What are diarrhea and dysentery?

Causes and Symptoms

A symptom of various diseases rather than a disease in itself, diarrhea is so difficult to define and can result from so many disparate causes that it is sometimes called the gastroenterologist’s nightmare. Dysentery (bloody diarrhea), a more threatening symptom, presents even further complexity.

Uncontrolled, some forms of diarrhea result in dehydration, weakness, and
malnutrition and quickly turn deadly. Diarrhea is implicated in more infant deaths worldwide than any other affliction. Even in mild forms, it produces so much distress in victims and has inspired so many remedies that its psychological and economic toll is monumental.

Common medical definitions of diarrhea seek to bring diagnostic precision to a nebulous complaint and to distinguish between acute and chronic forms and between organic and functional causes. Diarrhea is typically associated with increased amount and fluidity of fecal matter and frequent defecation relative to a person’s usual pattern. Acute diarrhea seldom lasts more than five days, although acute dysentery may continue up to ten days; most causes are infections, that is, resulting from the presence of microorganisms (viruses, bacteria, or parasites). Physicians differ over how long the symptoms must persist before a condition is identified as chronic diarrhea, proposing from two weeks to three months. Impaired functioning of the intestinal tract (functional diarrhea) is usually responsible for such chronic cases, although persistent malfunctions may originate from pathogens that in most cases provoke only acute diarrhea.

In a single day, water intake, saliva, gastric juice, bile, pancreatic juices, and electrolyte secretions in the upper small intestine produce about 9 to 10 liters of fluid in the average person. About 1 to 2 liters of this amount empty into the colon, and 100 to 150 milligrams are excreted in the stool; the rest is absorbed through the intestinal mucosa. If for any reason more fluid enters the colon than it can absorb, diarrhea results. Schemes classifying diarrhea according to the biochemical mechanisms causing it vary considerably, although authorities generally agree on three broad types of malfunction.

The first is secretory diarrhea. The intestines, especially the
small intestine, normally add water and electrolytes—principally sodium, potassium, chloride, and bicarbonate—into the nutrient load during the biochemical reactions of digestion. In a healthy person, more fluid is absorbed than is secreted. Many agents and conditions can reverse this ratio and stimulate the mucosa to exude more water than can be absorbed: toxin-producing bacteria; various organic chemicals, including caffeine and some laxatives; acids; hormones; some cancers; and inflammatory diseases of the bowel. Large stool volume (more than 1 liter a day), with little or no decrease during fasting and with normal sodium and potassium content in the body fluid, characterizes secretory diarrhea.

Second, the nutrient load in the gut may include substances that exert osmotic force but cannot be absorbed, causing osmotic diarrhea. Some laxatives (especially those containing magnesium), an inability to absorb the lactose in dairy products or the artificial fats and sweeteners in diet foods, and enzyme deficiencies are the principal causes. Stool volume tends to be less than 1 liter a day and decreases during fasting, and the sodium and potassium content of stool water is low.

Third, motility disorders occur when peristalsis, the natural wavelike contractions of the bowel wall that move waste matter toward the rectum for defecation, becomes deranged. Some drugs,
Irritable bowel syndrome (IBS), hyperthyroidism, and gut nerve damage (as from diabetes mellitus) may have this effect. Fluid passes through the intestines too quickly or in an uncoordinated fashion, and too little is removed from the waste matter.

These mechanisms do not conform exactly with popular names for diarrhea. For example, travelers’ diarrhea, the most infamous, comprises a diverse group of microorganism infections that come from drinking polluted water or eating tainted foods. When a person is not a native to an area, and so has little or no resistance to locally abundant pathogens, these pathogens can radically alter the balance of intestinal flora or attack the mucosa, increasing secretion and disrupting absorption and motility. Similarly, terms such as “Montezuma’s revenge,” “the backdoor trots,” and “beaver fever” can refer to a variety of organic diseases, although the last commonly refers to Giardia lamblia
infection.

Dysentery may occur with infectious diarrhea due to certain organisms, most commonly amoebas and other unicellular or multicellular parasites, or to bacterial organisms such as Shigella, Campylobacter, and some strains of Escherichia coli, or E. coli. Any pathogen or process that injures and inflames the bowel wall—ulcerating the mucosa—may cause blood and pus to ooze into the feces. Dysentery is also seen in inflammatory diseases of the bowel, such as ulcerative colitis
and Crohn’s disease. Severe diarrhea, with or without dysentery, may be associated with fever, chills, nausea, and in extreme cases, delirium, convulsions, coma, and death. Dehydration is the most common complication, but systemic infection may occur. Dysentery also may be associated with significant blood loss.

Although most diarrheas result from physiological mechanisms, one relatively rare form of chronic diarrhea ultimately has a psychological origin: laxative abuse. Physicians consider this curious phenomenon a specialized manifestation of Münchausen syndrome, named after the German soldier Baron Münchausen (1720–97), who was famous for his wild tales of military exploits and injuries in battles. To be admitted to hospitals, patients mutilate themselves in such a way that the injuries mimic acute, dramatic, and convincing symptoms of serious physiological diseases. Laxative abusers secretly dose themselves with nonprescription laxatives and suffer continual diarrhea, weight loss, and weakness. When they present themselves to physicians, they lie about taking laxatives, which makes a correct diagnosis extremely difficult. Even when confronted with irrefutable evidence of the abuse, they deny it and persist in taking the laxatives.

