D Inflammatory bowel disease
Definition
In the United States, between 200,000 and 300,000 individuals have inflammatory bowel disease, and approximately 30,000 new cases are diagnosed each year. The two major types of inflammatory bowel disease are Crohn’s disease and ulcerative colitis. Ulcerative colitis is an inflammatory disease, primarily of the mucosa of the rectum and distal colon. It is a chronic disease that is fraught with remissions and exacerbations.
Incidence and prevalence
Ulcerative colitis affects female patients more frequently than male patients and has a bimodal age distribution that shows a first peak incidence between ages 15 and 20 years and a second, smaller, peak between ages 55 and 60 years. The disorder is speculated to have a strong familial genetic predisposition, but psychological factors have also been implicated in its cause. Crohn’s disease most commonly occurs at about 30 years of age.
Pathophysiology
Crohn’s disease involves primarily the distal ileum and large colon in approximately 50% of patients. The remainder of patients experience disease that is localized to either the colon or portions of the small intestine (regional enteritis). The deeper layers of the intestinal mucosa are typically involved, a situation that leads to derangements in colonic absorption.
Clinical manifestations
Owing to the loss of functional absorptive surfaces in the large colon, patients with Crohn’s disease are often deficient in magnesium, phosphorus, zinc, and potassium. They also have deficiencies secondary to the loss of absorptive capability in portions of the small intestine. Protein-losing enteropathy is often encountered, as is anemia resulting from occult blood loss and deficiencies in vitamin B12 and folic acid. Iron deficiency secondary to insufficient intestinal absorption also contributes to development of an anemic state. Involvement of the distal ileum in the disease process results in deficiencies in vitamin B12 and in nutrients that are dependent on bile acids for absorption. Disturbance in the enterohepatic circulation of bile in the terminal ileum is reflected in complex nutrient deficiencies, including proteins, zinc, magnesium, phosphorus, fat-soluble vitamins, and vitamin B12. This state is typical of patients with chronic Crohn’s disease. Folate deficiency may also be present in patients with Crohn’s disease who receive sulfasalazine preparations.
Fistulas often develop between inflamed portions of the intestine and adjacent abdominal structures. Abdominal and pelvic abscesses, rectocutaneous fistulas, and perirectal abscesses have a high incidence in these patients. Increased calcium oxalate absorption in the terminal ileum frequently occurs, resulting in a high rate of renal calculi and cholelithiasis.
Treatment
Medical therapy for Crohn’s disease includes a variety of drugs and is given in the box below.
