The passage of food through the digestive tract is not a passive process. Gravity plays a minor role but movement is mainly made possible by the muscles present in the walls of the gut. These muscles contract and relax in a rhythmic fashion to push food through the digestive tract. These rhythmic contractions and relaxations are known as peristaltic movements. The movement of food through various parts of the digestive tract is not possible without these peristaltic gut movements.
Movement Through The Bowels
We often think that defecation starts and ends with the lower bowels like the colon. However, this would not be possible with movement at the start of the gut. The process of peristalsis or peristaltic movements of the gut muscles are not spontaneous or voluntary. These are mainly involuntary movements controlled by the nervous system. The muscles outside the gut wall, such as the muscles of the pelvic floor, also facilitate gut movements to some degree.
As the peristaltic movements push food through the upper parts of the gut, the food gets digested and nutrients are absorbed. By the time the food reaches the colon (lower gut), most of the nutrients have been absorbed. In the colon, water is reabsorbed from the gut lumen, resulting in formation of solid (yet soft) stools. The stool is stored in the colon till the time of defecation.
For the act of defecation, strong contractions of the muscles in the walls of colon push the stool into the rectum. When the walls of the rectum get stretched due to the stool, an urge to defecate is felt. This motivates the person to find an appropriate place and adopt the appropriate posture for defecation. Contraction of muscles in the abdominal and pelvic walls during straining, increases the pressure in the rectum and relaxes the anal sphincter muscles. This causes the stool to be squeezed out of the rectum, and it passes into the external environment through the anus.
Meaning of Weak Bowel Movement
The term “weak bowel movement” refers to different types of bowel symptoms. Two of the most common conditions characterized by weak bowel movements are constipation and bowel incontinence. In constipation, weak bowel movements lead to difficulties in passing stool. In bowel incontinence, a person is unable to hold defecation voluntarily. Both these conditions are very different. However, they are both classified as weak bowel movements since the underlying problem is similar: weak muscular actions in specific regions of the lower part of the bowels (colon, rectum, and anus).
Symptoms of Weak Bowel Movements
Even though both constipation and bowel incontinence are due to weak bowel movements, it may produce different symptoms.
By definition, constipation refers to a condition in which the frequency of defecation is less than three times per week. The stool itself is hard, and a person has great difficulty in eliminating it even after straining a lot. Other symptoms may also be present. For example, there may be a constant urge to defecate, and a feeling of incomplete defecation even after the act. This is also referred to as incomplete bowel movement.
A constipated person may also suffer from abdominal pain or cramps. Nausea and vomiting also occur, albeit rarely. Constipation is a very common problem that affects both children and adults. Even though it is not considered a serious ailment, constipation can be debilitating and can disrupt the quality of life significantly. Further complications, such as fecal compaction, could also occur.
Also read irregular bowel movements.
In contrast to constipation, which is characterized by a difficulty in passing stools, bowel incontinence refers to a condition in which a person has difficulty in preventing defecation. Even though bowel movements are largely involuntary, some voluntary control of defecation is possible. This allows a person to hold defecation till an appropriate place and time is found. However, this control is not absolute, and there is a point beyond which preventing defecation is not physiologically possible. In people who suffer from bowel incontinence, this threshold is much lower than in normal people.
The main symptom of bowel incontinence is an involuntary passing of fecal material, which results in the soiling of undergarments. The amount of fecal material that involuntarily gets out varies, and ranges from tiny amounts to a full bowel emptying. Bowel incontinence can either be acute or chronic. Acute bowel incontinence is typically seen in diarrhea, and happens only once or twice. Chronic bowel incontinence happens over a long time, and is usually a result of some permanent damage to the tissues that facilitate control of bowel movements.
Bowel incontinence is commonly associated with other conditions such as diarrhea, bloating, excessive gas production, and constipation. It is more common in women. However, it is not restricted to any gender or age. There is significant psychosocial impact of fecal incontinence, and the sufferers may have other psychological problems.
Also read leaky anus.
Causes of Weak Bowel Movements
There are multiple causes for different kinds of weak bowel movements. Some of the causes for constipation and bowel incontinence are discussed below but ut is important to understand that the exact cause of constipation is usually difficult to identify. Constipation could be a result of any of the following:
- Slow gut: Constipation is largely believed to be due to sluggish bowel movements. The exact cause is not always known. When no physical abnormalities in the bowels are detectable, then the constipation is termed as functional constipation.
- Lack of fiber: Fiber in the diet is important for proper stool formation and smooth bowel movements. Lack of dietary fiber may cause constipation.
- Inadequate hydration: Before defecation, stool becomes solid due to re-absorption of water in the colon. It remains soft even after this water re-absorption stage. However, too much re-absorption of water may lead to hardening of the stools, which can lead to constipation.
- Sedentary lifestyle: Lack of regular exercise and a sedentary lifestyle is associated with constipation.
- Obstruction in gut: Constipation may also occur if there is any obstruction to the movement of stools in any part of the gut.
- Muscle problems: Peristaltic movements of the colon are mediated by the rhythmic contractions and relaxations of the smooth muscles in the walls of the colon. Any problem with this musculature may affect transit of stools through the colon, and cause constipation.
- Nerve problems: Nerve problems in the colon or the rectum may also cause constipation due to faulty peristaltic movements.
Bowel incontinence could be found in any of the following conditions:
- Damage to the nerves of colon, rectum or anus.
- Problems with muscles of the lower gut or pelvic floor.
- Rectal prolapse.
- Surgery of rectum or anus.
- Acute diarrhea.
- Chronic constipation.
- Mental abnormalities (such as dementia).