Discospondylitis (also spelled diskospondylitis) is an infection of the intervertebral disc and adjacent vertebral endplates.
Overview and Clinical Importance
Discospondylitis (also spelled diskospondylitis) is an infection of the intervertebral disc and adjacent vertebral endplates. It is a relatively common spinal disorder in dogs that can cause significant morbidity including severe pain, neurological deficits, and even paralysis if left untreated. Understanding the pathophysiology, diagnostic approach, and treatment protocols is essential for the NAVLE, as this condition frequently appears in board examinations.
The condition is most commonly caused by hematogenous spread of bacteria from distant infection sites such as the urinary tract, oral cavity, skin, or heart valves. The lumbosacral junction (L7-S1) is the most frequently affected site, followed by thoracolumbar and cervical regions. Prompt recognition and appropriate antimicrobial therapy are crucial for successful outcomes.
| Route |
Description and Examples |
| Hematogenous Spread (Most Common) |
Bacteria or fungi enter bloodstream from distant sites: urinary tract infections, dental disease, bacterial endocarditis, skin infections, prostatitis |
| Direct Inoculation |
Penetrating wounds, bite wounds (especially in cats), surgical contamination, epidural injections |
| Migrating Foreign Bodies |
Plant awns (grass awns) that migrate through tissues; commonly affect L2-L4 region; more prevalent in certain geographic areas |
| Iatrogenic |
Post-spinal surgery (especially in overweight and large breed dogs), contaminated epidural procedures |
Etiology and Pathophysiology
Routes of Infection
Discospondylitis develops when infectious organisms gain access to the intervertebral disc space. The blood supply within the vertebral endplates consists of capillary beds with reduced blood flow velocity. Pores in the endplate that normally allow nutrient distribution also provide a route for organisms to enter the intervertebral disc. The minimal vascular supply of the intervertebral disc further enables infection establishment.
Routes of Infection
High-YieldThe lumbosacral junction (L7-S1) is the most commonly affected site in dogs, accounting for approximately 27% of cases. More than 40% of dogs with discospondylitis have MULTIFOCAL lesions, so always image the entire spine!
Causative Organisms
NAVLE TipALWAYS test for Brucella canis in ANY dog with discospondylitis regardless of reproductive status. While intact males in the southeastern/southwestern US are at higher risk, neutered dogs can also be infected. Brucella is ZOONOTIC - use appropriate PPE and inform owners of the public health risk!
| Organism Type |
Specific Pathogens |
Clinical Significance |
| Bacterial (Most Common) |
Staphylococcus spp. (S. pseudintermedius, S. aureus) - 60% of positive cultures
Streptococcus spp.
Escherichia coli
Brucella canis |
Respond to appropriate antibiotic therapy; Staphylococcus is treated empirically with first-generation cephalosporins |
| Brucella canis |
Gram-negative coccobacillus; accounts for less than 10% of cases but CRITICAL to identify |
ZOONOTIC - public health concern; incurable but manageable; requires lifelong therapy; screen ALL dogs with discospondylitis |
| Fungal |
Aspergillus spp. (A. terreus most common)
Paecilomyces spp.
Candida spp. |
German Shepherds are predisposed due to IgA deficiency; guarded to poor prognosis; requires lifelong antifungal therapy |
Signalment and Risk Factors
Breed Predispositions
| Characteristic |
Details |
| Overrepresented Breeds |
German Shepherd Dog (especially fungal), Doberman Pinscher, Great Dane, Labrador Retriever, Boxer, French Bulldog, Rottweiler, Weimaraner, Greyhound |
| Age |
Median age 7 years; dogs greater than 10 years most commonly affected; juvenile dogs can be affected (especially with Brucella - median age 4 years) |
| Sex |
Male dogs overrepresented (approximately 2:1 ratio); intact males at higher risk for Brucella |
| Risk Factors |
UTI, dental disease, chronic skin infections, prior spinal surgery (10% of cases), immunosuppression, steroid therapy, trauma |
Clinical Signs and Presentation
Clinical signs of discospondylitis are variable and can range from vague systemic illness to severe paralysis. Spinal hyperesthesia (pain) is the most common presenting complaint, occurring in over 80% of cases. Signs may wax and wane and often worsen with physical activity.
High-YieldDiscospondylitis should ALWAYS be considered in any dog with fever of unknown origin. However, only 8% of dogs are febrile at presentation, so a normal temperature does NOT rule out discospondylitis!
