causes of acute and chronic diarrhea

Common causes

There are many infectious and non-infectious causes of acute and chronic diarrhea. Viral, bacterial, and parasitic infections are associated with diarrhea that lasts several days to a few weeks, although some cases may linger – causing chronic diarrhea in those with suppressed immune systems (such as those who have HIV/AIDS, cancer, or organ transplants). These sources of diarrhea are infectious, with the virus, bacteria, or parasite shed into the stool and passed from person to person through oral contact with a contaminated surface. Eating food or drinking water that has been contaminated is the most frequent route of infection.

Once a person is infected, they may pass it on to others around them unless careful sanitation practices (especially thorough handwashing) are followed. This is especially a challenge in households with infected infants, in daycare centers, and in nursing homes. Sometimes an outbreak of bacterial or parasitic infection can be traced back to a particular restaurant or a single food item at a picnic. Sometimes it may be due to a contaminated water source.

Those who have traveled outside of the U.S. are often at a greater risk of exposure to viral, bacterial, and parasitic infections, especially when they visit developing nations. Something as simple as contaminated ice cubes, a fresh fruit salad, or food from a vendor’s stall can cause illness.

Common causes of acute diarrhea:

 Parasites: The most common parasites in the United States are Giardia lamblia (giardia), Entamoeba histolytica (E. histolytica), and Cryptosporidium parvum (crypto). These single cell parasites are found in mountain streams and lakes throughout the world and may infect swimming pools, hot tubs, and occasionally community water supplies. Other more worm-like parasites, such as roundworms or tapeworms, may also occasionally cause infections.

In other parts of the world, especially in developing nations and warm climates, pathogenic bacteria and a much wider range of parasites are frequently encountered. These parasites include flat worms, roundworms, hookworms, and flukes. Visitors usually become infected by eating or drinking something that has been contaminated with the parasites’ ova, but some of the parasites can also penetrate the skin.

 Viruses: Rotavirus is the most common cause of severe diarrhea among children. Other viruses include Norwalk, noroviruses (also called Norwalk-like viruses), adenoviruses, calciviruses, cytomegalovirus (CMV), and HIV. The CDC estimates that Norwalk and Norwalk-like viruses cause about 23 million cases of acute gastroenteritis a year in the U.S. - because they are easily transmitted in contaminated drinking wter and on the hands of infected persons. Noroviruses have been mentioned in the news as the cause of outbreaks of gastroenteritis on cruise ships, and they may cause illness in nursing homes, schools, the military, and anywhere that people congregate.

 Bacteria:

• Salmonella, often found in raw eggs, raw poultry and in pet reptiles
• Shigella, from fecally-contaminated food and water
• Campylobacter, from raw or undercooked poultry
• Escherichia coli 0157:H7 (E. coli), associated with raw or undercooked hamburger/beef, unpasteurized apple cider, and spinach. It causes bloody diarrhea and may lead to hemolytic uremic syndrome, a condition associated with red blood cell destruction and kidney failure.
• Others: Staphylococcus aureus and species of Yersinia and Vibrio

Acute diarrhea may also be due to Treatment with broad-spectrum antibiotics or to other medications that cause diarrhea as a side effect. Antibiotic treatment can decrease the normal flora – the “good” bacteria that inhabit the gastrointestinal tract, help digest our food, and provide a protective barrier against the “bad” bacteria. When the growth of the normal flora is inhibited, it allows easier access for a pathogen to grow and multiply. Toxins produced by the bacterium Clostridium difficile are often the culprit in antibiotic-related diarrhea.

Common causes of chronic diarrhea:

Chronic diarrhea, diarrhea that lasts for more than a few weeks, sporadic diarrhea, and diarrhea that alternates with constipation are most frequently associated with non-infectious causes of diarrhea. These may include diarrhea due to:

• Inflammatory bowel conditions, such as Crohn’s disease
• Bowel dysfunction – such as may be seen in irritable bowel syndrome
• Malabsorption disorders – such as cystic fibrosis
• Stomach or gallbladder surgery (the rate at which the food travels through the digestive tract may change)
• Food intolerance, such as lactose intolerance or celiac disease
• Chemotherapy or abdominal or gastrointestinal radiation
• Endocrine diseases, such as diabetes and thyroid disease
• Self-induced with laxatives
• Psychogenic causes such as stress

Chronic diarrhea in adults

A wide range of problems can cause chronic diarrhea; some of the most common causes include irritable bowel syndrome, inflammatory bowel disease (Crohn's disease and ulcerative colitis), malabsorption syndromes, and chronic infections. There are also many other less common causes of chronic diarrhea.

