Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Discitis and vertebral osteomyelitis
Musculoskeletal medicine and orthopaedics · UK scope · Sources checked 27 Aug 2026 · Clinical review pending
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Neurological compression, sepsis and spinal instability are emergencies
Vertebral infection may extend into the epidural space, collapse an endplate or produce bacteraemia while fever is absent; new weakness, saddle sensory change or bladder dysfunction can mark irreversible neural injury.
Action: Perform immediate neurological and sepsis assessment, obtain blood cultures, arrange urgent whole-region MRI with appropriate spinal coverage, give antibiotics immediately after cultures if septic or neurologically deteriorating, and involve spinal surgery urgently for epidural abscess, compression, instability, deformity or uncontrolled source.
Overview
Recognise spinal infection behind persistent back pain, identify sepsis, epidural compression and instability early, preserve microbiological diagnosis, use MRI appropriately, and combine antimicrobial, surgical and rehabilitation decisions.
Discitis and vertebral osteomyelitis form an infection spectrum involving the disc-endplate unit and adjacent vertebrae. Ask about pain onset, nocturnal and mechanical components, fever, recent bacteraemia, skin or urinary infection, vascular access, spinal procedure, injecting drug use, tuberculosis contact and travel. Record all antibiotics because culture suppression matters. Diabetes, renal replacement therapy, immune suppression, cancer and frailty increase risk. Children may refuse to sit, crawl or walk and can present with abdominal pain rather than localised spinal symptoms.
ABCDE assessment comes first. Then perform and document a complete neurological examination: limb power and sensation, reflexes, upper motor-neuron signs, gait when safe, saddle sensation, anal tone and bladder function. Examine the whole spine for focal percussion tenderness and deformity and the abdomen, flank and hip for psoas irritation. Search skin, lines, heart, urine and other bones or joints for source and spread. Repeat the neurological record after analgesia, imaging, transfer and any deterioration.
Practice
Two practice questions
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Question 1 of 2
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Musculoskeletal medicine and orthopaedicsOriginal SBA
Stable culture-negative discitis
A haemodynamically stable adult with no neurological deficit has MRI appearances of vertebral osteomyelitis, but two blood-culture sets are negative. What is the best next diagnostic step?
Sources and review status4 sources · checked 27 Aug 2026 · clinical review pending+
Sources
Sources and review status
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.
Obtain FBC, CRP, ESR, renal and liver profiles and two sets of blood cultures before treatment when feasible. Blood cultures can establish microbiology and sometimes avoid biopsy, especially with a convincing MRI and a typical organism. Persistent S. aureus bacteraemia requires repeat cultures, endocarditis assessment and a search for other metastatic sites. Normal white count or absent fever does not exclude disease. Tuberculosis, Brucella or fungal tests are selected from exposure and immune status rather than sent indiscriminately.
MRI is the preferred study because it shows disc and endplate inflammation, epidural disease, neural compression and paraspinal collections. Use contrast when renal function and the diagnostic question permit. Image the symptomatic region urgently and extend coverage when neurological findings, bacteraemia or multifocal pain suggest more levels. If MRI is contraindicated, spinal specialists and radiology combine CT, nuclear techniques or CT myelography for the safest answer. Plain radiographs provide alignment and collapse baseline but are insensitive early.
A stable, neurologically intact patient with negative blood cultures usually needs image-guided biopsy before antibiotics. Target disc, endplate or accessible paraspinal collection and send multiple samples for aerobic and anaerobic culture and histology, adding mycobacterial, fungal or molecular tests when indicated. If the first biopsy is non-diagnostic and suspicion remains high, review targeting, prior antibiotics and pathology, then repeat percutaneous or obtain open biopsy rather than declaring infection absent. Do not biopsy through a route that compromises later surgery.
Treatment urgency changes with physiology and neurology. Sepsis, instability or progressive deficit requires immediate antibiotics after rapidly obtainable blood cultures and urgent decompression or drainage; biopsy should be incorporated into surgery without delaying it. Stable disease waits for microbiological sampling, then receives organism-directed treatment through infection specialists. Many bacterial cases receive about six weeks of parenteral or highly bioavailable oral therapy, but organism, abscess drainage, implants and response determine the exact documented route and duration.
