Constipation

Introduction

Constipation is a common gastrointestinal symptom characterised by infrequent, difficult, or incomplete bowel movements. It is typically defined as having fewer than three bowel movements per week, often associated with straining, hard stools, or a sensation of incomplete evacuation. It may be functional (primary) or secondary to underlying causes such as medication, metabolic disorders, or structural abnormalities.

Peak Incidence

• Young children (particularly during weaning and toilet training, ages 1–4).
• Older adults, especially those >65 years, due to reduced mobility, medications, or comorbidities.

Pathophysiology

• Stool remains in the colon for prolonged periods, allowing excess water absorption, which leads to hard, dry stools and increased straining.
• May involve:
  • Slow colonic transit (primary constipation)
  • Pelvic floor dysfunction (e.g. anismus, rectocele)
  • Secondary causes (e.g. hypothyroidism, hypercalcaemia, medications like opioids, anticholinergics, iron supplements)

Symptoms

• Infrequent bowel movements (<3 per week)
• Straining during defecation
• Hard or lumpy stools
• Sensation of incomplete evacuation
• Abdominal bloating or discomfort
• Rectal discomfort or pain during defecation

Signs

May include:

• Abdominal distension
• Palpable lower quadrant mass (suggestive of faecal loading)
• Absent or reduced bowel sounds (if obstruction present)
• Anal fissures or haemorrhoids
• Hard stool or impaction on digital rectal examination (DRE)
• Rectal bleeding (from fissures or haemorrhoids)

Diagnosis

Clinical Evaluation

• Detailed history, medication review, and physical examination.
• Identify red flag symptoms requiring further investigation:
  • Unintentional weight loss
  • Loss of appetite
  • Rectal bleeding (melena, haematochezia)
  • Persistent abdominal pain or palpable mass
  • Family history of colorectal cancer or IBD
  • Sudden change in bowel habit, especially in patients >45–50 years
• Digital Rectal Examination (DRE):
  • To assess for faecal impaction, rectal mass, or anal tone.

Laboratory Tests (if secondary cause suspected)

• Full Blood Count (FBC) – anaemia
• Urea & Electrolytes – dehydration, renal function
• Bone profile – hypercalcaemia
• Thyroid Function Tests – hypothyroidism
• Blood glucose, HbA1c – diabetes mellitus

Imaging

• Abdominal X-ray – to detect faecal loading or bowel obstruction.
• Colonoscopy – if red flags present or for colorectal cancer screening.

Specialised Tests (secondary or refractory cases)

• Anorectal manometry – to assess defecatory disorders.
• Colonic transit studies – to diagnose slow transit constipation.

Complications

• Overflow diarrhoea
• Acute urinary retention
• Haemorrhoids
• Faecal incontinence
• Anal fissures
• Megacolon
• Rectal prolapse
• Bowel obstruction (in severe or neglected cases)
• Pelvic floor dysfunction, especially in women

Management

General Principles

• Identify and treat any underlying causes.
• Review and adjust any constipating medications (e.g. opioids, iron, anticholinergics).

Lifestyle Modifications

• Fibre intake: Increase to 25–30 g/day via diet or supplements (e.g. bran, psyllium).
• Fluid intake: Encourage adequate hydration.
• Physical activity: Promotes colonic motility.
• Bowel routine: Establish regular, unhurried toileting habits (e.g. post-meal timing, footstool use).

Pharmacological Treatments

Non-opioid induced constipation:

• First-line: Bulk-forming laxatives (e.g. ispaghula husk)
• Second-line: Osmotic laxatives (e.g. lactulose, macrogol)
• Third-line: Stimulant laxatives (e.g. senna, bisacodyl)

Opioid-induced constipation:

• First-line: Osmotic laxatives or stimulant laxatives
• Refractory cases: Peripherally acting μ-opioid receptor antagonists (e.g. naloxegol, methylnaltrexone)

Hard stool but not impacted:

• Stool softeners (e.g. docusate sodium)

Faecal Impaction:

• Emergency treatment:

  • Phosphate enema
  • Glycerin suppository
  • Manual disimpaction (if required)