Green Stool

What Causes Green Stools?

What Causes Green Stools – Nothing causes a great deal of worry to people than the unusual, unfamiliar appearance of green stools. People are so used to the appearance of well-formed, cylindrical, brown stools that this finding may cause people to seek immediate medical attention.

In order to understand the cause of brown stools, it’s important to discuss first the normal physiologic process how brown stools are formed from the chyme in the intestines until it becomes solid stools in the bowels.

What Causes Green Stools digestive system

Our discussion first starts with the digestive system. The digestive system is fully equipped to process food products for energy extraction and excretion of undigested material. The process of stool formation however, starts in the intestines.

After the food is broken down into a pasty substance called chyme, it is passed down through the very long small intestines so that maximum absorption of raw materials is achieved. This process is slow as bowel movement usually occurs once per day.

As such, the intestines take their time in processing the food. After a long journey through the small intestines, the food passes through the cecum and into the large intestines. This is where a majority of bacteria act on the semi-formed stool to turn it into its usual brown to yellowish color.

The large intestine is also the site of water reabsorption such that the stools take on a slightly solid consistency that is finally passed into the rectum and out the anus.

How are green stools formed?

What Causes Green Stools Gallstones vs bile stools

With a little deduction, one can say that the stools colored green have been colored the same by the bile fluid in the gallbladder by moving at a much faster rate than the usual emptying time. There are medical conditions that make the bowel moves its contents at a much faster rate than usual, here we discuss the most common ones.

Acute gastroenteritis is a common infectious disease that can be caused by a variety of bacteria. One of its effects is irritating the enteric cells of the intestines and stimulating increased peristalsis.

With greater waves and muscular contractions of the smooth muscles in the intestines, the food has less time to be processed and the bile goes along with the partially digested food chunks. This results into the stools being watery and green-colored.

Neural controls of the intestines and colon have intrinsic and extrinsic aspects. The intrinsic system also called the “enteric nervous system” has 3 different layers of myenteric, submucosa and mucosal layers. The myenteric layer is what affects the secretion, absorption and blood flow to the intestines which is a factor in the rate of emptying.

The extrinsic is more on sympathetic input i.e. fight or flight and has sympathetic inputs to sphincteric muscle and inhibitory input to non-sphincteric muscle. As such, a relaxed state allows faster emptying time than a person who is stressed.

On an average day, about 9 L of fluid enter the gastrointestinal tract. Less than 1 L of residual fluid reaches the colon. The fluid excretion in the average adult is at a mean 0.2 L every day. The colon has a large capacitance and may recover up to 4 times of its usual fluid excretion by 0.8 L if the reabsorption and transit process allows.

We will also need to discuss about diarrhea. Diarrhea is loosely defined as increased stool frequency that is comprised of watery or poorly formed stools.

For a Western standard, greater than 200g/day can be considered as diarrhea. There are also different classifications of diarrhea. There is acute which is <2 weeks, persistent diarrhea when lasting 2-4 weeks and finally chronic diarrhea if it’s greater than 4 weeks.

How do we Treat green stools?

More than 90% of cases of diarrhea are caused by infectious agents such as bacteria and viruses. These usually present with abdominal pain, fever and vomiting. The remaining 10% are caused by medications, toxic ingestions, some specific type of food intolerance.

Most of infectious cases come about as a result of fecal-oral transmission. Some cases may be improperly prepared food or even unhygienic practices such as eating with unwashed hands. In a healthy, non-immunocompromised person, the intestinal flora alone has 500+ taxonomically different bacteria. These resident bacteria play a role in suppressing the growth of pathogenic bacteria.

Some cases of antibiotic administration can cause pseudomembranous colitis because of Clostridium difficile. That’s why the immune system, if at peak condition, plays a key role in suppressing infections. If the immune system is bypassed and the bacteria manage to get a foothold, disease will develop.

Therefore, in a majority of cases, the main goal is to treat the underlying cause of the diarrhea paired with fluid replacement to replenish losses brought about by the vomiting and/or diarrhea. A physician may opt to use empiric therapy to destroy the rapidly multiplying bacteria until stool exam and culture will reveal the causative infectious agent.

After that, the physician may switch to a narrow-spectrum antibiotic to minimize the risk of drug resistance in bacteria. While the patient is being treated with antibiotics, anti-emetics may be prescribed to lessen the nausea and vomiting along with some acetaminophen to lower the fever.

If the case is moderately dehydrating, the patient may be prescribed agents such as Loperamide to reduce the diarrhea at 2 grams per day and not to exceed 8 grams per day. This shouldn’t be used in febrile dysentery because it may actually exacerbate the cause.

Once the immune system is able to do its job of identifying the offending organism, the body mounts a response and the bacteria are hopefully cleared from the system. The signs and symptoms stop and the patients are cured of the diarrhea.


Indeed green stools come about as a result of diarrhea, as already discussed, the green pigment comes from the bile that is secreted by the liver and becomes brownish-yellowish as the normal flora in the gut act upon it while it is in transit.

If ever these processes are disturbed because of the infection or some other cause, the intestines will do its best to remove the offending agent by increasing the emptying rate which results into diarrhea and green-stools. If you think that you are affected by diarrhea, seek immediate medical attention.

Dehydration is one of the dangers that come about with diarrhea and green stools will point to a deduction that something is adversely affecting the gastrointestinal system. With fluid replacement and antibiotic therapy, this disease is easily cured by todays medical standards.

Leave a Reply

Your email address will not be published. Required fields are marked *