Summary

Discitis (or Spondylodiscitis) is an infection of the intervertebral disc and adjacent vertebral bodies. It usually results from haematogenous spread (from skin, UTI, or endocarditis). The most common organism is Staphylococcus aureus (50%). The cardinal rule of management is "Biopsy BEFORE Antibiotics" (unless the patient is septic), as identifying the organism is critical for the 6-12 week treatment course. MRI is the gold standard investigation. Surgery is reserved for neurological compression, instability, or failure of medical management. [1,2,3]

Key Facts

• Most Common Organism: Staphylococcus aureus (MSSA/MRSA).
• Most Common Route: Haematogenous (Arterial supply to endplates).
• The "Golden Rule": Do NOT give antibiotics until you have a culture (Blood or Biopsy), unless the patient is septic (life-threatening). Suppressing the bug without ID leads to months of "blind" treatment.

Clinical Pearls

"The CRP Lag": CRP is the most sensitive marker for monitoring response. It rises quickly and falls associated with clinical improvement. ESR is slower ("lazy") and less useful for acute monitoring.

"Assume Endocarditis": If a patient has Staph Aureus in their blood and a sore back, you MUST Echo their heart. The spine and heart are linked by the bloodstream.

"Pott's Spine": Tuberculosis loves the spine (Thoracolumbar junction). It causes massive destruction with "Cold Abscesses" and kyphosis (Gibbus deformity) but often minimal systemic sepsis.

                 SUSPECTED DISCITIS
               (Back Pain + High CRP)
                        ↓
             NEUROLOGY / SEPSIS PRESENT?
             ┌──────────┴──────────┐
           YES                    NO
            ↓                     ↓
        START ABX            **HOLD ABX**
       (Target Sepsis)       (Wait for ID)
            +                     ↓
       URGENT MRI            URGENT MRI
       (Whole Spine)        (Whole Spine)
            ↓                     ↓
      SURGICAL OPINION       BLOOD CULTURES
      (Decompression?)            ↓
                             POSITIVE?
                           ┌──────┴──────┐
                         YES            NO
                          ↓             ↓
                      START ABX     CT BIOPSY
                      (Targetted)       ↓
                                    CULTURE?
                                  ┌─────┴─────┐
                                POS         NEG
                                 ↓           ↓
                             START ABX    2nd BIOPSY
                                          OR OPEN BX

1. Medical (The Mainstay)

• Stabilisation: Bed rest until CRP falls and pain improves. Bracing (TLSO) for comfort.
• Antibiotics:
  • Course: Typically 6-12 weeks total. (e.g., 2 weeks IV, 4-10 weeks Oral).
  • Choice: Guided by sensitivities. Common: Flucloxacillin (MSSA), Vancomycin (MRSA), Ceftriaxone (Gram Neg).
  • Stop criteria: CRP normal, Pain resolved, X-ray stable.

2. Surgical

• Indications:
  1. Neurological Deficit: Compression by abscess or bone.
  2. Sepsis: Uncontrolled despite Abx (needs drainage).
  3. Instability: Kyphosis/Collapse.
  4. Diagnosis: Failure of percutaneous biopsy (Open Biopsy).
• Procedure: Debridement + Stabilisation (Screws/Rods). Note: You CAN put metal into infection if you debride thoroughly.

IDSA Guidelines (2015)

• Strong recommendation for 6 weeks of antibiotic therapy for native vertebral osteomyelitis.
• Recommends holding antibiotics for biopsy in haemodynamically stable patients.

OVIVA Trial (Li et al. 2018)

• Oral vs IV Antibiotics for Bone/Joint Infection.
• Result: Oral antibiotics (after short IV induction) were non-inferior to prolonged IV therapy, provided the organism is sensitive and bioavailability is good. (Changed practice away from 6 weeks of PICC lines).

What is Discitis?

It is a bacterial infection of the spine. Germs from your blood (often from a skin scrape or urine infection) have settled in the backbone and started to eat away at the disc and bone.

Why do I need a biopsy?

We need to know exactly which germ is causing the infection so we can pick the perfect antibiotic bullet. Guessing can lead to failure.

Do I need surgery?

Usually No. Antibiotics are very powerful and can cure the infection, but they take a long time (months) to penetrate the bone. Surgery is only needed if the infection is squashing the spinal cord or if the spine is collapsing.

Q1: What are the indications for surgery in Discitis? A: 1. Neurological Deficit (Cord compression). 2. Instability/Deformity (Significant destruction). 3. Failure of Medical Management (Sepsis/CRP not improving). 4. Diagnosis (Need for open biopsy).

Q2: Which organism is associated with IV Drug Use? A: Pseudomonas aeruginosa. Though Staph Aureus is still the most common overall, Pseudomonas is disproportionately represented in IVDU and requires specific cover (Ceftazidime/Ciprofloxacin).

Q3: Describe the MRI findings of Discitis. A: T1: Hypointense (Dark) disc and marrow (edema). T2: Hyperintense (Bright/Hot) fluid signal in the disc and adjacent endplates. T1+Gad: Enhancement of the disc and vertebral bodies. Loss of the intranuclear cleft.

(End of Topic)