Crohn’s disease (CD) is a type of inflammatory bowel disease (IBD). IBD is characterized by inflammation in the gastrointestinal tract (GIT). The other major type of IBD is ulcerative colitis (UC). The main difference between CD and UC lies in the location and nature of inflammation. Inflammation in CD is intermittent, can occur in any part of GIT, and expands to all layers of GIT. Whereas, in UC the inflammation is continuous, occurs only in the rectum and distal parts of the large intestine such as the colon, and is confined to the innermost layer of the large intestine called the mucosa.

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The incidence and prevalence of CD vary markedly with geography, socioeconomic status, lifestyle, and ethnicity. It is more common in modernized countries and there is no significant difference between the male and female prevalence of CD. Most people are between the ages of 10 to 40 years at the time of diagnosis. CD forms a major portion of pediatric IBD, far greater than UC.

Symptoms

Since inflammation in CD can take place anywhere in the digestive tract, the symptoms are heterogeneous. The major symptoms are:

• Abdominal pain

• Diarrhea

• Rectal bleeding

Rectal bleeding is more common in UC, but it can also occur in CD. Other complications such as abscesses, fistulas, and anal tags can also be present in some disease phenotypes.

The extraintestinal symptoms are:

• Weight loss

• Fever

• Fatigue 

• Erythema nodosum

• Anemia

• Kidney damage

• Inflammation in the eyes

Diagnosis

Diagnosis of CD includes clinical presentation, patient’s medical history, and physical examination followed by investigations. The three major investigations include endoscopy, radio imaging, and biomarkers. Of these, endoscopy is the most important as it forms the backbone of CD diagnosis. Radio-imaging and biomarkers can be used to support diagnosis or evaluate the status of remission and the possibility of relapse. A biopsy is also performed with endoscopy for the histopathologic examination of a tissue specimen. The type of endoscopy performed depends on the site of inflammation.

​Ileocolonoscopy is the frequently used form of endoscopy in CD. There are various radio imaging techniques to look for strictures and other complications non-invasively. Biomarkers are not accurate in diagnosing CD. They have some applications in postoperative surveillance.

Treatment

Corticosteroids have long been used as the major drugs in managing IBD, but recently biologics have provided better and safer options. Aminosalicylates such as 5-Aminosalicylic acid are considered the first line of pharmacological treatment of CD. Antibiotics can control the population of harmful bacteria. Antimetabolites such as thiopurines and methotrexate are immunosuppressants that can reduce the chances of surgery. Infliximab, adalimumab, and certolizumab pegol are FDA-approved anti-TNF antibodies. They are usually preferred in patients who do not respond well to corticosteroids and immunosuppressants. Natalizumab, vedolizumab, and ustekinumab are all anti-integrin monoclonal antibodies. They work by blocking the transport of inflammatory cells into the gut by inhibiting integrins. Tofacitinib and filgotinib are emerging Janus kinase inhibitors that can be used in CD. Mongersen (an antisense oligonucleotide) and stem cell therapy are some of the other emerging therapeutics in the treatment of CD. Some studies report the benefits of cannabis in managing symptoms of CD; however, the evidence is inconclusive to suggest its use and the rate of surgery is high among CD patients. 

Dietary interventions are considered very important in IBD. Exclusive enteral nutrition has a good reputation for inducing much-needed remission without the use of corticosteroids. A variety of other diets such as partial enteral nutrition (PEN), CD exclusion diet (CDED), specific carbohydrate diet (SCD), and gluten-free diet (GFD)      also exist for IBD. Surgery can be simple to complex depending on the inflammation and condition of the patient. The decision to perform a surgery is multidisciplinary. Despite the diversity of available pharmacological options, the rates of surgery are still high. Drugs that accelerate mucosal healing are emerging. Such drugs will treat the actual pathophysiology instead of managing the symptoms.