Watery Stool and Liquid Diarrhea – Causes and Dangers

Normal Consistency of Stool

Stool (feces) may be of different consistency, shape and even color.  These different types of stool are medically characterized using the Bristol stool chart, which provides a graphical representation of various types of normal and abnormal stools.  Feces that are considered normal are elongated in shape like a sausage, and have a soft yet firm consistency. According to the Bristol stool chart, such normal stools are classified under type 3 and type 4 stool categories.

Water constitutes about 70% of the weight of stool under normal conditions. An increase in the water content of stool beyond 70% results in mushy or watery stools. According to the Bristol stool chart, mushy and watery stools are classified under type 6 and type 7 categories, respectively. Watery stools are usually associated with diarrheal illnesses. However, not all cases of watery stool are strictly classified as diarrhea.

Bristol Stool Chart sourced from Wikimedia Commons

The frequency and consistency of stool varies considerably even under normal conditions. Passing stools less than 3 times a day to more than 3 times a week is considered normal, even if the stool is mushy or watery. Diarrhea is defined as a condition in which a person passes stool more than 3 times a day or more than 200 grams (or mL) every day. Watery stool can, therefore, occur under both normal conditions and diarrheal illnesses.

What makes stool watery?

The food and fluids that we ingest travel from the mouth, down the throat and through the entire length of the alimentary canal before the undigested portions and wastes are eliminated as feces. During the long transit through the alimentary canal, the components of the food get digested through various mechanisms and the released nutrients are absorbed into the bloodstream.  The stool that remains at the end of the small intestine is a fluid mixture composed of undigested food, digestive enzymes, bile, water, bacteria, mucus and waste materials.

This fluid mixture of wastes is known as chyme. As the chyme passes through the colon, water is reabsorbed into the bloodstream. This solidifies the stool in the colon. The stool that is eventually passed out during defecation is firm yet soft. Watery stool results from the presence of excessive fluid in the chyme or a failure to reabsorb most of the water in the colon. A variety of disturbances in both the small intestine and the large intestine can contribute to the formation of watery stools. Diarrhea is typically a predominant symptom of intestinal diseases.

In liquid diarrhea where there is little to no solid material, the water reabsorption in the colon is drastically impaired. In addition, water may be pumped out or drawn out into the small and large intestines from the body. This type of liquid diarrhea can cause rapid dehydration in a very short period of time.

Dangers of Watery Stool

The most dangerous complication of passing watery stool in large quantity or over a long period of time is dehydration. Water and vital electrolytes are lost from the body at a rate that is quicker than the rate of their replenishment through oral consumption of food and drinks. Mild diarrheal illnesses can be managed through the intake of oral rehydration solutions that contain water and necessary electrolytes.

However, oral rehydration is not sufficient when dehydration is severe. In such cases, medical intervention, including hospitalization, becomes necessary. Rehydration and replenishment of essential electrolytes in such severe cases of dehydration is managed via the intravenous route. It is important to note that dehydration is a potentially lethal complication. Rehydration measures should begin as early as possible in order to prevent any fatal consequences.

Causes of Watery Stool

Watery stools occur mostly during diarrheal illnesses. Most of these diarrheal illnesses result from infectious diseases. However, there could also be other causes of watery stool.

Intestinal infections

Most cases of watery stools are caused by acute intestinal infections with various pathogenic bacteria or viruses. These infections are frequent causes of a variety of diarrheal illnesses. Acute diarrheal illness is commonly known as infectious gastroenteritis. Most of the time this is due to viruses that often enter through contaminated food and water. It is often referred to as the stomach flu.

Some acute infectious causes of diarrhea may also cause a bloody stool which is often considered to be more serious. At times the watery stool may also have an unusual appearance, like in cholera, where the stool appears a milky white color. Infectious diarrhea may also occur on a chronic basis. This is especially seen in people with a weak immune system (such as HIV/AIDS patients) or those with Clostridium difficile infection.

Malabsorption syndromes

Liquid diarrhea can also result from a variety of malabsorption syndromes. These conditions are characterized by a failure to reabsorb nutrients and water within the small and the large intestines. Problems with reabsorption may also result in increased amounts of fat within the stool. Such a condition is medically known as steatorrhea, and is characterized by greasy, floating stools.

Chronic intestinal inflammation

Ulcerative colitis and Crohn’s disease are examples of chronic intestinal inflammatory diseases that are characterized by watery stools. These inflammatory intestinal conditions are the two types of inflammatory bowel disease (IBD) and may either result in liquid diarrhea or watery stools without diarrhea. Mucus may also be present in the stool as well as blood at times.

Functional disorders of the bowel

Functional bowel disorders are characterized by impaired functioning of the bowels in the absence of any identifiable pathology. The most common functional bowel disorder is the irritable bowel syndrome (commonly abbreviated as IBS). Both constipation and diarrhea can occur in irritable bowel syndrome. Loose, watery stools are characteristic of irritable bowel syndrome with diarrhea (also referred to as IBS-D). Abdominal cramps are also frequently associated with this condition.

Food allergies or intolerance

Watery stools may also result from incomplete digestion of certain food ingredients due to a lack of the required enzyme in the gut. Lactose intolerance is a common example of food intolerance caused by the lack of lactase enzyme. In some cases, a person may also be allergic to certain components of the food (such as gluten protein). Watery stools may also occur upon consumption of foods with such allergens.

Poor dietary habits

Frequent consumption of spicy foods, caffeinated beverages, processed foods, and saturated fats may also cause loose or watery stools. The amount of such foods consumed in one sitting may also affect the characteristics of the stool. However, not everyone who consumes such foods has watery stools. Individual tolerances to such poor dietary habits vary from one person to another.

Medication and Substances

Watery stools could also result from intake of certain medication. Antibiotics and laxative are some of the medication that may affect bowel habit to varying degrees.. Narcotics and toxins can also irritate bowels and cause watery stools. Alcohol in large quantities may also irritate the bowel and lead to diarrhea. The diuretic effect of alcohol hastens dehydration due to watery stool.

Psychological Factors

Bowel movements can also be affected by psychological factors such as anxiety, stress, and depression. Watery stools can occur when a person is in a distressed emotional state. This may be due to the movement within the bowels being faster than normal which does not allow enough time for water to be reabsorbed in the colon. Liquid diarrhea is rare in these cases but stool may be loose or watery in consistency.

Other disorders

Diseases or disorders of organs other than the intestine may also cause watery stools. This may include:

  • Gallstone disease,
  • Pancreatitis
  • Liver diseases like hepatitis.
  • Hyperthyroidism

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