Overview of Digestive Diseases
What Is a Digestive Disease?
The digestive tract is a series of joined and coiled hollow tubes that stretch from the mouth to the anus. Digestive diseases range from the occasional upset stomach to the more life-threatening colon cancer and encompass disorders of the gastrointestinal tract, the liver, the gallbladder, and the pancreas. A digestive disease may be acute and self-limiting, chronic and debilitating, or sudden and devastating.
What Causes a Digestive Disease?
The cause and natural history of many digestive diseases remain unknown, but a digestive disease may develop congenitally or from multiple factors such as stress, fatigue, diet, or smoking. Abusing alcohol imposes the greatest risk for digestive diseases, particularly increasing the risk of esophageal, colorectal, and liver cancers. Depending on the diagnosis, treatment options include prescription and non-prescription medications, surgery, watchful waiting, dietary changes, exercise, chemotherapy, and home remedies such as castor oil.
Who Develops a Digestive Disease?
Each year 62 million Americans are diagnosed with a digestive disorder. The incidence and prevalence of most digestive diseases increase with age. Notable exceptions are intestinal infections such as gastroenteritis and appendicitis, which peak among infants and children. Other exceptions include hemorrhoids, inflammatory bowel disease, and chronic liver disease, which occur more commonly among young and middle-aged adults.
Women are more likely than men to report a digestive condition, particularly non-ulcer dyspepsia and irritable bowel syndrome (IBS). Whether women truly experience more troubles with their digestive systems than men is difficult to determine, but since women visit doctors more often than men, they have a greater opportunity to alert their doctors to their digestive problems.
How Are Digestive Diseases Diagnosed?
Most digestive diseases are very complex, with subtle symptoms. Because of this, patients may undergo extensive and expensive diagnostic tests. Reaching a diagnosis requires a thorough and accurate medical history and physical examination. Once complete, a doctor may recommend laboratory tests, which may include a blood test, an upper or lower GI series, an ultrasound, and endoscopic examinations of the colon, esophagus, stomach, or small intestine. For more complicated cases, a doctor may order more sophisticated tests such as a CAT (computerized axial tomography) scan or MRI.
Significant Digestive Conditions
Gallstones affect 20 percent of women and 10 percent of men, or approximately 20 million adult Americans. Each year nearly 600,000 patients undergo surgery to have their gallbladders removed, at an estimated cost of over $5 billion dollars. Most gallstones are solid masses, primarily of cholesterol. Gallstones develop in the gallbladder or less often in the bile ducts leading from the liver to the small intestine.
Most patients with gallstones never develop symptoms. However, some patients will develop symptoms of mid- or right-upper abdominal pain that may lead to complications such as acute cholecystitis and pancreatitis. Gallstones are rarely associated with gallbladder cancer.
Once a patient has been diagnosed with symptomatic gallstones, treatment options include surgery by open cholecystectomy or laparoscopic cholecystectomy, watchful waiting, or oral bile acid therapy in patients who cannot tolerate surgery. Laparoscopic cholecystectomy, introduced in the United States in 1988, has fast become the most popular treatment for gallstones.
This procedure uses a miniature video camera and several specialized instruments, which are inserted into the patient's abdomen through tiny incisions. Viewing the gallbladder on an external television monitor, the surgeon uses these instruments to dissect, clamp, and remove the gallbladder without opening the abdomen.
The procedure has several advantages over open surgery: less postoperative pain and disability, a shorter hospital stay, and a quicker recovery period, resulting in less time lost from work.
While most patients with symptomatic gallstones are candidates for laparoscopic cholecystectomy, the surgery is not recommended for patients with abdominal inflammation (peritonitis), acute pancreatitis, end-stage cirrhosis of the liver, or gallbladder cancer. Women in the third trimester of pregnancy should not undergo laparascopic cholecystectomy because of risk of damage to the fetus.
Gastroesophageal Reflux Disease and Related Disorders
Gastroesophageal reflux disease (GERD) is a digestive condition that affects nearly one-third of the American population. GERD is the backward flow of the stomach's contents into the esophagus. The lower esophageal sphincter (LES), the muscle that lies at the base of the esophagus and the stomach and helps keep food in the stomach, is usually weak in a patient with GERD.
Heartburn, which is characterized by burning pain that radiates through the chest, neck, and throat, is the most common symptom of GERD. Heartburn may occur when a person with GERD eats, bends, or lies down. Antacids may provide temporary relief from heartburn.
Doctors also believe that diet and lifestyle habits, hiatal hernia, obesity, and pregnancy contribute to GERD. Certain foods,including chocolate, fried or fatty foods, and alcohol may weaken the LES, permitting reflux and heartburn.
