Diagnosis of discitis/vertebral osteomyelitis involves clinical suspicion in patients with severe lower back pain and needs to be confirmed with investigations prior to starting treatment.
Increased suspicion is necessary in the elderly (particularly men), the immuno-compromised, a diagnosis of endocarditis and in patients who have undergone spinal surgery. The organisms are varied with skin flora predominating (Staphylococcus aureus including some MRSA) but also enteric gram-negative bacilli (urinary catheterisation), Pseudomonas aeruginosa and Candida sp (intravascular access sepsis), Groups B and G haemolytic streptococci (diabetes mellitus) and Tuberculosis.
Blood tests – raised WCC, ESR and CRP
Radiology – plain x-ray and MRI
Microbiology – organism needs to be identified with blood culture or CT guided aspiration, although the latter is preferable, with specimens sent for histologic examination and for aerobic and anaerobic bacterial, fungal, and mycobacterial cultures.
Bone scan – radionuclide scanning is performed only in selected patients where there is clinical suspicion but MRI cannot be performed.
If cultures of blood and the needle aspirate are negative and the clinical suspicion for discitis remains high a second CT guided aspiration is recommended. If this specimen is also non-diagnostic then best empirical therapy is started against common gram-positive (especially S. aureus), and gram-negative bacterial pathogens. If such therapy does not result in objective clinical improvement in three to four weeks, a third CT guided aspiration or possibly open surgical biopsy should be considered or else a change in empirical therapy guided by microbiological and/or Neuro-spine MDT advice.
A six week course of intravenous antibiotics is recommended, with blood markers weekly and MRI at 2 and 6 weeks, with clinical review at this time. If indicated at this juncture antibiotics could be reinstated for a further six weeks giving a full three month course.
Once antibiotics have been stopped it is essentially for the blood markers to be repeated at two and six weeks plus MRI at 6 weeks so that a full clinical and diagnostic re-evaluation can be made.
It is very rare for cases of discitis to require operative intervention but difficult cases can be referred to the Neuro-spine MDT for discussion.