MRI Spine — suspected infection / discitis

Whole-spine sagittal survey to detect non-contiguous involvement, then targeted sagittal and axial imaging of the affected segment including the paraspinal soft tissues and epidural space.

Typical, not policy

Timings, volumes and delays here are representative values drawn from published guidance. Scanner generation, injector, cardiac output and local preference all move them. Confirm against your department's own protocol before you rely on a number.

When to use it

Suspected spondylodiscitis or vertebral osteomyelitis: back pain with fever, raised inflammatory markers, bacteraemia or recent instrumentation.
Suspected spinal epidural abscess, particularly with neurological deficit — an emergency question.
Known bacteraemia with new spinal pain, including in intravenous drug use and haemodialysis patients.
Suspected tuberculous spondylitis, where paravertebral collections and skip lesions are characteristic.
Failure to improve on antibiotics, to reassess for a collection requiring drainage.

Technique

Sagittal T1, sagittal T2 and a fat-suppressed fluid-sensitive sequence such as STIR through the region, plus a whole-spine sagittal survey because non-contiguous involvement is well recognised.
Post-contrast fat-suppressed T1 in sagittal and axial planes through the abnormal levels.
Axial T2 and post-contrast axial T1 define epidural collection, canal compromise and psoas extension.
Diffusion-weighted imaging is increasingly used to separate infective from degenerative endplate change and has been proposed where gadolinium must be avoided, though it does not replace contrast for abscess delineation.

Where it goes wrong

Omitting contrast, which leaves phlegmon and abscess indistinguishable and therefore leaves the surgical decision unanswered.
Post-contrast T1 without fat suppression, in which enhancing marrow is masked by normal fat signal.
Imaging only the painful segment: skip and multilevel involvement is common in tuberculous and haematogenous disease.
Not extending axial coverage into the paraspinal and psoas compartments where the drainable collection actually is.
Very early infection can have near-normal marrow signal; a negative early scan does not close the question.

Clinical questions that reach this study

Suspected multiple sclerosis or first demyelinating event Suspected metastatic spinal cord compression Suspected cauda equina syndrome Suspected discitis, vertebral osteomyelitis or epidural abscess Low back pain without red flags Suspected inflammatory spinal cord lesion (transverse myelitis)Thoracic back pain and suspected thoracic myelopathy Thoracolumbar spine trauma Suspected myeloma — skeletal assessment Suspected bone metastases

Contrast

Gadolinium, intravenous

Macrocyclic gadolinium agent at a typical single dose of about 0.1 mmol/kg, with fat-suppressed T1 acquired after injection in at least two planes through the affected levels.

Contrast is what separates phlegmon from drainable epidural or paraspinal abscess, and that distinction changes management.

Acquisition

Breathing: Free breathing.
Preparation: For suspected MSCC state neurological findings and time of onset — this is a same-day pathway, not a routine list slot. Analgesia and positioning support should be arranged in advance; an incomplete study because the patient could not lie flat is a failed study. Gadolinium is not needed to answer the compression question and is added only for infection, inflammation or when a soft-tissue mass needs characterising.

Safety checks this protocol carries

Derived from the contrast agent and phases above, not authored here — which is why they cannot drift apart from what the protocol actually does.

MR safety screening for implants and foreign bodies· radiographer at scan