Crohn’s disease belongs to the group of disorders known as inflammatory bowel disease.
A diagnosis of “Crohn’s disease” means a patient has an inflammatory bowel disease, or IBD for short. In addition to Crohn’s disease, IBD also includes ulcerative colitis and microscopic colitis. All of these conditions are characterized by chronic inflammation, which is primarily located in the gut. The symptoms and the long-term outcomes of these conditions can vary greatly.
Crohn’s disease can affect all sections of the digestive tract, from the mouth to the anus, making it different from the other IBDs that usually affect the large intestine (colon) only. In addition, inflammation may extend from the mucosa of the gut into the underlying layers of the intestinal wall (called transmural inflammation). This chronic inflammation across the entire intestinal wall may lead to complications such as fistulas (abnormal passage between the gut and other organs) and/or narrowing of the intestine (stenosis).
The sections of the digestive tract affected by inflammation can vary from one patient to another. The disease most commonly afflicts the last segment of the small intestine (the terminal ileum), often together with the ascending colon.
The precise cause of Crohn’s disease is not currently known. It is that an interaction between certain genetic predispositions and environmental factors (such as smoking) may lead to chronic bowel inflammation. The immune system also plays a role in developing the disease.
It is estimated that approximately 200 out of every 100,000 people in Germany suffer from Crohn’s disease. The frequency of Crohn’s disease appears to be increasing across the world. Although the majority of these patients first develop the disease in their 20s, it can theoretically start at any age, including in children and older people.
The typical symptoms of Crohn’s disease are abdominal pain, abdominal cramps, diarrhea, and flatulence. Patients with severe cases may have up to 15 bowel movements per day, with stool that is watery but rarely contains blood.
Other common symptoms of Crohn’s disease include a loss of appetite, unwanted weight loss, fever, fatigue, and exhaustion. Patients may also develop malnutrition resulting from the nutrient loss caused by the diarrhea.
The chronic inflammation may lead to complications such as accumulation of pus (abscess) or narrowing of the intestine (stenosis). Patients may also develop fistulas, which are abnormal passages between the intestines and other organs, such as the abdominal cavity, or to the exterior by anal fistulas. These complications can lead to the formation of scar tissue in the intestines, which then results in a higher risk of intestinal blockage (partial or complete).
Patients with Crohn’s disease also frequently experience symptoms outside of the gut called extraintestinal manifestations, which may impact the liver, bile ducts, skin, eyes, and joints.
Doctors typically suspect Crohn’s disease based on a patient’s current symptoms, the patient’s medical history, and a clinical examination.
The purpose of collecting a patient’s medical history is to find out his or her current symptoms, how long they last, and how intense they are.
Patients are also asked about other risk factors like smoking. Also important to know is whether any of the patient’s family members is aware of having Crohn’s disease or another inflammatory bowel disease (IBD). The doctor should specifically ask about extraintestinal manifestations since these may represent the primary symptoms if the abdominal symptoms are mild.
During a physical examination, a patient’s weight and height are measured, and the abdomen and rectum are probed by touching.
Laboratory tests ordered by the doctor will provide an indication of general blood levels and especially about parameters of inflammation such as the C-reactive protein (CRP). Stool should be tested for levels of calprotectin and, if those tests are inconclusive, for autoantibodies.
If a patient’s medical history and physical examination provide indications of Crohn’s disease, further examinations are typically performed to confirm the diagnosis. These procedures include an ultrasound examination of the abdomen.
The final confirmation of the diagnosis is made by colonoscopy. A colonoscopy is an endoscopic examination to search for inflammation in the intestines and if found, to determine where the inflammation is located and how far it has spread. A colonoscopy can also be used to detect whether abscesses (accumulations of pus), fistulas (abnormal passage to other organs or the surface of the body) or narrowing of the intestine is present. Tissue samples (biopsies) can also be collected for examination under a microscope.
