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Constipation

SNOMED: 389082000982 words•Updated 03/03/2026
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Exam Tips

  • In OSCEs, define constipation by patient-normal pattern plus Rome-style features; do not rely on stool frequency alone.
  • Always ask and safety-net for red flags: rectal bleeding, weight loss, iron-deficiency anaemia, persistent abdominal pain, or new bowel habit change.
  • DRE is high-yield: can diagnose impaction, anorectal pathology, and suggest dyssynergia.
  • If overflow diarrhoea coexists with hard stool history, think faecal impaction rather than infective diarrhoea.
  • Treat impaction first, then stepwise maintenance (lifestyle -> osmotic +/- stimulant), and review constipating medicines.

Definition

Constipation is a symptom-based bowel disorder in which defecation is persistently difficult, infrequent, or perceived as incomplete, often with hard or lumpy stool and straining. In adults, fewer than 3 spontaneous bowel movements per week supports the diagnosis, but UK practice also emphasizes change from the person’s usual bowel pattern. Chronic constipation usually implies symptoms for at least 3 months, and may progress to faecal loading or impaction.

Pathophysiology

Constipation reflects disordered colonic transit, anorectal evacuation, or both. Slow-transit constipation involves reduced propulsive colonic motility, causing prolonged stool residence time, excess water reabsorption, and harder stool. Defecatory disorders (dyssynergic defecation) involve paradoxical pelvic floor/anal sphincter contraction or inadequate relaxation during straining, so stool reaches the rectum but is not expelled effectively. Secondary mechanisms include medication effects (for example opioid-mediated reduced enteric neuronal acetylcholine release and increased sphincter tone), metabolic/endocrine disturbance (for example hypothyroidism, hypercalcaemia), neurological disease, and structural colorectal pathology.

Risk Factors

  • Female sex
  • Older age and institutional living
  • Low-fibre or low-calorie intake
  • Poor fluid intake/dehydration
  • Reduced mobility or immobility
  • Toileting barriers (poor privacy, difficult access, ignoring urge)
  • Socioeconomic deprivation and lower educational attainment
  • Anxiety, depression, eating disorders, somatization
  • Pregnancy
  • Family history of constipation
  • Constipating medicines (opioids, antimuscarinics, tricyclic antidepressants, antipsychotics, calcium-channel blockers, iron/calcium supplements, diuretics)

Clinical Features

Symptoms

  • Infrequent bowel motions (often <3/week) or less frequent than personal baseline
  • Hard, dry, lumpy, pellet-like, or very large stools
  • Excessive straining
  • Sensation of incomplete evacuation
  • Sensation of anorectal blockage
  • Need for manual manoeuvres to pass stool
  • Abdominal bloating or distension
  • Lower abdominal discomfort/pain
  • Overflow loose stool or faecal leakage (suggesting impaction)
  • In older adults: delirium/confusion, anorexia, nausea, functional decline, urinary retention

Signs

  • Palpable faecal loading on abdominal or rectal examination
  • Abdominal distension
  • Anal fissure, haemorrhoids, skin tags, excoriation from leakage
  • Rectocele or rectal prolapse
  • Reduced or abnormal anal sphincter tone
  • Paradoxical sphincter contraction on bearing down (pelvic floor dyssynergia)
  • Red-flag signs: weight loss, rectal bleeding, abdominal mass, iron-deficiency anaemia

Investigations

Clinical diagnosis with focused history + Bristol Stool Form Scale:Typically type 1-2 stool forms and supportive symptom pattern; use stool chart for objective monitoring (See Figure: Bristol Stool Form Scale).
Digital rectal examination (DRE):May show hard stool in rectum, fissure/haemorrhoids, prolapse, rectocele, dyssynergic pelvic floor, or palpable rectal mass.
No routine blood/imaging tests if typical functional constipation and no red flags:Normal initial assessment with no features suggesting malignancy, obstruction, inflammatory disease, or significant systemic cause.
Targeted blood tests when secondary cause suspected (FBC, U&E, calcium, TFT, glucose +/- CRP):May identify anaemia, electrolyte disturbance, hypercalcaemia, hypothyroidism, renal dysfunction, or diabetes-related contributors.
Urgent lower GI cancer pathway assessment if alarm features:Required for sudden persistent bowel habit change, rectal bleeding, unexplained weight loss, abdominal/rectal mass, or iron-deficiency anaemia.

