Constipation (Adult)

1. Clinical Overview

Summary

Constipation is a highly prevalent gastrointestinal disorder characterised by infrequent bowel movements, difficulty passing stools, or a sensation of incomplete evacuation. [1] It affects approximately 16% of adults globally, with prevalence increasing significantly with age and disproportionately affecting women. [2]

The condition can be classified as primary (functional) or secondary to underlying pathology, medications, or metabolic disturbances. Functional constipation accounts for the majority of cases and is diagnosed using Rome IV criteria in the absence of alarm features. [3] Most patients with functional constipation respond well to lifestyle modifications, dietary changes, and first-line laxative therapy. However, a subset of patients develop chronic refractory symptoms requiring specialist investigation and advanced therapeutic approaches.

Understanding the pathophysiological subtypes—normal transit constipation, slow transit constipation, and defaecatory disorders—is crucial for tailoring management strategies effectively. [4]

Key Clinical Features

Clinical Pearls

Rome IV Diagnostic Criteria

• Must include ≥2 of 6 criteria for last 3 months (onset ≥6 months ago)
• Criteria: straining, hard stools, incomplete evacuation, anorectal blockage sensation, manual manoeuvres, less than 3 spontaneous bowel movements/week
• Loose stools rarely present without laxatives
• Insufficient criteria for IBS diagnosis [3]

High-Yield Clinical Points

• Medication review is essential: Opioids are the leading iatrogenic cause, followed by anticholinergics, calcium channel blockers, and iron supplements [5]
• Red flags mandate investigation: New onset > 50 years, rectal bleeding, weight loss, anaemia, family history of colorectal cancer
• Bristol Stool Chart correlation: Types 1-2 indicate constipation; patient-reported frequency alone is insufficient
• Functional defaecatory disorders: 30-50% of patients with chronic constipation have pelvic floor dysfunction or dyssynergic defaecation [4]
• Multifactorial in elderly: Polypharmacy, immobility, inadequate fluid/fibre intake, comorbidities all contribute

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2. Epidemiology

Prevalence and Incidence

Chronic constipation is one of the most common gastrointestinal complaints worldwide.

Incidence: Approximately 1.9% per year in community-dwelling adults, rising to 4-5% per year in those > 65 years. [6]

Risk Factors

Non-Modifiable Risk Factors

Modifiable Risk Factors

Socioeconomic Impact

• Healthcare Burden: Constipation accounts for ~3 million GP consultations annually in the UK [1]
• Direct Costs: Estimated at $11.7 billion annually in the United States (outpatient visits, medications, procedures) [10]
• Quality of Life: Significantly impaired, comparable to chronic conditions like diabetes and COPD [9]
• Work Productivity: Associated with increased absenteeism and presenteeism

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3. Aetiology and Pathophysiology

Classification of Constipation

Constipation is broadly classified into primary (functional) and secondary forms.

Primary (Functional) Constipation

Functional constipation comprises three pathophysiological subtypes identifiable through specialist testing: [4]

Pathophysiological Mechanisms in Functional Constipation [4,11]

1. Colonic Dysmotility: Reduced frequency and amplitude of HAPCs, which normally propel stool from proximal to distal colon
2. Pelvic Floor Dysfunction: Paradoxical puborectalis contraction or failure of anal sphincter relaxation creates functional outlet obstruction
3. Rectal Hyposensitivity: Elevated threshold for conscious rectal sensation leading to reduced urge to defaecate
4. Visceral Hypersensitivity: In some patients, heightened pain perception without true motility disorder

Secondary Constipation

Secondary constipation arises from identifiable underlying causes:

Medications (Most Common Secondary Cause) [5]

Metabolic and Endocrine Disorders

Neurological Disorders [12]

