Harrisons Manual of Medicine, 18th Ed.

CHAPTER 159. Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBD) are chronic inflammatory disorders of unknown etiology involving the GI tract. Peak occurrence is between ages 15 and 30 and between ages 60 and 80, but onset may occur at any age. Epidemiologic features are shown in Table 159-1. Pathogenesis of IBD involves activation of immune cells by unknown inciting agent (? microorganism, dietary component, bacterial or self-antigen) leading to release of cytokines and inflammatory mediators. Genetic component suggested by increased risk in first-degree relatives of pts with IBD and concurrence of type of IBD, location of Crohn’s disease (CD), and clinical course. Reported associations include HLA-DR2 in Japanese pts with ulcerative colitis and a CD-related gene called CARD15 on chromosome 16p. CARD15 mutations may account for 10% of CD risk. Other potential pathogenic factors include serum antineutrophil cytoplasmic antibodies (ANCA) in 70% of pts with ulcerative colitis (also in 5–10% of CD pts) and antibodies to Saccharomyces cerevisiae (ASCA) in 60–70% of CD pts (also in 10–15% of ulcerative colitis pts and 5% of normal controls). Granulomatous angiitis (vasculitis) may occur in CD. Acute flares may be precipitated by infections, nonsteroidal anti-inflammatory drugs (NSAIDs), stress. Onset of ulcerative colitis often follows cessation of smoking.

TABLE 159-1 EPIDEMIOLOGY OF IBD

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ULCERATIVE COLITIS (UC)

PATHOLOGY

Colonic mucosal inflammation; rectum almost always involved, with inflammation extending continuously (no skip areas) proximally for a variable extent; histologic features include epithelial damage, inflammation, crypt abscesses, loss of goblet cells.

CLINICAL MANIFESTATIONS

Bloody diarrhea, mucus, fever, abdominal pain, tenesmus, weight loss; spectrum of severity (majority of cases are mild, limited to rectosigmoid). In severe cases dehydration, anemia, hypokalemia, hypoalbuminemia.

COMPLICATIONS

Toxic megacolon, colonic perforation; cancer risk related to extent and duration of colitis; often preceded by or coincident with dysplasia, which may be detected on surveillance colonoscopic biopsies.

DIAGNOSIS

Sigmoidoscopy/colonoscopy: mucosal erythema, granularity, friability, exudate, hemorrhage, ulcers, inflammatory polyps (pseudopolyps). Barium enema: loss of haustrations, mucosal irregularity, ulcerations.

CROHN’S DISEASE (CD)

PATHOLOGY

Any part of GI tract, usually terminal ileum and/or colon; transmural inflammation, bowel wall thickening, linear ulcerations, and submucosal thickening leading to cobblestone pattern; discontinuous (skip areas); histologic features include transmural inflammation, granulomas (often absent), fissures, fistulas.

CLINICAL MANIFESTATIONS

Fever, abdominal pain, diarrhea (often without blood), fatigue, weight loss, growth retardation in children; acute ileitis mimicking appendicitis; anorectal fissures, fistulas, abscesses. Clinical course falls into three broad patterns: (1) inflammatory, (2) stricturing, and (3) fistulizing.

COMPLICATIONS

Intestinal obstruction (edema vs. fibrosis); rarely toxic megacolon or perforation; intestinal fistulas to bowel, bladder, vagina, skin, soft tissue, often with abscess formation; bile salt malabsorption leading to cholesterol gallstones and/or oxalate kidney stones; intestinal malignancy; amyloidosis.

DIAGNOSIS

Sigmoidoscopy/colonoscopy, barium enema, upper GI and small-bowel series: nodularity, rigidity, ulcers that may be deep or longitudinal, cobble-stoning, skip areas, strictures, fistulas. CT may show thickened, matted bowel loops or an abscess.

DIFFERENTIAL DIAGNOSIS

INFECTIOUS ENTEROCOLITIS

Shigella, Salmonella, Campylobacter, Yersinia (acute ileitis), Plesiomonas shigelloides, Aeromonas hydrophila, Escherichia coli serotype O157:H7, Gonorrhea, Lymphogranuloma venereum, Clostridium difficile(pseudomembranous colitis), tuberculosis, amebiasis, cytomegalovirus, AIDS.

OTHERS

Ischemic bowel disease, appendicitis, diverticulitis, radiation enterocolitis, bile salt–induced diarrhea (ileal resection), drug-induced colitis (e.g., NSAIDs), bleeding colonic lesion (e.g., neoplasm), irritable bowel syndrome (no bleeding), microscopic (lymphocytic) or collagenous colitis (chronic watery diarrhea)—normal colonoscopy, but biopsies show superficial colonic epithelial inflammation and, in collagenous colitis, a thick subepithelial layer of collagen; response to aminosalicylates and glucocorticoids variable.

