The food and beverages that we consume through the mouth travel down the alimentary canal before being transformed and expelled as feces. Along the way, various mechanical, chemical and enzymatic processes break down (digest) the components in the food, allowing absorption of the released nutrients.
The unabsorbed food components and waste produced in the intestine are then eliminated as feces. The passage of food, fluids and feces down the alimentary canal is mainly regulated by rhythmic contractions and relaxations of the walls of this passage. Gravity plays only a small role in enabling the movement of food in the bowels.
Motion Through The Bowels
The rhythmic contraction and relaxation of the walls of the bowel are termed as peristaltic movements of the gut. These rhythmic contractions and relaxations are caused by contraction and relaxation of the smooth muscles that are present in the walls of the bowels. These muscles are not under voluntary control. The type of movements that occur in different parts of the alimentary canal vary.
For example, the types of movements that happen in the small intestine and the large intestine are slightly different. There are two main types of movement that occur in the small intestine and the large intestine. These are:
- Segmentation contractions: Segmentation contractions mainly occur in the small intestine, where the majority of digestion and absorption of nutrients occurs. Segmentation contractions churn the food and expose the broken down mush for absorption of nutrients and water by the cells in the intestinal wall.
- Peristaltic waves: Peristaltic waves propel the food and feces onward through the intestinal passage.
A combination of peristaltic waves and segmentation contractions help in extraction and absorption of nutrients from the food that we eat, and also cause expulsion of waste as feces. Both types of contractions are initiated when the bowel walls get stretched by the incoming content (food or waste).
Nervous system input from brain and spinal cord also influence these contractions in both presence and absence of food. Additional factors influencing these bowel movements include physical exercise, the act of eating, psychological factors such as stress and other emotions, and even the time of day.
Problems With Bowel Motions
Bowel motility disorders (also called intestinal motility disorders), refer to conditions in which the bowel movements are abnormal. In rare cases, all motility may cease. However, in the majority of intestinal motility disorders, bowel motility happens either at an abnormally fast rate or at an abnormally slow rate. For example, bowel motility is abnormally rapid in case of diarrhea, and abnormally slow in case of constipation. In either case, processes of digestion, absorption and feces production are adversely affected.
Read more on lazy bowel syndrome.
Signs and Symptoms
Bowel motility disorders affect the processes of digestion, absorption, and movement of digested material through the intestine. Adverse effects on these processes causes a variety of signs and symptoms. Some of the common signs and symptoms of bowel motility disorders include:
- Acid reflux
- Regurgitation of food
- Bloating sensation caused by a distension of abdomen
- Abdominal discomfort
- Abdominal pain
- Malnutrition caused by inefficient digestion and absorption
- Loss of appetite
- Weight loss
Not all of the above mentioned signs and symptoms are present in all cases. The exact signs and symptoms present in an individual depends on the underlying cause of bowel motility disorder. Even for the same cause, signs and symptoms may vary between individuals.
Causes of Bowel Motility Disorders
Bowel motility disorders are mainly caused by a disruption of the coordinated contraction and relaxation that needs to happen in various parts of the gut. It is rare for the contractions to stop entirely. Intestinal motility may get affected due to the following causes:
Problem with gut muscles and nerves
The segmentation contractions and peristaltic waves in the gut are a result of coordination between the smooth muscles and the nerves of the gut. Therefore, nerve and muscle disorders may compromise bowel motility. In fact, bowel motility disorders are seen in some degenerative conditions of the nerve and the muscle.
Read more on weak bowel movements.
Side effects of certain medicines
Bowel motility can also be affected by certain medicinal drugs. For example, gut motility is known to be completely inhibited by opioid painkillers and anesthetics. Other drugs that can cause bowel motility disorders include chemotherapeutic agents, laxatives, tricyclic antidepressants, lithium, and diuretics.
Endocrine disorders such as hypothyroidism and diabetes are known to cause bowel motility disorders. Bowel motility disorder in diabetes is mainly due to diabetic neuropathy.
Constipation is seen in conditions such as pregnancy, inadequate fluid intake, and old age. Dietary factors and many other causes can also result in constipation. Irritable bowel syndrome is characterized by intestinal motility disorders. However, the cause is not known. Aging, nerve disease or injury, diabetes, and food intolerance are associated with fecal incontinence.
In some cases, bowel motility disorders may occur without any identifiable reason. These conditions with unknown causes are labeled as idiopathic.
Treatment for Bowel Motility Disorders
The appropriate treatment for a case of bowel motility disorder can only be determined after determining the cause and nature of the disorder. However, the cause is not apparent or identifiable in all cases. Medication and surgery are the two main modes of treatment used for bowel motility disorders.
Depending on the cause and nature of abnormal gut motility, a variety of medications are used. For example, anti-diarrheal medications (such as loperamide) are used to slow down gut contractions and motility. On the other hand, prokinetic agents are used to increase gut peristalsis and motility.
Opiod reversal agents (such as methylnaltrexone) are used to combat the effects of opiod painkillers on gut motility. Cholinergic agonists are used to stimulate parasympathetic nervous system that regulates gut motility. Antibiotics (such as erythromycin) are also used to increase the rate of gastric emptying.
In cases where medication is not effective, surgery may be considered. In acute cases that cause severe signs and symptoms, endoscopic decompression is the first line of treatment. Surgery is an option in chronic cases of bowel motility disorders. Surgical treatment may involve removal of a part of the intestine (also called intestinal resection).
Both small bowel resection and large bowel resection are possible surgical options. In cases of intestinal resection in which the remaining cut ends of the bowels are not close enough to be joined, an opening is made in the abdominal wall to connect the end of the bowel and provide an outlet for waste. This procedure is known as ostomy.