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Illustration of the anatomy of the digestive system, adult
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What is diarrhea?

Diarrhea is defined either as watery stool, or increased frequency, or both, when compared to a normal amount. It is a common problem that may last a few days and disappear on its own.

Diarrhea may be acute (short-term), which is usually related to bacterial or viral infections, or chronic (long-term), which is usually related to a functional disorder or intestinal disease.

What causes diarrhea?

Diarrhea may be caused by a number of conditions, including the following:

  • A bacterial infection

  • A viral infection

  • Food intolerances or allergies

  • Parasites

  • A reaction to medications

  • An intestinal disease, such as inflammatory bowel disease

  • A functional bowel disorder, such as irritable bowel syndrome

  • A result of surgery on the stomach or gall bladder

Many people suffer "traveler's diarrhea" caused by a bacterial infection or a parasite, or even food poisoning.

Severe diarrhea may indicate a serious disease, and it is important to consult your doctor if the symptoms persist or affect daily activities. Identifying the cause of the problem may be difficult.

What are the symptoms of diarrhea?

The following are the most common symptoms of diarrhea. However, each individual may experience symptoms differently. Symptoms may include:

  • Cramping

  • Abdominal pain

  • Bloating

  • Nausea

  • Urgent need to use the restroom

  • Fever

  • Bloody stools

  • Dehydration

  • Incontinence

Dehydration is one of the more serious side effects of diarrhea. Symptoms of dehydration include:

  • Thirst

  • Less-frequent urination

  • Dry skin and mucous membranes (dry mouth, nostrils)

  • Fatigue

  • Light-headedness, headaches

  • Increased heart rate

  • Depressed fontanelle (soft spot) on infant's head 

The symptoms of diarrhea may resemble other medical conditions or problems. Always consult your doctor for a diagnosis.

How is diarrhea diagnosed?

In addition to a complete physical examination, medical history, and laboratory tests for blood and urine, diagnostic procedures for diarrhea may include the following:

  • Stool culture. This is done to check for the presence of abnormal bacteria in the digestive tract that may cause diarrhea and other problems. A small sample of stool is collected and sent to a laboratory by your doctor's office. In two or three days, the test will show whether abnormal bacteria are present.

  • Sigmoidoscopy. A diagnostic procedure that allows the doctor to examine the inside of a portion of the large intestine, and is helpful in identifying the causes of diarrhea, abdominal pain, constipation, abnormal growths, and bleeding. A short, flexible, lighted tube, called a sigmoidoscope, is inserted into the intestine through the rectum. The scope blows air into the intestine to inflate it and make viewing the inside easier.

  • Colonoscopy. A procedure that allows the doctor to view the entire length of the large intestine, and can often help identify abnormal growths, inflamed tissue, ulcers, and bleeding. It involves inserting a colonoscope, a long, flexible, lighted tube, in through the rectum up into the colon. The colonoscope allows the doctor to see the lining of the colon, remove tissue for further examination, and possibly treat some problems that are discovered.

  • Imaging tests. These tests are done to rule out structural abnormalities.

  • Fasting tests. These tests identify food intolerance or allergies.

Treatment for diarrhea

Specific treatment for diarrhea will be determined by your doctor based on:

  • Your age, overall health, and medical history

  • Extent of the condition

  • Your tolerance for specific medications, procedures, or therapies

  • Expectations for the course of the condition

  • Your opinion or preference

Treatment usually involves replacing lost fluids, and may include antibiotics when bacterial infections are the cause.