Structural/Mechanical Causes

Other Causes

• Irritable Bowel Syndrome (IBS-C): Constipation-predominant IBS; abdominal pain relieved by defaecation, associated with bloating [13]
• Pregnancy: Progesterone-mediated smooth muscle relaxation + mechanical compression by gravid uterus
• Depression: Serotonergic dysregulation; gut-brain axis dysfunction [9]
• Chronic Kidney Disease: Fluid restriction, phosphate binders, reduced physical activity
• Systemic Sclerosis: Smooth muscle atrophy and fibrosis affecting GI tract

Molecular and Cellular Pathophysiology

Recent research has identified molecular mechanisms underlying functional constipation: [11]

1. Enteric Nervous System Dysfunction: Reduced density of interstitial cells of Cajal (ICC), which are gut pacemaker cells, in slow transit constipation
2. Neurotransmitter Imbalance: Altered serotonin (5-HT) signalling; reduced 5-HT4 receptor expression impairs prokinetic pathways
3. Inflammatory Mediators: Low-grade mucosal inflammation with mast cell infiltration in some functional constipation patients
4. Genetic Polymorphisms: Variants in 5-HT transporter gene (SLC6A4) associated with increased risk

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4. Clinical Presentation

Symptom Profile

Patients with constipation typically present with one or more of the following symptoms:

Rome IV Diagnostic Criteria for Functional Constipation [3]

Criteria must be fulfilled for the last 3 months with symptom onset at least 6 months prior to diagnosis.

Must include ≥2 of the following:

1. Straining during ≥25% of defaecations
2. Lumpy or hard stools (Bristol Type 1-2) in ≥25% of defaecations
3. Sensation of incomplete evacuation in ≥25% of defaecations
4. Sensation of anorectal obstruction/blockage in ≥25% of defaecations
5. Manual manoeuvres to facilitate ≥25% of defaecations (e.g., digital evacuation, pelvic floor support)
6. Fewer than 3 spontaneous bowel movements per week

AND:

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

Associated Symptoms and Complications

Clinical Presentation by Subtype

Normal Transit Constipation

• Symptoms: Hard stools, straining; frequency may be normal
• No systemic features
• Often respond to dietary fibre and bulk-forming laxatives

Slow Transit Constipation

• Symptoms: Infrequent bowel movements (often less than 1/week), minimal urge to defaecate, bloating
• More common in young women
• Poor response to fibre; may require prokinetic agents

Defaecatory Disorders (Dyssynergic Defaecation)

• Symptoms: Prolonged straining, sensation of blockage, need for manual assistance
• Excessive time spent on toilet (> 10 minutes)
• Often require biofeedback therapy

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5. Clinical Assessment and Examination

History Taking

A thorough clinical history is essential to differentiate functional from secondary constipation and identify alarm features.

Key Components of Constipation History

Physical Examination

General Examination

• General appearance: Cachexia (malignancy), signs of dehydration
• Thyroid status: Goitre, bradycardia, slow-relaxing reflexes (hypothyroidism)
• Skin: Pallor (anaemia), hyperpigmentation (Addison's disease)

Abdominal Examination

Perineal and Digital Rectal Examination (DRE) [14]

Essential in all patients with constipation unless contraindicated.

Red Flag Features Requiring Urgent Investigation

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6. Investigations

Initial (Primary Care) Investigations

In patients without red flags, baseline blood tests can identify common secondary causes.

Normal baseline bloods in absence of red flags: Functional constipation likely; trial of lifestyle modification + first-line laxatives

Red Flag Investigations (Structural Pathology)

Specialist Investigations (Refractory Constipation) [4,14]

Reserved for patients who fail to respond to first- and second-line laxative therapy after 6-12 months.