A complete clinical history is the cornerstone of the evaluation of GERD. Depending on the nature and severity of symptoms, patients may undergo an endoscopy or upper GI series. If baseline diagnostic tests prove inconclusive, a patient's doctor may rarely order a 24-hour pH monitoring test to assess the episodes of reflux and type of activity associated with the symptoms.
Lifestyle modifications such as eliminating cigarettes and avoiding high-fat foods may be key to effective antireflux treatment for patients. Patients who do not respond to lifestyle changes alone may find relief if antacid treatment is added. Antacids such as Tums and Gaviscon neutralize stomach acid for relatively short periods of time. Therefore, patients may need to take them frequently, usually 1 to 3 hours after meals and at bedtime, depending on the severity of their symptoms.
Histamine 2 (or H2-blockers), which suppress acid, are also prescribed to relieve symptoms of GERD. The H2-remedies currently available include cimetidine (Tagamet), famotidine (Pepcid), nizatidine (Axid), and ranitidine HCl (Zantac). H2-remedies, are now available to patients without a prescription. They may be taken from one to four times a day.
To treat resistent reflux symptoms, doctors may use higher or more frequent doses of H2-blockers, or switch to a more potent inhibitor of gastric acid secretion such as an acid pump inhibitor, or recommend antireflux surgery. For convenience and effectiveness, doctors are likely to prescribe an acid pump inhibitor to treat severe cases of GERD.
Omeprazole (Prilosec, Losec, or Antra), approved by the Food and Drug Administration (FDA) in 1989, is the first acid pump inhibitor to dramatically inhibit an enzyme, H+(hydrogen), K+(potassium)-ATPase, from producing stomach acid; lansoprazole (Prevacid) has also recently been approved. Recent studies show that omeprazole and lansoprazole provide complete relief of severe GERD symptoms within approximately 1 to 2 weeks.
Some patients with severe GERD or young patients who require continuous medical therapy may be good candidates for surgery. However, all patients should be given a trial of intensive medical therapy first. GERD is a chronic condition, but with diligence and careful medical evaluation and treatment, GERD patients can find relief.
Inflammatory Bowel Disease
Inflammatory bowel disease (IBD) refers to two chronic intestinal disorders: Crohn's disease and ulcerative colitis. IBD affects between 2 to 6 percent of Americans or an estimated 300,000 to 500,000 people. The causes of Crohn's disease and ulcerative colitis are not known, but a leading theory suggests that some agent, perhaps a virus or bacterium, alters the body's immune response, triggering an inflammatory reaction in the intestinal wall. The onset for both diseases peaks during young adulthood. An individual with either disease may suffer persistent abdominal pain, bowel sores, diarrhea, fever, intestinal bleeding, or weight loss.
If your doctor thinks you have either Crohn's disease or ulcerative colitis, a variety of procedures and tests such as endoscopy and barium GI studies are available to confirm disease. Once diagnosed, treatment options may include medications, dietary changes, and sometimes surgery, to remove diseased bowel.
Remission is possible in either condition, but both persist over an individual's lifetime.
Crohn's disease primarily involves the small bowel and the colon. It may cause the intestinal wall to thicken, which may narrow the bowel channel and block the intestinal tract. About 90 percent of patients with Crohn's disease experience frequent and progressive symptoms of abdominal pain, diarrhea, and weight loss. The most commonly used drugs to treat Crohn's are sulfasalazine, prednisolone, mesalamine, metronidazole, and azathioprine.
If a patient does not respond to oral medications, the doctor may recommend surgery. Although surgery relieves chronic symptoms, Crohn's disease often recurs at the location where the healthy parts of the bowel were rejoined. The length of time that a Crohn's patient is in remission is not predictable.
Ulcerative colitis (UC) is an inflammatory disorder affecting the inner lining of the large intestine. The inflammation originates in the lower colon and spreads through the entire colon. Blood in the stool is the most common and distinct symptom of ulcerative colitis. As with Crohn's disease, doctors diagnose ulcerative colitis by conducting a complete physical exam and other procedures such as barium enema and endoscopy.
Patients with mild or severe ulcerative colitis are initially treated with sulfasalazine. Other experimental drugs to treat ulcerative colitis include budesonide, tixocortol pivalate enema, and beclomethasone dipropionate enema. Despite new therapies, an estimated 20 to 25 percent of ulcerative colitis patients will need surgery. Surgery cures ulcerative colitis and most patients can go on to lead normal lives.
