Causes of Sudden (Acute) Diarrhea

Most cases of diarrhea are acute. This means it arises suddenly, is intense and lasts for only a short period of time. Typically with diarrhea this is just a few days and in many instances the diarrhea resolves on its own without any medical treatment. Sometimes it may persist for weeks and still be considered as acute. It is important to understand why acute diarrhea occurs and how to manage it to prevent complications until the diarrhea can resolve or be treated appropriately.

Definition of Acute Diarrhea

Diarrhea means having more than three loose bowel movements a day. It can also be defined as passing more than 200 grams or 200 milliliters of stool in a day but this is difficult to assess as the quantity of stool is not usually measures. Diarrheal stool tends to be very soft and mushy or can be entirely liquid.

Acute (Lat. acutus = sharp, pointed) diarrhea, by definition, lasts less than 2 weeks (1). As mentioned, it arises suddenly, within hours to days. The condition tends to present with intense symptoms and then resolves quickly with or without medical treatment, and usually does not cause any long term complications.

Signs and Symptoms

Diarrhea is a symptom and not a disease. Several diseases present with diarrhea as a symptom, along with a host of other symptoms. It is important to note that in infectious diarrhea, the diarrhea and other symptoms do not arise immediately after contracting the infection.

There is a period of no symptoms between the time of infection and the appearance of the first symptom. This is known as the incubation period. It can vary from minutes to hours and even days or weeks. Other signs and symptoms that may accompany diarrhea includes:

  • Abdominal pain and cramping
  • Nausea with or without vomiting
  • Excessive flatulence
  • Abdominal distension
  • Bloating – sensation of fullness
  • Loss of appetite

Other signs and symptoms that may also accompany diarrhea depends on the underlying cause. For example, in infections there may also be fever. It is also important to note that the symptoms of dehydration may also arise.

Read more on dehydration symptoms.

Causes of Acute Diarrhea

Most causes of acute diarrhea are due to infections. These infectious agents (viruses, bacteria or protozoa) can be easily spread through airborne droplets, fecal particles or ingestion of contaminated food or water. Depending on underlying diseases, acute diarrhea can occur due to other non-infectious causes. Sometimes acute diarrhea is a flareup of a chronic condition, such as acute episodes in inflammatory bowel disease (IBD).

Diarrhea occurs when movement through the bowel (bowel motility) is faster than normal, excess fluid is drawn from the body into the bowels, when water in the bowels cannot be reabsorbed in the colon and/or where there is inflammation or damage to the wall of the gastrointestinal tract. All of these factors disrupt the formation and expulsion of stool. Depending on the cause, the diarrhea may be due to one of these disruptions or multiple disruptions simultaneously.

A) Acute INFECTIOUS Diarrhea

This refers to diarrhea that arises suddenly and is caused by infectious agents such as viruss, bacteria or protozoa.

  • Bacterial diarrhea usually occurs in food poisoning due to infection with bacteria, like E. coli or Salmonella.
  • Parasitic diarrhea may be due to intestinal worms, or one-cell parasites known as protozoa like Entamoeba hystolytica, or Giardia.
  • Viral diarrhea mainly affects small children in kindergarten due to stool-to-mouth infection from other children, or (in poor countries) due to infection by water, contaminated by rotavirus.

B) Acute NON-INFECTIOUS Diarrhea

This refers to diarrhea due to wide range of causes but not caused by infections.

  • Food allergies may affect children or adults. Main causes are wheat, eggs, cow milk, soy, fish, shellfish, peanuts, and tree-nuts, but can be virtually any food.
  • Food intolerances where the gut cannot digest certain nutrients which then cause diarrhea. Example is lactose intolerance where the lack of the enzyme lactase prevents digestion of the milk sugar known as lactose.
  • Fish poisoning. Both ciguatera poisoning by big tropical fish like barracuda or meckerel, and scombroid poisoning by non-properly stored fish are common.
  • Psychological stress may cause sudden diarrhea.
  • Antibiotic-associated diarrhea may occur few days or several weeks after start of treatment with antibiotics by mouth.
  • Medications like laxatives or magnesium antacids stimulate bowel motility.
  • Chemotherapy and irradiation damage cells in intestinal lining.
  • Mushrooms (even non-poisonous), and poisonous plants like foxglove or oleander may cause severe diarrhea.
  • Pesticides, ingested or inhaled may cause severe diarrhea.
  • Ingestion of heavy metals, like arsenic or mercury may cause severe diarrhea.
  • Runner’s diarrhea often affects long-distance runners.
  • Diarrhea may occur in women before child-birth.
  • Acute flareups in irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD).

Treatment of Acute Diarrhea

The  main concern in acute diarrhea is dehydration. This loss of fluid and electrolytes has to be prevented or managed once it arises or it can lead to further complications and even result in death. Oral rehydrating solutions (ORS) are the best option to rehydrate as it has the optimal concentration of essential electrolytes that are lost with diarrhea and/or vomiting.

Medical treatment may still be required depending on the underlying cause of the diarrhea. Viral infections that result in diarrhea usually do not require specific medical treatment. This type of diarrhea tends to resolve on its own and any treatment is supportive. Bacterial diarrhea may require antibiotics. Probiotics may also be needed thereafter to restore the normal intestinal flora.

Antidiarrheals should be avoided unless absolutely necessary or prescribed by a medical professional. These drugs can stop the diarrhea but may cause retention of the offending agent and/or toxins that would be flushed out with the diarrheal stool.

Diet for Acute Diarrhea

Contrary to popular belief, acute diarrhea does not require a liquid diet. Bland solid foods should be consumed through the diarrheal illness. Meals should be balanced to ensure an adequate intake of macro- and micronutrients. However, if vomiting is also present then solid foods should be avoided until it resolves. Oral rehydrating solutions must be consumed during and between meals.

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