Sudden Onset of Diarrhea

Acute diarrhea is characterized by the sudden increase in the frequency of bowel movements and the passage of loose, watery, unformed stool. It is a common symptom of many gastrointestinal (GI) disorders.

In more than 90% of cases, acute diarrhea is caused by infectious agents (e.g., virus, bacteria, parasite), which often are ingested in food and water. Infectious diarrhea also may be accompanied by abdominal pain, vomiting, and fever.

Acute diarrhea usually is mild and resolves on its own (i.e., is self-limiting) in one or two days. However, the condition can be serious, especially in infants and young children, the elderly, and patients with a compromised immune system (e.g., patients who have HIV/AIDS).

In addition to infectious agents, other causes for acute diarrhea include the following:

  • Certain medications (e.g., antibiotics, nonsteroidal anti-inflammatory drugs [NSAIDs], chemotherapy drugs)
  • Intolerance to foods (e.g., lactose [sugar present in milk], gluten [protein in wheat])
  • Medical conditions (e.g., diverticulitis, ischemia [reduced blood flow in the intestines], intestinal obstruction)
  • Toxic substances (e.g., poisons, insecticides)

Other symptoms that may indicate a medical emergency in patients who have acute diarrhea include gross (visible) blood in the stool, fever above 101.3°F, and severe abdominal pain.

If an infectious cause (e.g., virus, bacteria, parasite) for acute diarrhea is suspected, stool cultures usually are performed. When these tests are inconclusive, or if a noninfectious cause (e.g., diverticulitis, intestinal obstruction) is suspected, other diagnostic tests (e.g., imaging tests, biopsy) may be performed.

Imaging tests include computed tomography (CT scan) and endoscopic procedures. In CT scan, x-rays are taken from many different angles to produce detailed images of the digestive tract. Endoscopic procedures (e.g., flexible sigmoidoscopy, colonoscopy) allow the physician to examine the gastrointestinal tract using a thin, flexible tube that contains a tiny light and camera (called an endoscope). If an abnormal area of tissue is detected, a small sample can be removed surgically using instruments that are passed through the endoscope and examined under a microscope (called biopsy).

In most cases, initial treatment for acute diarrhea involves fluid and electrolyte replacement. Electrolytes are substances (e.g., salts, minerals) in the body's tissues that are necessary for cell function. Physicians often recommend oral sugar-electrolyte preparations (e.g., sports drinks, Pedialyte) to help prevent dehydration. In severe cases, fluids may be administered intravenously (i.e., through a vein; IV).

Clear liquids (e.g., soup, broth, tea) and bland foods (e.g., rice, crackers, dry toast, bananas) may be helpful until the symptoms improve. Foods that aggravate diarrhea, such as dairy products and foods that are high in fat, sugar, or fiber should be avoided.

Medications (e.g., loperamide [Imodium], bismuth [Pepto-Bismol]) may be used to treat some types of acute diarrhea; however, these drugs should not be used to treat diarrhea caused by a bacterial or parasitic infection or certain medical conditions (e.g., diverticulitis, intestinal obstruction). Antibiotics may be prescribed to treat these infections. Certain medical conditions (e.g., diverticulitis, intestinal obstruction) may require surgery.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 28 Feb 2008

Last Modified: 11 Sep 2015