Irritable Bowel Syndrome
Irritable bowel syndrome (IBS) is a common functional disorder of the intestines estimated to affect 5 million Americans. The cause of IBS is not yet known. Doctors refer to IBS as a functional disorder because there is no sign of disease when the colon is examined. However, doctors believe that people with IBS experience abnormal patterns of colonic movement. The IBS colon is highly sensitive, overreacting to any stimuli such as gas, stress, or eating high-fat or fiber-rich foods.
Patients with IBS often experience alternating bouts of constipation and diarrhea. Although abdominal pain and cramps are among the most common IBS symptoms, pain or discomfort alone does not suggest IBS. However, when a bowel movement or the passage of gas temporarily relieves pain and cramps, a doctor may suspect IBS.
IBS is frequently diagnosed after doctors exclude more serious intestinal diseases through a detailed medical history and complete physical examination.
There is no standard way of treating IBS. Treatment depends on the severity, nature, and frequency of a patient's symptoms, and may range from lifestyle and dietary changes to antidepressants and psychotherapy.
Peptic Ulcer Disease
Peptic ulcer disease, estimated to affect 4.5 million people in the United States, is a chronic inflammation of the stomach and duodenum. Peptic ulcer disease is responsible for substantial human suffering and a large economic burden. Every year 4 million people report missing approximately 6 days from work because of their ulcers.
Peptic ulcers result from the breakdown of the lining of the stomach and duodenum caused by increased stomach acid and pepsin and Helicobacter pylori (H. pylori). One type of ulcer occurs in the stomach, the other in the duodenum, the first part of the small intestine. Duodenal ulcers are much more common than stomach ulcers, which have a greater risk of malignancy.
There are no specific symptoms of gastric and duodenal ulcers. However, upper abdominal pain and nausea are the most common symptoms of peptic ulcer disease. Ulcer pains usually occur an hour or two after meals, or in the early morning hours and abate after food or antacids have been eaten. Definitive diagnosis of peptic ulcer disease requires endoscopy, which also allows a doctor to obtain biopsy samples, if needed. The FDA's 1996 approval of a safe, effective breath test makes noninvasive diagnosis of ulcers possible.
In the 1950's, doctors thought stress and diet caused peptic ulcer disease. Treatment during those years concentrated on bed rest, bland foods, and in some cases, hospitalization.
But in 1982, Helicobacter pylori was isolated from gastric biopsies of patients with chronic gastritis, and is now believed to be the major cause of peptic ulcer disease. H. pylori is found in almost 100 percent of patients with duodenal ulcers and in 80 percent of patients with gastric ulcers.
Recently, an independent panel of medical experts convened by the NIH confirmed that using a combination of antimicrobial drugs for at least 2 weeks will eradicate H. pylori in a majority of patients, thus reducing the relapse rate of ulcers. A combination of Pepto-Bismol, tetracycline, and metronidazole effectively kills H. pylori in approximately 90 percent of patients. The FDA recently approved a two-drug combination of clarithromycin (Biaxin) and omeprazole (Prilosec) to cure stomach ulcers and prevent them from coming back.
Viral hepatitis consists of at least five different diseases (A, B, C, D, and E) caused by five different viruses. All five viruses can lead to acute hepatitis. Hepatitis B, C, and D may also cause chronic hepatitis.
Hepatitis A (HAV)
Hepatitis A virus (HAV), also known as infectious hepatitis, accounts for 32 percent of reported U.S. cases of hepatitis. HAV is spread by direct contact with an infected individual's feces or indirect fecal contamination of food, water, or food that comes from HAV-infected water sources. Failing to wash one's hands after handling dirty diapers or using the toilet may also spread HAV. Day care centers, restaurants, and crowded, unsanitary housing developments have the highest rates of HAV transmission. Symptoms of HAV may include fever, malaise, dark urine, light stool and jaundice.
An antibody blood test confirms the presence of HAV. Deaths are rare. The elderly and people suffering with immune system problems such as HIV/AIDS are most at risk of dying from HAV. A recently FDA-approved HAV vaccine is available to prevent this disease. Vaccine is recommended for travelers or for persons at high risk of acquiring HAV and for patients with liver disease.
Hepatitis B (HBV)
An estimated 5 percent of the world's population is infected with hepatitis B virus (HBV). In the United States, 300,000 new cases of HBV are reported yearly. Chronic liver disease develops in about 5 to 10 percent of patients with acute HBV infection. HBV may be spread by exposure to infected body fluids, urine, semen, and blood clotting products; from a mother to her infant at birth or soon after; or by unprotected sex with an infected person.
Patients infected with HBV may not experience any symptoms. If symptoms occur, they may include abdominal pain, anorexia, jaundice, malaise, nausea, and vomiting. Fever and joint pain may also develop. A simple and specific blood test for HBV antibodies confirms the presence of the virus.
