Constipation — Adult presentation in primary care
Covers new-onset, chronic, and opioid-induced constipation · Adults ≥18 · UK NHS pathway
Progress0 / 9
The full reasoning pathway — exclude obstruction and the NG12 red flags, classify primary (functional) vs secondary (metabolic / drug / neuro / structural), climb the laxative ladder by subtype, refer when refractory, and keep lifestyle alongside throughout.StartDecisionInvestigateActionReferStop / Admit
PresentationConstipation
Bristol stool form, frequency, straining, incomplete emptying, duration and change from baseline. Diet, fluids, mobility, mood; review drugs (opioids, iron, CCBs, TCAs, anticholinergics). PR exam before any stimulant (impaction, fissure, mass).
Bowel obstruction — severe pain, distension, vomiting, no flatus → admit
Rectal bleeding or iron-deficiency anaemia
Unexplained weight loss, abdominal/rectal mass
Persistent change in bowel habit ≥6 weeks aged ≥50/60
YES — red flag
Stop · escalateAdmit / 2WW
Obstruction → emergency admission. Cancer red flags → FIT + colorectal 2WW (don't wait for FIT if criteria already met).
NO — work up cause
Step 2 · InvestigateReversible causes
TSH, calcium, U&E, glucose/HbA1c; medication review. Coeliac serology if features. Bloods only where history suggests a secondary cause — most functional constipation needs none.
Step 7 · Action — stepwise laxativesTailor to the cause, review at each step
Functional: ① bulk-forming (ispaghula/Fybogel) with adequate fluid → ② add osmotic macrogol (Movicol) 1–3 sachets/day (preferred over lactulose) → ③ add stimulant (senna/bisacodyl, short-term).
Opioid-induced: osmotic + stimulant from the start (not bulk-forming); add a PAMORA (naloxegol 25 mg OD) if inadequate.
Refractory (women, ≥2 laxatives): prucalopride 2 mg OD (NICE TA211). Defaecatory dysfunction → biofeedback, not more oral laxative.
Step 6 · escalation thresholds
Step 6 · ReferEscalation thresholds
Emergency bowel obstruction / perforation, impaction unresponsive to disimpaction.
2WW · NICE NG12 change in bowel habit + rectal bleeding / weight loss, abdominal or rectal mass, iron-deficiency anaemia → FIT + colorectal pathway.
Gastroenterology / colorectal refractory after 6 months optimised treatment; pelvic-floor physio / continence nurse for defaecatory dysfunction (biofeedback).
Step 8 · lifestyle (alongside laxatives)
Step 8 · Lifestyle — essential, not optionalReduce relapse (40% at 6 mo without it)
Gradually increase dietary fibre to ~30 g/day · fluids ≥1.5 L/day · regular physical activity · toileting routine — respond to the urge, use a footstool, don't strain · review and reduce constipating drugs where possible. Lifestyle runs alongside every laxative step.
Step 9 · review & safety-net
Step 9 · Review & safety-netWhen to come back
999 if sudden complete obstruction, severe distension, rigid abdomen (perforation). Same-day GP if new rectal bleeding, weight loss, a rectal mass, or impaction not clearing. Review: response at 2–4 weeks, step up/down; attempt step-down at 3 months in mild cases; continue laxatives for the duration of opioid therapy; monitor U&E on long-term macrogol/stimulants.
⚠️ New constipation in an older adult is not automatically benign: a persistent change in bowel habit, especially with bleeding or weight loss, needs FIT and the colorectal pathway. And always do a PR before prescribing a stimulant — never give one into impaction.
01
Safety
Red Flags — Screen for serious pathology before assuming functional constipation
Any of the following → urgent action required. Do not manage as simple constipation until excluded.