Neuroanatomical Localization
| Sign Category |
Clinical Manifestations |
| Pain (Most Common - greater than 80%) |
Spinal hyperesthesia, reluctance to move, stiff gait, hunched posture, kyphosis, yelping when picked up, exercise intolerance |
| Neurological Deficits (30%) |
Ataxia, paresis (ambulatory or non-ambulatory), paralysis, proprioceptive deficits; severity depends on location and degree of spinal cord compression |
| Systemic Signs |
Fever (only 8% of cases - absence does NOT rule out infection!), lethargy, decreased appetite, weight loss |
| Lumbosacral Disease |
Stilted, short-strided pelvic limb gait, shifting leg lameness, pain on tail manipulation, difficulty sitting or rising, fecal/urinary incontinence |
| Cervical Disease |
Cervical pain, reluctance to lower head, pain on neck manipulation; neurological deficits less common unless severe compression |
Diagnostic Approach
Diagnostic Imaging
Diagnostic imaging is critical for confirming discospondylitis. Radiographic changes may lag 7-14 days (up to 2-4 weeks) behind clinical signs, requiring approximately 70% destruction of the vertebral endplates before changes become visible.
High-YieldIn a multi-institutional study of 386 dogs, 33% had NO radiographic evidence of discospondylitis but DID have lesions on advanced imaging. If clinical suspicion is high and radiographs are normal, pursue MRI! Additionally, radiographs showed only fair agreement with CT and poor agreement with MRI for detecting lesions.
Laboratory Diagnostics and Culture
NAVLE TipFor German Shepherd dogs with discospondylitis, ALWAYS screen for Aspergillosis using the galactomannan antigen EIA test (Mira Vista Labs) - it is 90% sensitive and specific for systemic aspergillosis. GSDs are predisposed due to IgA deficiency.
| Localization |
Expected Deficits |
Frequency |
| T3-L3 |
UMN paraparesis/paraplegia, normal to increased pelvic limb reflexes, Schiff-Sherrington posture if severe |
40% of cases |
| L4-S3 (Cauda Equina) |
LMN paraparesis, decreased pelvic limb reflexes, decreased tail tone, urinary/fecal incontinence |
29% of cases |
| C1-C5 |
UMN tetraparesis, cervical pain most prominent, normal to increased reflexes all limbs |
6% of cases |
| C6-T2 |
LMN thoracic limbs (decreased reflexes), UMN pelvic limbs (increased reflexes) |
3% of cases |
| Multifocal |
Variable deficits depending on affected sites; asymmetric signs possible |
22% of cases |
Treatment
Antimicrobial Therapy
Treatment consists of long-term antimicrobial therapy, typically for a minimum of 6-8 weeks, often extending to 6-12 months. Antibiotic selection should ideally be based on culture and sensitivity results. If an organism is not cultured (50-60% of cases), empirical therapy targeting the most common pathogen (coagulase-positive Staphylococcus) is appropriate.
Supportive Care and Pain Management
- Analgesics: Gabapentin (5-10 mg/kg PO q8-12h), Tramadol (2-5 mg/kg PO q8-12h), NSAIDs if no contraindications
- Exercise Restriction: Strict cage rest for 4-6 weeks to prevent pathological fractures
- Physical Therapy: Passive range of motion, hydrotherapy once pain is controlled
- Avoid Corticosteroids: Can impair resolution and increase risk of progressive neurological dysfunction (OR: 4.7)
High-YieldDogs should show clinical improvement (decreased pain, improved appetite) within 4-5 days of starting appropriate antibiotic therapy. If no improvement within 7-10 days, re-evaluate the case - consider resistant bacteria, fungal infection, or incorrect diagnosis.