EXTRAINTESTINAL MANIFESTATIONS OF UC AND CD

1. Joint: Peripheral arthritis—parallels activity of bowel disease; ankylosing spondylitis and sacroiliitis (associated with HLA-B27)—activity independent of bowel disease.

2. Skin: Erythema nodosum, aphthous ulcers, pyoderma gangrenosum, cutaneous Crohn’s disease.

3. Eye: Conjunctivitis, episcleritis, iritis, uveitis.

4. Liver: Fatty liver, “pericholangitis” (intrahepatic sclerosing cholangitis), primary sclerosing cholangitis, cholangiocarcinoma, chronic hepatitis.

5. Others: Autoimmune hemolytic anemia, phlebitis, pulmonary embolus (hypercoagulable state), kidney stones, metabolic bone disease.

TREATMENT Inflammatory Bowel Diseases (See Fig. 159-1)

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FIGURE 159-1 Medical management of IBD. 5-ASA, 5-aminosalicylic acid; CD, Crohn’s disease; UC, ulcerative colitis.

SUPPORTIVE Antidiarrheal agents (diphenoxylate and atropine, loper-amide) in mild disease; IV hydration and blood transfusions in severe disease; parenteral nutrition or defined enteral formulas—effective as primary therapy in CD, although high relapse rate when oral feeding is resumed; should not replace drug therapy; important role in preoperative preparation of malnourished pt; emotional support.

SULFASALAZINE AND AMINOSALICYLATES Active component of sulfasalazine is 5-aminosalicylic acid (5-ASA) linked to sulfapyridine carrier; useful in colonic disease of mild to moderate severity (1–1.5 g PO qid); efficacy in maintaining remission demonstrated only for UC (500 mg PO qid). Toxicity (generally due to sulfapyridine component): dose-related—nausea, headache, rarely hemolytic anemia—may resolve when drug dose is lowered; idiosyncratic—fever, rash, neutropenia, pancreatitis, hepatitis, etc.; miscellaneous—oligospermia. Newer aminosalicylates are as effective as sulfasalazine but with fewer side effects. Enemas containing 4 g of 5-ASA (mesalamine) may be used in distal UC, 1 nightly retained qhs until remission, then q2hs or q3hs. Suppositories containing 500 mg of 5-ASA may be used in proctitis.

GLUCOCORTICOIDS Useful in severe disease and ileal or ileocolonic CD. Prednisone, 40–60 mg PO qd, then taper; IV hydrocortisone, 100 mg tid or equivalent, in hospitalized pts; IV adrenocorticotropic hormone drip (120 U qd) may be preferable in first attacks of UC. Nightly hydro-cortisone retention enemas in proctosigmoiditis. Numerous side effects make long-term use problematic.

IMMUNOSUPPRESSIVE AGENTS Azathioprine, 6-mercaptopurine—50 mg PO qd up to 2.0 or 1.5 mg/kg qd, respectively. Useful as steroid-sparing agents and in intractable or fistulous CD (may require 2- to 6-month trial before efficacy seen). Toxicity—immunosuppression, pancreatitis, ?carcinogenicity. Avoid in pregnancy.

METRONIDAZOLE Appears effective in colonic CD (500 mg PO bid) and refractory perineal CD (10–20 mg/kg PO qd). Toxicity—peripheral neuropathy, metallic taste, ?carcinogenicity. Avoid in pregnancy. Other antibiotics (e.g., ciprofloxacin 500 mg PO bid) may be of value in terminal ileal and perianal CD, and broad-spectrum IV antibiotics are indicated for fulminant colitis and abscesses.

OTHERS Cyclosporine [potential value in a dose of 4 (mg/kg)/d IV for 7–14 days in severe UC and possibly intractable Crohn’s fistulas]; experimental—tacrolimus, methotrexate, chloroquine, fish oil, nicotine, others. Infliximab [monoclonal antibody to tumor necrosis factor (TNF)] 5 mg/kg IV induces responses in 65% (complete in 33%) of CD pts refractory to 5-ASA, glucocorticoids, and 6-mercaptopurine. In UC, 27–49% of pts respond.

Adalimumab is a humanized version of the anti-TNF antibody that is less likely to elicit neutralizing antibodies in the pt. Pegylated versions of anti-TNF antibody may be used once monthly.

Natalizumab is an anti-integrin antibody with activity against Crohn’s disease, but some pts develop progressive multifocal leukoencephalopathy.

SURGERY UC: Colectomy (curative) for intractability, toxic megacolon (if no improvement with aggressive medical therapy in 24–48 h), cancer, dysplasia. Ileal pouch—anal anastomosis is operation of choice in UC, but contraindicated in CD and in elderly. CD: Resection for fixed obstruction (or stricturoplasty), abscesses, persistent symptomatic fistulas, intractability.

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For a more detailed discussion, see Friedman S, Blumberg RS: Inflammatory Bowel Disease, Chap. 295, p. 2477, in HPIM-18.