Liquid Bowel Movement Causes (Watery Stool)

The Bristol Stool Scale is a chart that outlines 7 types of stool, from the very hard and large stool to entirely liquid stool at the other end.  Somewhere in the middle is what can be considered as normal stool (type 4). It is described as soft, smooth and sausage-like in shape. However, stool may not always be this ideal consistency and shape. Sometime the bowel movement can be liquid.

The digested and undigested material mixed with copious amount of water enter the colon where the water is gradually reabsorbed until the stool becomes solid. This reabsorption of water in the colon minimizes water loss through the stool. However is there is excess fluid in the bowels and the colon cannot reabsorb it sufficiently, the stool may be watery.

Causes of Watery Stool

There are a number of different causes of watery stool. Most cause acute changes in the consistency of stool. However, some can lead to chronic disturbances in bowel habit as well as the consistency and shape of the stool. It is technically referred to as diarrhea if the total daily output of stool exceeds 200mL/200g  and bowel movement is more than three times in a 24 hour period.


Gastrointestinal infections are one of the most common causes of acute watery stool. Gastroenteritis is often due to viral infections and is short-lived. The symptoms like profuse diarrhea, vomiting and abdominal pain are usually intense for 2 to 3 days but in some cases it can persist for longer even up to several weeks. Bloody diarrhea is usually indicative of more serious acute infections which may need medical attention or it can lead to serious complications.

Chronic infections leading to persistent watery diarrhea is more likely seen in people who are immune compromised like with HIV/AIDS. The opportunistic infections that may arise may be ongoing since the immune system does not have the ability to counteract it. Sometimes people who are not immune compromised may also be at risk of chronic bowel infections especially when antibiotics are used for prolonged periods of time. This is ongoing antibiotic associated diarrhea (AAD).

Food Intolerance

Foods that cannot be digested may act as solutes in the bowels. This draws out water into the bowels and prevents it from being reabsorbed in the colon to form solid stool. Although the human body cannot digest fiber the problem is usually with other foods. Lactose intolerance is the most common type of food intolerance. It is a result of the body being unable to break down the sugars that naturally occur in milk due to a deficiency in the enzyme lactase.

Food intolerances are sometimes confused with food allergies. In the latter, the presence of a certain food in the gut triggers an inflammatory reaction due to activation of the immune system. The allergic reaction and intolerance may produce similar symptoms. However, these are two separate conditions and person with an allergy may not have any deficiency of enzymes which leads to the accumulation of undigested nutrients in the bowels that triggers diarrhea.

Malabsorption Syndromes

This refers to conditions where the bowel is diseased or defective in a way that prevents nutrients from being absorbed from the gut. As with a food intolerance the residual nutrients in the bowels causes a watery diarrhea. Fructose malabsorption is one such type where the body cannot absorb fruit sugars. Sometimes malabsorption is not related to underlying genetic defects but arises with inflammatory bowel conditions. The inflammation affects the normal absorptive ability of the intestines.

Bowel Diseases

Chronic bowel conditions like inflammatory bowel disease (IBD) can impair nutrient absorption which may then lead to water accumulating in the bowels. Movement of food through the bowels can also be faster than usual which impairs water reabsorption and lead to watery diarrhea. Bleeding and even mucus in the stool may be seen in these conditions. Apart from IBD, celiac diseases is another long term condition that arises when the bowel comes in contact with certain foods.

Functional Bowel Disorders

A functional bowel disorder is not a disease in terms of there being inflammation or some other anomaly. It is instead a condition where the normal activity if either overactive or underactive. Irritable bowel syndrome (IBS) is a functional bowel disorder. In IBS with diarrhea the movement through the gut is faster than normal leading to bouts of diarrhea. In addition the muscle in the bowel wall may go into spasm which is the reason for abdominal cramps that is typical of IBS.


Certain foods can irritate the bowel lining and cause watery stool. This is often seen with chili and other spices. However, an excess of otherwise mild foods can also lead to diarrhea. It has also been found that a modern diet of heavily refined foods especially when fresh fruit and vegetables is avoided may also lead to loose stool that can be watery. It is usually easy to spot the food trigger as symptoms may start a short while after consuming the problem meal.


A number of different pharmaceutical drug can contribute to fluid stool. The risk of such bowel disturbances occurring is usually indicated on the packaging or information leaflet. Toxins are one type of chemical that can cause watery stool like when bacterial toxins in contaminated water or food is ingested. Illicit drugs and alcohol are other chemicals that lead to watery stool but the tolerance may vary from one person to another.

Digestive System Problems

Apart from the bowels, diseases or disorders affecting the other digestive organs can also lead to watery stools. This is seen when the pancreas, gallbladder and even the liver is the problem. Pancreatitis, gallstones and hepatitis (liver infection) are some of the conditions where diarrhea is a prominent symptom.


Anxiety, depression and psychological stress can have an effect on movement through the bowels. Usually it results in diarrhea as bowel motility is faster than normal. Water is not properly reabsorbed and the disturbance that may occur with the digestion and absorption of nutrients may all lead to watery diarrhea. It is usually acute and will quickly resolves once the cause of the mental stress resolves.

More Related Topics