What red flag in back pain requires urgent imaging?

• A. Radicular pain without bowel/bladder dysfunction
• B. Fever at night
• C. Localized mechanical back pain without neurological signs
• D. Cauda equina signs (saddle anesthesia or new bowel/bladder dysfunction)

Answer: (D)

Cauda equina syndrome is a neurosurgical emergency. When back pain is accompanied by saddle anesthesia or new bowel or bladder dysfunction, it means acute compression of the lumbosacral nerve roots. This can rapidly progress to irreversible urinary and bowel incontinence and leg weakness if not decompressed promptly, so urgent MRI to identify the compression and rapid spine/surgical consultation are required.

Other scenarios may raise concern (fever at night can suggest infection or malignancy, and isolated radicular pain or localized mechanical pain without neuro signs is often nonurgent), but they do not imply the same immediate threat to continence and motor function as cauda equina signs.