Atlas of pathophysiology, 2 Edition

Part II - Disorders

Gastrointestinal Disorders

Crohn's Disease

Crohn's disease, also known as regional enteritis or granulomatous colitis, is inflammation of any part of the GI tract (usually the terminal ileum), extending through all layers of the intestinal wall. It may also involve regional lymph nodes and the mesentery.

Age Alert

Crohn's disease is most prevalent in adults ages 20 to 40.

Causes

Unknown

Possible contributing conditions

·         Lymphatic obstruction

·         Allergies, immune disorders

·         Infection

·         Genetic predisposition

Pathophysiology

Whatever the cause of Crohn's disease, inflammation spreads slowly and progressively. Enlarged lymph nodes block lymph flow in the submucosa. Lymphatic obstruction leads to edema, mucosal ulceration and fissures, abscesses, and sometimes granulomas. Mucosal ulcerations are called skipping lesions because they aren't continuous, as in ulcerative colitis.

Oval, elevated patches of closely packed lymph follicles—called Peyer's patches—develop in the lining of the small intestine. Subsequent fibrosis thickens the bowel wall and causes stenosis, or narrowing of the lumen. The serous membrane becomes inflamed (serositis), inflamed bowel loops adhere to other diseased or normal loops, and diseased bowel segments become interspersed with healthy ones. Finally, diseased parts of the bowel become thicker, narrower, and shorter.

Signs and symptoms

·         Steady, colicky pain in right lower quadrant

·         Cramping, tenderness

·         Weight loss

·         Diarrhea, steatorrhea, bloody stools

·         Low-grade fever

·         Anal fistula

·         Perineal abscess

Diagnostic test results

·         Fecal occult blood test reveals minute amounts of blood in stools.

·         Small bowel X-ray shows irregular mucosa, ulceration, and stiffening.

·         Barium enema reveals the string sign (segments of stricture separated by normal bowel) and possibly fissures and narrowing of the bowel.

·         Sigmoidoscopy and colonoscopy reveal patchy areas of inflammation (helps to rule out ulcerative colitis), with cobblestone-like mucosal surface. With colon involvement, ulcers may be seen.

·         Biopsy reveals granulomas in up to one-half of all specimens.

·         Blood tests reveal increased white blood cell count and erythrocyte sedimentation rate, and decreased potassium, calcium, magnesium, and hemoglobin levels.

Treatment

·         Corticosteroids, immunosuppressants

·         Sulfasalazine

·         Metronidazole

·         Antidiarrheals (not in patients with significant bowel obstruction)

·         Narcotic analgesics

·         Antibiotics, such as infliximab, for patients with fistulous disease

·         Stress reduction and reduced physical activity

·         Vitamin supplements (iron supplements)

·         Avoidance of fruits and vegetables; high-fiber, spicy, or fatty foods; dairy products; carbonated or caffeine-containing beverages; foods or liquids that stimulate intestinal activity

·         Surgery, if necessary

P.171

BOWEL CHANGES IN CROHN's DISEASE

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