Rectal bleeding (bright red / dark) Especially if unprovoked, mixed with stool, or with altered stool — 2WW lower GI cancer referral
Unintentional weight loss ≥5% in 6 months With new constipation → 2WW colorectal cancer. Check FBC, CRP, CEA
Change in bowel habit >6 weeks age >60 New looser stools OR constipation → 2WW colorectal referral per NICE NG12
Iron-deficiency anaemia Unexplained IDA in men or postmenopausal women → 2WW lower GI. Check ferritin, FBC
Abdominal / rectal mass Palpable mass on examination → same-day surgical assessment or urgent imaging
Onset <6 weeks age >50 (no prior history) No obvious cause → same-day or urgent lower GI assessment
Family history Lynch syndrome / FAP With new bowel change → accelerated 2WW genetic / colorectal referral
NICE NG12 mandates 2WW referral for adults ≥40 with rectal bleeding + change in bowel habit, or ≥60 with change in bowel habit alone. Colorectal cancer affects ~43,000 UK patients/year; early diagnosis is the single biggest determinant of survival (90% 5-year survival Stage I vs 10% Stage IV). Missing a palpable mass or saddle anaesthesia can result in irreversible harm — cauda equina decompression must occur within hours. Volvulus and obstruction have 15–20% mortality if treatment delayed beyond 24h.
02
Diagnose
Confirm constipation — Use Rome IV criteria and Bristol Stool Chart
Constipation is a symptom-based diagnosis. Apply Rome IV criteria — ≥2 criteria for ≥3 months (onset ≥6 months ago).
Types 1–2 = constipated · Types 3–4 = normal · Types 5–7 = loose/diarrhoea. Ask patient to identify their typical stool type
Key history questions
Onset, frequency, consistency, straining, blood, mucus, pain, diet change, new medications, obstetric history (women), systemic symptoms
Medication review
Opioids, iron supplements, calcium channel blockers (verapamil), antidepressants (TCAs), antipsychotics, antihistamines, anticholinergics — all cause constipation
Baseline severity
Use Patient Assessment of Constipation Symptoms (PAC-SYM) or ask: "How many days per week do you open your bowels?" to track response to treatment
Rome IV criteria standardise diagnosis and avoid over-medicalising normal variation. Many patients with ≤3 stools/week feel fine — it's the symptom burden that matters. Medication-induced constipation accounts for ~25% of cases in primary care and is often reversible without laxatives. Establishing a baseline enables you to assess treatment response objectively at follow-up.
03
Diagnose
Classify the type of constipation — drives treatment choice
Primary / Functional
No identifiable organic cause. Subdivide: Normal transit (most common — stool moves normally, perception altered), Slow transit (prolonged colonic transit — severe, infrequent), Defaecatory dysfunction (outlet obstruction, pelvic floor dyssynergia)
Secondary — Metabolic
Hypothyroidism (check TSH), hypercalcaemia (check Ca²⁺), hypokalaemia, diabetes, uraemia. Treat underlying cause first
Secondary — Neurological
Parkinson's disease, MS, spinal cord lesion, autonomic neuropathy. Often severe, refractory to standard laxatives
Opioids (most common — present in 40–95% of patients on regular opioids), iron, calcium channel blockers, TCAs. Review and switch/add peripherally-acting mu-opioid receptor antagonist (PAMORA) if opioid-induced
IBS-C
Constipation + abdominal pain relieved by defaecation + Rome IV IBS criteria. Manage as IBS with specific pathway
Classification directly changes treatment. Hypothyroidism-associated constipation resolves with levothyroxine — laxatives are a sticking-plaster. Opioid-induced constipation does not respond adequately to bulk-forming laxatives; it requires osmotic/stimulant laxatives or PAMORAs (naloxegol, methylnaltrexone). Defaecatory dysfunction responds to biofeedback pelvic floor physiotherapy, not laxatives. Getting this right at Step 3 avoids months of ineffective treatment.
04
Diagnose
Targeted examination — PR exam mandatory in new-onset or unexplained constipation
Abdomen
Palpate all 4 quadrants. Faecal loading (doughy, indentable masses in LIF/RIF). Organomegaly. Tenderness. Visible distension or peristalsis
Perianal inspection
Haemorrhoids, fissures (look for sentinel tag), skin tags, prolapse, soiling. Do not proceed to PR if fissure causing severe pain without LA cream first
Digital rectal exam (PR)
Anal tone (low = sphincter injury/neurological; high = dyssynergia/fissure). Faecal impaction (hard stool in rectum). Masses. Tenderness. Empty rectum does not exclude slow-transit constipation
Thyroid
Goitre → check TFTs if not recently done
Neurological screen
If saddle anaesthesia, urinary symptoms, or leg weakness → check perianal sensation, anal wink reflex, and arrange urgent MRI spine
BMI / nutrition
Low BMI + constipation → consider eating disorder, malnutrition, or cancer
PR examination is essential before prescribing stimulant laxatives — giving bisacodyl to a patient with faecal impaction worsens pain and may cause perforation. An anal fissure will be perpetuated if the underlying constipation is not treated. High anal tone suggests dyssynergia — these patients need specialist anorectal physiology, not more laxatives. Missing a rectal mass on PR examination is an avoidable medicolegal failure.
