Paradoxical Diarrhea or Overflow Diarrhea

This type of diarrhea is really due to having constipation

It may seem as though a person would have either diarrhea or constipation but it is possible to have both at the same time. This is what’s known as paradoxical diarrhea or overflow diarrhea.

Diarrhea (having watery stools) is a common digestive problem that affects people at all stages of life. There are many different causes of diarrhea, which may make it difficult to diagnose and treat. Even so, most episodes of diarrhea last a few days and go away on their own.

Constipation, which is hard stools that are difficult to pass, is another condition that affects anyone from children to adults. Constipation might occur for a few days or be chronic (occurring over a long period of time). Bowel movements are on a spectrum, and every person will have their own version of “normal.”

A woman holds a hot water bottle against her abdomen as though she's in pain.
Grace Cary / Moment / Getty Images

Understanding the Digestive System

The way we nourish our bodies and get the fuel to function is by eating. However, our bodies can’t easily turn food into a form that can be used by our cells. That’s where the digestive system comes in. The digestive system begins in the mouth and continues on through the body from the esophagus, stomach, and intestines, to the anus, where stool leaves the body. 

Digestion begins in the mouth, where food is chewed. There are enzymes in saliva (spit) that help start the break down of food that’s continued through the digestive tract. Chewed food is swallowed and moves down the throat (esophagus) into the stomach.

In the stomach, food is broken down further with the digestive juices and with the stomach muscles that mix everything together. Once the stomach has done its work, food moves into the small intestine. There, more digestive juices are added to the mix. Nutrients are absorbed from the food at this point so that they can be used in the body. 

What’s left after food passes through the small intestine and vitamins and minerals are absorbed next goes into the large intestine. The large intestine is where the water is absorbed from the stool and it becomes thicker.

The stool then reaches the rectum, where it is held until the body has an urge to have a bowel movement. During a bowel movement, the stool is passed out of the body through the rectum.

This is the way the digestive process functions when everything is working well. However, there are many reasons why the digestive system can encounter difficulty. When things go wrong it could result in constipation and/or diarrhea.

What Causes Diarrhea

Diarrhea is having liquid stools three or more times in a day. Most people know what it’s like to have diarrhea that comes on suddenly and lasts for a few days before it resolves on its own.

In many cases, diarrhea that goes on for a few days is caused by an infection with a parasite, virus, or bacteria. Viruses that cause diarrhea spread rapidly from person to person. Coming down with diarrhea after a close contact does (like a family member) might mean that there’s a virus going around.

Bacteria can also cause diarrhea, especially those that are spread through food or water (foodborne disease or “food poisoning”). Some types of bacteria that cause diarrhea are more common in developing parts of the world. Parasites that cause diarrhea are not common in developed parts of the world but may be more prevalent in developing areas.

Outside of viruses, parasites, and bacteria, there is a spectrum of diseases and conditions that can cause diarrhea. Lactose intolerance, irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), and celiac disease are causes of chronic diarrhea (that goes on for more than a few days).

Some medications, such as antibiotics, can also cause diarrhea. This usually clears up after the course of the drug is completed.

What Causes Constipation

Having a bowel movement fewer than two or three times a week may be constipation. In constipation, stool tends to be hard and it’s also difficult and potentially even painful to pass. It may involve straining or pushing to have a bowel movement.

Constipation tends to be common in children, and adults may experience it a few times a year. Some of the causes of constipation include not eating enough fiber or drinking enough water and a low level of physical activity. Traveling or stress also causes some people to become constipated.

In children, holding in bowel movements can lead to constipation. This can result in a cycle of painful bowel movements, which a child holds in order to avoid the pain, which leads to more constipation.

Medications are also a major cause of constipation, especially in older adults. Some of the medications that may cause constipation include opioid pain medications, antihistamines, antacids, and antidepressants.

Conditions that may cause constipation include IBS, thyroid disease, Parkinson's disease, and multiple sclerosis. Colon cancer is also linked to constipation but it is not a common cause and there may be other symptoms such as blood in the stool, pain, weight loss, or fatigue.

How Constipation Causes Paradoxical Diarrhea

When a person experiences diarrhea, it may lead to thoughts about having eaten a food that may have upset the stomach or of having a virus that’s causing it. What may not immediately come to mind is that diarrhea could actually be caused by constipation. 

Constipation may be transitory and only last for a few days. But in some cases, it can become chronic. Not going to the bathroom for an extended period of time can cause the fecal matter (poop) to build up in the digestive tract. This can result in what’s called fecal impaction.

Fecal impaction is when there is a large, hard mass of stool in the intestine. This stool is so hard and so stuck that it can’t be passed. It might also be called impacted stool, impacted bowel, or impacted colon).

A person who has a fecal impaction could find that they have watery stools but yet are not really moving their bowels. In fact, it might be difficult to contain the stool in the rectum and it may be leaking out (causing bathroom accidents or incontinence).