Spinal surgery addresses compression, instability, deformity and uncontrolled source rather than simply the MRI label. Drain epidural or large paraspinal collections, decompress threatened neural structures, debride non-viable tissue and stabilise when destruction makes the spine unsafe. Instrumentation may be necessary in an infected field to restore stability and is planned by specialist teams. Percutaneous drainage can control selected psoas or paraspinal collections. Persistent bacteraemia or pain despite susceptible drugs means reconsider source, abscess and diagnosis.
Monitor pain pattern, neurological function, mobility, fever and CRP. ESR may fall slowly. Clinical improvement and falling markers generally outweigh persistent MRI abnormalities, which can lag and even appear worse during healing; repeat MRI for new deficit, recurrent bacteraemia or poor response. Provide venous-thrombosis prevention, nutrition, pressure care, bowel and bladder support and early rehabilitation. At discharge, specify activity and brace advice, antimicrobial monitoring and emergency return for weakness, numbness, saddle change, bladder symptoms, fever or escalating pain.
Key points
Suspect vertebral osteomyelitis when new or worsening focal back or neck pain accompanies fever, raised inflammatory markers, bacteraemia or a relevant exposure; fever may be absent.
Document power, sensation, reflexes, gait if safe, saddle sensation, anal function and bladder symptoms at presentation and after every clinical change.
Obtain two sets of blood cultures plus FBC, CRP, ESR, renal and liver profiles; persistent S. aureus bacteraemia warrants spinal assessment even when back pain is understated.
MRI of the affected spinal region is the preferred diagnostic imaging; include enough coverage to define epidural and paraspinal extension and broaden imaging when multifocal disease is plausible.
In a stable neurologically intact patient, withhold empirical antibiotics until blood cultures and image-guided or operative biopsy are obtained when microbiology remains unknown.
In sepsis, haemodynamic instability, neurological progression or impending compression, take rapid blood cultures and start treatment immediately; diagnostic yield never outranks life or neural function.
Surgery is indicated for neurological compression, instability, progressive deformity, uncontrolled abscess, persistent bacteraemia or failure of correctly directed medical treatment.
Aetiology
01
Haematogenous seeding
Bloodstream organisms lodge in vertebral endplate circulation, commonly from skin, urinary, vascular-access or endovascular infection, and spread across the disc-endplate unit.
02
Post-procedural inoculation
Spinal surgery, injection, biopsy or instrumentation can directly introduce organisms and changes the relevance of implants, wound status and resistant flora.
03
Contiguous extension
Deep pressure injury, mediastinal, retroperitoneal or paraspinal infection can reach vertebrae directly and may require separate drainage.
04
Host and exposure factors
Older age, diabetes, renal failure, immunosuppression, injecting drug use, tuberculosis exposure and endemic travel widen pathogen probability.
Pathophysiology
1
Endplate infection
Bacterial seeding produces marrow inflammation and endplate erosion; in adults infection then crosses the disc and enters the adjacent vertebral body.
2
Paraspinal extension
Purulence tracks into psoas or paravertebral tissue and may form collections that perpetuate bacteraemia and pain.
3
Epidural spread
Inflammatory tissue or abscess narrows the canal, compromising cord, cauda equina or roots through pressure and vascular injury.
4
Mechanical collapse
Progressive endplate and vertebral destruction causes kyphosis, instability, neurological risk and load-dependent pain even after microbiological control.
5
Persistent bloodstream source
Endocarditis or infected access can repeatedly seed the spine, making local treatment fail until the primary source is controlled.
Clinical features and red flags
Focal infection pattern
Persistent focal spinal pain with raised CRP, bacteraemia or systemic risk should prompt MRI even when temperature and radiographs are normal.
New limb weakness, sensory level, saddle anaesthesia, urinary retention or incontinence, reduced anal tone or rapidly changing radicular pain requires emergency spinal imaging and surgical review.
Shock, confusion, rising lactate, persistent S. aureus bacteraemia or rigors indicates systemic danger and removes any plan to delay treatment for biopsy.
Investigations
01Two blood-culture setsFirst step
Why
Identify haematogenous organisms before antibiotics.
