A variety of organisms can infect the gastrointestinal tract, from viruses and bacteria to protozoa and worms. Some produce short-lived upsets with gastroenteritis, nausea, diarrhea, and emesis (vomiting). Others, such as typhoid, cholera, and dysentery, are more serious, even fatal.
An ulcer is a lesion of the skin or a mucous membrane marked by inflammation and tissue damage. Ulcers caused by the damaging action of gastric, or peptic, juices on the lining of the GI tract are termed peptic ulcers. Most peptic ulcers appear in the first portion of the duodenum. The origins of such ulcers are not completely known, although infection with a bacterium, Helicobacter pylori, has been identified as a major cause. Heredity and stress may be factors as well as chronic inflammation and exposure to damaging drugs, such as
aspirin, or to irritants in food and drink. Current treatment includes the administration of antibiotics to eliminate H. pylori infection and use of drugs that block the action of histamine, which stimulates gastric secretion. Ulcers may lead to hemorrhage or to perforation of the digestive tract wall.
Ulcers can be diagnosed by endoscopy (Fig. 12-5) and by radiographic study of the GI tract using a contrast medium, usually barium sulfate. A barium study can reveal a variety of GI disorders in addition to ulcers, including tumors and obstructions. A barium swallow is used for study of the pharynx and esophagus; an upper GI series examines the esophagus, stomach, and small intestine.
The most common sites for cancer of the GI tract are the colon and rectum. Together these colorectal cancers rank among the most frequent causes of cancer deaths in the United States in both men and women. A diet low in fiber and calcium and high in fat is a major risk factor in colorectal cancer. Heredity is also a factor, as is chronic inflammation of the colon (colitis). Polyps (growths) in the intestine often become cancerous and should be removed. Polyps can be identified and even removed by endoscopy.
One sign of colorectal cancer is bleeding into the intestine, which can be detected by testing the stool for blood. Because this blood may be present in very small amounts, it is described as occult ("hidden") blood. Colorectal cancers are staged according to Dukes classification, ranging from A to C according to severity.
The interior of the intestine can be observed with various endoscopes named for the specific area in which they are used, such as proctoscope (rectum), sigmoidoscope (sigmoid colon) (Fig. 12-6), colonoscope (colon).
In some cases of cancer, and for other reasons as well, it may be necessary to surgically remove a portion of the GI tract and create a stoma (opening) on the abdominal wall for elimination of waste. Such ostomy surgery (Fig. 12-7) is named for the organ involved, such as ileostomy (ileum) or colostomy (colon). When a connection (anastomosis) is formed between two organs of the tract, both organs are included in naming, such as gastroduodenostomy (stomach and duodenum) or coloproctostomy (colon and rectum).
FIGURE 12-6. Sigmoidoscopy. The flexible fiberoptic endoscope is advanced past the proximal sigmoid colon and then into the descending colon.
FIGURE 12-7. Location of various colostomies. The shaded portions represent the sections of the bowel that have been removed or are inactive. (A) Sigmoid colostomy. (B) Transverse colostomy. (C) Ileostomy.
A hernia is the protrusion of an organ through an abnormal opening. The most common type is an inguinal hernia, described in Chapter 14 (see Fig. 14-4). In a hiatal hernia, part of the stomach moves upward into the chest cavity through the space (hiatus) in the diaphragm where the esophagus passes through (see Fig. 6-5). Often this condition produces no symptoms, but it may result in chest pain, dysphagia (difficulty in swallowing), or reflux of stomach contents into the esophagus.
In pyloric stenosis, the opening between the stomach and small intestine is too narrow. This usually occurs in infants and in male more often than in female subjects. A sign of pyloric stenosis is projectile vomiting. Surgery may be needed to correct it.
Other types of obstruction include intussusception (Fig. 12-8), slipping of a part of the intestine into a part below it; volvulus, twisting of the intestine (see Fig. 12-8); and ileus, intestinal obstruction often caused by lack of peristalsis. Hemorrhoids are varicose veins in the rectum associated with pain, bleeding, and, in some cases, prolapse of the rectum.
Diverticula are small pouches in the wall of the intestine, most commonly in the colon. If these pouches are present in large number the condition is termed diverticulosis, which has been attributed to a diet low in fiber. Collection of waste and bacteria in these sacs leads to diverticulitis, which is accompanied by pain and sometimes bleeding. Diverticula can be seen by radiographic studies of the lower GI tract using barium as a contrast medium, a so-called barium enema (Fig. 12-9). Although there is no cure, diverticulitis is treated with diet, stool softeners, and drugs to reduce motility (antispasmodics).
FIGURE 12-8. Intestinal obstruction. (A) Intussusception. (B) Volvulus, showing counterclockwise twist.
FIGURE 12-9. Lower gastrointestinal series (barium enema) showing lesions of enteritis (straight arrows) and thickened mucosa (curvedarrows). (Reprinted with permission from Erkonen WE, Smith WL. Radiology 101: Basics and Fundamentals of Imaging. Philadelphia: Lippincott Williams & Wilkins, 1998.)
Two similar diseases are included under the heading of inflammatory bowel disease (IBD): Crohn disease and ulcerative colitis, both of which occur mainly in adolescents and young adults. Crohn disease is a chronic inflammation of segments of the intestinal wall, usually in the ileum, causing pain, diarrhea, abscess, and often formation of an abnormal passageway, or fistula. Ulcerative colitis involves a continuous inflammation of the lining of the colon and usually the rectum.
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