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Diarrhea – Types, Causes, Diagnosis and Treatment

Diarrhea is an increase in the frequency of bowel movements and the liquidity of stool. In patients with diarrhea, defecation may occur more than three times a day and firmness of stool can range from soft to liquid in texture. Diarrhea is due to a disruption of the digestive process. It occurs when too much of unabsorbed fluid remains in the intestines. When this occurs, the stool that is passed through the anus is loose and watery.

Symptoms Accompanying Diarrhea

Diarrhea is a common symptom of many health conditions and is often accompanied by other symptoms that may help the doctor to detect the underlying cause. For instance, abdominal cramping and pain, blood in the stool and fever are often due to infection while nausea and vomiting may also indicate gastrointestinal infections. Dehydration, on the other hand, is a common consequence of severe chronic diarrhea, as the body loses significant amounts of water and salt and for some people it can be even life-threatening.

Types of Diarrhea

When it comes to the duration of diarrhea, it can be either short-term (acute) or long-term (chronic). It is common to experience acute diarrhea at some point in our lives. Most episodes of acute diarrhea usually last only a few days and resolve spontaneously. Infections and side effects of various medications are among the most common causes of acute diarrhea. We speak of chronic diarrhea when it lasts for at least four weeks. This type of diarrhea may indicate a more serious problem that requires medical treatment. Irritable bowel syndrome happens to be the most frequent cause of chronic diarrhea in developed countries.

Diarrhea can also be categorized into different types according to the processes that drive it. A common reason for diarrhea is the rapid transit of stool through the digestive tract that occurs with motility disorders such as irritable bowel syndrome. Other types of diarrhea by process include:

  • Osmotic diarrhea occurs when sugars, sugar alcohols and certain minerals in the intestines fail to be absorbed into the bloodstream. These unabsorbed substances draw water into the intestines, resulting in watery stool. Lactose and sorbitol intolerances are among common causes of osmotic diarrhea. Osmotic diarrhea usually goes away once the offending foods are excluded from the diet.
  • Secretory diarrhea happens when the intestines release water and salt into the stool, making it watery. Infections that release toxins are the most common cause of secretory diarrhea. These toxins then cause the intestines to secrete water and salt. Another possible factor stimulating secretions of water and salt by the intestines are carcinoid tumors. Poor absorption of fatty acids and bile acids by the intestines, commonly found in patients with celiac disease or inflammatory bowel disease, can also lead to secretory diarrhea. Fasting usually does not help improve secretory diarrhea.
  • Exudative diarrhea occurs when irritation or inflammation of the lining of the colon causes the release of blood and other fluids. It can be caused by a variety of conditions such as inflammatory bowel disease, some cancers or tuberculosis.

It is normal for different types of diarrhea to occur at the same time. With many conditions it is rare to have solely osmotic or solely secretory diarrhea, as many inflammatory and viral conditions can cause both types of diarrhea to occur simultaneously.

Potential Causes of Diarrhea

Diarrhea can be a symptom of a medical condition, a side effect of various medications and a result of specific dietary choices. Hence, possible causes of diarrhea include:

  • Viral infection is one of the most common causes of diarrhea, with rotavirus being the most frequent cause in children. Diarrhea is also a primary symptom of intestinal flu and gastroenteritis caused by noroviruses. By damaging the lining of the small intestine, viruses interfere with normal absorption of fluids and nutrients, contributing to diarrhea.
  • Bacteria and parasites can be ingested through contaminated water or food. They may release toxins that cause the intestines to secrete water and salt, making the stool runny.
  • Motility disorders. Problems with the movement of stool through the digestive tract can also lead to diarrhea. When food moves too quickly through the digestive tract, not enough fluids are absorbed from the food, leading to watery stool. Motility disorders can be due to an overactive thyroid gland, scleroderma, irritable bowel syndrome, stress, anxiety and antacids that contain magnesium.
  • Intestinal disorders or inflammation may inhibit absorption of fluids from food in the intestines, resulting in diarrhea. Examples include celiac disease, inflammatory bowel disease and dysentery.
  • Medications. There are many medications that can have diarrhea as their side effect. Antibiotics often disrupt the natural balance of microorganisms in the intestines, leading to digestive problems including diarrhea. Weight loss drugs, laxatives, antidepressants, blood pressure lowering agents and cancer medications can also cause diarrhea. Diarrhea, which is a side effect of medications, resolves once the aggravating substance is discontinued.
  • Surgical procedures may cause changes within the digestive tract that can result in diarrhea. Examples include bowel resections, dumping syndrome (a common consequence of gastric surgery) and bacterial overgrowth as a result of intestinal surgery.
  • Caffeine and alcohol stimulate the passage of stool, which can move too quickly through the digestive tract to allow for normal fluid absorption, resulting in watery stool.
  • Artificial sweeteners largely used as sugar substitutes, such as sorbitol (mentioned above as one of the main causes of osmotic diarrhea), are sometimes not absorbed into the bloodstream from the intestines, leading to runny stool.
  • Lactose intolerance is inability to digest milk sugar called lactose and it was mentioned above as one of the main causes of osmotic diarrhea.
  • Ingestion of environmental toxins such as insecticides from fruits and vegetables or eating poisonous mushrooms may also cause diarrhea.

Diagnosing Diarrhea

Short-term diarrhea, which goes away by itself, usually does not need any testing. But there are several tests available that can be used to determine the causes of persistent diarrhea, including:

  • Blood tests are performed to search for evidence of disease that may be causing the diarrhea.
  • Stool tests are ordered to determine the presence of bacteria, parasites or other signs of infection that may be responsible for the diarrhea.
  • Endoscopy enables to identify any abnormalities in the digestive tract that may be causing the diarrhea. Biopsies and static pictures may be taken during this procedure. A colonoscopy is similar, but the tube is inserted via the anus.
  • Fasting tests are used to exclude certain food components causing an allergy or food intolerance that could be behind the diarrhea. Fasting tests also enable to determine whether a change in diet affects the diarrhea.

Treatment of Diarrhea

Since diarrhea is a symptom of another health condition, treatment options typically depend on its underlying cause. If diarrhea is due to a viral infection, it is usually left untreated to resolve spontaneously. The diarrhea that is caused by foodborne bacteria or parasites may require antibiotics to fight the infection. When food intolerance or wrong diet is responsible for diarrhea, changes to diet by removing and adding certain types of foods may help resolve it. For chronic conditions, such as inflammatory bowel disease or irritable bowel syndrome, specific medical treatment may be needed.

Prescription and over-the-counter medications that can help stop diarrhea include adsorbents binding fluids, anti-motility medications which slow down the contractions of intestinal muscles and various other medications used to treat underlying conditions, causing diarrhea. For instance, antispasmodics may be used to relieve the pain and cramping associated with irritable bowel syndrome.