Surgical Indications
Surgical intervention is required in approximately 10% of cases. Indications include:
- Severe spinal cord compression with significant neurological deficits
- Vertebral instability or subluxation
- Sublumbar abscess requiring drainage
- Epidural empyema (though some cases can be managed medically)
- Failure to respond to appropriate antimicrobial therapy
| Modality |
Characteristic Findings |
Advantages/Limitations |
| Radiography |
Irregular endplate lysis
Disc space collapse/narrowing
Sclerosis of adjacent vertebrae
Spondylosis deformans |
Widely available and cost-effective; changes lag 7-14 days behind clinical signs; 33% of dogs have no radiographic abnormalities but positive advanced imaging |
| CT |
Endplate erosion/osteolysis
Periosteal proliferation
Better bone detail than radiographs
Vacuum phenomenon possible |
Earlier detection than radiographs; excellent bone detail; multiplanar reconstruction; useful for CT-guided biopsy |
| MRI (Gold Standard) |
STIR hyperintensity of disc and endplates
T2 hyperintensity, T1 hypointensity
Contrast enhancement
Paraspinal soft tissue changes |
EARLIEST detection; best for soft tissue assessment, epidural empyema, spinal cord compression; 4 dogs had lesions only visible on MRI (not radiographs or CT) |
Monitoring and Prognosis
Monitoring Protocol
- Clinical Examinations: Every 1-2 months during treatment
- Radiographic Monitoring: Every 4-6 weeks; first recheck at 6-8 weeks after starting treatment
- C-Reactive Protein: Useful inflammatory marker; normalization supports treatment response
- Treatment Duration: Continue antibiotics for 2-4 weeks AFTER complete radiographic resolution
- Radiographic Resolution: May take 6+ months; characterized by ankylosis (vertebral fusion) and replacement of lytic bone with osseous proliferation
Prognosis by Etiology
Risk Factors for Poor Outcome
- Prior Trauma: 9-fold increased risk of relapse (OR: 9.0)
- Prior Steroid Therapy: 4.7-fold increased risk of progressive neurological dysfunction
- Severe neurological deficits at presentation
- Multifocal disease
- Premature discontinuation of antimicrobial therapy
| Test |
Positivity Rate |
Most Common Isolates |
Notes |
| Blood Culture |
27% |
Staphylococcus spp. (61%), Streptococcus spp. (11%), Pasteurella spp. (8%) |
Collect before antibiotics; multiple samples increase yield |
| Urine Culture |
28% |
Staphylococcus spp. (39%), E. coli (29%), Streptococcus spp. (13%) |
Essential in all cases; cystocentesis preferred |
| Disc Culture |
41% |
Staphylococcus spp. (69%), Pseudomonas (8%), E. coli (8%) |
CT or fluoroscopy-guided; indicated if blood/urine cultures negative |
| Brucella Serology |
6.6% positive |
RSAT (screening), 2ME-RSAT, AGID (confirmatory) |
TEST ALL DOGS - zoonotic concern! |
| Fungal Testing |
21% of tested |
Aspergillus spp. (75% of positives); galactomannan antigen for GSDs |
Consider if not responding to antibiotics; German Shepherds at high risk |
| Etiology |
First-Line Treatment |
Duration |
Notes |
| Bacterial (Empiric) |
Cephalexin 22-30 mg/kg PO q8-12h
OR
Amoxicillin-clavulanate 15-25 mg/kg PO q12h |
Minimum 6-8 weeks; often 6-12 months |
Continue until 2-4 weeks after radiographic resolution; first-gen cephalosporins have good bone penetration |
| Severe Neurologic Deficits |
Cefazolin 22 mg/kg IV q8h for 5-7 days, then transition to oral |
IV for 5-7 days, then oral long-term |
Hospitalization required; IV access ensures adequate drug levels |
| Brucella canis |
Doxycycline 5-10 mg/kg PO q12h
PLUS
Enrofloxacin 10-20 mg/kg PO q24h
OR aminoglycoside first 7-14 days |
LIFELONG - incurable |
Neuter/spay; zoonotic precautions; reportable disease in many states; euthanasia may be recommended |
| Fungal (Aspergillosis) |
Itraconazole 5 mg/kg PO q24h (may increase to 10 mg/kg) |
Lifelong in most cases; minimum 6-12 months |
Guarded to poor prognosis; A. terreus resistant to amphotericin B; monitor liver enzymes |
| Etiology |
Prognosis |
Key Considerations |
| Bacterial (Non-Brucella) |
GOOD with early treatment |
Relapse rate approximately 12%; worse prognosis with severe neurologic deficits, trauma history, or prior steroid use |
| Brucella canis |
GUARDED - incurable |
Can be managed but not cured; lifelong therapy; quality of life often acceptable; consider euthanasia due to zoonotic risk |
| Fungal |
GUARDED to POOR |
Median survival 30 days in one study; lifelong antifungal therapy required; high risk of disseminated disease; some cases managed successfully long-term |