Case 21.4 – Constipation [SDL]

Definition of Constipation:

Constipation is a common symptom characterized by:

• Infrequent bowel movements (typically <3 per week)
• Difficulty or straining during defecation
• Passage of hard or lumpy stools
• Sensation of incomplete evacuation
• Sensation of anorectal obstruction/blockage
• Need for manual maneuvers to facilitate defecation

Prevalence: ~15-20% of the general population, increasing with age and more common in women.

Rome IV Diagnostic Criteria for Functional Constipation:

Diagnosis requires at least 2 of the following criteria for ≥25% of defecations over the last 3 months (with symptom onset at least 6 months prior to diagnosis):

1. Straining during defecation
2. Lumpy or hard stools (Bristol Stool Form Scale types 1-2)
3. Sensation of incomplete evacuation
4. Sensation of anorectal obstruction or blockage
5. Manual maneuvers to facilitate defecation (e.g., digital evacuation, support of pelvic floor)
6. Fewer than 3 spontaneous bowel movements per week

Additional criteria:

• Loose stools are rarely present without the use of laxatives
• Insufficient criteria for diagnosis of irritable bowel syndrome (IBS)

Bristol Stool Form Scale (relevant types for constipation):

• Type 1: Separate hard lumps, like nuts (difficult to pass)
• Type 2: Sausage-shaped but lumpy
• Types 1 and 2 indicate constipation
• Types 3 and 4 are considered normal

Classification of Constipation:

• Primary (Functional) Constipation:
  • Normal transit constipation: Most common type (~60%)
    • Normal colonic transit time
    • Often related to dietary factors, lifestyle
  • Slow transit constipation: (~15%)
    • Delayed movement of stool through colon
    • More common in young women
    • May be related to colonic neuromuscular dysfunction
  • Defecatory disorders (dyssynergic defecation/pelvic floor dysfunction): (~25%)
    • Inability to coordinate pelvic floor and anal sphincter muscles during defecation
    • Paradoxical contraction or inadequate relaxation of pelvic floor
• Secondary Constipation: Due to underlying medical conditions, medications, or structural abnormalities

Common Causes of Secondary Constipation:

1. Medications:

• Opioid analgesics: Most common medication cause (codeine, morphine, tramadol, etc.)
• Anticholinergic drugs: Antidepressants (TCAs), antihistamines, antipsychotics, antiparkinson drugs
• Antacids: Aluminum- and calcium-containing
• Iron supplements
• Calcium channel blockers: Verapamil, diltiazem
• Diuretics: Can cause dehydration
• NSAIDs
• Antispasmodics
• 5-HT3 antagonists (ondansetron)

2. Endocrine/Metabolic Disorders:

• Hypothyroidism: Important to exclude
• Hypercalcaemia: From any cause (malignancy, hyperparathyroidism, etc.)
• Diabetes mellitus: Autonomic neuropathy affecting gut motility
• Hypokalaemia
• Hypomagnesaemia
• Uraemia (chronic kidney disease)

3. Neurological Conditions:

• Parkinson's disease
• Multiple sclerosis
• Spinal cord injury or disease
• Stroke
• Autonomic neuropathy
• Hirschsprung's disease (usually presents in infancy)

4. Gastrointestinal Disorders:

• Colorectal cancer: MUST exclude in patients with red flags
• Strictures (inflammatory, ischaemic, malignant)
• Anal fissure (pain on defecation leading to stool withholding)
• Haemorrhoids
• Rectal prolapse
• Diverticular disease

5. Systemic Diseases:

• Systemic sclerosis (scleroderma)
• Amyloidosis
• Dermatomyositis/polymyositis

6. Psychological/Psychiatric:

• Depression
• Eating disorders (especially anorexia nervosa)
• Anxiety

7. Lifestyle/Dietary Factors:

• Low fibre diet
• Inadequate fluid intake
• Immobility/reduced physical activity
• Ignoring urge to defecate (behavioral)

Red Flag Features Warranting Urgent Investigation:

The presence of any of these features should prompt investigation to exclude colorectal cancer or other serious pathology:

