is not adequate, surgery may be indicated. While surgery does not cure Crohn’s disease, it can treat the complications and symptoms, and usually can allow people to remain free of symptoms for long periods of time – perhaps several years. The most common surgery is called resection. The diseased portion of the intestine is removed and the healthy parts are reconnected. The goal of resection is to relieve the symptoms and complications of Crohn’s disease when they are not being well controlled by medication. Another type of surgery is called strictureplasty which is used if there are a number of narrowing of the intestine. In this type of surgery the strictured area is widened without removing any portion of the intestine. This is done to keep as much normal intestine as possible.