What is the next step in management for a female patient with constant, dull back pain (9/10 intensity) radiating to the midback, accompanied by numbness at the site of pain, who has not responded to physical therapy and is concerned about a possible herniated disc?

Obtain MRI of the Lumbar Spine Now

This patient requires MRI imaging at this point because she has subacute back pain (2+ months duration) that has failed conservative management including physical therapy, and her symptoms are worsening rather than improving. 1

Why Imaging is Indicated Now

The key guideline thresholds have been met:

• Duration criterion: Pain has persisted beyond 4-6 weeks of conservative treatment 1
• Failed conservative management: Physical therapy has not only been ineffective but symptoms are worsening 1
• Severity: Pain intensity of 9/10 with functional impairment (difficulty lifting child) warrants further evaluation 1
• Subacute timeframe: At 2+ months, this falls into the subacute category (4-12 weeks) where imaging is appropriate when conservative measures fail 1

The American College of Radiology specifically states that imaging is considered for patients who have had up to 6 weeks of medical management and physical therapy that resulted in little or no improvement 1. This patient clearly meets this criterion.

Critical Red Flag Assessment First

Before ordering the MRI, you must systematically exclude emergent conditions:

• Cauda equina syndrome: Ask specifically about urinary retention (not just frequency), fecal incontinence, saddle anesthesia, and bilateral leg weakness 1, 2
• Malignancy: Assess for unexplained weight loss, night pain that wakes her from sleep, history of cancer, age >50 1, 2
• Infection: Fever, recent infection, IV drug use, immunocompromised status 1, 2
• Fracture: Significant trauma history, osteoporosis, chronic steroid use 1, 2

The patient reports no weakness, no incontinence, and no perineal numbness, which makes cauda equina syndrome unlikely but does not completely exclude it 1.

Why MRI Rather Than Plain Radiographs

While plain radiographs can be considered as initial imaging 2, MRI is the superior choice in this clinical scenario because:

• The patient's concern is specifically for herniated disc, which requires MRI for diagnosis 3
• Numbness at the pain site suggests possible nerve involvement requiring soft tissue evaluation 1
• Plain radiographs cannot visualize disc pathology, nerve root compression, or soft tissue abnormalities 1
• At 2+ months with worsening symptoms despite PT, you need definitive imaging to guide further management 1

Management While Awaiting MRI

Continue conservative measures but modify the approach:

• Medication optimization: Prescribe NSAIDs if not already maximized (first-line pharmacologic treatment) 2, 4
• Activity modification: Advise remaining active but avoiding specific aggravating movements (like lifting her child) 2, 4
• Stop ineffective physical therapy: Since PT is making pain worse, discontinue current regimen 1
• Consider spinal manipulation: This has moderate evidence for both acute and chronic low back pain and may provide benefit while awaiting imaging 5

Common Pitfalls to Avoid

Do not delay imaging further in this case. The guideline recommendation against early imaging applies to acute uncomplicated low back pain in the first 4-6 weeks 1. This patient is beyond that window with failed conservative treatment and worsening symptoms 1.

Do not assume "nonspecific low back pain" without imaging. While 85% of low back pain is nonspecific 1, this patient has concerning features (severe pain, numbness, functional impairment, worsening with PT) that warrant investigation 1.

Do not order whole spine imaging. Target the lumbar spine based on her symptom location 1.

Next Steps After MRI

If MRI confirms herniated disc with nerve root compression:

• Most disc herniations resolve with conservative treatment; only 5-10% require surgery 6
• Continue conservative management for at least 6 weeks total unless progressive neurologic deficits develop 6
• Refer to spine surgeon only if: definite disc herniation on imaging + corresponding neurologic deficit + failure of 6 weeks conservative therapy 6
• Consider epidural steroid injections if radicular symptoms are prominent (moderate evidence) 7

If MRI is negative for significant pathology, consider facet joint or sacroiliac joint dysfunction and reassess treatment strategy 1, 8.