What’s happening is that there is watery stool behind the fecal impaction and it is seeping out around the hard mass of stool. This liquid stool is often foul-smelling. It can lead some people to think that they’re having diarrhea when the real problem is the impacted stool.

The problem is further compounded when the rectum is distended (enlarged) because of the greater volume of the stool. The internal anal sphincter relaxes, contributing to the stool leaking out of the rectum. In addition, the large intestine may respond by producing more fluid. This results in an even greater volume of watery stool that can’t be contained by the rectum.

Causes of Fecal Impaction

Some people who have constipation may take medication, called laxatives, to try to go to the bathroom. Some types of laxatives are safe to use long-term but others can cause dependence. That means that eventually, with long-term use of some laxatives, the body is unable to have a bowel movement without them.

Fiber supplements (psyllium, calcium polycarbophil, or methylcellulose) and osmotic laxatives are usually safe for long-term use.

Stimulant laxatives, which work by increasing the movements of the muscles in the intestine, or stool softeners which work by causing more water to be drawn into the intestine, are not usually recommended for long-term use. When a laxative is stopped, it can cause the constipation to return or to get worse.

Fecal impaction is a significant problem for older adults, especially those that are in care facilities. Pain medication such as opioids can contribute to the development of constipation because they slow down the action of the bowel. Being unable to move around, such as being bedridden, can also contribute to constipation.

Removing an Impaction

In some cases, the hard mass of stool in the rectum can be removed manually. That means that a health care professional may insert a lubricated finger into the rectum and dislodge the stool. Other tools might be used, such as an anoscope (which is used to look inside the anus), to remove the stool.

An enema is another way to remove a fecal impaction. This is true especially when the impaction is not as close to the anus. The enema might need to be given by a healthcare professional using special tools to ensure that the enema liquid goes further up into the digestive tract.

Laxatives might also be used for impacted stool that is further up in the digestive tract and can’t be reached with an enema. Surgery might be used for removing the fecal matter, but this is not common. The use of surgery might be considered more often for those who have had prior surgery on the anal area. This can include surgery on anal fistulas or hemorrhoid removal.

Paradoxical Diarrhea In Children

Bathroom accidents or soiling the underwear with stool in children is called encopresis. One potential cause of encopresis is having constipation. Children with constipation may hold their stools, resulting in impaction and then liquid stool that leaks from the rectum.

Kids who experience encopresis may go to the bathroom infrequently and may have hard, small stools when they do go. In some cases, parents may think that children experiencing encopresis might have diarrhea. Children are unable to control the stool leakage that occurs because of constipation.

Similar to adults, the treatment is to avoid constipation by drinking enough water, eating foods that contain fiber, and decreasing those foods that may contribute to constipation (such as bread, bananas, rice, and cheese).

There may be a behavior component in some children, and consulting a pediatrician about soiling underwear is important to understanding how to treat the problem.

Preventing Paradoxical Diarrhea

Preventing paradoxical diarrhea means preventing constipation. Having bowel movements that are soft and easily passed may mean making diet and lifestyle changes. Sitting down to have a bowel movement and not ignoring the urge to “go" is an important first step.

Eating more fiber, especially foods such as whole grains, legumes, fruits, vegetables, and nuts can also help prevent constipation. Fiber supplements, which are bulk-forming laxatives, may also be used to keep stools soft and easily passed. Drinking more water may also help keep stools soft.

Laxatives might help in preventing constipation. However, it is important to consult a physician before taking stimulant laxatives because of the risks involved in using them long-term. For short-term use, these laxatives are often safe. However, the underlying cause of constipation needs to be addressed if it is continuing long enough that laxatives are needed for more than a few days.

Some people also use enemas for their constipation, but it’s important to note that using enemas long-term can have risks. Using an enema once in a while shouldn’t be an issue but they are not a solution for chronic constipation.

When to See a Doctor

Diarrhea and/or constipation that comes and goes for a few days usually isn’t a reason to see a physician. However, when there are any concerning signs or symptoms such as dehydration, blood or mucus in the stool, light-headedness or dizziness, an increased heart rate, or severe abdominal pain, a doctor should be consulted as soon as possible.

Constipation that goes on long enough that it causes paradoxical diarrhea may need treatment. In some cases, there may be a need to find out why constipation is occurring in order to prevent it from happening again. This is especially true after having tried bulk-forming laxatives and lifestyle changes and constipation continues.

A Word From Verywell

Diarrhea and constipation are common, but that doesn’t mean that they can’t be serious. Having hard stools that lead to an impaction and overflow diarrhea can be uncomfortable, messy, and cause embarrassment. Chronic constipation is a reason to work with a physician to determine the cause and move towards finding a long-term solution.

For older adults, especially those that are in care facilities, the management of constipation is important and should be addressed right away. Paradoxical diarrhea is problem enough, but it should also be understood that fecal impaction and the treatment for it have the potential to cause long-term complications.  

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