Back Pain

Differential Diagnosis

Occasional Diagnoses

Rare Diagnoses

  • Spinal Stenosis
  • Osteomalacia
  • Aortic Aneurysm
  • Spondylolisthesis
  • Osteomyelitis
  • Malingering
  • Pancreatic Carcinoma

Ready Reckoner

Key distinguishing features of the most common diagnoses

Mechanical PainDisc ProlapseSpondylosisPyelonephritis/ Renal StonesPelvic Infection
Leg Pain or Numbness PresentPossibleYesPossibleNoNo
Unilateral SymptomsPossibleYesPossibleYesPossible
Depressed ReflexesNoPossiblePossibleNoNo
Abdominal TendernessNoNoNoPossibleYes

Possible Investigations


Possible:Urinalysis, MSU, FBC, ESR/CRP, plasma electrophoresis, blood calcium, PSA.

Small Print:Lumbar spine X-ray, renal investigations, HLA-B27, CT or MRI scan, bone scan, investigations for GI cause, ultrasound, DXA scan.

  • Urinalysis useful if UTI suspected: Look for blood, pus and nitrite as markers of infection; confirm with MSU; blood alone suggests possible stone.
  • ESR/CRP elevated in malignant and inflammatory disorders.
  • FBC: Hb may be reduced in malignancy; a high WCC raises the possibility of osteomyelitis.
  • Plasma electrophoresis: Paraprotein band in myeloma.
  • Blood calcium: Elevated in myeloma and bony secondaries; reduced in osteomalacia.
  • PSA: If disseminated prostate cancer suspected.
  • Lumbar spine X-ray usually unhelpful in mechanical pain. Consider if no resolution by 6 weeks to investigate possible underlying pathology. In younger patients, it may help diagnose sacroiliitis or spondylolisthesis; in older people, it is useful to check for vertebral collapse. Generally, if imaging is required, CT or MRI may be more helpful.
  • Bone scan: Will detect bony secondaries and bone infection.
  • CT or MRI scan usually a specialist’s request: Good for spotting spinal stenosis, significant prolapsed disc and discrete bony lesions.
  • Investigations for GI cause might include endoscopy (for DU), serum amylase (for pancreatitis) and CT scan (for carcinoma of pancreas).
  • Ultrasound: For aortic aneurysm.
  • Renal investigations: For recurrent pyelonephritis and possible renal or ureteric stones.
  • DEXA scan: May be required to confirm suspicion of osteoporosis.

Top Tips

  • The vast majority are ‘mechanical’, and most of these improve regardless of treatment modality in 6–8 weeks; a positive and optimistic approach is important.
  • Patients often expect an X-ray or scan. Resist requests unless appropriate – and explain why. Even if the patient doesn’t make this request, consider volunteering why you’re not ordering any investigations, as this can help maintain confidence in the doctor–patient relationship, especially if the symptoms take some time to settle.
  • If the problem is recurrent, exclude significant pathology then explore the patient’s concerns. In simple recurrent mechanical back pain, it is worth discussing preventive measures and educating the patient for self-management of future episodes.
  • True malingering is not common, but back pain is favoured among malingerers because of its subjectivity. Beware of patients who apparently cannot straight-leg raise, yet have no problem sitting up on the couch.

Red Flags

  • The traditional ‘red flags’ in back pain are thought to be of very limited use because of poor specificity and sensitivity. The only ones regarded as genuinely helpful are, for spinal fracture, older age, trauma, the presence of contusions or abrasions and steroid use, and, for spinal malignancy, a past history of cancer. Current consensus is that slavish adherence to red flags should be avoided and instead the overall clinical picture and progress assessed – although an ESR/CRP may be useful in ruling out significant disease.
  • Bilateral sciatica, saddle anaesthesia and bowel and/or bladder dysfunction suggests central disc protrusion – this is a neurosurgical emergency.
  • Consider prostatic cancer in men over 55 with atypical low back pain. Do a PR exam, together with PSA and bone assay.
  • Back pain without any restriction of spinal movement, or which is not exacerbated by back movement, suggests that the source of the problem lies elsewhere – consider renal, aortic or gastrointestinal disease, or pelvic pathology in women.
  • Tearing interscapular or lower pain in a known arteriopath suggests dissecting aortic aneurysm – admit straight away.

Published: 2nd August 2022 Updated: 21st March 2024

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