Constipation: A Common Health Problem

adminMarch 25, 2024

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Introduction

Constipation is a common functional gastrointestinal disorder, with prevalence in the general population of approximately 20%. In the elderly population the incidence of constipation is higher compared to the younger population, with elderly females suffering more often from severe constipation¹.

It is a pathological decrease in bowel movements associated with unpleasant sensations ranging from slight discomfort to bloating to pain. Indeed, patients from rural areas even report headaches and stiffness of neck. Whilst these symptoms may seem scientifically unsound, their suffering is real and could actually have a scientific explanation in that impulses arising from the normally-empty rectum now filled with fecal matter reach conscious level.

Constipation rarely causes any complications or long-term health problems and treatment is usually effective, particularly if it is started promptly. However, long-term (chronic) constipation may lead to complications²

Chronic constipation

Chronic constipation refers to the presence of two or more of the following symptoms for the last three months³

Passing fewer than three stools a week
Having lumpy or hard stools
Having to strain to stimulate bowel movements
Feeling as though there is a blockage in the rectum that prevents bowel movements
Feeling as though stool cannot be completely emptied from the rectum
Needing help to empty the rectum, such as having to press on the abdomen and using a finger to remove stool from the rectum. Vaginal splinting (use of fingers to press on the vagina to help ease stool out of the rectum) is also used

Physiology of defaecation

Bowel habits are very variable, the range of frequency of evacuation accepted as being three times a week to three times a day. External influences like being out of the house, or intense interest in work, or psychological factors could also affect the frequency. Many people do not like using public toilets and the urge to evacuate is suppressed. As we grow older, stool quantity is reduced and all reflexes become less efficient. As a consequence, elderly people need to ensure that they evacuate regularly. The late Professor U Aung Than Batu often mentioned that he would add the time for evacuation to the time required for preparing to go out in the morning. This is a good practice that elderly people should adopt.

The defaecation reflex

Defaecation is a reflex integrated at the level of the spinal cord (Fig.1). The rectum is normally empty, but distension of the rectum by the arrival of faecal matter initiates contractions of the sigmoid colon and rectum and causes the desire to defaecate. The pelvic nerve serves as both the afferent and efferent limbs, just like in the micturition reflex. The sympathetic nerve to the internal (involuntary) sphincter is excitatory whilst the parasympathetic nerve (pelvic nerve S2, 3, 4) is inhibitory. The first urge to void is felt at an intrarectal pressure of 18 mm Hg but can be controlled by contraction of the external sphincter (under the control of the pudendal nerve, a somatic nerve). Initiation of evacuation is a voluntary act. Control is lost when the intrarectal pressure exceeds 55 mm Hg1 as in diarrhoea; or when the external sphincter is ineffective.

Fig.1 The defecation reflex

The pelvic nerve (S2, 3, 4 parasympathetic nerve) stimulates the colon and rectum to contract and the internal anal sphincter to relax. Defaecation may be prevented by contraction of the external sphincter. Source: Human Anatomy and Physiology. EN Marieb& K Hoehn.9^thed.Pearson.

Voluntary defaecation can be initiated by straining before the pressure that relaxes the internal sphincter is reached. Normally, the angle between the anus and the rectum is approximately 90 degrees (Fig.2) and this, plus contraction of the puborectalis muscle prevents defaecation. With straining, the glottis is closed, abdominal muscles contract, intra-abdominal pressure rises (the “Valsalva manoeuvre”), the pelvic floor is lowered 1 to 3 cm and the puborectalis muscle relaxes. The anorectal angle is reduced to 15 degrees or less (the squatting type lavatory is believed to lessen the angle even more). This is combined with relaxation of the external sphincter and defaecation occurs. The puborectalis muscle (which forms the levatorani muscle together with the pubococcygeus and iliococcygeus muscles) forms a sling around the lower rectum when it meets the fibres from the opposite side. It acts in association with the internal and external anal sphincter in the process of defecation.

