Crohn's disease is an inflammation of the gastrointestinal (GI) tract that may affect the deepest layers of the intestinal walls. Unlike ulcerative colitis, which is confined to the colon, Crohn's disease may appear anywhere from the mouth to the anus, including in the esophagus, duodenum, appendix, stomach, small intestine, and colon. 

In 45 percent of cases, Crohn's disease is located in the area between the small and large intestines known as the ileum and the cecum (the ileocecal region). One of the main characteristics of a chronic inflammatory bowel disease (IBD) such as Crohn's is the development of ulcers, or open sores, in the GI tract.

Types and Location of Ulcers

Depending on where the disease strikes, a person suffering from Crohn's may experience ulcers throughout the colon or a string of contiguous ulcers in only one part of it. In other parts of the GI tract, ulcers may be scattered in clusters with intact, healthy tissue in between. Chronic inflammation can also lead to ulcers in the genital area (perineum) or the anus. 

Occasionally, Crohn's sufferers will develop painful sores in the mouth, known as aphthous ulcers. These oral ulcers usually appear during a flare-up of intestinal inflammation. They can resemble the more common canker sore or, occasionally, much larger ulcers will appear. 

Though extremely rare, pyostomatitis vegetans is an oral type of Crohn's disease that results in multiple abscesses, pustules, and ulcers in the oral cavity. These sores may be treated with oral and topical corticosteroids as well as immune-modulating drugs. However, sometimes these types of oral ulcers may be a side-effect of medications such as antibiotics that are used to treat IBD themselves and may cause thrush, an oral fungal infection. Immune-modulating drugs may also leave a person susceptible to viral infections such as herpes simplex (HSV) or cytomegalovirus (CMV).  

Ulcers and Their Effects

Because Crohn's disease affects deeper tissue than ulcerative colitis, serious side effects due to ulcers may occur. These include:

Visible Bleeding 

Although visible bleeding is rare, it may occur if an ulcer tunnels into a large blood vessel or artery. The body usually acts quickly to seal off the bleeding vessel and, for many people, this type of incident occurs only once. However, surgery may be required if bleeding becomes recurrent or persistent.  


Even when visible bleeding is absent, a person with Crohn's disease will often develop iron-deficiency anemia due to multiple ulcers (open sores) in either the small intestine or colon. These ulcers can result in continuous, chronic, low-grade blood loss. A person with extensive Crohn's disease of the ileum or someone who has had an ileum resection may develop anemia due to an inability to absorb enough vitamin B12. 


If an ulcer breaks through an intestinal wall, it creates what is known as a fistula. A fistula is an abnormal connection between different parts of the intestine, or between the intestine and the skin or another organ such as the bladder. An internal fistula may cause food to bypass areas of the bowel completely, resulting in inadequate absorption. External fistulas may cause the bowel to drain onto the skin, resulting in a life-threatening abscess if left untreated. In Crohn's patients, the most common type of fistula is found in the anal area (perianal).

Massive Hemorrhage

Very rarely, a person with Crohn's disease will experience sudden, massive bleeding. The bleeding may occur at any time, both during a flare-up or while the disease is in remission. In the event of a massive hemorrhage, surgery is usually required to remove the diseased segment—whether it’s the colon or part of the small intestine—in order to save the patient's life or to prevent another life-threatening hemorrhage in the future. 


In the case of mouth ulcers, a topical oral anesthetic such as lidocaine may help to numb the pain. Typically, a topical corticosteroid is mixed with the anesthetic as well. Those with severe Crohn's of the ileum or an ileum resection will need to be given vitamin B12. 

Also, recent studies have found that immunosuppressive drugs such as azathioprine, 6-mercaptopurine, and methotrexate, as well as biologicals like anti-TNF agents may heal (not cure) Crohn's disease in some patients. 

A person who has had a hemorrhage may wish to consult a doctor to see if it may be possible to heal their disease in lieu of surgery.