05
Diagnose
Investigations — targeted, not routine; exclude secondary causes
Secondary causes are present in ~10–15% of constipation cases — hypothyroidism is detected in 5% of women presenting with constipation. Hypercalcaemia is often asymptomatic but causes severe refractory constipation. Over-investigating functional constipation wastes NHS resource and delays treatment. Stool calprotectin has 83% sensitivity for IBD — a useful GP-level test before referring for colonoscopy in diagnostic uncertainty.
06
Refer
Referral criteria — know when primary care management is insufficient
999 Emergency
Acute complete obstruction, peritonism, haemodynamic instability, suspected volvulus or perforation
Same-day
Suspected faecal impaction with overflow, acute urinary retention with constipation (neurological concern), high-grade cauda equina symptoms
2WW Colorectal
Per NICE NG12: age ≥40 rectal bleeding + change in bowel habit · age ≥50 unexplained rectal bleeding · age ≥60 change in bowel habit or IDA · palpable rectal/abdominal mass
Urgent gastroenterology
Suspected IBD (elevated calprotectin, bloody mucus, systemic symptoms) · New-onset constipation with iron deficiency in any age
Defaecatory dysfunction → pelvic floor biofeedback. Refer to continence nurse or specialist physiotherapist
Primary care manages
New functional constipation · Medication-induced constipation · Mild–moderate severity · Adequate response to laxatives
NICE NG12 2WW criteria have strong evidence — failure to refer appropriately is a leading cause of delayed colorectal cancer diagnosis in the UK. Defaecatory dysfunction (outlet obstruction / dyssynergia) responds to biofeedback physiotherapy in 70–80% of cases — this is more effective than any laxative for this subtype and cannot be delivered in primary care. Identifying who needs specialist input early avoids prolonged ineffective treatment.
07
Treat
Treatment ladder — stepwise laxative therapy with patient-specific branching
Always combine with lifestyle (Step 8). Choose first-line based on constipation type.
Macrogol (Movicol) 1–3 sachets/day + Senna 15mg nocte. Do NOT use bulk-forming agents alone
Faecal impaction (acute)
High-dose macrogol Acute
Macrogol 8 sachets/day for 3 days (Movicol-half: 16 sachets/day). Do NOT give stimulant alone without disimpaction
Step 1Ispaghula husk (Fybogel) 1 sachet BD — bulk-forming. Review in 2–4 weeks. If adequate response, continue. Ensure fluid intake
Step 2Add osmotic laxative: Macrogol (Movicol) 1–3 sachets/day OR Lactulose 15ml BD (less preferred — causes bloating). Can combine with Step 1
Step 3Add stimulant laxative: Senna 15mg nocte OR Bisacodyl 5–10mg nocte. Short-term use. Review need at each appointment. Can combine Steps 1+2+3
Step 4Opioid-induced: PAMORA — Naloxegol 25mg OD (NICE TA345) or Methylnaltrexone SC if oral route not possible. For inadequate response to combined laxatives
Step 5Refractory / specialist: Prucalopride 2mg OD (NICE TA211 — women with chronic constipation, inadequate response to ≥2 laxatives). Linaclotide if IBS-C (NICE TA318)
Renal function if on long-term macrogol (elderly/CKD) · Electrolytes if on stimulants long-term · Review opioid dose — reduce if possible
Duration
Treat underlying cause. Functional constipation: minimum 4 weeks, reassess. Opioid-induced: treat for duration of opioid therapy
Bulk-forming agents (NNT ~3 for improved stool frequency) work by increasing stool bulk and water content — they require adequate hydration to work. Macrogol is preferred over lactulose (Cochrane review: superior efficacy, less bloating). Stimulant laxatives are effective but concern about long-term colonic dependency exists — evidence is limited but monitoring is reasonable. Prucalopride (5-HT₄ agonist): NICE TA211 supports use in women failing 2+ laxatives — NNT ~5 for one additional complete spontaneous bowel movement per week. Naloxegol (PAMORA) peripherally blocks opioid receptor in gut without reversing analgesia — KODIAC trials showed significant improvement in opioid-induced constipation vs placebo.
