Reasoning GP · Algorithm · 1-page summary
Low back pain in adults
For: adults 16+ with low back pain, with or without leg pain, in primary care. Not for: under 16s. Pain >12 weeks: re-screen here, then use the chronic back pain algorithm.
Core rule: ask about bladder, bowel and saddle sensation at every back-pain consultation and document the answer. Any new positive answer means immediate emergency transfer, not community MRI. Most of the rest is non-specific: reassure, keep active, do not image.
0Stop — emergency now — before any history
- Cauda equina — any one feature: new urinary retention, poor flow or altered bladder sensation; urinary or faecal incontinence; saddle or perineal numbness; bilateral sciatica or bilateral neurology; progressive weakness or gait disturbance → Immediate ED / acute spinal
- Cord compression: progressive bilateral leg weakness, upper motor neuron signs (clonus, hyperreflexia), thoracic pain with neuro symptoms, falls → Immediate ED / acute spinal. Known cancer + neuro signs → MSCC coordinator / acute oncology now.
- Ruptured AAA or dissection: abdominal pain, collapse, syncope, pulsatile mass, tearing pain to the back → 999. Anticoagulated + new neuro deficit (epidural haematoma) → 999
- While waiting: urgent MRI is arranged by the receiving service — do not delay transfer for community imaging. Document motor, sensory, reflex, gait and bladder findings. Suspected MSCC with neuro signs: dexamethasone 16 mg promptly, in liaison with the MSCC service.
1Triage by duration — once block 0 is clear
| Duration | Action |
|---|---|
| <6 weeks | Self-limiting in most → block 5. |
| 6–12 weeks | Not settling: reassess the diagnosis and look for new symptoms; STarT Back medium/high → physio / exercise. |
| >12 weeks | Re-screen red flags (every visit) and inflammatory pattern; exercise-led self-management; deprescribe → chronic pathway. |
2Screen — one row is enough
- Cancer (current or past) + spinal pain suggesting metastases, no neuro signs → MSCC advice ≤24 h; MRI within 1 week.
- Infection: severe spinal pain + fever or systemic illness, IV drug use, immunosuppression, recent spinal procedure → Same-day hospital if unwell, neuro symptoms or strongly suspected.
- Fracture: significant trauma, or osteoporosis or steroids with sudden focal pain → imaging per local pathway; unstable, neuro deficit or cannot mobilise → Same-day hospital
- New significant motor deficit (foot drop, quadriceps weakness) → consider Same-day hospital
- 60+, persistent bone/back pain → FBC, calcium, ESR/PV, protein electrophoresis, free light chains; myeloma? → Suspected cancer pathway
- 60+, weight loss + back pain → consider direct-access CT ≤2 weeks (pancreas). Persistent non-mechanical thoracic pain → urgent imaging.
3Assess — once blocks 0–2 are answered
☐ Gait, midline tenderness ☐ L4/L5/S1 power, reflexes, sensation and SLR, both sides, if leg or neuro symptoms ☐ Perianal sensation if bladder, bowel or saddle symptoms ☐ Abdomen (pulsatile mass, renal angle), temperature ☐ STarT Back for each new episode
Not in primary care: routine imaging for non-specific pain or uncomplicated sciatica; a "cancer screen" (PSA, CA125).
4Classify — the 3 Ns — if the screen is negative
- Non-specific (most) — ± buttock/thigh pain, normal neurology → block 5.
- Sciatica — leg worse than back, dermatomal below knee, positive SLR.
- Spinal stenosis — bilateral leg pain on walking, eased by sitting or leaning forward.
- Inflammatory (axial SpA) — onset <45, >3 months, night waking, buttock pain, better with movement or NSAIDs → block 6.
- Referred — renal, AAA, pancreas, pelvis, zoster; not altered by spinal movement.
- Uncertain — say so; review sooner, reassess the diagnosis.
5Treat today — doses: SPC and local formulary
- All: reassure, stay active, no bed rest, exercise, stay at work.
- Consider oral NSAID (e.g. ibuprofen 400 mg TDS, naproxen 500 mg BD), lowest dose, shortest time, after GI, renal, hepatic, CV risk check; gastroprotect by risk. Avoid: GI bleed, heart failure, anticoagulant, pregnancy. Not paracetamol alone.
- Weak opioid (e.g. codeine 30–60 mg QDS) acute pain only, if NSAID unsuitable or ineffective; small supply, stop plan; counsel driving.
- Do not offer: gabapentinoids; oral steroids, benzodiazepines (sciatica); antidepressants for back pain; opioids for chronic pain; acupuncture.
6Refer routinely
- STarT Back medium/high → MSK physio (high: closer follow-up). Depression or anxiety → treat in its own right (NHS Talking Therapies).
- Persistent or severe radicular pain, severe neurogenic claudication → MSK / spinal (imaging there).
- Axial SpA with ≥4 NICE NG65 features, or 3 + HLA-B27 positive → rheumatology.
- Disabling pain despite conservative care → pain / MSK service; prolonged work absence → occupational health.
7Never reassure by
- A normal perianal exam or bladder scan — CES can be incomplete.
- A normal temperature, CRP or ESR when infection is possible.
- A negative HLA-B27 or CRP in suspected axial SpA.
- A normal examination in a patient with cancer — think MSCC.
- An established "chronic back pain" label — red flags can develop later.
- Mild bilateral leg symptoms — they still raise concern.
8Safety-net — say it, then document it
A&E now “Go to A&E straight away if you can't pass urine or it feels different, lose control of your bladder or bowel, feel numb around your back passage or genitals, or both legs become weak or numb, or you can't walk. Sudden severe back pain with collapse — call 999.” Same day: “Fever with back pain, a new foot drop or spreading tingling, severe pain despite painkillers, a fall that may have broken a bone, or unexplained weight loss — contact us today.”
Every consultation, including remote: ask and document bladder, bowel and saddle answers. Review individualised; sooner if not improving or new neurology.
✓Safe to leave primary care only if — all five, documented
No block 0–2 row applies; bladder, bowel, saddle asked
Neurology examined if leg or neuro symptoms
One of the 3 Ns fits, or uncertainty stated; STarT Back done
NSAID risks checked; any opioid has a stop plan
Safety-net given; review owner and timing set
Summary of the full Reasoning GP back pain algorithm, which holds the detail, examination, chronic pathway and evidence. Sources: NICE NG59 (psychological therapy and combined programme recommendations withdrawn July 2026), NG234, NG65, NG12 (updated April 2026), NG193, CG173; STarT Back (Keele). Clinical reference — follow local emergency, MSCC and spinal pathways and check doses in the SPC and your local formulary.