Colonic Transit Studies

Anorectal Physiology Tests [14]

When to Refer for Specialist Tests

Criteria for referral to gastroenterology/colorectal surgery: [16]

1. Failure to respond to lifestyle modifications + 2 or more classes of laxatives over 6-12 months
2. Symptoms suggestive of defaecatory disorder (prolonged straining, sensation of blockage, digital assistance)
3. Suspected slow transit constipation (very infrequent bowel movements, minimal response to fibre)
4. Red flags requiring endoscopic investigation

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7. Management

Management of constipation follows a stepwise approach, beginning with lifestyle modifications and escalating through pharmacological agents based on response. [1,16]

Step 1: Lifestyle and Dietary Modifications

Evidence-based lifestyle interventions: [7,8]

Dietary Sources of Fibre:

• Soluble fibre (fermentable): Oats, psyllium, beans, lentils, fruits → soften stools, promote bacterial fermentation
• Insoluble fibre: Wheat bran, whole grains, vegetables → increase stool bulk and transit

Note: Excessive fibre supplementation can worsen symptoms in slow transit constipation or defaecatory disorders. [7]

Step 2: First-Line Pharmacological Therapy

Bulk-Forming Laxatives (First-Line) [1,16]

Efficacy: ~50-60% of patients with normal transit constipation respond. Less effective in slow transit. [7]

Step 3: Second-Line Pharmacological Therapy

If bulk-forming laxatives fail after 2-4 weeks, add or switch to osmotic laxatives.

Osmotic Laxatives [1,16]

Evidence: Macrogol superior to lactulose in RCTs (better stool frequency, consistency, fewer side effects). [18]

Step 4: Third-Line Pharmacological Therapy

Stimulant Laxatives [1,16]

Safety: Long-term stimulant use is safe; no evidence of dependence or colonic damage. [19]

Step 5: Specialist Pharmacological Therapy (Refractory Constipation)

Prokinetic Agents [20]

When to Use:

• Refractory to conventional laxatives
• Documented slow transit constipation
• IBS-C with significant pain (linaclotide preferred)

Special Situations

Opioid-Induced Constipation (OIC) [22]

Highly prevalent (40-80% of chronic opioid users) and often refractory to standard laxatives.

Faecal Impaction [1]

Defaecatory Disorders (Dyssynergic Defaecation) [14,23]

Laxatives alone are ineffective; biofeedback therapy is treatment of choice.

Pregnancy

• First-line: Dietary fibre, fluid intake, exercise
• Safe laxatives: Bulk-forming (ispaghula), lactulose, macrogol (limited data but likely safe)
• Avoid: Stimulant laxatives in first trimester (theoretical risk); magnesium salts near term (risk of neonatal hypermagnesaemia)

Elderly and Frail Patients [6]

• Address polypharmacy (review opioids, anticholinergics)
• Ensure adequate hydration and mobility
• Low threshold for disimpaction
• Maintenance laxatives (macrogol + stimulant commonly required)

Step 6: Surgical Interventions

Reserved for highly selected patients with refractory slow transit constipation who have failed all medical therapy. [24]

Important: Surgery should only be considered after multidisciplinary assessment including psychology evaluation (high comorbidity with somatisation, depression).

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8. Prognosis and Outcomes

Natural History

Response to Treatment

Long-Term Complications

Prognostic Factors

Favourable Prognosis:

• Normal transit constipation
• Recent onset
• Good response to initial laxative therapy
• Absence of psychological comorbidity
• Identifiable and reversible secondary cause (e.g., hypothyroidism, medication)

Unfavourable Prognosis:

• Slow transit constipation
• Defaecatory disorder (without access to biofeedback)
• Long symptom duration (> 10 years)
• Refractory to multiple laxative classes
• Significant anxiety/depression/somatisation [9]
• History of physical or sexual abuse (associated with functional GI disorders)

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9. Differential Diagnosis

Constipation is a symptom, not a diagnosis. It is crucial to exclude secondary causes and sinister pathology.

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10. Prevention and Patient Education

Primary Prevention

Patient Education: Layperson Explanation

What is constipation?

Constipation means you have difficulty opening your bowels. This might mean:

• Going less than 3 times per week
• Having to strain a lot
• Passing hard, dry stools (like pebbles)
• Feeling like you haven't completely emptied your bowels

What causes it?