Fig.2 The anorectal angle at rest and during straining,
Source: Ganong.s Review of Physiology. Ed, KE Barrett & SM Barman.International edition,.McGrawMedical

Factors influencing defaecation

Defaecation may be influenced by psychological, neural, hormonal, mechanical and the bulk and consistency of stools. Some people defer defaecation until they get back home or finish tasks being done, with the consequence that more water is reabsorbed in the colon. The stools become harder and difficult to evacuate. Autonomic neuropathy affects the reflex. It is recommended that constipation is a symptom that should be specifically asked for in patients with longstanding diabetes mellitus. Stress hormones can affect motility and progesterone, produced in large amounts in pregnancy, may cause constipation due to its relaxing action on smooth muscles. The thyroid hormones affect gut motility and hypothyroidism may present as constipation. Electrolyte disturbances can also be a cause of constipation in the elderly. Diverticulosis may cause constipation as stools cannot pass with ease through the affected area. Although faeces are not composed of undigested food, diet has an influence on bowel habits. The defaecation reflex is initiated by the arrival of fecal matter in the sigmoid colon and rectum, the volume of fecal matter should be sufficient to stretch the wall of the colon. Fibre contained in vegetables and fruit give roughage and increase stool bulk. Large quantities of water also help.

The gastrocolic reflex

Potty training in children depends on this reflex. When food or drink enter the stomach, impulses arise from the stomach to stimulate the contraction of the colon, probably also through the action of gastrin released from the stomach. Many adults also drink water or a beverage on waking up and rely on this reflex.

Alteration in the gastrocolic reflex has been a suspected aetiology in patients with irritable bowel syndrome (IBS). Patients with IBS have demonstrated a stronger colonic response to the gastrocolic reflex

The Mass Reflex

This reflex may be used to give a degree of bladder and bowel control in patients with spinal cord injury. It may be initiated by stroking the skin of the thigh, and results in evacuation of the bladder and rectum accompanied by sweating, pallor and blood pressure swings in addition to the withdrawal response.

Stress and constipation.

Researchers have also identified several ways in which stress can cause constipation4:

In stressful situations, the body’s adrenal glands release epinephrine, which plays a role in the so-called fight-or-flight response. It causes the body to divert blood flow from the intestines toward vital organs, such as the heart, lungs, and brain. As a result, intestinal movement slows down, and constipation can occur.
In response to stress, the body releases more corticotrophin-releasing factor (CRF) in the bowels. This hormone acts directly on the intestines, which it can slow down and cause to become inflamed. The intestines have different types of CRF receptors, some of which speed up processes in the intestines, while others slow them down.
Stress causes increased intestinal permeability. This permeability allows inflammatory compounds to come into the intestines, which can lead to a feeling of abdominal fullness – a common complaint among people who struggle with constipation.
Stress may affect the normal healthy bacteria in the gut. Research has not confirmed this theory, but many people believe that stress may reduce the number of healthy gut bacteria in the body, thus slowing digestion.

Prevention of constipation

Constipation is uncomfortable and inconvenient. If untreated, chronic constipation might result in hemorrhoids, anal fissure, fecal impaction or rectal prolapsed. A healthy lifestyle and bowel training5can prevent constipation. Bowel training or retraining refers to behavioral programs designed to help people with bowel disorders (inability to control bowel movements, incomplete emptying, or chronic constipation) establish or re-establish control. Bowel training involves three basic principles:

Improve consistency of stool:
The optimal goal for stool consistency is a formed, soft stool
Hard stools are difficult to evacuate and leakage is more likely if stools are liquid. One should eat well-balanced, regularly timed meals that are high in fibre. Dietary fibre refers to the parts of the food that humans are unable to digest. This includes whole grains, legumes, fresh fruits, and vegetables. Fibre adds bulk to the stool, eliminates excess fluids, and promotes more frequent and regular movements. With increasing fibre it is important to drink enough fluids. If fluid intake is inadequate, the stool becomes hard because less water is retained in the large intestine. The amount of fibre and fluids necessary for optimal bowel function varies among individuals.
Establish a regular time for elimination.
A bowel training program needs to occur at the same time each day and should not be rushed.
Stimulate emptying on a routine basis
A stimulus of some kind may be needed to help empty the rectum. The stimulus will vary from individual to individual. The stimulus creates peristalsis of the colon. A meal or hot drink may stimulate some persons. Others may need to use suppositories, enemas or laxatives (only under the advice of a physician) or a combination of the above. One should use the least stimulus that is effective to promote evacuation.

References

Rogue.MV &Bouras.EP. 2015. “Epidemiology and management of chronic constipation in elderly patients”.Clin.Interv.Aging, 10. 919-930.
https://www.nhsinform.scot/illnesses-and-conditions/stomach-liver-and-gastrointestinal -tract/constipation
https://www.mayoclinic.org/diseases-conditions/constipation/symptoms-causes/syc-20354253
Nail R, 2019.” How is stress linked with constipation?” Medical News Today https://www.medicalnewstoday.com › articles
Bowel Control Bowel Retraining: Strategies for Establishing Bowel Control https://aboutconstipation.org › Treatmen