Irritable bowel syndrome — Irritable bowel syndrome (IBS) is one of the most common causes of chronic diarrhea. IBS can cause crampy abdominal pain and changes in bowel habits (diarrhea, constipation, or both). IBS can develop after having an infection. (See "Patient information: Irritable bowel syndrome".)

Inflammatory bowel disease — There are several types of inflammatory bowel disease, two of the most common of which are Crohn's disease and ulcerative colitis. These conditions may develop when the body's immune system attacks parts of the digestive tract. (See "Patient information: Crohn's disease" and "Patient information: Ulcerative colitis".)

Infections — Intestinal infections are a cause of chronic diarrhea. Infections that cause chronic diarrhea can be seen in people who travel or live in tropical or developing countries. Intestinal infections can also develop after eating contaminated food or drinking contaminated water or unpasteurized ("raw") milk. (See "Patient information: Food poisoning (food-borne illness)".)

Endocrine disorders — An overactive thyroid (hyperthyroidism) can cause chronic diarrhea and weight loss. Diabetes can cause chronic diarrhea if the nerves that supply the digestive tract are injured.

Food allergy or sensitivity — Food allergies and hypersensitivity can cause chronic diarrhea. People with celiac disease often have diarrhea and weight loss. (See "Patient information: Celiac disease in adults".)

Medicines — Medicines (prescription and nonprescription), herbs, and dietary supplements can cause diarrhea as a side effect. To determine if a medicine could be the cause of your diarrhea, review your list of medicines with your doctor, nurse, or pharmacist. This information may also be available on the medicine bottle or paperwork that comes with most prescriptions.

CHRONIC DIARRHEA EVALUATION

You should seek medical attention if you have loose or watery stools that last more than three weeks. You may need to be seen sooner than this if you have complications of diarrhea (eg, bloody diarrhea, fever, dehydration, or weight loss).

During your visit, it is important to mention when your diarrhea began, any recent changes in medicines or medical problems, and if you have had accidents (leaking or smearing of stool in the underwear).

Tests — Blood, stool, and urine tests can help to find the underlying cause of diarrhea. If these tests do not find the cause, other approaches may be needed, including X-rays or procedures, such as colonoscopy or sigmoidoscopy. Your primary care provider can order these tests or refer you to a specialist (a gastroenterologist). (See"Patient information: Colonoscopy" and "Patient information: Flexible sigmoidoscopy".)

In some cases, your doctor or nurse will recommend a trial of treatment before more invasive tests (see 'Treatment trial' below).

CHRONIC DIARRHEA TREATMENT

Treatment of chronic diarrhea aims to eliminate the underlying cause (if the cause is known), firm up the bowel movements, and treat any diarrhea-related complications.

Treating the cause — The underlying cause of chronic diarrhea should be found and treated whenever possible. For example, infections may be treated with antibiotics. In people with Crohn's disease or ulcerative colitis, long-term treatment and follow-up is needed.

In some cases, treatment may be as simple as eliminating a food or medicine.

• For people with lactose intolerance, this may include foods or drinks that contain lactose (table 1).
• Other ingredients that are known to cause diarrhea include sugar-free products made with sorbitol and foods made with fat replacements (eg, Olestra®).
• Certain medicines can also cause diarrhea (such as laxatives and antacids).

Treating diarrhea — In some people, the goal is simply to have less diarrhea. This approach is often used before testing, when the results of tests are normal or not helpful, or if diarrhea is caused by a chronic medical problem.

Diarrhea treatments include:

• Bismuth (sold as Kaopectate®, Pepto-Bismol®)
• Treatments that bulk the stools, such as a high-fiber diet or fiber supplement (see "Patient information: High fiber diet")
• Antidiarrhea medicines, such as loperamide (sold as Imodium®, available without a prescription) or prescription medicines, such as diphenoxylate (Lomotil®)
• Octreotide, a prescription medicine that might be given to people with severe diarrhea

Treatment trial — Your doctor or nurse might recommend trying a treatment before further testing. This approach can help to narrow down the list of possible causes of your diarrhea.

Treatments that might be offered include:

• A trial of antibiotics, for an infection
• Stopping a medicine
• Changing your diet, for a possible food allergy or problem absorbing nutrients (such as lactose intolerance)

Treating complications — Chronic or severe diarrhea can lead to potentially serious complications, including dehydration and malnutrition. While you are being evaluated, you should be sure to drink plenty of fluids. You are drinking enough fluids if your urine is a light yellow color.

If you are not able to drink enough fluids and you become dehydrated, you may be given fluids into a vein (IV) to replace the fluids and electrolytes (salts) lost in diarrhea. This will not cure your diarrhea, but it can prevent more serious complications.

WHERE TO GET MORE INFORMATION

Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed every four months on our Web site (www.uptodate.com/patients).

Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.