Most cases are "functional," meaning there's no serious underlying disease. Common causes include:

• Not eating enough fibre (fruits, vegetables, whole grains)
• Not drinking enough water
• Not being active enough
• Certain medications (especially strong painkillers like codeine or morphine)
• Sometimes medical conditions like an underactive thyroid

How can I help myself?

1. Eat more fibre: Aim for 5 portions of fruits and vegetables daily, choose wholegrain bread and cereals
2. Drink plenty: 6-8 glasses (1.5-2 litres) of water per day
3. Stay active: Walk, swim, or exercise for 30 minutes most days
4. Don't ignore the urge: Go to the toilet when you feel the need
5. Take your time: Don't rush on the toilet, but don't strain excessively
6. Try a footstool: Putting your feet on a small stool when sitting on the toilet can help

What treatments are available?

If lifestyle changes don't help after a few weeks, your doctor may recommend:

• Laxatives: These are medicines that help you go more easily. There are several types; your doctor will advise which is best for you.
  • "Bulk-forming (e.g., Fybogel): Add bulk to stools"
  • "Osmotic (e.g., Movicol, Lactulose): Draw water into the bowel"
  • "Stimulant (e.g., Senna): Stimulate bowel muscles"

When should I see a doctor?

See your GP if:

• You're over 50 and constipation is new
• You have blood in your stools
• You've lost weight without trying
• You have severe pain
• Lifestyle changes and over-the-counter laxatives haven't helped after 2-4 weeks

Seek urgent medical attention if:

• You cannot pass wind or stools at all (complete blockage)
• You have severe abdominal pain and vomiting

Is it serious?

Most constipation is not serious and can be managed with diet, lifestyle, and laxatives if needed. However, it's important to see your doctor to rule out any underlying conditions, especially if you have warning signs.

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11. Evidence Base and Guidelines

Major Clinical Guidelines

Key Randomised Controlled Trials

Systematic Reviews and Meta-Analyses

• Fibre supplementation: Cochrane review found soluble fibre (psyllium) effective (RR for treatment failure 0.47, 95% CI 0.23-0.96), but insoluble fibre (bran) not superior to placebo [7]
• Exercise: Meta-analysis showed physical activity reduced colonic transit time by ~12 hours and improved constipation symptoms [8]
• Prucalopride: Meta-analysis of 5 RCTs (n=2,639) showed prucalopride significantly increased ≥3 SBMs/week (RR 2.09, 95% CI 1.76-2.48) [20]
• Surgery for slow transit: Systematic review found 50-90% satisfaction after subtotal colectomy, but ~30% develop new GI symptoms (diarrhoea, bloating, pain) [24]

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12. Red Flags and Safety Netting

Absolute Red Flags (Urgent Referral/Investigation Required)

Relative Red Flags (Prompt Investigation)

• Acute onset severe constipation with pain/vomiting: Suspect obstruction → emergency imaging (AXR/CT)
• Change in bowel habit (constipation alternating with diarrhoea): Consider IBS-C vs colorectal pathology; lower threshold for investigation if > 50y
• Faecal incontinence (overflow): Suspect faecal impaction → DRE, consider AXR
• Severe refractory constipation: Refer to gastroenterology for specialist tests (transit studies, anorectal physiology)

Safety Netting Advice for Patients

When to seek urgent medical attention:

• Unable to pass wind or stools at all
• Severe abdominal pain with vomiting
• Passing fresh blood or black, tarry stools
• Unexplained weight loss

When to see your GP:

• Constipation not improving after 2-4 weeks of lifestyle changes and laxatives
• New onset if you're over 50
• Persistent symptoms despite multiple laxative trials

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13. Summary: Key Take-Home Points