No cure is available for HBV. Interferon alfa, approved by the FDA to treat adults with chronic hepatitis B, is effective in 40 to 50 percent of patients at most. However, an FDA-approved HBV vaccine protects 90 to 95 percent of healthy persons. The Centers for Disease Control and Prevention (CDC) recommend universal vaccination for all infants and those at risk for infection either because of job or lifestyle habits.
Hepatitis C (HCV)
Infecting about 200,000 Americans each year, HCV (formerly called non-A, non-B hepatitis) is becoming the most commonly diagnosed hepatitis. HCV disproportionately affects African-American and Hispanic males. Recent data from the CDC indicate that HCV is now the second leading cause of death among African-American males aged 18 to 34 living in Harlem.
Approximately 3 million people in the United States are chronically infected with HCV. Hepatitis C is primarily spread by exposure to contaminated blood or needles. While sex with an infected person and mother-to-child transmission have been suspected to spread HCV, the mode of transmission for 43 percent of cases is unknown. HCV-infected patients rarely clear the virus and at least 80 percent of those infected become chronic disease carriers. Symptoms for HCV are similar to other types of hepatitis.
A specific blood test for hepatitis C antibodies identifies persons with HCV. There is no vaccine and no cure for HCV, but 50 percent of patients with acute cases of HCV recover without treatment. Interferon alfa-2b has been approved for treating hepatitis C. Interferon alfa appears to shorten recovery time and reduce the severity of flare-ups. HCV, like hepatitis B, also increases a person's risk of developing liver cancer.
Hepatitis D virus (HDV) was first described in 1977 in patients infected with chronic hepatitis B virus (HBV). When HDV occurs in patients who already have chronic HBV, it is considered a superinfection; when patients develop acute cases of both HBV and HDV at the same time, HDV is considered a co-infection. Persons co-infected with acute HBV-HDV usually go into remission. In contrast, 90 percent of individuals with HDV superinfection develop persistent HDV infection, which eventually leads to chronic liver disease.
HDV may be spread by exposure to contaminated blood products or needles and by unprotected sex with an infected person. There are blood tests available to diagnose HDV, but they are less accurate and sensitive than the tests used to diagnose HAV and HBV. Controlling and preventing HBV would eliminate the spread of HDV.
The transmission of hepatitis E virus (HEV) has not been documented in the United States. This is, however, a common cause of acute hepatitis in underdeveloped areas of the world and travelers to these areas can acquire this form of hepatitis. Hepatitis E causes acute hepatitis that usually resolves itself. Pregnant women are prone to have severe hepatitis from this virus. There are no known means of prevention or cure of hepatitis E other than strict hygienic precautions when visiting areas where hepatitis E is common.
Economic Impact and Scope of Digestive Diseases
Digestive diseases cost nearly $107 billion in direct health care expenditures in 1992. Digestive diseases result in nearly 200 million sick days, 50 million visits to physicians, 16.9 million days lost from school, 10 million hospitalizations, and nearly 200,000 deaths per year. The most costly digestive diseases are gastrointestinal disorders such as diarrheal infections ($4.7 billion); gallbladder disease ($4.5 billion); colorectal cancer ($4.5 billion); liver disease ($3.2 billion); and peptic ulcer disease ($2.5 billion).
Cancers of the digestive tract, which includes the colon, the gallbladder, and the stomach, are responsible for 117,000 deaths yearly. Noncancerous digestive diseases cause 74,000 deaths a year, with 36 percent caused by chronic liver disease and cirrhosis.
Of the 440 million acute noncancerous medical conditions reported in the United States annually, more than 22 million are for acute digestive conditions, with 11 million from gastroenteritis and 6 million from indigestion, nausea, and vomiting.
Digestive diseases have an enormous impact on health and the health-care system in the United States. New technologies and new drugs have revolutionized the understanding and treatment of peptic ulcer disease and GERD. Successful outcomes of future research will hopefully continue to reduce the economic and health care costs related to diagnosing and treating digestive diseases.
Research In Digestive Diseases
The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) was established by Congress in 1950 as one of the Institutes of the National Institutes of Health (NIH). The mission of the NIH is to direct and support biomedical research that will lead to better human health.
The NIDDK conducts and funds a range of research in digestive diseases and nutrition-related diseases, many of them chronic. Much of NIDDK's research in digestive diseases is conducted through the Silvio O. Conte Digestive Disease Centers Program, which began in the mid-1970's with the funding of two centers: the University of California, San Francisco and the Albert Einstein University, New York.
Since then, the program has grown to 12 Digestive Disease Centers conducting basic and clinical research in digestive, hepatic, and pancreatic disorders.
Source: National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health