• Age ≥50 years with new-onset constipation
• Rectal bleeding: Especially if mixed with stool or dark blood
• Unexplained iron deficiency anaemia
• Unintentional weight loss
• Abdominal pain or mass
• Change in bowel habit (especially alternating constipation and diarrhoea)
• Family history of colorectal cancer (especially in first-degree relative <60 years)
• Family history of inflammatory bowel disease
• Symptoms/signs of intestinal obstruction: Severe abdominal pain, vomiting, abdominal distension
• Palpable abdominal or rectal mass

Investigation for Red Flags:

• Urgent colonoscopy or CT colonography if red flags present
• Typically within 2 weeks if suspected cancer (urgent suspected cancer pathway)

Other Alarm Features Suggesting Specific Conditions:

• Overflow diarrhoea: Suggests faecal impaction
• Ribbon-like stools: May suggest rectal or sigmoid pathology
• Severe straining with inability to expel stool despite urge: Suggests pelvic floor dysfunction
• Digital manipulation required: Suggests defecatory disorder

Initial Assessment:

History:

• Duration and characteristics of constipation
• Stool frequency and consistency (Bristol Stool Chart)
• Associated symptoms (pain, bloating, bleeding)
• Red flag features (see previous question)
• Dietary history (fibre and fluid intake)
• Medication review (opioids, anticholinergics, etc.)
• Past medical history (thyroid disease, diabetes, neurological conditions)
• Psychosocial factors
• Impact on quality of life

Examination:

• General examination (weight, signs of systemic disease)
• Abdominal examination (masses, faecal loading, organomegaly)
• Digital rectal examination (DRE):
  • Essential in all patients with constipation
  • Assess for faecal impaction, masses, anal fissures, haemorrhoids
  • Assess anal tone and pelvic floor function
  • Check for blood

Initial Investigations:

For patients WITHOUT red flags (simple constipation):

• Blood tests (to exclude secondary causes):
  • Full blood count: Check for anaemia
  • Thyroid function tests (TSH, free T4): To exclude hypothyroidism
  • Calcium: To exclude hypercalcaemia
  • Glucose/HbA1c: If diabetic symptoms or risk factors
  • Urea and electrolytes: Check potassium, assess renal function
  • Coeliac serology: If other suggestive features
• Often, initial empirical treatment can be started without extensive investigation if no red flags and blood tests normal

For patients WITH red flags:

• Above blood tests PLUS:
• Urgent referral for colonic imaging:
  • Colonoscopy: Gold standard
    • Allows direct visualization and biopsy
    • Can identify polyps, cancer, inflammation
  • CT colonography (virtual colonoscopy): Alternative if colonoscopy not possible/declined
    • Less invasive
    • Cannot biopsy or remove polyps
  • Flexible sigmoidoscopy: Limited examination of left colon/rectum
    • May miss proximal lesions
    • May be used in specific circumstances

Specialized Investigations (if constipation refractory to initial treatment):

• Colonic transit studies:
  • Radiopaque markers ingested, X-rays taken to track passage
  • Differentiates slow transit vs normal transit vs outlet obstruction
  • Wireless motility capsule increasingly used
• Anorectal manometry:
  • Assesses anal sphincter pressures and rectal sensation
  • Identifies dyssynergic defecation (pelvic floor dysfunction)
• Balloon expulsion test:
  • Simple bedside test
  • Inability to expel inflated balloon suggests defecatory disorder
• Defecography (evacuation proctography):
  • Fluoroscopic or MRI assessment during simulated defecation
  • Identifies structural/functional abnormalities (rectal prolapse, rectocele, intussusception)

When to Refer to Secondary Care:

• Red flag features present
• Failure to respond to appropriate laxative therapy
• Suspected defecatory disorder
• Symptoms significantly impacting quality of life
• Need for specialized investigations

Management of Constipation - Stepwise Approach:

Step 1: Lifestyle and Dietary Modifications (First-line for all patients):

Dietary advice:

• Increase fibre intake:
  • Aim for 25-30g per day
  • Gradually increase to minimize bloating and gas
  • Sources: whole grains, fruits, vegetables, legumes, nuts
  • Both soluble fibre (oats, psyllium) and insoluble fibre (wheat bran, vegetables)
  • Note: Fibre less effective in slow transit constipation or defecatory disorders
• Adequate fluid intake:
  • Aim for 1.5-2 litres per day
  • Especially important when increasing fibre
• Reduce intake of:
  • Processed foods
  • Excessive dairy (can be constipating in some people)
  • Alcohol and caffeine (can be dehydrating)

Lifestyle modifications:

• Regular physical activity:
  • Aim for 30 minutes most days
  • Walking, swimming, yoga
  • Helps stimulate bowel motility
• Establish regular bowel habits:
  • Respond promptly to the urge to defecate
  • Allow adequate time for bowel movements
  • Consider toilet routine after breakfast (gastrocolic reflex)
  • Adopt optimal position: feet on stool, leaning forward
• Avoid straining: Can lead to haemorrhoids, anal fissures

Medication review:

• Review and modify constipating medications where possible
• If opioids necessary: consider prophylactic laxatives
• Switch to alternatives if appropriate

Step 2: Laxative Therapy (if lifestyle measures insufficient):

First-line laxatives:

• Bulk-forming laxatives:
  • Examples: Ispaghula husk (Fybogel), methylcellulose, sterculia
  • Mechanism: Increase stool bulk and stimulate peristalsis
  • Onset: 2-3 days
  • Advantages: Natural, safe for long-term use
  • Important: MUST take with adequate fluid (risk of obstruction otherwise)
  • Contraindications: Faecal impaction, suspected bowel obstruction
• Osmotic laxatives:
  • Macrogols (polyethylene glycol - PEG):
    • Examples: Movicol, Laxido
    • Mechanism: Retain water in bowel, softening stool
    • Onset: 1-2 days
    • Advantages: Well tolerated, effective, safe long-term
    • Often considered first choice
  • Lactulose:
    • Mechanism: Osmotic effect, softens stool
    • Onset: 2-3 days
    • Disadvantages: Flatulence, bloating common; sweet taste
    • Less favored than macrogols

Second-line laxatives (if first-line ineffective or not tolerated):

• Stimulant laxatives:
  • Examples: Senna, bisacodyl, sodium picosulfate
  • Mechanism: Stimulate intestinal motility and secretion
  • Onset: 6-12 hours (oral), 15-60 minutes (suppositories)
  • Can cause abdominal cramps
  • Safe for long-term use despite historical concerns
• Stool softeners:
  • Docusate sodium
  • Mechanism: Reduces surface tension, allowing water penetration
  • Modest efficacy

Combination therapy:

• If single agent ineffective: combine osmotic + stimulant laxative
• E.g., macrogol + senna

Step 3: Specialist Laxatives (if refractory to conventional laxatives):

• Prucalopride:
  • 5-HT4 receptor agonist
  • Stimulates colonic motility
  • For women with chronic constipation inadequately relieved by laxatives
  • Requires specialist initiation
• Linaclotide:
  • Guanylate cyclase-C agonist
  • Increases intestinal fluid secretion and transit
  • Licensed for IBS with constipation
• Lubiprostone:
  • Chloride channel activator
  • Increases intestinal fluid secretion
• Naloxegol, methylnaltrexone:
  • Peripherally acting μ-opioid receptor antagonists
  • Specifically for opioid-induced constipation
  • Block constipating effects of opioids without affecting analgesia

Step 4: Treatment of Faecal Impaction:

• Oral therapy:
  • High-dose macrogols (e.g., 8 sachets of Movicol daily initially)
  • Continue until disimpaction achieved
• Rectal therapy:
  • Suppositories: Bisacodyl or glycerol
  • Enemas: Phosphate enema, sodium citrate (Micralax)
  • Docusate enemas if hard impacted stool
• Manual evacuation:
  • Last resort if other measures fail
  • May require sedation
• Prevention of recurrence: Maintenance laxatives

Step 5: Treatment of Defecatory Disorders:

• Biofeedback therapy:
  • First-line for dyssynergic defecation
  • Teaches coordination of pelvic floor and abdominal muscles
  • Effective in ~70% of patients
  • Requires specialist physiotherapy
• Laxatives often ineffective in isolation for defecatory disorders

Step 6: Surgical Options (rarely required):

• For highly selected patients with refractory slow transit constipation
• Options:
  • Subtotal colectomy with ileorectal anastomosis
  • Sacral nerve stimulation
• Only after thorough investigation and failure of all medical therapies
• Significant morbidity risk

Important Principles:

• Start with lifestyle modifications for all patients
• Add laxatives if lifestyle measures insufficient
• Titrate laxative dose to effect
• Long-term laxative use is safe and often necessary
• Regular review and adjustment of treatment
• Address underlying causes (medications, metabolic disorders)
• Manage patient expectations - improvement, not necessarily cure

Constipation in the Elderly:

Constipation is very common in the elderly, affecting up to 50% of nursing home residents and ~25% of community-dwelling elderly.