Interpretation and limitations
A typical bloodstream isolate plus compatible MRI may establish treatment; persistent positivity demands endocardial and metastatic-source assessment.
02FBC, CRP, ESR and organ profile
Why
Assess inflammation, differential diagnoses and treatment safety.
Interpretation and limitations
CRP is useful for direction, ESR falls slowly and a normal white count does not exclude infection; renal function affects contrast and dosing.
03Preferred spinal MRIPreferred
Why
Define disc-endplate infection, epidural compression and paraspinal spread.
Interpretation and limitations
Obtain urgently for neurological symptoms; degenerative and postoperative changes can mimic infection, so anatomy and microbiology remain essential.
04Plain radiographs
Why
Establish alignment, collapse and later structural progression.
Interpretation and limitations
Normal early films are common; progressive endplate loss and deformity support delayed disease but should not be awaited.
05Image-guided biopsy
Differential diagnosis
01
Malignancy
Metastasis, myeloma and lymphoma cause night pain, collapse and marrow signal; distribution, blood tests and planned histology distinguish them from infection.
02
Degenerative Modic change
Endplate oedema and back pain can mimic discitis on MRI, but disc signal, paraspinal inflammation, cultures and clinical trajectory refine probability.
03
Compression fracture
Osteoporotic or traumatic collapse produces focal pain without infection, although bacteraemia can seed a recently injured level.
04
Inflammatory spondyloarthritis
Inflammatory back pain, sacroiliitis and enthesitis suggest immune disease, but immunosuppression should not begin until infection is considered.
05
Tuberculous or fungal infection
Indolent constitutional symptoms, large paraspinal collection and exposure history require extended culture and histology rather than routine bacterial assumptions.
Management
01CompressionProtect neural function nowFirst stepNew neurological deficit, cauda-equina symptoms, epidural abscess with compression or unstable collapse is present.+
1Immobilise and move safely, repeat the neurological record and obtain emergency MRI with relevant spinal coverage.
2Call spinal surgery, anaesthesia and infection teams while obtaining blood cultures and treating sepsis.
3Start immediate intravenous therapy after rapid cultures and proceed to decompression, drainage and operative samples when indicated.
4Manage bladder, pressure areas, thrombosis risk and rehabilitation from the first resuscitative phase.
02StableIdentify the organism before treatmentThe patient is haemodynamically stable, neurologically intact and has no impending structural emergency.+
1PreferredObtain two blood-culture sets, inflammatory and organ profiles and preferred MRI.
Complications
01
Epidural abscess
Canal infection can produce rapid cord or cauda-equina injury, paralysis and sphincter dysfunction requiring emergency decompression and drainage.
02
Vertebral collapse
Bone destruction leads to instability, deformity, chronic mechanical pain and sometimes fixation or reconstruction after infection control.
03
Sepsis and endocarditis
Bacteraemia can cause shock or reveal an endovascular source that continues metastatic spinal and systemic seeding until definitively treated.
04
Paraspinal or psoas abscess
Deep collections cause persistent fever, hip-flexion pain and treatment failure and may need percutaneous or operative drainage.
05
Chronic pain and deconditioning
Prolonged immobility, muscle loss and structural damage impair gait, independence and return to work despite microbiological cure.
Monitoring and follow-up
Repeat a documented neurological examination immediately after any change in pain, mobility, bladder or bowel function.
Track observations, CRP and blood-culture clearance and interpret ESR as a slower marker.
Review renal, liver and marrow indices and interaction-sensitive medicines throughout prolonged antimicrobial therapy.
Assess mechanical pain, alignment and mobility and obtain radiographs when collapse or deformity could be progressing.
Reserve repeat MRI for neurological change, recurrent bacteraemia or poor clinical and biochemical response rather than routine image normalisation.
Follow strength, gait, continence, pain, nutrition, pressure risk and return to independence through rehabilitation.
Special situations
Fever absence is common
Subacute vertebral infection often presents as persistent focal pain without fever, especially in older or immunocompromised adults.
Blood cultures may prevent biopsy
A plausible bloodstream organism with characteristic MRI can provide a microbiological diagnosis, but contaminants and atypical organisms need scrutiny.
MRI healing lags
Marrow and endplate abnormalities can persist despite recovery, so routine imaging normalisation should not determine antibiotic duration.
