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 |
|
| Physical |
|
| Psychological |
|
Secondary (Organic) Constipation
| Medications | High-yield ones (non-exhaustive list):
|
| Organic causes | Endocrine and metabolic causes:
Neurological causes:
GI causes:
|
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
Acute constipation can cause:
- Faecal loading / impaction
- Urinary retention
- Delirium
- Nausea, loss of appetite
Chronic constipation is associated with
- Haemorrhoids
- Anal fissure
- Diverticulitis
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
Faecal impaction is a clinical diagnosis made on digital rectal examination (demonstrating rectum full or stool or hard, immovable stool in the rectum)
Plain abdominal X-ray is NOT routinely required, but is used if there is diagnostic uncertainty (e.g. equivocal digital rectal examination). Typical findings:
- Dilated bowel loops
- Faecally loaded colon (speckled, granular appearance in the colon)
Management
Overview of the main laxative classes:
| Drug class | MoA | Key examples |
|---|---|---|
| Bulk-forming agents | Absorb water → ↑ stool bulk → stimulate peristalsis |
|
| Osmotic laxatives | Draw water into bowel → soften stool |
|
| Stool softeners (surfactants) | Reduce surface tension → allow water / fat to penetrate stool → soften stool |
|
| Stimulant laxatives | Stimulate enteric nerves → ↑ colonic motility |
|
Faecal Loading / Impaction
Patients with faecal loading / impaction typically need pharmacological management / intervention to achieve complete disimpaction.
| Step 1 |
|
| Step 2 (if oral laxative is ineffective) |
|
| Step 3 |
|
An enema is indicated immediately in adults with faecal impaction, if there are ANY of the following: [Ref]
- Signs of bowel obstruction
- Severe symptoms (e.g. severe abdominal pain, vomiting, haemodynamic instability)
- Oral laxatives and suppositories are not feasible (e.g. due to altered mental status, inability to swallow)
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
It is important to ensure adequate fluid intake when using bulk-forming laxatives because these agents rely on water absorption to increase stool bulk and promote bowel movements.
Inadequate fludi intake can lead to 1) bloating 2) hardening of stool and 3) risk of bowel obstruction
This requirement for adequate fluid intake is especially important with bulk-forming laxatives compared to other classes of laxatives:
- Osmostic laxatives do not dependent on fluid intake as they draw water into the colon independently
- Stimulant laxatives simply acts to increases motility
- 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)
Avoid giving bulk-forming laxatives to manage opioid-induced constipation.
This is because they do not address the underlying reduction in colonic motility caused by opioids and may worsen symptoms by increasing stool bulk without improving transit.
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
It is also important to identify and manage any underlying secondary causes of constipation, and if possible to reduce or stop drugs that may cause constipation.
Pharmacological Management (Laxatives)
Start with step 1, and step up accordingly if ineffective / inadequate response:
| Step 1 | Bulk-forming laxative (+ ensure adequate fluid intake It is important to ensure adequate fluid intake when using bulk-forming laxatives because these agents rely on water absorption to increase stool bulk and promote bowel movements. Inadequate fludi intake can lead to 1) bloating 2) hardening of stool and 3) risk of bowel obstruction This requirement for adequate fluid intake is especially important with bulk-forming laxatives compared to other classes of laxatives:
|
| Step 2 | Add or switch to osmotic laxative
|
| 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 Prucalopride is a prokinetic drug MoA: selective 5-HT4 (serotonin) receptor agonist → increase peristalsis |
Gradually titrate the laxative dose(s) up or down aiming to produce soft, formed stool without straining at least 3 times per week.
Once the patient is able to produce soft, formed stool without straining → gradually reduce and stop the laxatives
- If >1 laxatives has been used → reduce and stop one laxative at a time
- If possible, reduce and stop the stimulant laxative first