Crohn disease (CD) is an inflammatory disease of the bowel of unknown etiology, most commonly involving the terminal ileum and manifesting primarily with diarrhea, abdominal pain, fatigue, and weight loss.

CD

Regional enteritis

Inflammatory bowel disease (IBD)

• Physical exam findings vary depending on disease location and severity
• Abdominal tenderness, mass, or distention
• Chronic or nocturnal diarrhea
• Weight loss, fever, night sweats
• Hyperactive bowel sounds in patients with partial obstruction, bloody diarrhea
• Delayed growth and failure of normal development in children
• Perianal and rectal abscesses, perianal fistulas (Fig. E1), anal tags (Fig. E2), multiple sinuses and scarring (Fig. E3), mouth ulcers, cobblestone appearance of oral mucosa (Fig. E4), and atrophic glossitis
• Extraintestinal manifestations (Table E1): Joint swelling and tenderness, hepatosplenomegaly, erythema nodosum (Fig.E5), pyoderma gangrenosum (Fig. E6), clubbing, tenderness to palpation of the sacroiliac joints
• Symptoms may be intermittent, with varying periods of remission
• Overall, 45% to 50% of patients have ileocolonic inflammation, 30% have isolated small bowel disease, 20% have isolated colonic disease, and 5% have isolated upper GI or perianal manifestations

Unknown. Pathophysiologically, Crohn disease involves an immune system dysfunction.

• Ulcerative colitis (Table 2)
• Infectious diseases (tuberculosis, Yersinia, Salmonella, Shigella, Campylobacter)
• Parasitic infections (amebic infection)
• Pseudomembranous colitis
• Ischemic colitis in elderly patients
• Lymphoma
• Colon carcinoma
• Diverticulitis
• Radiation enteritis
• Collagenous colitis
• Fungal infections (Histoplasma, Actinomyces)
• Anorectal and colon diseases, formerly referred to as gay bowel syndrome
• Carcinoid tumors
• Celiac sprue
• Mesenteric adenitis

• Decreased hemoglobin and hematocrit from chronic blood loss, effect of inflammation on bone marrow, and malabsorption of vitamin B₁₂
• Hypokalemia, hypomagnesemia, hypocalcemia, and low albumin in patients with chronic diarrhea
• Vitamin B₁₂ and folate deficiency
• Elevated erythrocyte sedimentation rate and CRP
• Positive anti-Saccharomyces cerevisiae antibodies
• Elevated INR (due to vitamin K malabsorption)
• Fecal calprotectin has been reported as useful in screening of patients with suspected IBD. Based on a pretest probability of 32% in adults, an abnormal calprotectin test result increases the posttest probability to 91%, and a normal result reduces the probability of IBD to 3%. False elevations may occur with other gastrointestinal diseases such as bacterial, viral, and protozoal causes of infective diarrhea

Endoscopic features of Crohn disease include asymmetric and discontinued disease, deep longitudinal fissures, cobblestone appearance, and presence of strictures (Fig. E7). Crypt distortion and inflammation are also present. Granulomas may be present.

• CT of abdomen (Fig. 8) may show thickening of the terminal ileum and is helpful in identifying abscesses, fistulas (Fig. E9), and other complications.
• Magnetic resonance enterography (MRe) is superior to other imaging modalities in its ability to distinguish active from chronic fibrotic disease. It is, however, more expensive.
• In 10% to 15% of patients with IBD, a clear distinction between ulcerative colitis and Crohn disease cannot be made. In general, Crohn disease can be distinguished from ulcerative colitis by the presence of transmural involvement and the frequent presence of noncaseating granulomas and lymphoid aggregates on biopsy.

• Nutritional supplementation is needed in patients with advanced disease. Total parenteral nutrition may be necessary in selected patients.
• Low-residue diet is necessary when obstructive symptoms are present.
• If diarrhea is prominent, increased dietary fiber and decreased fat in the diet are sometimes helpful.
• Psychotherapy is useful for situational adjustment crises. A trusting and mutually understanding relationship and referral to self-help groups are very important because of the chronicity of the disease and the relatively young age of the patients.
• Avoid oral feedings during acute exacerbation to decrease colonic activity: A low-roughage diet may be helpful in early relapse.

