Runny Stool (Bowel Movements) Causes, Diet and Treatment

The digestive system is central to proper nutrition as food consumed is gradually digested and nutrients are absorbed. Waste substances are eventually expelled as stool during a bowel movement. The pattern of these bowel movements and the consistency of stool can sometimes become abnormal, with diarrhea on one end and constipation at the other extreme. Both diarrhea and constipation are symptoms of underlying diseases and referred to by a host of non-medical terms.

What is runny stool?

Runny stool is a common non-medical term to describe diarrhea or watery stool. Diarrhea is medically defined as having three or more bowel movements in a day, often where the stool is watery. Another less commonly used definition for diarrhea is passing more then 200 milliliters or 200 grams of stool within a 24 hour period. It is also referred to as a ‘runny tummy’ or the ‘runs’.

Normally stool should be soft, smooth and sausage-shaped. However, runny stool is instead of a watery consistency apart from having more than three bowel movements within 24 hour period. Sometimes this watery stool may be passed out only once or twice or even persist despite not exceeding normal bowel movement frequency. Therefore the term runny stool is a broad term to describe a host of conditions which present with diarrhea.


Causes of Runny Stool

The causes of diarrhea can be broadly divided into infectious and non-infectious causes. Most of the time acute diarrhea is due to infectious causes while chronic diarrhea tends to be due to non-infectious causes. However, acute diarrhea can also arise from non-infectious causes.

Infectious Causes

Most infectious causes of diarrhea are caused by viruses, bacteria and protozoa. Fungal infections of the digestive tract may also lead to diarrhea but this is uncommon and mainly seen in people with a weakened immune system.

  • Viruses are a common cause of diarrheal outbreaks, particularly in young children.
  • Bacteria are also common causes of diarrhea and often spread through contaminated food and water.
  • Protozoa are less common and is also more likely to be spread through contaminated food and water.

Non-Infectious Causes

Most non-infectious causes of diarrhea are due to foods when there is a problem with digestion and absorption of nutrients like with lactose intolerance and fructose malabsorption. Some drugs can cause diarrhea as a side effect such as certain antibiotics.

Chronic diseases where diarrhea is a prominent symptom may occur for a host of different reasons, such as autoimmune disorders such as inflammatory bowel disease (IBD). Sometimes the exact cause cannot be identified and this may be referred to as functional diarrhea as in irritable bowel syndrome (IBS).

constipation diarrhea

Runny Stool Diet and Lifestyle

  • Rehydrate constantly with an appopriate oral rehydrating solution (ORS) that has the optimal balance of water and electrolytes. Sodas and fruit juices are not suitable.
  • Maintain a bland balanced diet throughout the duration of the diarrhea to prevent nutritional deficiencies. A completely liquid diet is not necessary unless there is vomiting.
  • Rest is important to assist with recovery. Strenuous physical activity must be avoided as it can worsen dehydration as additional fluid and electrolytes would be lost with perspiration.
  • Avoid alcohol and caffeine as it can worsen diarrhea and exacerbate dehydration since these substances are diuretics (promote water loss through urine).
  • Do not consume large amounts of dairy. Some people experience secondary lactose intolerance during and immediately after a diarrheal illness which worsens the diarrhea when dairy is consumed.

Read more on how to stop diarrhea.

Preventing Runny Stool

Diarrheal illnesses can be prevented to some extent. Most cases of diarrhea are caused by the transmission of infectious agents from person to person or through food and water.

  • Wash hands regularly, especially after using the toilet and before eating. Fecal particles contain infectious agents that can cause diarrhea.
  • Use antiseptic handwash or soap. Wash the hand thoroughly and spend extra time lathering and rubbing the fingers in particularly.
  • Hand sanitizers are also useful when washing with running water and an antiseptic soap is not an option. These santiziers should be applied liberally, especially on the fingers, and rubbed thoroughly.
  • Do not eat food from establishments that are have questionable hygiene standards. Travelers in particular need to be extremely cautious about the source of food when in unfamiliar territory.
  • Ensure that drinking water and water used for the preparation of food is clean. Travelers should only opt for reputable brands of drinking water when in other countries and avoid drinking from rivers and lakes.
  • Vaccines are available to prevent common viral diarrhea in children which is usually caused by the rotavirus. However, these vaccines cannot prevent all other types of infectious and non-infectious diarrhea so the other preventative measures above still need to be followed.

Diarrhea Rehydration

Treatment for Runny Stool

Most of the time acute diarrhea does not require any specific medical treatment unless it is severe, persists beyond a few days and results in complications like dehydration. Supportive measures alone are usually sufficient, which includes rehydration, rest and proper nutrition. However, chronic diarrhea usually requires intervention as the underlying cause needs to be accurately identified, treated and managed.

  • Antibiotics may be prescribed to treat bacterial and protozoal diarrhea. Usually antivirals are not necessary for viral diarrhea as it tends to resolve on its own.
  • Antidiarrheal agents like loperamide are usually not recommended for the treatment of diarrhea. However, these drugs can be useful for stopping diarrhea for short periods of time.
  • Antispasmodics may help relieve the abdominal cramps associated with diarrhea and some combination antispasmodic-antidiarrheal drugs can also stop the diarrhea.
  • Stool thickeners like psyllium may assist in forming more solid stools and can be helpful when the underlying cause has resolved but the diarrhea persists.
  • Probiotics are recommended to restore the normal intestinal flora (“good bowel bacteria”) such as Lactobacillus, especially when antibiotics are being used or the diarrhea persists after treatment of the cause.

Although most acute diarrheal illnesses can be self-managed, professional medical attention is necessary if the diarrhea is severe and worsening, if dehydration is progressing despite oral rehydration or if there is bloody stool.

Last updated on September 25, 2018.

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