The process of defecation begins with a strong urge to defecate. This compelling urge to defecate drives a person to find a suitable location for defecation (such as a toilet) and adopt a suitable body position for the act of passing stools. The urge to defecate is a normal physiological sensation that is triggered by the several factors.
Why do we feel the urge to pass stool?
These are some of the factors:
- Accumulation of wastes and water in the colon causes the walls of the colon to stretch. The stretching of the walls of the colon contributes to the urge for defecation.
- An increase in intra-abdominal pressure also contributes to the urge for defecation.
- Stimulation of the bowels by nerve signals initiate the defecation reflexes.
- The urge to defecate becomes especially strong when the rectum fills up with feces.
As the rectum fills up with stools, the internal and external anal sphincters relax to allow the stools to pass out of the rectum. Once the rectum becomes empty, the urge to defecate subsides completely.
Read more on tenesmus.
In toilet -trained individuals, the urge to defecate normally occurs at similar times every day. Early morning hours are the most frequent times when the urge for defecation occurs. However, the urge to defecate could also be triggered at other times by various stimuli. Some of these stimuli include:
- Consumption of a large meal.
- Certain strong emotions.
- Pressure on the abdominal region.
- Physical activity such as brisk walking.
It is important to note that the above mentioned stimuli do not precipitate an urge to defecate on all occasions. Still, they are considered normal triggers of the urge for defecation. Good bowel habits enable one to empty the bowels regularly. Therefore, the bowels are not sensitive to these factors at all times.
Abnormal Defecation Urge
Under some circumstances, the urge for defecation may not be normal. The urge for defecation is considered abnormal when it does not precede a bowel movement and does not subside after a bowel movement. Even after sitting and straining, a person is unable to have a bowel movement in these cases. Such a persistent urge for defecation can be very uncomfortable, and even painful at times.
If a bowel movement does occur immediately, there may still be a constant feeling of incomplete bowel evacuation. There may also be itching, tenderness and pain in the rectum. This abnormal urge for defecation is technically referred to as tenesmus. It can either be intermittent or persistent. Intake of a large meal, physical activity, pressure on abdomen, and strong emotions can trigger or intensify this abnormal urge to defecate.
The normal urge to defecate is triggered when the walls of the colon and rectum get stretched due to accumulation of wastes and water. The urge to defecate may also be triggered by pressure on the walls of the colon from within the abdomen. The stretching of the walls of the colon and rectum triggers nerve impulses that are relayed to the spinal cord and back to initiate the defecation process. This neural pathway is known as the defecation reflex.
There are two types of defecation reflexes involving the colon and the rectum. They are the inhibitory myenteric reflex and the parasympathetic defecation reflex. Defecation reflexes can also involve other regions of the gut, and even other organs within the abdomen (such as stomach, small intestine, bladder, kidney and peritoneum).
Irritation, disease or stimulation of these organs can also trigger an urge for defecation that can eventually cause a bowel movement. However, the colon and the rectum are the most likely places where the defecation reflex begins.
Read more on bowel movement urging.
Causes of Abnormal Defecation Urge
The following are some of the causes of an abnormal urge for defecation.
Constipation is the most common cause of an abnormal urge to defecate. The urge to defecate can either be intermittent or constant. However, the urge is temporary. Constipation is not a disease, but a symptom. In most cases, the cause of constipation is not known.
The urge for defecation is common in hemorrhoids, which is one of the complications of constipation. Hemorrhoids refer to inflamed veins in the rectum and the anus. Tenesmus is likely to occur in cases of thrombosed hemorrhoids.
Inflammatory bowel disease
Inflammatory bowel disease (commonly abbreviated as IBD) refers to chronic inflammation of the walls of the bowels. Crohn’s disease and ulcerative colitis are the two main kinds of inflammatory bowel diseases.
Irritable bowel syndrome
Irritable bowel syndrome (commonly abbreviated as IBS) is a functional disorder of the intestine. This syndrome is characterized by episodes of constipation, diarrhea, abdominal cramps and bloating. The exact cause of irritable bowel syndrome remains unknown.
Infectious colitis refers to an infection of the colon caused by bacteria, parasites or viruses. Infectious colitis is often associated with an overgrowth of natural intestinal bacteria.
Abnormal growths such as tumors, polyps and cancers in the colon and the rectum may also be associated with an abnormal urge for defecation.
Proctitis refers to an inflammation of the rectum. This condition is often caused by an injury or infection in the rectum.
Other colorectal causes
Fecal impaction, obstipation, rectal prolapse, ischemic proctocolitis, rectal perforation, foreign body in the rectum, and perirectal abscess can all cause an abnormal urge for defecation.
Anal fissures, abscesses, fistulas, cryptitis and cancer may also cause an abnormal urge for defecation.
In females, tenesmus can be caused by endometriosis, female urethral syndrome and paraurethral gland infection. In rare cases, pelvic inflammatory disease may also cause tenesmus.
In males, inflammation of the prostate gland and prostate cancer can cause tenesmus.
Other potential causes of tenesmus include pelvic tumors, pinworms in intestine, overuse of laxatives, and AIDS enteropathy. It is important to note that these conditions do not always cause tenesmus.
Treatment for Abnormal Urging
As described above, there are a number of potential causes of tenesmus (abnormal urge for defecation). Since tenesmus is a symptom rather than a disease, treatment needs to be directed at the underlying cause of this abnormal urge for defecation.
Constipation and hemorrhoids are the two main causes of tenesmus. These conditions can be managed by certain dietary and lifestyle measures such as increased fiber intake, increased physical activity, avoiding excessive straining or sitting in the toilet for long periods of time, and using laxatives.