Treatment and Therapy

Almost everyone, at one time or another, produces stools that seem somehow unusual. If the bowel movement comes swiftly and is preceded by intestinal cramps and if the stool has anything from a watery to an oatmeal-like consistency, victims are likely to believe that they have diarrhea. Such episodes seldom indicate anything except perhaps a dietary excess or a temporary motility disturbance. Normal bowel movement returns on its own, and no medical treatment is called for. When loose feces are uncontrollable, even explosive, however, and other symptoms coexist, such as nausea, bleeding, fever, bloating, and persistent intestinal pain, the distress may indicate serious illness.

Because so many organic and functional diseases can lead to diarrhea, physicians follow carefully designed algorithms when treating patients. Essentially, such an algorithm seeks to eliminate possibilities systematically. Step by step, physicians interview patients, conduct physical examinations, and, when called for, perform tests that gradually narrow the range of possible causes until one seems most likely. Only then can the physician decide upon an effective therapy. This painstaking approach is necessary because treatments for some mechanisms of diarrhea prove useless against or worsen other mechanisms. If the underlying disease is complex or uncommon, the process can be long and frustrating.

One treatment, however, always precedes a complete investigation. Because dehydration is the most immediately serious effect of diarrhea, the physician first tries to prevent or reduce dehydration in a patient through oral rehydration; that is, the patient is given fluids with electrolytes to drink. Often, mineral water or clear fruit juice with soda crackers is sufficient to restore fluid balance.

If the diarrhea lasts fewer than three days and no other serious symptoms accompany it, the physician is unlikely to recommend treatment other than oral rehydration because whatever caused the upset is already resolving itself. If the diarrhea is persistent, however, the physician queries the patient about his or her recent experience. Fever, tenesmus (the urgent need to defecate without the ability to do so satisfactorily), blood in the stool, and abdominal pain will suggest that a pathogen has infected the patient. If the patient has recently eaten seafood, traveled abroad, suffered an immune system disorder, or engaged in sexual activity without the protection of condoms, the physician has reason to suspect that viruses, bacteria, or parasites are responsible.

At that point, a stool sample is taken. If few or no white cells turn up in the stool, then the diarrhea has not caused inflammation. Several common bacteria and parasites, usually contracted during travel, induce diarrhea without inflammation, most notably some types of E. coli, cryptosporidium, rotavirus, Norwalk virus, and Giardia lamblia. Further tests, such as the culturing and staining of stool samples and electron microscopy of stool or bowel wall tissue, will distinguish between bacterial and parasite infection. Most noninflammatory bacterial diarrheas are allowed to run their course without drug therapy; only the effects of the diarrhea (especially dehydration) are treated. If the agent responsible is a parasite, the patient is given specific antiparasite medications.

The presence of white cells in the stool is evidence of inflammatory diarrhea, and the physician considers a completely separate group of microorganisms, especially Shigella, Salmonella, amoebas, and various forms of E. coli. Because the inflammation may cause bleeding and pockets of pus, which in turn can lead to anemia and fever, inflammatory diarrhea often requires aggressive treatment. Cultures help identify the specific microorganism involved, and that identification enables the physician to select the proper antibiotic to kill the infecting agents.

If cultures, microscopic examination of stool samples, biopsies, or staining fails to identify a microorganism (and some, such as the parasite Giardia lamblia, are difficult to spot), the physician suspects that the diarrhea derives from a source other than an infectious agent. IBS, a chronic and relapsing disorder, may be making its first appearance. Overuse of antibiotics, antacids, or laxatives is frequently the cause, in which case the cure is simple; elimination of the drugs clears up the symptom.

When neither drugs nor IBS is responsible, the physician looks for other diseases, organic or functional; these can range from the readily identifiable to the obscure, and they are often chronic. Chemical tests, for example, can show that a patient has enzyme deficiencies that produce intolerance to types of food, such as dairy products, or conditions resulting from malfunctioning organs, such as hyperthyroidism and pancreatic insufficiency. Looking through an endoscope, a long, flexible fiber-optic tube, the physician can locate diarrhea-causing tumors or the abrasions and inflammation typical of colitis and Crohn’s disease. Yet neither tests nor direct examination may pin down the dysfunction. For example, diarrhea figures prominently among a group of symptoms, probably derived from assorted dysfunctions, that characterize IBS.

Cancers, Crohn’s disease, and some forms of colitis can be alleviated with surgery, although in the case of
Crohn’s disease the relief from diarrhea may be only temporary. The surgery itself, however, may impair bowel function, worsening diarrhea rather than stopping it. Food intolerances are managed by removing the offending food from the patient’s diet; similarly, some types of colitis and IBS sometimes improve after the physician and patient experiment with altering the patient’s diet. Medications are available that supplement or counteract the biochemical imbalances created by malfunctioning organs, such as treatment for hyperthyroidism. Yet, in many cases, the disease must simply be endured and the diarrhea can only be palliated with bulking agents, which often contain aluminum and bismuth, or opiates, such as morphine and codeine, which slow peristalsis.

