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🦴 Back pain
Ask about the bladder, the bowels and the saddle before anything else — then ask whether this pain is mechanical at all. Sudden, tearing, febrile, or with any neurology, is not a bad back.
| Cauda equina syndrome Must exclude | Saddle anaesthesia, urinary retention or incontinence, bilateral sciatica, reduced anal tone. Painless retention with overflow is a LATE, high-risk feature and is easily missed because the patient volunteers no urinary complaint — it is not the sign to wait for. Ask about saddle sensation and bladder function while the picture is still incomplete.Emergency MRI — tonight, not tomorrow. Ask about the bladder and examine the perineum in every acute back pain. |
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| Spinal cord compression Must exclude | Back pain with any neurology below the level — weakness, sensory level, brisk reflexes, upgoing plantars. Known malignancy makes this the working diagnosis until imaged.Dexamethasone 16mg and urgent whole-spine MRI within 24 hours. Do not wait for a level to become obvious. |
| Ruptured AAA Must exclude | Sudden back or flank pain with collapse in an older patient. Routinely mistaken for renal colic. Consider AAA particularly in older patients with first-presentation renal-colic-like pain.Do not send them to the CT scanner alone. Vascular surgery, permissive hypotension. |
| Aortic dissection Must exclude | Tearing interscapular pain, maximal at onset, with a blood pressure differential between arms or new aortic regurgitation. Can present as back pain with no chest pain at all.CT aortogram. Do NOT anticoagulate. |
| Spinal epidural abscess Must exclude | Fever, spinal tenderness and progressive neurology — but the classic triad is present in a minority. Intravenous drug use, diabetes, recent spinal procedure, bacteraemia, or an indwelling line.Blood cultures and urgent MRI of the WHOLE spine. Do not give antibiotics before cultures unless septic — and do not let a normal X-ray reassure you. |
| Pyelonephritis Time-sensitive | Loin pain with fever, rigors and vomiting, usually with urinary symptoms but not always. Tender renal angle.Cultures and antibiotics. Imaging if septic or not improving — an obstructed infected kidney needs draining, not just treating. |
| Renal colic Time-sensitive | Loin-to-groin pain, unable to lie still, with haematuria. Writhing rather than lying rigid is the distinction from peritonism.NSAID first line, non-contrast CT KUB. Fever with an obstructing stone is an emergency. |
| Vertebral fracture Time-sensitive | Sudden focal pain, often on trivial movement or with no trauma at all. Osteoporosis, long-term steroids, myeloma, or height loss and kyphosis.X-ray, and think about WHY it broke — a fragility fracture is an osteoporosis diagnosis and a bone-protection prescription. |
| Myeloma / hypercalcaemia Time-sensitive | Back pain with anaemia, renal impairment, hypercalcaemia or unexplained fractures. Pain at rest and at night that is not relieved by lying down.Calcium, renal function, FBC, and a myeloma screen. Bone pain plus a raised calcium is not a coincidence. |
| Acute pancreatitis Time-sensitive | Epigastric pain boring THROUGH to the back, relieved by sitting forward, with vomiting. Gallstones and alcohol.Lipase or amylase. Back pain with epigastric tenderness earns one. |
| Perforated peptic ulcer Time-sensitive | Sudden severe epigastric pain radiating to the back with a rigid abdomen. NSAIDs and steroids.Erect CXR or CT. Surgeons. |
| Sickle cell crisis Time-sensitive | Severe back, chest or limb pain in a known sickle patient. The pain is real and is routinely under-treated.Strong analgesia within 30 minutes, oxygen, fluids. Chest signs mean acute chest syndrome. |
| Herpes zoster Time-sensitive | Burning dermatomal pain that PRECEDES the rash by days, so the back can hurt for 48 hours with nothing to see.Antiviral within 72 hours of the rash. Worth considering in unilateral band-like pain with a normal examination. |
| Ankylosing spondylitis Consider | Inflammatory back pain — young onset, insidious, morning stiffness over 30 minutes, BETTER with exercise and worse with rest, waking in the second half of the night.Not an on-call diagnosis, but an on-call referral. The average delay to diagnosis is measured in years. |
| Mechanical back pain Common | Pain related to movement and posture, no red flags, no neurology, normal observations. Much the commonest cause and the correct answer most of the time.A positive diagnosis once the red flags are actively excluded — analgesia and movement, not bed rest and imaging. |
15 differentials · 11 open a full pathway in the app.