Agreeing on a simple
And straightforward
Definition of constipation

What is an simple, acceptable and practical definition of constipation?

In an address given at the Massachusetts General Hospital in 1935, Sir Arthur Hurst proclaimed: «No organ in the body is so misunderstood, so slandered and maltreated as the colon»(1).

Sadly, the quote still applies today. This makes it difficult to come up with a definition of constipation that all sufferers can agree upon. Even today, constipation means different things to different people.

In this article, we will first take a look at the functioning of the colon in the gastro-intestinal tract, and its key role in constipation. In a second part, we will come up with a simple definition of constipation that everyone can understand.

Note that we won't cover the different causes and remedies yet. This is an introductory article setting the foundation for the other sections of this web site. After all, we first need to agree upon a definition of constipation before discussing how to correct it.

The colon and its role

The digestive tract is one long dis-assembly chain. Through a series of tubes and tanks, its purpose is to break down foods into components that the body can assimilate. Assimilation into the blood stream and lymphatic system occurs in part in the stomach, and mostly in the small intestine. Once the small intestine is done with absorption, it evacuates the food residues into the colon. Understanding the role of the colon is necessary to arrive at a definition of constipation.

The colon is at the end of the line. It is composed of four parts, four different sections of the same tube if you will:

  • The ascending colon
  • The transverse colon
  • The descending colon
  • The sigmoid colon

Let’s look at the picture below.

The colon serves 3 main purposes:

  1. To reclaim the water and electrolytes that have been invested in the digestion of the food.
  2. To develop a colony of good bacteria that will digest the remaining dietary fibers that could not be broken down earlier. Those bacteria will transform unusable material into essential nutrients for our body.
  3. To excrete the remaining residues from digestion in a timely and orderly manner.

Is the colon just a dumb evacuation tube?

Not at all. First, our body is tuned toward conservation of fluids and important minerals (like sodium and magnesium). About 5 gallons of fluid reaches the colon every day, divided up between what we drink and the internal fluids generated during digestion (acid, bile, etc)(2). Most of this fluid has to be reclaimed by the body or we would quickly become dehydrated.

At the beginning of the dehydration process, in the ascending colon, things are still fairly liquid. They will be soft but solid when they reach the descending colon.

Second, we should not discount the role of the friendly bacteria in the colon, breaking down what we cannot digest (certain fibers) and creating waste products that are used as nourishment by our colon’s cells. The good bugs also produce vitamin K, vitamin B1, B2 and B12, absorbed through the colon lining into our system.

The conveyor’s belt

Here is how things move through the colon. Understanding this will help us better grasp some of the physiological issues brought forth in our definition of constipation.

For most of the digestive tract, food moves down by “peristalsic” movement. Peristalsis is a wave-like motion that contracts the tube above the mass of food, relax the tube below the mass of food, with a net result of pushing the mass down in a smooth and continuous manner.

Things happen differently in the colon. Dehydrating the food residues takes time, and the residues remain in the colon for 30 hours on average(2). As a result, there is a lot of mixing movements happening without forward motion, to let things soak in.

Then once in a while, a large forward moving contraction will occur. They only happen 6 to 8 times a day, and are very strong, beginning in the ascending colon and ending in the rectum. Those contractions will often trigger a bowel movement(2).

To summarize:

  1. First, there is a lot of in-place “washing machine” like churning to enable the water to be reabsorbed and the bacteria to be thoroughly mixed with the residues.
  2. Second, once in a while, a large push forward will happen, moving the processed residues one step closer to the exit, and allowing new residues to come in from the small intestine

The end of the chain

At the end of the colon, we have the rectum and the anus. The rectum is the final storage place for the feces before they are evacuated.

The rectum has stretch receptors. When the rectum is stretched by the incoming feces, those receptors will fire-off a message to the central nervous system, which will relay the signal to the brain.

The brain will then make us aware of the urge to evacuate, something we call the “defecation reflex”. The expulsion will take place through a combination of voluntary actions (we start to push) and involuntary processes (automatically handled by our internal muscles without us being aware of it). This involuntary process is handled by what is called the "autonomic nervous system". The autonomic nervous system is mainly responsible for nerve and muscle actions taking place below our level of consciousness.

If we decide not to act upon this signal, the feces may be returned to the upper colon for further storage and dehydration. Not something to look for when we are already constipated, as the stools will become drier as a result. But something that happen quite a lot in this day and age.

Here is an interesting point to note. You remember seeing pictures from old books or magazines showing people defecating? If yes, you probably remember that they were always depicted in the squatting position. Defecation in a seated position only started with the advent of the modern toilets. It is still common practice in some developing countries.