The surest protection from diarrhea of all types is a balanced, moderate, pathogen-free diet, although diet alone seldom prevents organic diseases. When dietary control is difficult, such as when a person travels, other measures may help. Bacterial infection accounts for 80 percent of cases of travelers’ diarrhea, so some physicians recommend regular doses of antibiotics or a bismuth subsalicylate preparation to kill off the pathogens before they can cause trouble. Such prophylactic treatment is controversial because the drugs, taken over long periods, can have serious side effects, including rashes, tinnitus (ringing in the ear), sensitivity to sunlight, and shock. Also, preventive doses of drugs may give travelers a false sense of security so that they fail to exercise caution in eating foreign foods. Widespread use of antibiotics for this purpose fosters the emergence of bacteria that are resistant to them, ultimately making the treatment of disease more difficult.

Perspective and Prospects

In effect, diarrhea is an urgent message from the body that something is wrong. Although it is often difficult for a physician to interpret, persistent diarrhea sends a signal that cannot be ignored without endangering the patient. Similarly, when significant numbers of people in an area suffer diarrhea, the disease is an urgent social and political message to local governments: public health is endangered, and steps must be taken to improve living conditions.

Although some endemic diarrheal diseases do exist in wealthy industrialized countries such as the United States, most severe, long-lasting plagues of diarrhea occur in impoverished nations that have inadequate sanitation systems and poor standards for food handling. Most viral, bacterial, and parasitic diarrheas are transmitted by food and water. Any food can harbor bacteria after being grown in or washed with infected water. Meat is especially vulnerable during slaughtering, but refrigerating, drying, salting, fermenting, freezing, or irradiating it prevents the bacteria from proliferating to numbers that cause illness. If the food is stored in a warm place, as is often the case in countries lacking the resources for refrigeration or other safe storage techniques, the diarrhea-causing organisms can spoil the food in hours. Spoiled food becomes a particular nuisance when served at restaurants or by street vendors, because great numbers and varieties of people are infected.

Organisms that cause many forms of diarrhea travel in human excrement. When an infected person defecates, the organism-rich stool enters the sewer system, and if that system is not well designed, the infected excrement may leak into the local water supply, spreading the infection when the water is consumed or used to wash food. Furthermore, infected persons, if they fail to wash themselves well, may have traces of excrement on their hands, and when they touch food during its preparation or touch other people directly, the organism can find a new host.

In 1989, the
World Health Organization (WHO) issued ten rules for safe food preparation in an attempt to improve food-handling practices worldwide and combat diarrheal diseases. The effort, it was hoped, would reduce infant mortality in developing countries, since diarrheal dehydration kills children younger than two years of age at rates disproportionate to other age groups. The WHO advises food handlers to choose foods that are already processed, to cook foods thoroughly, to serve cooked foods immediately, to store foods carefully, to reheat foods thoroughly, to prevent raw and cooked foods from touching, to wash their hands repeatedly, to clean all kitchen surfaces meticulously, to protect foods from insects and rodents, and to use pure water.

Eliminating endemic infectious diarrheal diseases would improve general health significantly throughout the world, since diarrhea is one of the most incapacitating of afflictions even in its mild forms. International travel would also become safer. Noninfectious diarrhea from chronic functional diseases will remain a knotty problem, but it is rare in comparison to acute infectious diarrhea and cannot be transmitted, so has little or no effect on public health.

Bibliography

A.D.A.M. Medical Encyclopedia. "Diarrhea." MedlinePlus, January 27, 2012.

Biddle, Wayne. A Field Guide to Germs. 2d ed. New York: Anchor Books, 2002.

Carson-DeWitt, Rosalyn. "Diarrhea." HealthLibrary, March 4, 2013.

DuPont, Herbert L., and Charles D. Ericsson. “Drug Therapy: Prevention and Treatment of Traveler’s Diarrhea.” New England Journal of Medicine 328 (June 24, 1993): 1821–26.

Gracey, Michael, ed. Diarrhea. Boca Raton, Fla.: CRC Press, 1991.

Janowitz, Henry D. Your Gut Feelings: A Complete Guide to Living Better with Intestinal Problems. Rev. ed. New York: Oxford University Press, 1995.

McCoy, Krisha. "Amoebic Dysentery." HealthLibrary, November 26, 2012.

Parker, James N., and Philip M. Parker, eds. The Official Patient’s Sourcebook on Diarrhea. San Diego, Calif.: Icon Health, 2002.

Peikin, Steven R. Gastrointestinal Health. Rev. ed. New York: Quill, 2001.

Saibil, Fred. Crohn’s Disease and Ulcerative Colitis: Everything You Need to Know. Rev. ed. Toronto, Ont.: Firefly Books, 2009.

Scarpignato, Carmelo, and P. Rampal, eds. Traveler’s Diarrhea: Recent Advances. New York: S. Karger, 1995.

Thompson, W. Grant. Gut Reactions: Understanding Symptoms of the Digestive Tract. New York: Plenum Press, 1989.