Stability is source control
An infected collapsing segment may remain painful and unsafe after bacterial control and sometimes requires fixation in the treated field.
Biopsy also excludes cancer
Histology is essential when imaging and cultures are atypical because malignancy can produce the same destructive pattern.
Back pain can identify endocarditis
Vertebral infection may be the metastatic clue that leads to diagnosis of a persistent cardiac source.
Common pitfalls
01
Reassuring a high-risk patient because fever, white count or initial radiographs are normal.
02
Failing to document saddle sensation, bladder function and serial power before and after transfer.
03
Starting empirical antibiotics in a stable intact patient before obtainable blood cultures and biopsy.
04
Delaying treatment or decompression in sepsis or neurological decline to preserve biopsy yield.
05
Using persistent MRI signal alone to prolong treatment despite clinical and CRP recovery.
06
Missing endocarditis, psoas abscess, multifocal disease or structural instability when response fails.
Culture-directed treatment is commonly prolonged; serial symptoms and CRP guide response, while routine follow-up MRI is reserved for poor or discordant clinical progress.
Progressive deformity, severe mechanical pain, vertebral collapse or inability to mobilise raises concern for structural instability and neurological threat.
A new murmur, embolic features, injecting-drug exposure, vascular access or several painful sites suggests endocarditis or multifocal infection and requires source and metastatic-focus assessment.
Why
Recover tissue microbiology and histology when blood cultures are non-diagnostic.
Interpretation and limitations
Perform before antibiotics in a stable intact patient; send organism-specific studies from exposure and repeat or use open biopsy if high suspicion persists.
06CT
Why
Define cortical destruction, guide biopsy and plan fixation.
Interpretation and limitations
CT is less sensitive to early marrow and epidural disease and becomes an alternative only when MRI cannot answer safely.
07Echocardiography when indicated
Why
Investigate an endovascular source of sustained bacteraemia.
Interpretation and limitations
Use the endocarditis pathway for persistent S. aureus cultures, murmur, emboli or other clinical indications rather than routine screening alone.
2If blood cultures do not establish microbiology, arrange image-guided biopsy and histology before antibiotics.
3Start culture-directed therapy after sampling and define route, monitoring and duration with infection specialists.
4Assess source, endocarditis risk, abscess drainage, stability, mobilisation and the need for brace or surgery.
03Non-responseReassess source, stability and diagnosisPain, CRP, neurological findings or bacteraemia fails to improve on apparently active treatment.+
1Verify organism, susceptibility, dose, adherence and blood-culture clearance and search for a continuing bloodstream source.
2Repeat neurological examination and MRI for retained epidural or paraspinal abscess and progressive collapse.
3Repeat biopsy or obtain open tissue when cultures remain negative and malignancy or unusual infection is possible.
4EscalationEscalate drainage, debridement or stabilisation and revise the antimicrobial plan from new anatomical evidence.
Key medicines and prescribing safety2 treatments · regimens, roles and cautions+
Treats bloodstream and vertebral pathogens while emergency surgery controls epidural or structural threat.
Empirical intravenous therapy for unstable spinal infection
After two rapidly obtainable blood-culture sets, give the full adult regimen in the trust's severe spinal-infection and sepsis protocol immediately when haemodynamic instability, neurological progression or impending compression is present; obtain operative cultures without delaying decompression.
Agent choice must cover locally likely organisms and account for allergy, renal function, MRSA risk, prior isolates, vascular access and injecting exposure; stable intact patients should be biopsied before empirical therapy whenever safely possible.
Eradicates infection after microbiological diagnosis and drainage while avoiding unnecessary intravenous access when a reliable active oral drug exists.
Culture-directed vertebral-osteomyelitis course
For most bacterial native vertebral osteomyelitis, prescribe the organism-specific parenteral or highly bioavailable oral regimen for about 6 weeks, documenting the exact drug, dose, route, monitoring and stop or review date and extending only for a defined microbiological or source-control reason.
Tuberculosis, fungal disease, Brucella, retained implants, undrained abscess and endocarditis follow different courses; review interactions, renal and hepatic function, marrow toxicity, absorption and adherence with infection specialists.