What is the workup for discitis (inflammation of the intervertebral disc)?

From the Guidelines

The workup for discitis should include a thorough history and physical examination, followed by laboratory tests including complete blood count, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and blood cultures (at least two sets), and imaging studies with MRI with contrast as the gold standard diagnostic test 1. The diagnosis of discitis can be challenging, and a high index of clinical suspicion is required to initiate the clinical workup.

Key Components of the Workup

• Laboratory tests: complete blood count, ESR, CRP, and blood cultures (at least two sets) to help identify the presence of an infection and guide antibiotic therapy 1
• Imaging studies:
  • Plain radiographs of the affected spinal region to assess for any structural abnormalities
  • MRI with contrast as the gold standard diagnostic test to evaluate the extent of the infection and guide treatment 1
  • CT scan may be useful if MRI is contraindicated

Tissue Sampling and Antibiotic Therapy

• A tissue sample for microbiological diagnosis should be obtained through CT-guided biopsy or surgical biopsy before starting antibiotics when possible 1
• If blood cultures are positive, biopsy may be deferred
• Empiric antibiotic therapy should be initiated after cultures are obtained, typically with vancomycin 15-20 mg/kg IV every 8-12 hours plus ceftriaxone 2g IV daily for broad coverage of Staphylococcus aureus (including MRSA) and gram-negative organisms
• Once the pathogen is identified, antibiotics should be narrowed accordingly

Treatment and Monitoring

• Treatment typically continues for 6-12 weeks, with transition to oral antibiotics when clinically improving
• Infectious disease consultation is recommended for antibiotic management
• Pain control, spinal immobilization, and early physical therapy are important adjunctive measures
• Surgical intervention may be necessary for patients with neurological deficits, spinal instability, or failure of medical management
• Close monitoring with serial ESR/CRP measurements helps assess treatment response
• Early diagnosis and appropriate treatment are crucial to prevent complications such as spinal deformity, neurological deficits, or chronic pain 1

From the Research

Discitis Workup

• The workup for discitis typically involves a combination of clinical findings, laboratory tests, and imaging studies 2, 3, 4, 5, 6
• Laboratory tests may include complete blood count, C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and blood cultures 2, 4, 5, 6
• Imaging studies may include magnetic resonance imaging (MRI), computed tomography (CT) scans, and plain radiographs 2, 3, 4, 5, 6
• Biopsy may be performed to obtain a definitive diagnosis and guide treatment 3, 5, 6

Diagnostic Yield of Biopsy

• The diagnostic yield of image-guided biopsy for discitis-osteomyelitis has been reported to be around 34-41% 3, 6
• Factors associated with higher biopsy yield include elevated ESR, epidural collection on MRI, and disc sampling 3, 6
• Biopsy results can impact clinical management, including changing antibiotic therapy or starting new treatments 3, 6

Timing of Biopsy

• The optimal timing of biopsy in relation to blood culture results is not well established 5
• Waiting 2 days for preliminary blood culture results may avoid unnecessary biopsy in some patients, but does not significantly impact hospital length of stay 5

Clinical Management

• Clinical management of discitis typically involves antibiotic therapy and spinal immobilization 2, 4
• Operative intervention may be necessary in some cases, such as those with neurologic worsening or failure to respond to nonoperative treatment 4
• Biopsy results can inform clinical management and guide treatment decisions 3, 6