INFLAMMATORY BOWEL DISEASE

INFLAMMATORY  BOWEL DISEASE

Inflammatory bowel disease (IBD) is a term comprising 2 disease entities: Crohn disease (CD) and ulcerative colitis (UC). They can be discussed simultaneously because of the large degree of overlap in terms of presentation, testing, and treatment. Both CD and UC are idiopathic disorders of the bowel associated with diarrhea, bleeding, weight loss, fever, and abdominal pain. Both are most accurately diagnosed with endoscopy and sometimes with barium stud- ies, “string sign” on small bowel follow through after barium meal in CD, and both are treated with anti-inflammatory medications, such as mesalamine, azathioprine, and 6-mercaptopu- rine (6MP). Steroids are used for acute exacerbations of both diseases.

Clinical Presentation. IBD presents with fever, diarrhea, weight loss, and, occasionally, abdomi- nal pain and bleeding. The extraintestinal manifestations of IBD are episcleritis, scleritis and iri- tis, sclerosing cholangitis, joint pains, and skin manifestations, such as pyoderma gangrenosum or erythema nodosum.

Crohn disease is more likely to be associated with a palpable abdominal mass because CD has granulomas in the bowel wall that are transmural in nature. This can lead to the different loops of bowel being inflamed and sticking together, forming a mass. The abdominal masses of CD can be palpated and cause pain. CD is not necessarily continuous, and one hallmark of the disorder is that there are “skip lesions,” or areas of normal tissue in between the areas of disease.

UC is limited exclusively to the large bowel. It is exclusively a mucosal disease, and although it can cause bleeding, it does not result in fistula formation. UC has no skip lesions, no fistula formation, and no oral or perianal involvement. UC is more likely to cause bloody diarrhea.

Note

Sclerosing cholangitis does not correlate to disease activity.

Both forms of IBD can lead to colon cancer after 8 to 10 years of involvement of the colon. If the CD does not result in colonic involvement, then it will not lead to cancer. Complications of Crohn disease are calcium oxalate kidney stones, diarrhea, and cholesterol gallstones.

Diagnosis. IBD is diagnosed with endoscopy and sometimes with barium studies. (CD can result in deficiency of vitamin B12, calcium, vitamin K, and iron because of malabsorption.) Anti–Saccharomyces cerevisiae antibodies (ASCA) are associated with CD, and antineutrophil cytoplasmic antibody (ANCA) is associated with UC. If a patient is ASCA positive and ANCA

negative, then he or she has a >90% chance of having CD. If the patient is ASCA negative and ANCA positive, there is a >90% chance of having UC.

Prothrombin time may be prolonged in CD because of vitamin K malabsorption. Kidney stones form more often in CD because the fat malabsorption results in a low calcium level and an increased absorption of oxalate, which forms kidney stones.

Treatment. Mesalamine derivatives are the mainstay of therapy for IBD in all of its forms. Pentasa is a form of mesalamine released in both the upper and lower bowel; hence, it is used in CD. Asacol is a form of mesalamine released in the large bowel, and it is most useful for UC. Rowasa is used exclusively for rectal disease. Sulfasalazine was used in the past for the same effect. The difficulty with sulfasalazine is that the high load of sulfa delivered causes a number of adverse effects, such as rash, hemolysis, and allergic interstitial nephritis. Sulfasalazine also causes reversible infertility in men and leukopenia by its sulfapyridine group.

Acute exacerbations of IBD are treated with high-dose steroids. Budesonide is a form of steroid that is ideal for IBD. It has a strong local effect when used orally, but is largely cleared by the liver in a first-pass effect. This limits the amount of systemic toxicity. Azathioprine and 6-mercaptopu- rine are associated with drug-induced pancreatitis, but are still used on a long-term basis to try to keep patients off steroids. Ciprofloxacin and metronidazole are used for CD in those with perianal disease. Infliximab is used for CD in those who form fistulae or have disease refractory to the other

forms of therapy. There has been re-activation of tuberculosis with infliximab, and it is important to test for latent tuberculosis with a purified protein derivative (PPD) prior to treatment. If the PPD is positive, then patients should receive isoniazid. The most common side effect of infliximab is arthralgias. Balsalazide and olsalazine are other forms of mesalamine that are only active in the colon and are used occasionally.

Surgery is curative in UC; almost 60% of patients will require surgery within 5 years after diagnosis due to refractory symptoms or severe disease. Surgery is not very effective in CD and disease tends to reoccur at the site of anastomosis.