After an ultrasound and a colonoscopy have been performed, an X-ray of the abdomen, computed tomography (CT) or magnetic resonance imaging (MRI) may be performed to clarify any special circumstances. An endoscopy of the stomach or small intestine (double-balloon enteroscopy) may be necessary to evaluate the situation in the upper digestive tract.
There is currently no cure for Crohn’s disease. The goal of treatment is therefore to reduce the symptoms of the disease and keep the inflammation in check in order to achieve a period without disease activity (remission). Once this is achieved, the goal is to maintain this remission for as long as possible and to avoid any complications.
Treatment is usually with medications, which are chosen based on the degree of the patient’s acute inflammation: mild, moderate, or severe. Typically, the first medication prescribed during the acute phase is a corticosteroid (also sometimes called a steroid) to effectively fight against the inflammation. For patients with mild to moderately active Crohn’s disease, guidelines recommend drugs containing the active ingredient budesonide. Budesonide is a special form of corticosteroid that is only released and broken down at specific sites in the body, which helps to greatly reduce its side effects. When used to treat Crohn’s disease, drugs containing budesonide are released at the junction of the small intestine and the large intestine, which is the region that is frequently inflamed in Crohn’s patients. In other words, the drug is the most active at fighting inflammation precisely where it is needed most. Budesonide is then transported from the gut into the liver, where it is broken down. The levels of budesonide circulating in the blood are thus very low, keeping side effects in the body to a minimum. This explains why patients experience many fewer side effects with budesonide than with other steroids known as systemic corticosteroids that are active throughout the entire body. Budesonide is available in several different formulations.
If the symptoms of the disease cannot be reduced using budesonide, other options include both systemic corticosteroids as well as immunosuppressants (drugs that dampen the immune system), primarily the drugs azathioprine or methotrexate. These drugs suppress immunological activity and thereby inflammatory reactions, helping lower the need for steroids. However, it needs to be considered that it takes between 3 and 6 months before immunosuppressants reach their full effectiveness. If a patient’s Crohn’s disease does not improve within this time frame, the next step is typically medications called biologics, which are produced using biotechnological methods. The most common types of biologic medication are antibodies that target specific pro-inflammatory signaling molecules in the body.
Once remission is achieved, maintenance therapy is given to prevent disease flare-ups. The primary goal of treatment is to achieve corticosteroid-free remission, to avoid the wide range of side effects caused by corticosteroids.
There is no specific diet that can treat Crohn’s disease. However, due to the risk of malnutrition, patients should ensure a balanced diet. At the same time, patients should of course also stop eating any foods they have difficulty digesting.
Surgery may be required in severe cases that cannot be managed using medication alone, and for patients with complications like fistulas or stenoses. However, removing an inflamed section of the intestine does not cure the disease, since the inflammation can spread to other regions of the digestive tract. For this reason, surgery always has the goal of maintaining as much of the gut as possible.
The diarrhea that occurs in Crohn’s disease may lead to certain nutritional deficiencies, especially of vitamins, minerals, and trace elements. If this happens, these nutrients must be replaced by taking supplements that ensure the body’s metabolism is working as well as possible.
One important lifestyle change is to quit smoking, which is a risk factor for developing Crohn’s disease and for possible complications in people who suffer from the disease.
Like all chronic diseases, Crohn’s disease presents special challenges in daily life. Psychotherapy or other mental health care may be beneficial for dealing with the disease. Self-help support groups can also be helpful for sharing experiences with other people suffering from Crohn’s disease.
Outlook and prognosis
Crohn’s disease typically progresses with flare-ups. There are two types of phases: phases of acute disease with symptoms that are sometimes severe, and phases with only low disease activity. However, relapses (recurrences) may occur after varying lengths of low activity. When inflammation flares back up, another course of medication usually brings the disease back into remission.
It is very difficult or even impossible to predict whether an individual case of Crohn’s disease will have mild or severe inflammation, or whether and how often relapses will occur especially without observing a patient for a long time.
Based on our current understanding, Crohn’s disease has little to no impact on life expectancy as long as it is detected early and treated properly. This is why regular check-ups by a doctor are important for early detection and treatment of impending flare-ups or complications.