“Disc bulge”, “protrusion”, “extrusion” and “herniation” are words from scan reports that describe how far disc material extends beyond its normal edge. They sound alarming, but bulges and protrusions are very common in people with no pain at all, and even true herniations often shrink on their own. What matters most is whether the finding matches your symptoms.
The words on the report
The intervertebral disc has a tough outer ring and a softer centre. See the intervertebral disc.
| Term | What it describes |
|---|---|
| Bulge | The disc extends a little beyond its edge over a broad part of its circumference; very common with age |
| Protrusion | A more focal bulge; the base is wider than the part that sticks out |
| Extrusion | Disc material pushed further out, through the outer ring; the part outside is wider than its base |
| Sequestration | A fragment that has separated from the disc |
| Herniation | The umbrella term for protrusion, extrusion and sequestration |
| “Slipped disc” | A common phrase, but discs do not slip out of place; see do discs slip? |
How common they are without pain
A systematic review pooled scans of 3,110 people who had no back pain and reported how often findings appeared by age:1
| Finding | Age 20 | Age 50 | Age 80 |
|---|---|---|---|
| Disc bulge | 30% | 60% | 84% |
| Disc protrusion | 29% | 36% | 43% |
| Disc degeneration | 37% | 80% | 96% |
So a bulge on a report is, for many adults, an ordinary finding. It does not on its own explain back pain.
Disc bulges and protrusions are common in pain-free people and become more common with age. A scan finding needs to match the symptoms, typically leg pain in the area supplied by the affected nerve, before it is treated as the cause.1
When it does matter
A herniation becomes clinically important when it presses on a nerve root and causes leg symptoms that fit that nerve: sciatica, numbness or weakness. Even then, the outlook is usually good: extruded and larger herniations are the ones most likely to shrink, typically over months, while symptoms often improve within weeks.2 See can a herniated disc heal on its own?
Should you get a scan?
Usually not for back pain alone. NICE advises against imaging for non-specific low back pain unless the result would change management, for example when surgery is being considered.3 A scan can find age-normal changes that lead to worry and unnecessary treatment. See when imaging is useful.
When to see a clinician
For leg pain with numbness or weakness, or pain that does not settle over a few weeks. Urgently for bladder or bowel changes, saddle numbness or weakness in both legs; see red flags.
Footnotes
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Systematic literature review of imaging features of spinal degeneration in asymptomatic populations. 2015. ↩
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Prediction and mechanisms of spontaneous resorption in lumbar disc herniation: narrative review. 2024. ↩
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Low back pain and sciatica in over 16s: assessment and management (NICE guideline NG59). 2026. ↩
General information, not medical advice. Every claim carries its source; where the evidence is thin, the page says so.Editorial policy · How we grade evidence · All sources · Disclaimer