Squatting is the ideal defecation position, because our thighs press into our colon, enhancing the whole muscular expulsion process. It is like squeezing on a tube of toothpaste. It is unfortunate we have lost this habit. Squatting after a meal also enhances the whole digestion process. You may want to give this a try, unless you have hemorrhoids.

An alternative is to adopt a better sitting position while on the toilets. Use a foot rest to lift your knees higher than your buttocks. Lean forward and place your elbows on your knees. Keep your back straight, and push.

The Bristol Stool form scale

This is another name you will come across in your research on constipation. The Bristol scale is used to classify the form and shape of your stools. Here is how it goes(3):

  • Type 1: Separate hard lumps, like nuts (hard to pass)
  • Type 2: Sausage-shaped, but lumpy
  • Type 3: Like a sausage but with cracks on its surface
  • Type 4: Like a sausage or snake, smooth and soft
  • Type 5: Soft blobs with clear cut edges (passed easily)
  • Type 6: Fluffy pieces with ragged edges, a mushy stool
  • Type 7: Watery, no solid pieces. Entirely liquid

The scale is good to know in order to communicate with your doctor. If you suffer from irritable bowel syndrome for instance, with alternating constipation and diarrhea, you could say your bracket is between 6 and 2, or worse between 7 and 1, or any other combinations. It gets the point better.

Constipation spans across types 1 and 2. This scale helps us come up with a partial definition of constipation (through stool shape and consistency), but is not a be-all and end-all.

Putting it all together - a tentative definition of constipation

In a world where everything needs classification, it is very tempting to try to establish an exact definition of constipation.

Doctors need a classification, a way to diagnose precisely a condition, and that is understandable. They tend to use the ROME III diagnostic criteria(4), which we will cover in a separate article. We will talk about it because we need to stay educated about the diagnostic process a doctor runs on us. We also want to ask the right question when we visit our health care provider. They may also use the Bristol scale previously mentioned, or a combination of both.

But for you and me, we can certainly stick to a simple, non scientific definition of constipation. I personally know when I am constipated. I don’t need any questionnaire. Here is how it feels.

I have to strain and push more than usual
Stools are not coming out on their own. When we are chronically constipated, we tend to forget that during normal defection, there is barely any straining or forcing required. The defecation process is efficient enough to push the feces out mostly through an involuntary wave. With a little pushing on our part of course to get things started. Involuntary here means we have little control over it, once triggered by our push, most of the evacuation should happen on its own.

Pushing too hard, for too long, over periods of time, means we run the risk to develop the dreaded hemorrhoids. We will cover hemorrhoids in more details in a separate article.

Stools are hard, lumpy, feeling spiky and hard
This is more serious than the previous point. Sometimes the harshness creates what feels like a tear. Sometimes there is bleeding. And often there is pain, and lots and lots of frustration. In the isolation of the bathroom, tears are not unusual. To me, this should be at the top of any definition of constipation.

I have a sensation of incomplete defecation
Things are not coming out anymore, but I know I have not emptied my bowels. I still feel some bulging in my belly, a little distension. I don’t feel empty and clean.

I have a sensation of obstruction
This is what medical practitioners call “impaction”. The plug seems to be right there, behind the anus muscle. But the plug seems so big, hard and dry that I cannot evacuate it. Some may feel tempted to insert a finger to help pass the plug, or try an enema. This is pretty serious too.

Does frequency matter?
The ROME III criteria lists fewer than three bowel movements per week(4). I think this is a bit arbitrary. Granted, we are all supposed to have a bowel movement once a day. But practically in our modern society, a lot of people go less often, maybe every other day, sometimes once every three days without necessarily being constipated. I am personally not comfortable making frequency a big deal in any definition of constipation.

We are reaching the end of this article. I know you don't need an exact definition of constipation. You are mostly looking for remedies.

But all of the information we covered above is important. We need to be able to put words on this condition, to describe it clearly. This will help us better communicate with our loved ones, with our doctor, and with the community of sufferers around us. We are not alone. As a group, we can help each others.

Information is knowledge, knowledge is power.

References for "Definition of Constipation"

(1) The Lancet 29 June 1935 (Volume 225 Issue 5835 Pages 1483-1487 DOI: 10.1016/S0140-6736(01)12507-9)

(2) William E. Whitehead, “Gastrointestinal Motility Disorders of the Small Intestine, Large Intestine, Rectum, and Pelvic Floor”. International Foundation for Functional Gastrointestinal Disorders fact sheet 2001.

(3) Lewis SJ, Heaton KW (1997). "Stool form scale as a useful guide to intestinal transit time". Scand. J. Gastroenterol. 32(9): 920– doi:10.3109/00365529709011203.

(4) See

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