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A 38-year-old man presents to the emergency department with a two-day history of severe lower back pain radiating down the back of his left thigh and calf into the sole of his foot, following heavy lifting at work. Over the last 12 hours he has developed numbness around his perineum and inner thighs, difficulty initiating urination, and progressive weakness in both legs. On examination he is distressed; there is bilateral ankle weakness, reduced ankle reflexes, saddle (perianal) anaesthesia, and a palpably distended bladder.
Questions
a) What is the diagnosis and why is it an emergency? (2 marks)
The diagnosis is cauda equina syndrome — a large central lumbar disc herniation (or other mass) compressing the sacral nerve roots of the cauda equina. The cardinal features are saddle (perianal) anaesthesia, urinary retention/difficulty, and bilateral neurological signs (progressive leg weakness, reduced reflexes). It is a surgical emergency because delayed decompression leads to permanent paralysis, bladder and bowel incontinence, and sexual dysfunction.
b) List four red flags you must actively screen for in any patient with low back pain. (2 marks)
- Cauda equina features (saddle anaesthesia, bladder/bowel dysfunction, bilateral neurology, progressive weakness).
- Significant trauma, age over 50, or long-term corticosteroids (vertebral fracture).
- Fever, weight loss, night sweats, immunosuppression or IV drug use (spinal infection).
- History of cancer with new progressive or night pain (spinal metastasis); also inflammatory back pain in the young (axial spondyloarthritis).
c) Outline the acute management of this patient. (4 marks)
- Recognise the emergency and arrange an urgent MRI of the lumbar spine (whole spine if multifocal suspicion) today.
- Immediate neurosurgical/orthopaedic referral for urgent surgical decompression, ideally within 24 to 48 hours of symptom onset to maximise neurological recovery.
- Urinary catheterisation for retention; keep nil by mouth for theatre; provide analgesia and protect pressure areas.
- Baseline bloods (FBC, U&E, coagulation, group and save), a post-void residual bladder scan to document retention, and a clear neurological examination (motor power, reflexes, sensory including saddle area and anal tone) documented before surgery.
d) How would you manage a 30-year-old with acute non-specific low back pain for one week and no red flags? (2 marks)
- Education and reassurance that the pain is mechanical and self-limiting (over 90 percent recover within six weeks); advise to stay active and return to work; avoid bed rest.
- Simple analgesia — paracetamol or NSAIDs (e.g. ibuprofen 400 mg three times daily) at the lowest effective dose for the shortest time; avoid opioids. Add heat and short-term manual therapy/spinal manipulation if needed. Do not arrange routine imaging or refer for injections/surgery.