1. Constipation is common: Affects 16% of adults globally; prevalence increases with age, more common in women
2. Rome IV criteria: Diagnosis of functional constipation requires ≥2 of 6 criteria for ≥3 months
3. Exclude secondary causes: Medication review (especially opioids), thyroid function, calcium, glucose
4. Red flags mandate investigation: Age > 50 with new onset, rectal bleeding, weight loss, anaemia → urgent colonoscopy
5. Stepwise management: Lifestyle → bulk-forming → osmotic (macrogol preferred) → stimulant laxatives
6. Refractory constipation: Consider specialist referral for transit studies and anorectal physiology tests
7. Defaecatory disorders: Require biofeedback therapy (not laxatives alone)
8. Opioid-induced constipation: Peripheral μ-antagonists (naloxegol) highly effective
9. Surgery is rare: Reserved for highly selected slow transit constipation cases refractory to all medical therapy
10. Quality of life: Significantly impaired; treat depression/anxiety as part of holistic approach

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14. Clinical Vignettes for Revision

Vignette 1: Functional Constipation

Case: A 32-year-old woman presents with 9 months of infrequent bowel movements (2-3 times per week), hard stools (Bristol Type 1), and straining. She has no rectal bleeding, weight loss, or abdominal pain. Examination is unremarkable. Bloods (FBC, TFTs, calcium) are normal.

Question: What is the most appropriate initial management?

Answer

Diagnosis: Functional constipation (meets Rome IV criteria: less than 3 BMs/week, hard stools, straining for > 3 months)

Initial Management:

1. Lifestyle advice: Increase dietary fibre to 25-30g/day, ensure 1.5-2L fluid intake, regular exercise
2. First-line laxative: Bulk-forming agent (ispaghula husk 3.5g daily)
3. Review in 2-4 weeks: If no response, escalate to osmotic laxative (macrogol)

No need for investigations (no red flags, age less than 50, normal bloods).

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Vignette 2: Red Flag Presentation

Case: A 62-year-old man presents with 3 months of worsening constipation, passing only 1-2 stools per week. He reports a 6kg weight loss and occasional dark stools. Examination reveals conjunctival pallor. FBC shows Hb 98 g/L (MCV 74 fL). Faecal occult blood test is positive.

Question: What is the most appropriate next step?

Answer

Red Flags Present:

• Age > 60 with new constipation
• Weight loss
• Iron deficiency anaemia (low Hb, low MCV)
• FOB positive (suggests GI blood loss)

Most Appropriate Next Step: Urgent 2-week wait referral for colonoscopy (or CT colonography if colonoscopy contraindicated/declined)

Differential Diagnosis: Colorectal cancer (left-sided lesion causing obstruction) vs other GI pathology

Note: Bidirectional endoscopy (gastroscopy + colonoscopy) indicated for iron deficiency anaemia to exclude upper GI source.

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Vignette 3: Opioid-Induced Constipation

Case: A 58-year-old woman with metastatic breast cancer on regular morphine (MST 60mg BD) develops severe constipation (1 bowel movement per week, hard stools, severe straining). She is already taking senna 15mg BD and macrogol 2 sachets daily with minimal benefit.

Question: What is the most appropriate addition to her treatment?

Answer

Diagnosis: Opioid-induced constipation (OIC) refractory to standard laxatives

Most Appropriate Treatment: Peripheral μ-opioid receptor antagonist (PAMORA)

• Naloxegol 25mg once daily (first-line PAMORA in UK)
• Alternative: Methylnaltrexone 12mg SC alternate days

Mechanism: Antagonises peripheral opioid receptors in GI tract → restores bowel function without affecting central analgesia

Evidence: RCTs show naloxegol significantly more effective than placebo in OIC (44% vs 29% achieving ≥3 SBMs/week) [22]

Alternative Approach: Consider switching to oxycodone/naloxone combination (naloxone acts locally in gut).

