What is the recommended diagnostic work‑up and management (including empiric antibiotics, treatment duration, and surgical indications) for acute discitis?

Acute Discitis: Diagnostic Work-up and Management

Diagnostic Work-up

Obtain MRI with contrast immediately as the gold standard imaging modality, which demonstrates disc space inflammation, vertebral endplate changes, and paraspinal/epidural soft tissue involvement with superior sensitivity and specificity compared to other modalities. 1

Initial Laboratory Assessment

• Draw ESR, CRP, and blood cultures before initiating antibiotics 1
• Blood cultures are positive in only a minority of cases (approximately 1 in 10 patients with positive disc cultures have negative blood cultures), making tissue diagnosis critical 2
• Consider brucella or mycobacterial testing if epidemiologically relevant (endemic area exposure, appropriate risk factors) 1

Tissue Diagnosis - Critical Priority

Obtain CT-guided or fluoroscopy-guided percutaneous disc biopsy for microbiologic and histopathologic examination before starting antibiotics whenever possible. 1, 3

• Send specimens for comprehensive cultures: aerobic, anaerobic, mycobacterial, fungal, and Brucella if indicated 1
• Request both microbiologic cultures AND histopathology on all specimens to confirm diagnosis and guide further testing, especially if cultures are negative 1
• If initial biopsy grows skin contaminants (coagulase-negative staphylococci except S. lugdunensis, Propionibacterium, diphtheroids) without concomitant bloodstream infection, obtain a second biopsy 1
• If first biopsy is nondiagnostic, add fungal and mycobacterial cultures plus bacterial nucleic acid amplification testing to stored specimens 1
• If second biopsy remains nondiagnostic, consider percutaneous endoscopic discectomy and drainage or open excisional biopsy 1

Imaging for Entire Spine

Consider imaging the entire spine (not just symptomatic level) in: 1

• IV drug users
• Tuberculosis or endemic infections
• Initial imaging showing multilevel involvement

Empiric Antibiotic Therapy

Begin empiric antibiotics only after obtaining blood cultures and ideally after tissue biopsy, targeting Staphylococcus aureus as the most common pathogen, with vancomycin as initial therapy pending culture results. 1, 2

• Adjust antibiotics based on culture and susceptibility results
• Transition to oral agents with excellent bioavailability (fluoroquinolones, linezolid, trimethoprim-sulfamethoxazole) once clinical improvement occurs and CRP decreases 1
• Early switch to oral therapy (after median 2-3 weeks IV) is safe if CRP has decreased and significant abscesses have been drained 1

Treatment Duration

Administer antimicrobial therapy for 6 weeks total duration, as this has been shown non-inferior to 12 weeks in randomized controlled trial. 1

• A randomized trial of 351 patients demonstrated 90.9% cure rate with 6 weeks versus 90.9% with 12 weeks 1
• Duration may be extended beyond 6 weeks for specific organisms (Brucella requires 3 months with doxycycline-based regimens) 1
• Most patients can transition from IV to oral therapy after 2-4 weeks if clinically improving 1

Surgical Indications - Absolute

Proceed with urgent surgical intervention for: 1, 3

• Progressive neurologic deficits (radiculopathy, myelopathy, spinal cord compression) - this is a surgical emergency 1, 3
• Progressive spinal deformity with instability despite adequate antimicrobial therapy 1
• Spinal instability with or without pain despite adequate medical therapy 1
• Epidural abscess with mass effect causing neural compression 3

Surgical Indications - Relative

Consider surgical debridement with or without stabilization for: 1

• Persistent or recurrent bloodstream infection without alternative source 1
• Intractable pain worsening despite appropriate medical therapy 1
• Large epidural abscess formation 1
• Failure of medical treatment 1

When NOT to Operate

Do not perform surgical debridement in patients with worsening bony imaging findings at 4-6 weeks if clinical symptoms, physical examination, and inflammatory markers are improving. 1

• Radiographic worsening of vertebral body and disc findings commonly occurs despite clinical improvement, particularly in the first 4 weeks 1
• This radiographic phenomenon should not trigger unnecessary surgery or antibiotic prolongation 1

Monitoring and Follow-up

Clinical Assessment at 4 Weeks

• Monitor ESR and CRP after approximately 4 weeks of therapy in conjunction with clinical assessment 1
• ESR >50 mm/hour and CRP >2.75 mg/dL after 4 weeks confer higher risk of treatment failure 1
• CRP improves more rapidly and correlates more closely with clinical status than ESR 1
• Interpret inflammatory markers in concert with clinical status - many patients with persistently elevated markers have successful outcomes 1

Follow-up Imaging Strategy

Do not routinely order follow-up MRI in patients demonstrating favorable clinical and laboratory response to therapy. 1

• Follow-up MRI performed <4 weeks may falsely suggest progressive infection despite clinical improvement 1
• Radiographic inflammation may persist for months to years without clinical relevance 1

Obtain follow-up MRI only in patients with poor clinical response to therapy, emphasizing evolutionary changes in paraspinal and epidural soft tissues (not bone). 1

• Soft tissue findings (paravertebral and epidural changes, abscesses) correlate better with clinical status and outcomes than bony changes 1
• Worsened soft tissue findings at 4-8 weeks associate with treatment failure rates up to 44% 1

Critical Pitfalls to Avoid

• Do not delay tissue diagnosis - up to 30% of cases have negative routine bacterial cultures, requiring evaluation for atypical organisms 3
• Do not rely solely on blood cultures - disc biopsy has higher yield than blood cultures 2
• Do not interpret persistent pain, residual neurologic deficits, elevated inflammatory markers, or radiographic findings alone as treatment failure 1
• Do not operate based on imaging worsening alone if the patient is clinically improving 1

Multidisciplinary Referral Indications

Refer urgently (same day) to tertiary neuroscience center for: 3

• Any neurological deficits
• Signs of spinal cord compression
• Inability to care for self without help

Refer within 48 hours for: 3

• Patients unable to self-care but with available support

Refer within 1 month for: 3

• Diagnostic uncertainty after initial work-up
• Failed first-line treatments
• Rapid clinical deterioration

The referral center should have neurosurgical expertise in spinal infections, interventional radiology for biopsy guidance, advanced MRI capabilities, and multidisciplinary team meetings for complex cases 3.