Causes and Symptoms
What and how people eat, their digestion, and their toilet habits affect their health more than any other voluntary daily activity. Breathing, circulation, and the brain’s control of most bodily functions normally take place without conscious thought. The intake of nourishment, by contrast, affords a great variety of choices. Accordingly, poor or self-destructive eating and toilet habits lie behind many gastrointestinal (GI) disorders. Yet not all disorders result from an individual’s habits. Many arise because of a person’s cultural or physical environment, some are hereditary or congenital, and a fair amount have no known cause. All told, more than one hundred disorders may originate in the GI tract and related organs, including infections, cancer, dysfunctions, obstructions, autoimmune diseases, malabsorption of nutrients, and reactions to toxins taken in during eating, drinking, or breathing. Furthermore, diseases in other organs, systemic infections such as lupus, immune suppression such as that caused by Acquired immunodeficiency syndrome (AIDS), reactions to altered body conditions as during pregnancy, and psychiatric problems can all affect the gut.
The symptoms of GI disorders range from mildly uncomfortable to life-threatening, although seldom does any single symptom except massive bleeding lead quickly to death. Indigestion, bloating, and gas send more people to gastroenterologists than any other set of symptoms, and they often reflect nothing more than overeating. Pain anywhere along the gut, aversion to food (anorexia), and
nausea are general symptoms common to many disorders, although noncardiac chest pain is likely to come from the esophagus while pain in the abdomen points to a stomach or intestinal problem. Red blood in the stool indicates bleeding in the intestines, black (digested) blood suggests bleeding in the upper small bowel or stomach, and vomited blood indicates injury to the stomach or esophagus—all dangerous signs that require prompt medical attention. Chronic diarrhea, fatty stool, constipation, difficulty in swallowing, hiccuping, vomiting, and cramps point to disturbances in the GI tract’s orderly, wavelike contractions or absorption of nutrients and fluid. Dysentery (bloody diarrhea) usually comes from severe inflammation or lesions caused by viruses, bacteria, or other parasites. Malnourishment is a sign of badly disordered digestion, and ascites (fluid accumulation in body cavities) can result from serious disease in the liver or pancreas. Likewise, jaundice, the yellowing of the skin or eyes because of high bilirubin levels, signals problems in the liver, pancreas, or their ducts.
The large number and complexity of GI disorders do not allow a quick, comprehensive summary. Fortunately, many are uncommon, and the most frequent problems can be described through a tour of the GI tract. The GI tract is basically a tube that moves food from the mouth to the anus, extracting energy and biochemical building blocks for the body along the way. Thus, a disorder that interrupts the flow in one section of the intestines can have secondary effects on other parts of the gut. Disorders seldom affect one area alone.
The esophagus. The GI tract’s first section, the esophagus, is simply a passageway from the mouth to the stomach. Although it rarely gets infected, the esophagus is the site of several common problems, usually relatively minor, if painful. Muscle dysfunctions, including slow, weak, or spasmodic muscular movement, can impair motility and make swallowing difficult, as can strictures, which usually occur at the sphincter to the stomach. The mucosal lining of the esophagus is not as hardy as in other parts of the gut. When acid backflushes from the stomach into the esophagus, it inflames tissue there and can cause burning and even bleeding, a condition popularly known as
heartburn and technically called gastroesophageal reflux disease (GERD). Retching and vomiting, usually resulting from alcohol abuse or associated with a hiatal hernia, can tear the mucosa. Smokers and drinkers run the risk of esophageal cancer, which can spread down into the gut early in its development and can be deadly; however, it accounts for only about 1 percent of cancers. Most esophageal conditions can be cured or controlled if diagnosed early enough.
The stomach. To store food and prepare it for digestion lower in the gut, the stomach churns its contents into a homogenous mass and releases it in small portions into the small bowel; meanwhile, the stomach also secretes acid to kill bacteria. Bacteria that are acid-resistant, however, can multiply there. One type, Helicobacter pylori, is thought to be involved in the development of
ulcers and perhaps cancer. Overuse of aspirins and other nonsteroidal anti-inflammatory drugs (NSAIDs) can also cause stomach ulcers. A variety of substances, including alcohol, can prompt inflammation and even hemorrhaging. Stomach cancer
has been shown to strike those who have a diet high in salted, smoked, or pickled foods; the most common cancer in the world, although not in the United States, it has a low survival rate. When stomach muscle function fails, food accumulates until the stomach overstretches and rebounds, causing vomiting. Some foods can coalesce into an indigestible lump, and hair and food fibers can roll into a ball, called a bezoar; such masses can interfere with digestion.
The small intestine
. The five to six meters of looped gut between the stomach and colon is called the small intestine. It secretes fluids, hormones, and enzymes into food passing through, breaking it down chemically and absorbing nutrients. Although cancers seldom develop in the small intestine itself, they frequently do so in the organs connected to it, the liver and pancreas. The major problem in the small bowel is the multitude of diseases causing diarrhea, dysentery, or ulceration: They include bacterial, viral, and parasitic disease; motility disorders; and the chronic, progressive inflammatory illness called Crohn’s disease, which also ulcerates the bowel wall. Although most diarrhea is temporary, if it persists diarrhea severely weakens patients through dehydration and malnourishment. For this reason, diarrheal diseases caused by toxins in water or food are the leading cause of childhood death worldwide. An increasingly common disorder of the small bowel is celiac disease, or gluten enteropathy, an autoimmune disease that results in malabsorption. Furthermore, the small bowel can become paralyzed, twisted, or kinked, thereby obstructing the passage of food. Sometimes its contents rush through too fast, a condition called dumping syndrome. All these disorders reduce digestion, and if they are chronic, then malnutrition, vitamin deficiency, and weight loss ensue.
