What type of MRI (Magnetic Resonance Imaging) is recommended for a patient with severe back pain and new onset urinary symptoms?

MRI Type for Severe Back Pain with New Onset Urinary Symptoms

MRI lumbar spine without IV contrast is the most appropriate initial imaging study for a patient with severe back pain and new onset urinary symptoms, as it can accurately detect cauda equina syndrome and assess soft-tissue pathology, vertebral marrow, and spinal canal patency. 1

Rationale for MRI Selection

• MRI lumbar spine without IV contrast is most useful in evaluating suspected cauda equina syndrome (CES), which should be considered in patients with back pain and new urinary symptoms 1
• A prospective cohort study by Bell et al. recommends urgent MRI assessment in all patients who present with new-onset urinary symptoms in the context of low back pain or sciatica 1
• MRI provides high-resolution, multiaxial, multiplanar views with high contrast between soft tissues, allowing excellent evaluation of anatomic detail and biochemical composition of the lumbar spine 2

Clinical Significance of Urinary Symptoms with Back Pain

• New onset urinary symptoms in the context of severe back pain may indicate cauda equina syndrome, which is a medical emergency requiring prompt diagnosis and treatment 1
• Urinary symptoms may manifest as retention, incontinence, or overactive bladder, all of which can be caused by compression of the cauda equina 3
• Delayed diagnosis and treatment of cauda equina syndrome can lead to permanent neurological damage and persistent urinary dysfunction 3

Alternative MRI Protocols

• MRI lumbar spine without and with IV contrast: While this can be helpful to delineate the etiology of CES when clinical suspicion of underlying malignancy, infection, or inflammation exists, it is not typically needed as the initial study 1
• MRI lumbar spine with IV contrast alone: Not typically performed independently as an initial study, as its interpretation is most informative when correlated with standard noncontrast sequences 1

Alternative Imaging Modalities

• CT lumbar spine without IV contrast: While this can answer whether cauda equina compression is present, MRI is superior in soft-tissue contrast and characterizing the etiology of CES 1
• A retrospective review showed that 50% thecal sac effacement on CT predicted significant spinal stenosis, and <50% thecal sac effacement reliably excluded cauda equina impingement, using MRI as the reference standard 1
• CT myelography: Can be useful for assessing the patency of the spinal canal/thecal sac but has the disadvantage of requiring lumbar puncture for intrathecal injection of myelographic contrast 1

Special Considerations

• A single 3-D heavily T2-weighted fat-saturated sequence protocol has been shown to be a rapid, highly sensitive tool for evaluating CES in the emergency department 1
• There is no relevant literature to support the use of radiography, whole-body FDG-PET/CT, or bone scan with SPECT or SPECT/CT in the initial imaging of suspected CES 1
• Patient-reported symptom information should be correlated with MRI findings to distinguish presumptive pain generators from incidental abnormalities 4

Clinical Approach

1. Obtain urgent MRI lumbar spine without IV contrast when a patient presents with severe back pain and new urinary symptoms 1
2. Consider adding contrast (MRI without and with IV contrast) only if there is clinical suspicion for underlying malignancy, infection, or inflammation 1
3. If MRI is contraindicated or unavailable, CT lumbar spine without IV contrast can be used to assess for cauda equina compression 1
4. Proceed with appropriate treatment based on imaging findings, with surgical decompression typically indicated for confirmed cauda equina syndrome 3