Synopsis
Recognise a symptom-defined cauda equina emergency, use examination and bladder scanning without false reassurance, and route suspected disc-related compression to emergency MRI and definitive spinal review.
- Suspected cauda equina syndrome is a symptom-and-trajectory emergency: no single symptom, sign or combination has adequate diagnostic accuracy to rule it in or out.
- Current national criteria use back and/or leg pain plus a relevant symptom of recent onset, 14 days or fewer, or deterioration; ongoing symptoms in that window go to hospital now.
- Negative physical tests do not override positive subjective symptoms. Digital rectal examination is not necessary in the national pathway; record subjective perianal sensation.
Key red flags
Back and/or leg pain plus new or worsening difficulty initiating micturition or impaired sensation of urinary flow within the previous 14 days.
New altered perianal, perineal or genital sensation in the S2–S5 distribution; ask directly and record the patient’s own description.
Loss of rectal-fullness sensation, new bowel dysfunction attributable to sacral nerve dysfunction, or new sexual dysfunction or genital sensory loss.
Severe or progressive bilateral neurological leg deficit; bilateral radicular pain alone is a warning that needs an urgent pathway and explicit safety netting.
An apparently normal digital rectal examination, preserved voluntary anal contraction or low post-void residual does not rule out cauda equina syndrome.
Recent spinal intervention, anticoagulation, infection risk, trauma or cancer suggests a rarer compressive cause and requires the relevant parallel pathway rather than assuming disc prolapse.
Ask separately about bladder filling, ability to initiate, sensation of urinary flow, straining and continence. Retention is a late phenotype; altered sensation can be the earlier signal.
Ask about altered sensation around anus, perineum and genitals, wiping, intercourse and genital arousal or function. Use neutral language, clarify laterality and compare with baseline.
Loss of rectal-fullness sensation is more specific to sacral dysfunction than constipation alone. Clarify awareness, continence, medication and longstanding bowel disease.
Preserved ability to void does not make compression safe. In incomplete CES, sacral sensory or urinary-flow change may exist before established painless retention; the treatment aim is to prevent further irreversible deficit.
Reasoning priorities
Confirm or exclude cauda equina compression, localise the lesion and identify disc, tumour, infection, blood or another cause.
Request immediately when current criteria are met; the 2026 national pathway specifies completion as soon as possible and within 4 hours of request. A radiological lesion must be matched to symptoms, but negative examination does not justify withholding MRI.
Worked reasoning
A patient with back and bilateral leg pain reports new difficulty starting urine and reduced flow sensation; lower-limb power is full and PVR is 90 mL.
- Treat the new subjective urinary-flow symptoms as a positive CES feature; do not let full power or PVR below 200 mL exclude compression.
- Record onset, progression, lower-limb findings and subjective perianal sensation, then make an emergency referral to the nearest facility able to provide emergency MRI.
- Request MRI immediately; the national pathway target is as soon as possible and within 4 hours of the radiology request. Keep the patient nil by mouth while awaiting the result.
- If MRI shows cauda equina compression, contact the spinal surgeon immediately and transfer images and documentation; if it does not, investigate alternatives and give explicit deterioration safety netting.
- Do not transfer the disc-related operative timing categories to abscess, haematoma, tumour or trauma; activate the matching cause-specific pathway.