Normal stool or feces is soft, firm and elongated in shape. However, there is a wide variation in the characteristics of stool among people. These variations may be caused by both pathological and non-pathological causes. It is often difficult to accurately communicate the nature of the stool. For this reason, the Bristol stool chart is often used to classify stool on the basis of its physical characteristics.
In the Bristol stool chart, stool is categorized into seven different types, encompassing the entire range of stools having hard to watery consistency. According to the Bristol chart, normal stool is categorized as type 3 or type 4 stool. Hard stools are categorized as type 1 or type 2 stool, and watery stools are categorized as type 6 or type 7 stool.
A runny stool or a watery bowel movement occurs in diarrhea. The medical definition of diarrhea is based on the frequency of passing stool and the amount of stool passed within a 24 hour period. A common definition of diarrhea is having more than 3 bowel movements or passing more than 200g of feces within a 24 hour period. This does not take into account the actual consistency of the stool. However, watery stool is commonly referred to as diarrhea.
Read more on normal vs abnormal stool.
About 75% of the stool is comprised of water. Despite this, normal stool has a firm consistency. Diarrheal conditions such as food poisoning and gastroenteritis are characterized by stools that are mostly watery. The stool in such conditions loses its solid or semi-solid consistency.
Mechanisms of Diarrhea
The main sources of water in the intestine are the foods and beverages we consume. Other sources include the mucus that covers the lining of the gastrointestinal tract, bile from the gallbladder, and digestive juices secreted by various glands in the gastrointestinal tract. Most of the water within the lumen of the intestine gets reabsorbed during transit through the colon.
In diarrheal conditions, an excessive amount of water is retained in the feces as it passes through the intestine. The following are the main diarrheal mechanisms through which excessively watery stools may form:
Reabsorption of water from the stool within the bowels depends on the formation of an appropriate osmotic gradient across the intestinal wall. In some diarrheal conditions, there is an increased amount of solute within the lumen of the bowels. This high concentration of solutes disrupts the normal osmotic gradient, and causes water retention within the colon.
As a result of water retention, stools become watery or runny. This type of diarrhea is referred to as osmotic diarrhea. Examples of conditions that may cause osmotic diarrhea include food intolerance, increased gastrointestinal motility, use of laxatives, use of antacids containing magnesium, and malabsorption syndromes.
In secretory diarrhea, the amount of water and electrolytes in the gut is more than what the intestine can reabsorb. Examples of conditions that may cause secretory diarrhea include heavy metal poisoning, food poisoning, side-effects of certain medicines, laxative use, and endocrine tumors.
Exudative diarrhea is mainly seen in gastroenteritis. In addition to being runny, the stool in exudative diarrhea may also contain pus or blood. The most common cause of exudative diarrhea is an infection. For this reason, exudative diarrhea is also referred to as infectious or inflammatory diarrhea. Exudative diarrhea can result from infection caused by a variety of pathogens, including bacteria, protozoa, and viruses.
These pathogens interfere with the absorptive functions of the gut wall, resulting in watery stools. Destruction of the epithelial lining may also occur, resulting in exudation of serum and blood into the gut lumen. The presence of pathogens also triggers an attack by the white blood cells of the immune system. These immune cells release chemicals that cause inflammation, resulting in secretory diarrhea.
Read more on watery stool.
Treatment of Runny Stool
Acute diarrhea, in most cases, does not require any specific medical treatment. In many cases, the diarrhea is self-resolving. Certain supportive measures may help during the recuperation phase. The following are some of the commonly prescribed supportive measures during diarrhea:
- Frequent intake of an appropriate oral rehydration solution (commonly abbreviated as ORS) is necessary to prevent dehydration caused by diarrhea.
- Body must be given sufficient rest for recovery and to prevent fatigue and dehydration.
- Consumption of light, bland, and balanced diet is essential. Substances such as dairy products, caffeine and alcohol should be avoided since they worsen diarrhea and dehydration.
In cases where the diarrhea does not resolve in a few days (or causes serious complications such as dehydration), medical treatment may become necessary. A diagnosis of the underlying cause of the diarrhea in these cases is necessary for the implementation of an appropriate treatment regimen. The following are some of the common treatments for diarrhea:
- Antibiotics: Antibiotics are prescribed when diarrhea is caused by a bacterial or protozoan infection. Diarrhea caused by viral infections usually resolve on their own and do not require any antiviral medications.
- Antidiarrheal agents: Antidiarrheal agents can stop diarrhea for a short amount of time. An example of antidiarrheal medication is loperamide. However, these medications are usually not prescribed during diarrhea.
- Antispasmodics: Antispasmodic medications may be used to provide relief from any accompanying abdominal cramps. A combination of antidiarrheal and antispasmodic drugs may also be used to stop the diarrhea.
- Stool thickeners: In conditions where the diarrhea persists even after the underlying cause has been treated, one may use stool thickeners (such as psyllium husk) to make the stools more solid.
- Probiotics: In conditions where the diarrhea persists after treatment of the underlying cause or when antibiotics have been used to treat the diarrhea, probiotics may be recommended. Probiotics help in restoring the normal flora of the intestine.
Preventing Runny Stool
Many diarrheal conditions are caused by infections. The infectious agents that cause diarrhea are easily transmitted from person to person. Following are some of the precautions that one can take to prevent the spread of diarrheal infections:
- Maintaining hygiene of the hands is very important. This means washing hands thoroughly with soap and water after every meal or after going to the toilet. In places where soap and water is not available, one may use hand sanitizers.
- One should refrain from consuming foods and beverages from places that use unhygienic practices in meal preparation.
- Use bottled drinking water while traveling.
- In children, certain diarrheal diseases (such as those caused by rotavirus) may be prevented through vaccination.