Chronic Constipation | Causes, Types & Treatment

Chronic constipation - constipation lasting 3 months or more - has three distinct physiological subtypes that require different approaches. Most cases are functional (no structural cause) and respond to dietary and lifestyle changes. Persistent chronic constipation that does not respond to treatment needs anorectal evaluation and colonoscopy to identify structural, motility, or functional causes.

Chronic constipation is not a single condition - it is a symptom complex with multiple physiological subtypes. The distinction between these subtypes matters because treatment differs significantly. A patient with slow transit constipation needs a different management approach from one with obstructed defecation syndrome, even though both present with chronic difficulty with bowel movements.

Three Subtypes of Chronic Constipation

How Each Subtype Presents

Normal transit constipation

Patient complains of hard or lumpy stools that require effort to pass, even though bowel movements may occur 3-4 times per week. Adequate fibre and water intake typically resolves this. Often linked to stress, irregular meals, and insufficient dietary fibre.

Slow transit constipation

Patient has very infrequent bowel movements - sometimes just once or twice per week or less. They do not feel the urge to defecate. Abdominal bloating is prominent. Even high-dose laxatives may have limited effect. This subtype is more common in women and may require specialist assessment including colonic transit study and possibly stimulant laxative regimens or newer motility agents.

Obstructed defecation syndrome (ODS)

Patient strains excessively at stool, has a sensation of blockage or obstruction at the anal passage, and often achieves only partial evacuation. They may need to press around the perineum, splint the vagina, or use digital assistance. ODS is commonly caused by paradoxical puborectalis contraction (the muscle contracts instead of relaxing during defecation), rectocele (a bulging of the rectum into the vagina), or enterocele. Diagnosed by anorectal manometry, defecography, and examined by colorectal specialist.

Red Flags

Investigations for Chronic Constipation

• Blood tests: TSH (hypothyroidism), blood glucose (diabetes), calcium, full blood count (anaemia)
• Colonoscopy: Essential when red flags present or above age 45. Excludes colorectal polyps, cancer, stricture, and inflammatory bowel disease.
• Anorectal manometry: Measures sphincter pressures, rectal sensation, and the defecation reflex. Diagnoses paradoxical puborectalis contraction (ODS), Hirschsprung's disease, and sphincter dysfunction.
• Defecography (proctography): Dynamic X-ray or MRI study of defecation. Identifies rectocele, enterocele, rectal intussusception, and pelvic floor weakness.
• Colonic transit study: Patient swallows radio-opaque markers; X-rays at day 3 and day 5 show how quickly markers move through the colon. Diagnoses slow transit constipation.

Treatment by Subtype

Normal transit constipation

• High-fibre diet (25-35g/day) and 2-3L water per day
• Regular exercise
• Osmotic laxatives (lactulose, PEG) for short-medium term
• Isabgol (psyllium husk) as a daily supplement

Slow transit constipation

• High-dose osmotic laxatives
• Stimulant laxatives (bisacodyl, senna) - under medical supervision
• Newer prokinetic agents (prucalopride, linaclotide) - specialist prescription
• Surgery (subtotal colectomy) - only for highly refractory cases after full evaluation

Obstructed defecation syndrome

• Biofeedback therapy - retraining paradoxical puborectalis contraction; highly effective for functional ODS
• Pelvic floor physiotherapy
• Surgical correction for rectocele when large and symptomatic - laparoscopic or transanal approach

Frequently Asked Questions