Constipation is defined as infrequent bowel movements (two or fewer per week), difficulty in passing stools, hard or dry stools, and a sensation of incomplete evacuation. It is common among the elderly (up to 20%), middle-aged adults (8%) and young people (around 3%).
It is not a disease but a symptom of an underlying problem. Common contributing factors include poor diet, low fibre intake, dehydration, lack of exercise, certain disease conditions and multiple medications.
Causes of Constipation
a) Gastrointestinal Causes
- Obstruction due to ulcers or cancer
- Irritable bowel syndrome
- Diverticulitis
- Hemorrhoids
- Anal fissures
- Ulcerative proctitis
- Colorectal tumors
b) Metabolic & Endocrine Causes
- Diabetes mellitus
- Hypothyroidism
- Panhypopituitarism
- Pheochromocytoma
- Hypocalcemia
c) Pregnancy
Hormonal changes and reduced bowel movement can cause constipation during pregnancy.
d) Neurogenic Causes
- Head trauma
- Brain or spinal tumors
- Stroke
- Parkinson’s disease
e) Psychogenic Causes
- Depression
- Anxiety
- Ignoring bowel movements regularly
Pathophysiology
The gastrointestinal tract is divided into the upper and lower tract. The upper tract digests food, while the lower tract conserves water, forms stool and eliminates waste.
Stool movement depends on peristalsis—wave-like muscle contractions that push contents forward. When stool reaches the rectum most water is absorbed, making it solid.
Normal intestinal function relies on:
- Osmotic gradients regulating water and electrolyte absorption
- Autonomic nervous system control
Slower intestinal transit means more water is absorbed, making stools hard and dry.
Key mechanisms causing constipation:
- Increased fluid absorption
- Reduced intestinal motility
- Drugs with anticholinergic effects (e.g., antihistamines, antidepressants)
- Opioids → increase sphincter tone, suppress peristalsis and reduce rectal sensitivity
Management of Constipation
General Measures
- Increase dietary fibre (fruits, vegetables, cereals)
- Drink at least 2 litres of water per day
- Regular exercise
- Avoid excessive coffee and tea
- Establish routine bowel habits
- Identify and manage the underlying medical condition
- Review medications that cause constipation and adjust if needed
Pharmacological Management
Laxatives are chosen based on required speed of action.
1. Laxatives that Soften Stool in 1–3 Days
a) Bulk-Forming Laxatives
Increase stool bulk by absorbing water → stimulate peristalsis. Useful for chronic constipation.
b) Emollient (Stool Softener) Laxatives – Docusates
- Act as surfactants — mix water and fats with stool
- Increase secretion of water/electrolytes in intestine
- Useful to prevent constipation, not treat it
- Helpful after heart attack, rectal surgery, or anal disorders where straining must be avoided
c) Lactulose & Sorbitol
Lactulose is an osmotic laxative retained in the colon. Useful in elderly patients but may cause flatulence, cramps or diarrhea.
Sorbitol is equally effective and more economical; preferred for functional constipation.
2. Laxatives that Produce Semi-Fluid Stool in 6–12 Hours
a) Stimulant Laxatives
- Bisacodyl
- Senna
Increase intestinal motility and secretion; useful for acute constipation.
3. Laxatives that Cause Watery Evacuation in 1–6 Hours
a) Saline Cathartics
- Contain magnesium, sulfate, phosphate or citrate ions
- Produce strong osmotic effect → retain water in intestine
- Work within a few hours (or within 1 hour rectally)
Used for:
- Bowel cleansing for diagnostic procedures
- Treatment after poisoning
- Eliminating parasites after anti-helminthic treatment
Example: Milk of magnesia — safe for occasional use but not for routine daily treatment.
b) Castor Oil
Converted to ricinoleic acid in the intestine → stimulates secretion and motility. Acts within 1–3 hours. Not recommended for routine use due to strong purgative action.
c) Polyethylene Glycol (PEG) Solutions
Cause rapid evacuation; used mainly for colon cleansing.
Rectal Agents
a) Glycerin Suppository
- Works by osmotic action in rectum
- Onset in less than 30 minutes
- Safe for children and adults
- May cause mild rectal irritation
b) Tap-Water Enema
- 200 mL water can stimulate bowel movement within 1.5 hours
- Useful for simple, occasional constipation
Detailed Notes:
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