Management

Lifestyle Modifications

  • Clarify normal bowel pattern and set realistic goals (symptom control, regular comfortable stool rather than daily stool)
  • Increase dietary fibre gradually (aim about 20-30 g/day total intake) and optimize hydration
  • Regular physical activity and mobility support
  • Toileting routine after meals (gastrocolic reflex), unhurried privacy, respond promptly to urge to defecate
  • Review and reduce constipating drugs where possible
  • Treat faecal impaction first before maintenance regimen

Pharmacological Treatment

Bulk-forming laxative

  • Ispaghula husk 1 sachet in water once or twice daily (can increase if needed)

Useful if low fibre intake; ensure adequate fluid to reduce obstruction risk. Avoid if suspected bowel obstruction or severe faecal impaction until impaction is treated.

Osmotic laxatives (first-line common UK choice)

  • Macrogol 3350 compound: 1 sachet daily, titrate up to 2-3 sachets/day
  • For faecal impaction: macrogol up to 8 sachets/day in divided doses for up to 3 days
  • Lactulose 15 mL twice daily then adjust (commonly 10-15 mL twice daily maintenance)

Macrogols often preferred in chronic constipation and in impaction pathways. Avoid/caution in bowel obstruction; monitor for bloating and electrolyte disturbance in frail patients.

Stimulant laxatives

  • Senna 15 mg at night (usual range 7.5-30 mg nocte)
  • Bisacodyl 5-10 mg at night orally
  • Bisacodyl suppository 10 mg rectally when rapid effect needed

Add if stool remains difficult despite osmotic therapy or if opioid-related hypomotility. Contraindicated in intestinal obstruction/acute surgical abdomen.

Stool softener / rectal options

  • Docusate sodium 100 mg twice to three times daily (up to 500 mg/day in divided doses)
  • Glycerol suppository 4 g PR as needed

Can be useful when straining should be minimized (for example painful anorectal disease). Rectal therapies may be needed in distal loading.

Second-line specialist options for chronic idiopathic constipation after laxative failure

  • Prucalopride 2 mg once daily (1 mg once daily if older/frail or severe renal impairment)
  • Linaclotide 290 micrograms once daily
  • Lubiprostone 24 micrograms twice daily

Use according to UK licensing/local specialist guidance. Exclude mechanical obstruction first. Prucalopride is contraindicated in intestinal perforation/obstruction and severe inflammatory bowel conditions.

Opioid-induced constipation (if persistent despite laxatives)

  • Naloxegol 25 mg once daily (reduce to 12.5 mg if not tolerated or interacting medicines)
  • Methylnaltrexone 12 mg subcutaneously on alternate days (weight-adjusted alternatives per product guidance)

Peripherally acting mu-opioid receptor antagonists can help refractory opioid constipation. Avoid in known or suspected GI obstruction; check interaction profile (especially CYP3A4 inhibitors with naloxegol).

Surgical / Interventional

  • Manual disimpaction/enemas for severe refractory faecal impaction
  • Biofeedback therapy for confirmed dyssynergic defecation (specialist pelvic floor service)
  • Selected refractory slow-transit constipation: specialist consideration of subtotal colectomy with ileorectal anastomosis after full physiological work-up

Complications

  • Faecal loading and impaction
  • Overflow faecal incontinence
  • Haemorrhoids and anal fissure
  • Megacolon from chronic retention
  • Bowel obstruction, stercoral ulceration, or perforation (rare but serious)
  • Rectal prolapse
  • Urinary retention, recurrent UTIs, obstructive uropathy
  • Reduced quality of life, social distress, and recurrent hospital admission

Prognosis

Prognosis is variable and depends on cause, comorbidity, and adherence to long-term bowel habit measures. Many patients need prolonged lifestyle and laxative therapy, and symptoms can persist for years, especially in IBS-C and severe functional constipation. Although usually not life-threatening, morbidity is substantial; faecal impaction can require urgent hospital treatment.

Sources & References

💊BNF Drug References(27)

✅NICE Guidelines(1)

📖Textbook References(6)

  • Guyton and Hall Textbook of Medical Physiology (John E. Hall, Michael E. Hall) (Z-Library).pdf(pp. 826)[context]
  • Guyton and Hall Textbook of Medical Physiology (John E. Hall, Michael E. Hall) (Z-Library).pdf(pp. 794)[context]
  • Guyton and Hall Textbook of Medical Physiology (John E. Hall, Michael E. Hall) (Z-Library).pdf(pp. 829)[context]
  • Guyton and Hall Textbook of Medical Physiology (John E. Hall, Michael E. Hall) (Z-Library).pdf(pp. 826)[context]
  • Guyton and Hall Textbook of Medical Physiology (John E. Hall, Michael E. Hall) (Z-Library).pdf(pp. 826)[context]
  • [Williams, Bailey and Love's Short Practice of Surgery] Norman Williams, Christopher Bulstrode, P Ronan O'Connell - Bailey & Love's Short Practice of Surgery 26E (2013, CRC Press) - libgen.li.pdf(pp. 1195, 1196)[context]

Sources

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