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Vignette 4: Defaecatory Disorder

Case: A 45-year-old woman describes 2 years of severe difficulty passing stools despite having daily urge to defaecate. She spends > 20 minutes straining on the toilet and often requires digital assistance. She feels incomplete evacuation. Standard laxatives (ispaghula, macrogol, senna) have been ineffective. DRE reveals paradoxical contraction of puborectalis on attempted defaecation.

Question: What is the most appropriate investigation and treatment?

Answer

Diagnosis: Defaecatory disorder (dyssynergic defaecation / pelvic floor dyssynergia)

Clinical Clues:

• Prolonged straining
• Need for digital assistance
• Sensation of incomplete evacuation
• Paradoxical contraction on DRE
• Poor response to laxatives

Most Appropriate Investigation: Anorectal manometry + balloon expulsion test

• Confirms dyssynergia (paradoxical anal pressure increase or inadequate relaxation during simulated defaecation)
• Balloon expulsion: inability to expel balloon within 1-3 minutes

Most Appropriate Treatment: Pelvic floor biofeedback therapy (4-6 sessions)

• Teaches coordinated pelvic floor relaxation
• 70-80% of patients improve [23]
• Far superior to laxatives alone for this condition

Note: Laxatives alone will NOT treat dyssynergia effectively.

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16. References

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16. Knowles CH, Scott SM, Legg PE, et al. Level of classification performance of KESS (symptom scoring system for constipation) validated in a prospective series of 105 patients. Dis Colon Rectum. 2002;45(6):842-849. doi:10.1007/s10350-004-6299-0

17. Takano S, Sands DR. Influence of body posture on defecation: a prospective study of "The Thinker" position. Tech Coloproctol. 2016;20(2):117-121. doi:10.1007/s10151-015-1402-6

18. Attar A, Lémann M, Ferguson A, et al. Comparison of a low dose polyethylene glycol electrolyte solution with lactulose for treatment of chronic constipation. Gut. 1999;44(2):226-230. doi:10.1136/gut.44.2.226

19. Müller-Lissner S, Kamm MA, Scarpignato C, Wald A. Myths and Misconceptions About Chronic Constipation. Am J Gastroenterol. 2005;100(1):232-242. doi:10.1111/j.1572-0241.2005.40885.x

20. Tack J, van Outryve M, Beyens G, Kerstens R, Vandeplassche L. Prucalopride (Resolor) in the treatment of severe chronic constipation in patients dissatisfied with laxatives. Gut. 2009;58(3):357-365. doi:10.1136/gut.2008.162404

21. Rao S, Lembo AJ, Shiff SJ, et al. A 12-week, randomized, controlled trial with a 4-week randomized withdrawal period to evaluate the efficacy and safety of linaclotide in irritable bowel syndrome with constipation. Am J Gastroenterol. 2012;107(11):1714-1724. doi:10.1038/ajg.2012.255

22. Chey WD, Webster L, Sostek M, Lappalainen J, Barker PN, Tack J. Naloxegol for opioid-induced constipation in patients with noncancer pain. N Engl J Med. 2014;370(25):2387-2396. doi:10.1056/NEJMoa1310246

23. Rao SSC, Seaton K, Miller M, et al. Randomized controlled trial of biofeedback, sham feedback, and standard therapy for dyssynergic defecation. Clin Gastroenterol Hepatol. 2007;5(3):331-338. doi:10.1016/j.cgh.2006.12.023

24. Knowles CH, Grossi U, Chapman M, Mason J. Surgery for constipation: systematic review and practice recommendations: Results III: Rectal wall excisional procedures (Rectopexy, STARR, Transtar). Colorectal Dis. 2017;19 Suppl 3:49-72. doi:10.1111/codi.13775

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26. Serra J, Pohl D, Azpiroz F, et al. European society of neurogastroenterology and motility guidelines on functional constipation in adults. Neurogastroenterol Motil. 2020;32(2):e13762. doi:10.1111/nmo.13762

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