The large intestine. The small intestine empties into the large intestine, or colon, the last meter of the GI tract; here the water content of digestive waste matter (about a liter a day) is reabsorbed, and the waste becomes increasingly solid along the way to the rectum, forming feces. Unlike the small bowel, which is nearly sterile under normal conditions, the colon hosts a large population of bacteria that ferments the indigestible fiber in waste matter, and some of the by-products are absorbed through the colon’s mucosa. Bacteria or parasites gaining access from the outside world can cause diarrhea by interfering with this absorption (a condition called malabsorption) or by irritating the mucosa and speeding up muscle action. For unknown reasons, the colon can also become chronically inflamed, resulting in cramps and bloody diarrhea, an illness known as ulcerative
colitis;
Crohn’s disease also can affect the colon. Probably because it is so often exposed to a variety of toxins, the colon is particularly susceptible to cancer in people over fifty years old: Colorectal cancer accounts for the fourth highest number of cancer deaths worldwide, in an equal proportion of men and women. As people age, the muscles controlling the colon deteriorate, sometimes forming small pouches in the bowel wall, called diverticula, that can become infected (diverticulitis). In addition, small knobs called polyps can grow, and they may become cancerous. One of the most common lower GI disorders is constipation, which may derive from a poor diet, motility malfunction, or both.
The rectum. The last segment of the colon, the
rectum collects and holds feces for defecation through the anus. The rectum is susceptible to many of the diseases affecting the colon, including cancer and chronic inflammation. The powerful anal sphincter muscle, which controls defecation, can be the site of brief but intensely painful spasms called proctalgia fugax, which strikes for unknown reasons. The tissue lining the anal
canal contains a dense network of blood vessels; straining to eliminate stool because of constipation or diarrhea or simply sitting too long on a toilet can distend these blood vessels, creating hemorrhoids, which may burn, itch, bleed, and become remarkably uncomfortable. If infected, hemorrhoids or anal fissures may develop painful abscesses (sacs of pus). Extreme straining can cause the rectum to turn inside out through the anus, or prolapse.
The liver. The GI tract’s organs figure prominently in many disorders. The liver is a large spongy organ that filters the blood, removing toxins and dumping them with bile into the duodenum. A number of viruses can invade the liver and inflame it, a malady called
hepatitis. Acute forms of the disease have flulike symptoms and are self-limited. Some viruses, however, as well as alcohol or drug abuse and worms, cause extensive cirrhosis (the formation of abnormal, scarlike tissue) and chronic hepatitis. Although only recently common in the United States, viral hepatitis has long affected a large number of people in Southeast Asia; because hepatitis can trigger the mutation of normal cells,
liver cancer is among the most common cancers worldwide. Hepatitis patients often have jaundice, as do those who, as a result of drug reactions, cancer, or stones, have blocked bile flow. Because of congenital or inherited errors of metabolism, excess fat, iron, and copper can build up in the liver, causing upper abdominal pain, skin discolorations, weakness, and behavioral changes; complications can include cirrhosis, diabetes mellitus, and heart disease.
The gallbladder
. A small sac that concentrates and stores bile from the liver, the gallbladder is connected to the liver and duodenum by ducts. The concentrate often coalesces into stones, which seldom cause problems if they stay in one place. If they block the opening to the gallbladder or lodge in a duct, however, they can cause pain, fever, and jaundice. Although rare, tumors may also grow in the gallbladder or ducts, perhaps as a result of gallstone obstruction.
The pancreas. Lying just behind the stomach, the pancreas produces enzymes to break down fats and proteins for absorption and insulin to metabolize sugar; a duct joins it to the duodenum. The pancreas can become inflamed, either because of toxins (largely alcohol) or blockage of its duct, usually by gallstones. Either cause precipitates a painful condition,
pancreatitis, that may last a few days, with full recovery, or turn into a life-threatening disease. If the source of inflammation is not eliminated, then chronic pancreatitis may develop and with it the gradual loss of the pancreas’ ability to make enzymes and insulin. Severe abdominal pain, malnutrition, diarrhea, and diabetes may develop. Pancreatic cancer has a very poor prognosis, with five-year survival less than 5 percent in most cases. Scientists are unsure of the causes; pancreatitis, gallstones, diabetes, and alcohol have been implicated, but only smoking is well attested to increase the risk of contracting pancreatic cancer, which is
very lethal and difficult to treat. It is estimated that cigarette smoking is responsible for 30 percent of pancreatic cancer cases.
Functional diseases. Finally, some disorders appear to affect several parts of the GI tract at the same time, often with no identifiable cause but with chronic or recurrent symptoms. Gastroenterologists call them functional diseases, and they afflict as much as 30 percent of the population in Western countries. People with
Irritable bowel syndrome (IBS) complain of abdominal pain, urgency in defecation, and bloating from intestinal gas; they often feel that they cannot empty their rectums completely, even after straining. Functional dyspepsia manifests itself as upper abdominal pain, bloating, early feelings of fullness during a meal, and nausea. Also included in this group are various motility disorders in the esophagus and stomach, whose typical symptom is vomiting, and pseudo-obstruction, a condition in which the small bowel acts as if it is blocked but no lesion can be found. Many gastroenterologists believe that emotional disturbance plays a part in some of these diseases.
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