Red flags in low back ache

If any of the following flags are seen in a patient with low back ache, imaging with MRI is recommended. CT only if MRI is contraindicated.

cauda equina syndrome (urinary retention, faecal incontinence, saddle anesthesia)
severe unremitting worsening of pain at night – infection or tumor
significant trauma – fracture
unexplained weight loss, fever, HIV, history of cancer – infection or tumor
use of intravenous drugs or steroids – infection or compression fracture
widespread neurological signs – tumor or neurological disease
>50 years, particularly >65 years with new onset back pain
duration > 6 weeks
prior surgery