Spondylodiscitis: Spinal Infection of the Disc

Spondylodiscitis is a serious infection of the spine that affects an intervertebral disc and the bone of the vertebrae immediately above and below it. Because back pain is so common, the diagnosis can be missed early, yet timely recognition and treatment are important to prevent complications. It is worth stressing at the outset that spondylodiscitis is an infection — it is not the same as spondylolisthesis, a mechanical condition in which one vertebra slips over another. The similar names are a frequent source of confusion.

What is spondylodiscitis?

Spondylodiscitis describes infection centred on the intervertebral disc (discitis) that involves the adjacent vertebral endplates and bone (vertebral osteomyelitis). In adults the disc has a poor blood supply, so infection usually begins in the bone of the endplate and spreads into the disc space.

Most cases are caused by bacteria, with common skin and urinary organisms among the usual culprits. In many parts of the world, including the Indian subcontinent, tuberculosis is an important cause and is sometimes considered separately as spinal tuberculosis.

Which parts of the spine are affected?

Spondylodiscitis most often affects the lumbar (lower back) and thoracic (mid-back) regions, although any level can be involved. Typically a single disc and the two neighbouring vertebrae are affected. As the infection progresses it can erode bone, form a collection of pus (abscess), and in some cases press on nearby nerves or the spinal cord.

Causes and risk factors

The infecting organisms usually reach the spine through the bloodstream from another site of infection, such as the urinary tract, skin or chest. Less commonly, infection follows a spinal injection, procedure or surgery.

Risk factors include:

• Diabetes mellitus.
• A weakened immune system, including long-term steroid use.
• Intravenous drug use.
• Recent infection or bloodstream infection elsewhere.
• Chronic kidney disease or dialysis.
• Older age and general frailty.

Symptoms and warning signs (red flags)

The hallmark is persistent back pain that is often severe, unrelieved by rest, and may be worse at night. Many people also have fever, chills or night sweats, although fever is not always present. Localised tenderness over the affected part of the spine is common, and movement is usually painful.

Seek urgent assessment if back pain is accompanied by any of these red flags:

• Fever, chills or night sweats.
• New weakness, numbness or pins-and-needles in the limbs.
• Problems with bladder or bowel control.
• Unexplained weight loss.
• A recent infection elsewhere in the body or recent spinal procedure.

These features raise concern about infection and possible nerve or spinal cord involvement, which require prompt attention.

How spondylodiscitis is diagnosed

MRI is the most sensitive imaging test and can show changes in the disc, endplates and surrounding tissues, as well as any abscess. Blood tests typically reveal raised inflammatory markers such as ESR and CRP, and a raised white cell count may be present.

Identifying the responsible organism is central to treatment. Blood cultures are taken, and an image-guided biopsy of the affected disc or bone is often performed to confirm the diagnosis and guide the choice of antibiotic. Tests for tuberculosis are considered where it is a likely cause.

Non-surgical treatment

The mainstay of treatment is antibiotic therapy, ideally targeted to the identified organism. Treatment is usually prolonged, given over several weeks, and is monitored with repeat blood tests and clinical review. Where tuberculosis is the cause, a specific multi-drug regimen is used over a longer period.

Supportive measures include rest, adequate pain relief, and bracing to reduce movement and discomfort while the spine heals. Treating the original source of infection and managing contributing conditions such as diabetes are also important. Most people respond well to non-surgical treatment when it is started promptly.

When surgery is considered

Surgery is reserved for specific situations rather than being routine. It may be considered when there is a significant abscess needing drainage, spinal instability or progressive bone destruction, nerve or spinal cord compression causing neurological symptoms, or failure to respond to appropriate antibiotic treatment. The aims are to remove infected tissue, relieve pressure on nerves, and stabilise the spine where necessary.

When to see a spine specialist

Anyone with persistent, unexplained back pain — particularly when it is severe, worse at night, or accompanied by fever, chills or weight loss — should be assessed without delay, and especially if they have diabetes, reduced immunity or a recent infection. New weakness, numbness or bladder or bowel changes are urgent. Early specialist assessment allows the diagnosis to be confirmed and treatment to begin promptly, which gives the best chance of a full recovery.