• Corticosteroids are used to induce remission. They have been the mainstay for treating moderate to severe active Crohn disease. Prednisone 40 to 60 mg/day is useful for acute exacerbation. Steroids are usually tapered over approximately 2 to 3 mo. Some patients require a low dose for a prolonged period of maintenance.
• Steroid analogues are locally active corticosteroids that target specific areas of inflammation in the gastrointestinal tract. Budesonide is available as a controlled-release formulation and is approved for mild to moderate active Crohn disease involving the ileum and/or ascending colon. The adult dose is 9 mg qd for a maximum of 8 wk.
• Patients responding to glucocorticoids are transitioned to immunomodulators as their glucocorticoid is tapered.
• Immunosuppressants such as azathioprine or mercaptopurine are used for maintenance of remission. Methotrexate is an alternative agent.
• Metronidazole 500 mg qid may be useful for colonic fistulas and treatment of mild to moderate active Crohn disease. Ciprofloxacin 1 g qd has also been found to be effective in decreasing disease activity.
• TNF inhibitors are agents useful to induce remission and maintain remission in patients with moderate to severe Crohn disease. Infliximab, a chimeric monoclonal antibody targeting tumor necrosis factor-α, is effective in the treatment of enterocutaneous fistulas. This medication can induce clinical improvement in 80% of patients with Crohn disease refractory to other agents. It can be used in combination with other medications such as azathioprine in patients with severe Crohn disease. A PPD test should be done before using this medication. Adalimumab and certolizumab are other TNF inhibitors also effective in inducing remissions and may be useful in adult patients with Crohn disease who cannot tolerate infliximab or have symptoms despite receiving infliximab therapy. Efficacy is better when an anti-TNF is used together with an immunomodulator.
• Natalizumab, a selective adhesion-molecule inhibitor, has been reported to be effective in increasing the rate of remission and response in patients with active Crohn disease. It is effective for patients in whom anti-TNF therapy has been unsuccessful. Prior to using natalizumab, serologic testing should be done for JC virus, which causes multifocal leukoencephalopathy (PML), and if the patient is seronegative, the risk of PML from natalizumab is low. Vedolizumab is another IV integrin receptor antagonist recently FDA approved for moderate to severe Crohn disease patients who have not responded to or cannot tolerate standard treatment. Vedolizumab use is not associated with high risk of PML. Ustekinumab, a monoclonal antibody to the P₄0 subunit of interleukin-12 and interleukin-23, has shown efficacy for induction and maintenance therapy for Crohn disease. It has been FDA-approved for moderate to severely active Crohn disease unresponsive to immunomodulators or corticosteroids or a tumor necrosis factor inhibitor.
• Hydrocortisone enema bid or tid is useful for proctitis.
• Most patients who have anemia associated with Crohn disease respond to iron supplementation. Erythropoietin is useful in patients with anemia refractory to treatment with iron and vitamins.

• Monitor disease activity with symptom review and laboratory evaluation (complete blood count and sedimentation rate).
• Liver tests and vitamin B₁₂ levels monitored on a yearly basis.

There is no cure for CD, and most patients require at least one surgical resection. One tenth of patients have prolonged remission, three quarters have a chronic intermittent disease course, and one eighth have an unremitting course. Patients with IBD are at increased risk of colon cancer.

Surgical referral is needed for complications such as abscess formation, obstruction, fistulas, toxic megacolon, refractory disease, or severe hemorrhage. Approximately 40% to 50% of patients will require some type of bowel surgery within the first 5 yr of Crohn disease. A conservative surgical approach is necessary because surgery is not curative. Multiple surgeries may also result in short bowel syndrome.

Crohn Disease (Patient Information)