Risk Factors in the Elderly:

• Polypharmacy:
  • Multiple constipating medications (opioids, anticholinergics, calcium supplements, iron)
  • Medication interactions
• Reduced mobility:
  • Decreased physical activity
  • Difficulty accessing toilet
  • Bed-bound or chair-bound patients
• Dietary factors:
  • Reduced appetite and food intake
  • Low fibre diet (soft diet often easier to chew)
  • Reduced fluid intake (fear of incontinence, reduced thirst sensation)
  • Dental problems affecting food choices
• Comorbidities:
  • Diabetes with autonomic neuropathy
  • Parkinson's disease
  • Stroke
  • Hypothyroidism
  • Dementia (ignoring urge to defecate)
• Physiological changes:
  • Decreased colonic motility
  • Weakened pelvic floor muscles
  • Reduced rectal sensation
• Behavioral factors:
  • Privacy concerns in institutional settings
  • Ignoring urge to defecate
  • Depression

Special Considerations in Elderly Patients:

• Higher threshold for investigating:
  • New-onset constipation in elderly → higher risk of colorectal cancer
  • Lower threshold for colonoscopy/imaging
• Medication review crucial:
  • Identify and modify constipating medications
  • Consider alternatives or dose reduction
• Careful laxative selection:
  • Bulk-forming laxatives: require adequate fluid intake (risk of obstruction if inadequate)
  • Macrogols: generally well tolerated, good first choice
  • Lactulose: may cause excessive gas/bloating
  • Stimulant laxatives: useful but can cause urgency (problematic if mobility issues)
  • Start low, go slow with dose titration
• Monitor for complications:
  • Faecal impaction more common
  • Increased risk of overflow incontinence
• Practical assistance:
  • Ensure easy access to toilet facilities
  • Privacy and dignity
  • Adequate time allowed for bowel movements
  • Raised toilet seat, grab rails if needed
• Regular bowel routine:
  • Scheduled toileting after meals
  • Important in institutional care settings

Complications of Chronic Constipation:

Anorectal Complications:

• Haemorrhoids:
  • From chronic straining
  • Can cause bleeding, pain, prolapse
• Anal fissure:
  • Tear in anal mucosa from passage of hard stool
  • Causes severe pain on defecation and bright red bleeding
  • Can lead to further constipation (pain-avoidance behavior)
• Rectal prolapse:
  • Protrusion of rectal mucosa or full-thickness rectum
  • From chronic straining
  • May require surgical repair

Faecal Impaction:

• Accumulation of hard, dry stool in rectum/colon
• Cannot be passed voluntarily
• Particularly common in elderly, immobile, or institutionalized patients
• Consequences:
  • Overflow diarrhoea (spurious diarrhoea): Liquid stool bypasses impaction
  • Urinary retention or incontinence (mass effect on bladder)
  • Delirium (especially in elderly)
  • Abdominal pain and distension
• Treatment: Disimpaction (oral macrogols, enemas, manual evacuation)

Stercoral Ulceration and Perforation:

• Rare but serious complication
• Pressure necrosis of colonic wall from hard faecal mass
• Can lead to perforation and peritonitis
• High mortality, especially in elderly

Urinary Complications:

• Urinary retention: Particularly in elderly women
• Urinary incontinence: From bladder compression
• Recurrent UTIs: From incomplete bladder emptying

Cardiovascular Complications:

• Syncope: From excessive straining (Valsalva maneuver)
• Arrhythmias: Vagal stimulation during straining
• Particular risk in elderly with cardiac disease

Psychological Impact:

• Anxiety and depression
• Reduced quality of life
• Social isolation
• Preoccupation with bowel function

Other Complications:

• Volvulus: Rare, bowel twisting, more common with chronic constipation
• Megacolon/megarectum: Chronic dilatation from long-standing constipation
• Pelvic organ prolapse: From chronic straining

Prevention of Complications:

• Early identification and treatment of constipation
• Regular bowel regimen, especially in at-risk populations
• Avoid prolonged straining
• Adequate hydration and nutrition
• Regular monitoring in institutionalized/immobile patients
• Patient education about maintaining bowel health