Background Information

Definition

Constipation is a heterogeneous, symptom-based disorder.

Patients describe defecation that is problematic because of:

• Infrequent and/or hard stools, or
• Difficulty passing stools (often involving straining), or
• Sensation of incomplete emptying or anorectal blockage

Classification

There are a few terms that should not be mixed up:

Chronic constipation	Symptoms present for at least 3 months
Functional (primary / idiopathic) constipation	Chronic constipation without a known cause
Secondary (organic) constipation	Constipation caused by medication or an underlying medical condition
Faecal loading / impaction	Retention of faeces to the extent that spontaneous evacuation is unlikely

Aetiology

Functional (Idiopathic / Primary) Constipation

Risk factors include:

Social	Low fibre diet or low calorie intake Lack of exercise or reduced mobility Difficult access to toilet, or changes in normal routine or lifestyle Limited privacy when using the toilet Low educational levels or socio-economic deprivation A family history of constipation
Physical	Female sex Older age Pyrexia, poor fluid intake/dehydration, immobility Sitting position on a toilet seat (compared with the squatting position for defecation)
Psychological	Anxiety / depression Eating disorders Somatisation disorders History of sexual abuse

Secondary (Organic) Constipation

Medications

High-yield ones (non-exhaustive list): Iron supplements Opioids (e.g. morphine, codeine, tramadol, oxycodone) Drugs with anticholinergic properties Antimuscarinics Antihistamines TCAs (e.g. amitriptyline) Antipsychotics (e.g. olanzapine, clozapine) Calcium channel blockers (esp. verapamil) Ondansetron

Organic causes

Endocrine and metabolic causes: Hypercalcaemia Hypothyroidism Hypokalaemia Hypermagnesaemia Neurological causes: Parkinson’s disease (constipation is one of the main prodromal features) Diabetes with autonomic neuropathy Spinal cord injury GI causes: IBS-C (technically a functional cause, not an organic cause) Obstructive lesion Colorectal cancer Colonic strictures (e.g. from diverticulitis, Crohn’s) Haemorrhoids and anal fissure Rectal prolapse (can cause both constipation and incontinence) Rectocele (stools get trapped in the bulging pouch) Post-natal perineal tear (esp. 3rd and 4th degree)

Diagnosis

Constipation

NICE CKS states to suspect constipation in adults with ANY of the following:

• Infrequent bowel movements (<3 times a week)
• Difficulty passing stools (there may be daily bowel movements, but associated with excessive straining)
• Sensation of incomplete emptying / anorectal blockage

 

Additional symptoms:

• Lower abdominal pain / discomfort
• Abdomen distension
• Bloating

Faecal Loading / Impaction

NICE CKS states to suspect faecal loading / impaction if:

• Hard, lumpy stools
• Having to use manual methods to extract faeces
• Overflow faecal incontinence / loose stools

 

Faecal loading / impaction can cause:

• Overflow diarrhoea / faecal incontinence
• Acute bowel obstruction

Management

Overview of the main laxative classes:

Drug class	MoA	Key examples
Bulk-forming agents	Absorb water → ↑ stool bulk → stimulate peristalsis	Ispaghula husk (Fybogel®) Methylcellulose Sterculia
Osmotic laxatives	Draw water into bowel → soften stool	Macrogols (Movicol®) Lactulose Magnesium salts
Stool softeners (surfactants)	Reduce surface tension →  allow water / fat to penetrate stool → soften stool	Docusate sodium (has also stimulant properties) Glycerol suppositories (has also stimulant properties) Enema containing arachis oil (groundnut oil, peanut oil)
Stimulant laxatives	Stimulate enteric nerves → ↑ colonic motility	Senna Bisacodyl Sodium picosulfate Co-danthramer and co-danthrusate (only used in terminally ill patients due to potential carcinogenicity and genotoxicity)

Faecal Loading / Impaction

Patients with faecal loading / impaction typically need pharmacological management / intervention to achieve complete disimpaction.

Step 1	Hard stools → oral macrogol (high-dose), then add a stimulant laxative if ineffective after a few days Soft stools → oral stimulant laxative
Step 2 (if oral laxative is ineffective)	Suppository Bisacodyl (a stimulant laxative) for soft stools Glycerol (an osmotic laxative) +/- bisacodyl for hard stools Mini enema (docusate or sodium citrate)
Step 3	Enema (sodium phosphate or arachis oil)

Short-Term Constipation (<3 Months)

First, advice on lifestyle measures (see the conservative management section under chronic constipation below)

 

If ineffective → offer treatment with oral laxatives:

• 1st line: bulk-forming laxative (+ ensure adequate fluid intake)
• Step up:
  • If stools remain hard → add or switch to an osmotic laxative
  • If stools are soft (but difficult to pass) / person complains of inadequate emptying → add a stimulant laxative

Opioid-Induced Constipation

1st line:

• Stimulant laxative, AND
• Osmotic laxative or docusate sodium (has both stool softening and stimulant properties)

Further therapy to consider (if there is inadequate response to other laxatives):

• Naloxegol (a peripherally acting opioid receptor antagonist)
• Methylnaltrexone bromide (a peripherally acting opioid receptor antagonist)

Chronic Constipation (3 or More Months)

Approach:

• First attempt lifestyle measures (conservative management)
• If lifestyle measures are ineffective → offer laxatives

Conservative Management

Advise the following to all patients:

• Eating a healthy balanced diet containing whole grains, fruits and vegetables
• Increase fibre intake (30g per day)
• Drink adequate fluids
• Increase activity and exercise levels (if below recommended levels)
• Advice on toileting routines
  • Regular, unhurried toilet routine, giving time to ensure that defecation is complete
  • Respond immediately to the sensation of needing to defecate

Pharmacological Management (Laxatives)

Start with step 1, and step up accordingly if ineffective / inadequate response:

Step 1	Bulk-forming laxative (+ ensure adequate fluid intake)
Step 2	Add or switch to osmotic laxative 1st line: macrogol 2nd line: lactulose
Step 3	Add a stimulant laxative (if stools are soft but difficult to pass / there is a sensation of incomplete emptying)
Step 4	If at least 2 laxatives from different classes have been tried at highest tolerated recommended doses for at least 6 months → consider prucalopride

References