Understanding Colonic Function

Colonic Function

Colonic Function Absorption

The water content of faecal matter is reduced to 1000 1500 ml per day. Thus stools become solid. Similarly, sodium, potassium and bile salts are also absorbed.
The significance of this is in cases of diarrhoea, there is loss of water, sodium, potassium and other electrolytes (choleretic diarrhoea).
Amino acids and fatty acids are also absorbed slowly in the colon. After ileal resection, bile salts enter the colon and irritate the colon resulting in diarrhoea.

Colonic Function Secretion

Motility

Colon has four types of motility: Propulsive, retropulsive, mass peristalsis and gastrocolic reflux. Thus, contents travel aborally. Retropulsive activity is more in the right colon, these allowing the contents to ‘churn’ more and more. Mass contractions are found more in the left colon—especially after meals.

Factors which stimulate the colonic motility:

Colonic Function Motility Constipation:

It depends upon several factors such as food habits, genetics, and social customs.
Generally, a patient is said to have constipation if he passes less than 2 stools per week.
In addition to the low-fibre diet, emotional feelings and many rectal diseases also cause constipation. Example—prolapsed rectum, solitary rectal ulcer syndrome. Colonic diseases such as megacolon—
Hirschsprung disease is an important cause of constipation in children.
Increasing constipation in elderly patient suggest carcinoma in the left colon. Needs to be evaluated by colonoscopy.

Colonic Function Recycling

Recycling of various nutrients takes place in the colon.
Examples: Fermentation of carbohydrates, short chain fatty acids and urea cycling.
Butyrate is the main product of bacterial fermentation. It is required mainly as a fuel for colonic epithelium.
To accomplish this, the colon depends highly on its bacterial flora, especially for degeneration and fermentation ability.
So broad-spectrum antibiotics inhibit production of butyrates and produce diarrhoea.

Colonic Function Constipation:

Digestion and absorption
In a child—Hirschsprung’s disease
Adult women—idiopathic/following childbirth
Middle-aged women—following hysterectomy
Elderly man—carcinoma left colon
Constipation with severe pain—anal fissure
Depression patient—psychotropic drugs—used to treat schizophrenia, antidepressants and antiepileptic drugs

Colonic Bacteria

Anaerobic bacteria: They constitute more than 99%. The most common pathogen is Bacteroides fragilis (1010/g of faeces). Other organisms are clostridia, cocci, etc.
Aerobic bacteria: Escherichia coli is the most common organism about 107/g of faeces. Other organisms are Klebsiella, Proteus and Enterobacter.
Normal function: Bacteria degrade bile pigments, thus resulting in brown-coloured stools. They also help in colonic motility and absorption. Fatty acids produced by bacteria supply nutrition to the colonic epithelium. Bacteria also supply vitamin K to the host.

Prebiotics and Probiotics

Colonic Function Prebiotics:

Prebiotics are non-digestible food ingredients that stimulate the growth and/or activity of bacteria in the digestive system in ways claimed to be beneficial to health.
Traditional dietary sources of prebiotics include soybeans, inulin sources (such as Jerusalem artichoke, jicama, soya and chicory root), raw oats, unrefined wheat, unrefined barley, and yacon.

Colonic Function Probiotic:

Probiotic is defined as a “live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance”.
They are non-degradable oligosaccharides. They stimulate the growth of beneficial intestinal bacteria.
Probiotics are dietary supplements which contain live cultures of bacteria and yeast that are beneficial to colonic and host function. The common species used as probiotics are Lactobacillus and Bifidobacterium.
Probiotics stimulate immune function, exhibit anti-inflammatory properties and suppress pathogenic organism.

Prebiotics and Probiotics Clinical application:

When a person takes antibiotics, both the harmful bacteria and the beneficial bacteria are killed. Bacterial change in flora alters carbohydrate metabolism with decreased short-chain fatty acid absorption and results in osmotic diarrhoea.
In a similar fashion, antibiotic therapy causes an increase in the growth of Clostridium difficile. Thus, probiotics have been recommended for antibiotic-induced diarrhoea.
Also, they have been used to treat diarrhoea in ulcerative colitis, in pouchitis (inflammation of the pouch after total proctocolectomy for ulcerative colitis) and in necrotising colitis in children.