# Pyogenic Spondylodiscitis > Pyogenic spondylodiscitis for NEET-PG Orthopaedics: haematogenous disc infection, MRI findings, Staphylococcus aureus and contrast with TB spine. - Canonical URL: https://prepelephant.com/topics/neet-pg/orthopaedics/pyogenic-spondylodiscitis - Exam / course: NEET-PG · Subject: Orthopaedics - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-14 - Last updated: 2026-10-14 - Reference basis: Apley's System of Orthopaedics and Fractures; Maheshwari's Essential Orthopaedics - How to cite: "Pyogenic Spondylodiscitis", PrepElephant, https://prepelephant.com/topics/neet-pg/orthopaedics/pyogenic-spondylodiscitis ## Direct answer Pyogenic spondylodiscitis is bacterial infection of an intervertebral disc and the adjacent vertebral endplates, most often spreading through the bloodstream from a distant focus. It typically affects the lumbar spine, and Staphylococcus aureus is the commonest causative organism. Diagnosis rests on MRI, and most patients are managed with prolonged antibiotics, with surgery reserved for neurological deficit, instability or failed medical treatment. ## What you must remember - **Route:** haematogenous spread from a distant focus such as the urinary tract, skin, respiratory tract or endocarditis; direct spread after spinal surgery or injection is less common. - **Site:** the lumbar spine is most affected, and the disc is involved early, which separates it from tuberculosis. - **Organism:** Staphylococcus aureus is the commonest; blood cultures come first, and image-guided biopsy identifies the organism when they are negative. - **MRI pattern:** disc space narrowing with T2 hyperintensity, endplate destruction, T1 hypointense marrow and contrast enhancement, often with paravertebral or epidural extension. - **Biomarkers:** raised ESR and CRP track the disease and its response to treatment, but they are not specific. - **Medical treatment:** intravenous antibiotics tailored to culture, switched to oral therapy when the patient improves, usually for about six weeks, with bracing and pain control. - **Surgical indications:** neurological deficit, spinal instability, a large abscess, or no improvement despite adequate antibiotics. ## A staged approach from suspicion to biopsy A 62-year-old man with a recent urinary catheter infection develops severe low back pain and fever. The diagnosis rests on imaging, and the organism is identified from blood or from a biopsy. 1. **Suspect in the febrile back:** back pain with fever and a distant focus, particularly a urinary or intravenous source, should prompt spinal imaging. 2. **Image with MRI:** MRI shows disc space narrowing, endplate erosion and contrast enhancement, and it reveals any epidural or paravertebral extension. 3. **Take blood cultures first:** blood cultures before antibiotics often identify the organism without an invasive procedure. 4. **Biopsy if cultures are negative:** image-guided needle biopsy of the disc or vertebral body gives histology and culture when the blood is sterile. 5. **Start antibiotics on the organism:** intravenous therapy tailored to culture is given first, with a switch to oral therapy once the patient improves. 6. **Complete the course:** therapy usually continues for about six weeks, with ESR and CRP trends used to monitor response. 7. **Escalate for failure:** a neurological deficit, instability, a large abscess or no improvement on adequate antibiotics leads to surgical debridement and stabilisation. ## Traps the exam sets Examiners test whether you can separate pyogenic infection from tuberculosis and resist early surgery. - **Trap:** labelling every spinal infection as tuberculosis. **Correct:** pyogenic infection involves the disc early and often a single level, whereas tuberculosis spreads beneath the anterior longitudinal ligament. - **Trap:** operating early on every spondylodiscitis. **Correct:** most patients respond to antibiotics and bracing, so surgery is reserved for deficit, instability or failure of medical therapy. - **Trap:** trusting a negative blood culture to exclude infection. **Correct:** image-guided biopsy establishes the diagnosis and organism when blood cultures are sterile. ## Frequently asked questions ### Which spinal region is most often affected by pyogenic spondylodiscitis? The lumbar spine is the region most often affected by pyogenic spondylodiscitis. The intervertebral disc is typically involved early, which helps distinguish it from spinal tuberculosis on examination and imaging. ### Which MRI features suggest pyogenic spondylodiscitis? MRI features of pyogenic spondylodiscitis include disc space narrowing, T2 hyperintensity of the disc, endplate erosion and contrast enhancement of the involved vertebral bodies. Paravertebral or epidural extension strongly supports a diagnosis of spinal infection. ### What is the usual antibiotic duration in pyogenic spondylodiscitis? Antibiotic therapy for pyogenic spondylodiscitis usually lasts about six weeks, starting intravenously on culture results and changing to oral therapy when the patient improves. Surgery is added only for neurological deficit, instability or failure of medical treatment. ### When is biopsy needed in pyogenic spondylodiscitis? Image-guided needle biopsy is needed in pyogenic spondylodiscitis when blood cultures are negative and the organism remains unknown. Biopsy also helps separate infection from tumour and tuberculosis when the clinical picture is unclear. ### How does tuberculous spondylitis differ from pyogenic spondylodiscitis on imaging? Tuberculous spondylitis spreads beneath the anterior longitudinal ligament and spares the disc until late, often involving more than one level. Pyogenic spondylodiscitis involves the disc early and usually a single level, which aids radiological differentiation.