Inflammatory bowel disease (IBD), an autoimmune disorder of unknown origin that primarily affects the GI tract, is estimated to afflict 1.4 million people in the United States.1 IBD has two major forms: ulcerative colitis, which involves the mucosa and is confined to the colon, and Crohn’s disease, which involves all four layers of the bowel and can occur in any part of the GI tract. This article will focus on the diagnosis, complications, and management of Crohn’s disease.
While generally under the care of a gastroenterologist, most patients with Crohn’s disease also routinely follow up with their primary-care provider. An understanding of the disorder, its treatment, and its potential complications is helpful in the co-management of the disease.
Approximately 50% of people with IBD have Crohn’s disease.1 It typically occurs in those aged 15-35 years but can present at any time in life. Crohn’s affects men and women equally, although some studies have suggested a slightly higher risk in women.1,2 Worldwide, Crohn’s seems to have a propensity for northern climates, and the United States is not immune to this trend, as evidenced by a rate that is twice as high in Northern California as compared with Southern California.3-5 Crohn’s is a chronic, incurable disease that leaves the patient with a lifetime of relapses and remissions.5
The cause remains elusive, but both genetics and environment are thought to play a role.2,6 Twins and other family members have an increased risk of developing the condition, lending credence to the theory that Crohn’s is an inherited disease.2
Crohn’s has historically been considered an autoimmune disease,2 with the immune system targeting the GI tract. While the etiology is unknown, the result is an inflammatory reaction within the GI tract that results in ulceration, bleeding, diarrhea, nausea, vomiting, and weight loss. The inflammatory reaction in Crohn’s disease involves all layers of the bowel (transmural involvement), potentially resulting in perforation, abscess, and fistula formation.2 There are several theories for the development of Crohn’s disease, but none has as yet been proven. It is similar to Johne’s disease in cattle, which is a result of bovine infection with Mycobacterium paratuberculosis.7
With this in mind, one theory holds that Crohn’s disease results from an intestinal infection that provokes a normal immune response. However, in genetically susceptible individuals, the immune system is unable to shut down after the infection is eradicated, and it continues to attack healthy intestinal tissue. This has yet to be proven.
While the terminal ileum is the site most commonly affected, Crohn’s disease can occur in any area of the GI tract from the mouth to the anus. Nearly 50% of patients will present with disease involving the terminal ileum and proximal colon, 33% will have disease confined to the distal small bowel, 25% will have colonic involvement only, and 2% will have esophageal disease.2 Upper-intestinal disease usually occurs in association with ileocolonic disease.