Which of the following constitutes a red flag that would prompt imaging in acute back pain?

• A. Cauda equina symptoms
• B. Mild axial pain after activity
• C. Age 25 with onset last 2 days
• D. No red flags

Answer: (A)

Red flags guide us to imaging when acute back pain might hide a serious problem. Cauda equina symptoms are a urgent red flag because they suggest compression of the lower spinal nerve roots that can lead to permanent neurologic damage if not treated quickly. Signs include saddle anesthesia, new or worsening bowel or bladder dysfunction, and progression of leg weakness or sensory loss. When this pattern appears, urgent MRI is needed to identify compression and plan decompression if necessary.

The other scenarios describe typical, non-emergent acute back pain. Mild axial pain after activity is common musculoskeletal strain. Being 25 years old with onset over a couple of days is not itself a red flag. No red flags means imaging isn’t indicated.