08
Lifestyle
Non-pharmacological interventions — essential alongside all laxatives
Lifestyle is treatment, not afterthought. These interventions have level 1 evidence and should be addressed in every consultation.
Fluid intake Minimum 1.5–2L water/day. Dehydration directly worsens transit time. Reduce caffeine and alcohol which worsen dehydration
Physical activity 150 min moderate exercise/week. Walking 30 min/day reduces constipation by 30%. Physical activity stimulates colonic peristalsis via neurological and hormonal mechanisms
Toilet habit — defaecation timing Use the gastrocolic reflex: sit on toilet 20–30 min after breakfast. Never ignore the urge. Allow adequate time — do not rush
Toilet posture Use a footstool (Squatty Potty position — feet 20–30cm raised) to anorectal angle. Reduces straining significantly — evidence from RCTs
Medication review Stop or switch constipating medications where clinically safe. Discuss opioid dose reduction or rotation with pain team if appropriate
Stress and anxiety Gut-brain axis: CBT and mindfulness improve functional constipation. Refer to IAPT / primary care wellbeing if anxiety identified
Bowel diary Ask patient to complete 1-week bowel diary (BSC type, frequency, straining, pain). Invaluable for monitoring response and specialist referral
A Cochrane review (2016) found dietary fibre supplementation significantly improves stool frequency vs placebo (RR 1.59). Physical activity reduces colon transit time by up to 30% in sedentary individuals. Correct toilet posture (squatting angle) reduces anorectal angle, decreasing straining effort — RCT evidence shows 80% of patients achieve faster complete evacuation. These interventions cost nothing, have no side effects, and should be prescribed with the same specificity as medications.
09
Safety
Follow-up & monitoring — safety-net, reassess, and step down
2–4 weeks
First review: treatment response, stool frequency/consistency, side effects (bloating, colic). Adjust laxative dose or add next step if insufficient response
6–8 weeks
Reassess symptom severity. Check bloods if ordered. If no improvement despite Step 3 → consider referral and specialist investigation
3 months
Full review: is laxative still needed? Attempt step-down in mild cases. Reassess dietary adherence, medication causes
Ongoing (opioid-induced)
Laxative treatment should continue for the duration of opioid therapy — review at every opioid prescription review
999 Safety-net
Sudden complete obstruction, severe abdominal distension, haemodynamic collapse, signs of perforation (severe pain, rigid abdomen, fever)
Same-day GP Safety-net
Any new rectal bleeding · Significant weight loss · Anal/rectal mass found · Worsening pain · Faecal impaction not resolving after 3 days of treatment
Return to Step 1
If new red flags emerge at ANY point — immediately re-screen. Constipation can mask new colorectal malignancy even in previously established "functional" patients
Laxative effectiveness declines over time if underlying lifestyle factors are not addressed — systematic review shows 40% relapse rate at 6 months without lifestyle modification. Long-term stimulant laxative use requires electrolyte monitoring (risk of hypokalaemia). A patient with "established" functional constipation who develops new rectal bleeding needs re-screening — interval colorectal cancers do occur. Structured safety-netting is an RCGP SCA competency marker — document what you told the patient to watch for.
Educational use only. Pathway based on: NICE NG12 (Suspected cancer recognition 2015, updated 2023) · NICE CG99 (Constipation in adults) · NICE TA211 (Prucalopride) · NICE TA345 (Naloxegol) · NICE TA318 (Linaclotide for IBS-C) · BSG guidelines on constipation · Rome IV diagnostic criteria · British National Formulary (BNF). Always adapt to individual patient context and local clinical guidelines.