A caudal injection is a type of epidural steroid injection that delivers anti-inflammatory medication into the lower part of your spinal canal through a small natural opening at the base of your tailbone called the sacral hiatus. It’s one of the most common procedures used to treat lower back pain that radiates into the legs, and it’s considered the safest of the three epidural injection approaches because the needle enters well below where the spinal cord ends.
How a Caudal Injection Works
Your spinal cord is surrounded by a fluid-filled space called the epidural space. When a nerve in your lower back becomes compressed or inflamed, pain signals travel from that area down into your buttocks, hips, or legs. A caudal injection places a steroid (to reduce inflammation) and a local anesthetic (for immediate but temporary numbing) directly into the epidural space near those irritated nerves.
The injection enters through the sacral hiatus, a small gap in the bone at the very bottom of your spine, just above your tailbone. From there, the medication spreads upward through the epidural space to reach the inflamed nerves in the lower lumbar region. The total volume injected typically ranges from 5 to 25 mL, with smaller volumes used for smaller or more frail patients. This larger volume compared to other epidural approaches allows the medication to spread across a wider area, which is useful when pain involves multiple spinal levels.
Conditions It Treats
Caudal injections are primarily used for sciatica and other forms of radiculopathy, the medical term for pain caused by a pinched or irritated nerve root. The underlying causes of that nerve irritation vary, but the most common include:
- Herniated discs pressing against a nerve
- Spinal stenosis in the lower back, where the spinal canal narrows
- Degenerative disc disease, the gradual breakdown of spinal discs with age
- Spondylolisthesis, where one vertebra slips forward over the one below it
- Failed back surgery syndrome, ongoing pain after a previous spinal procedure
That last condition is especially relevant. The caudal approach is often preferred for people who have had prior lumbar surgery because scar tissue from those operations can distort the normal anatomy higher in the spine, making other injection routes riskier or technically difficult. Entering from the sacral hiatus avoids that scar tissue entirely.
How It Compares to Other Epidural Injections
There are three ways to deliver steroids into the epidural space: caudal, interlaminar (entering between the vertebrae in the mid-back area), and transforaminal (entering near a specific nerve root from the side). Each has tradeoffs.
The caudal approach offers the safest needle trajectory of the three because the entry point is far from the spinal cord and major nerve structures. The tradeoff is that it delivers medication less precisely than a transforaminal injection, which targets a single nerve root directly. For pain that’s clearly coming from one specific nerve, a transforaminal approach may be more effective. But when pain is more diffuse, when the anatomy is altered by surgery, or when the goal is broader coverage of the lower spine, the caudal route is often the better choice.
What the Procedure Feels Like
You’ll lie face down on a procedure table. The skin over your tailbone area is cleaned and numbed with a local anesthetic, so the main thing you’ll feel is pressure rather than sharp pain. The physician uses real-time imaging, typically fluoroscopy (a type of live X-ray), to guide the needle into the sacral hiatus. A small amount of contrast dye is injected first to confirm the needle is in the right space before the medication is delivered.
The entire procedure usually takes 15 to 30 minutes. You’ll spend some time afterward in a recovery area being monitored, and you’ll need someone to drive you home. Most people can return to normal activities within a day or two, though it’s common to feel some soreness at the injection site for 24 to 48 hours. The local anesthetic in the injection may provide temporary numbness or leg weakness that wears off within a few hours.
How Well It Works
Pain relief from a caudal injection isn’t immediate in terms of the steroid’s effect. The local anesthetic may numb your pain right away, but that wears off within hours. The steroid component typically takes two to seven days to reach its full anti-inflammatory effect.
A systematic review of the available evidence found that success rates ranged from 40% to 58% at three months, 25% to 67% at six months, and 58% to 61% at one year. That wide range reflects the reality that results depend heavily on the underlying condition. People with disc herniations and clear nerve compression tend to respond better than those with more generalized back pain. The review found moderate-quality evidence that caudal injections are effective for pain and reduced function associated with disc herniation and chronic pain after back surgery at three, six, and twelve months.
If the first injection provides partial but incomplete relief, a repeat injection may be offered. Guidelines from Medicare limit these injections to a maximum of four sessions per spinal region in a twelve-month period, and treatment extending beyond twelve months generally requires additional justification.
Risks and Side Effects
Caudal injections are low-risk procedures, but they’re not risk-free. The most common side effect is temporary soreness at the injection site. Some people experience a brief increase in their usual pain for a day or two before the steroid takes effect.
Because the injection delivers a corticosteroid, repeated injections over time can cause systemic effects like temporary blood sugar spikes (relevant if you have diabetes), fluid retention, or mood changes. These effects are generally mild and short-lived but are one reason the number of injections per year is capped.
Rare but more serious complications include infection at the injection site, bleeding into the epidural space, and accidental puncture of the membrane surrounding the spinal fluid (which can cause a severe headache). The use of imaging guidance during the procedure has significantly reduced the risk of misplaced injections.
Who Should Not Get One
Certain blood-thinning medications are contraindicated with any procedure that enters the epidural space, because bleeding in that area can compress nerves. If you take a blood thinner or antiplatelet medication, your physician will give you specific instructions about when to stop the medication before the procedure and when it’s safe to restart. The required hold times vary by medication, so this is something to discuss well in advance of your scheduled injection.
Active infections, particularly skin infections near the injection site or systemic infections with fever, are also reasons to postpone the procedure. Allergies to the steroid or anesthetic being used, uncontrolled bleeding disorders, and pregnancy are additional contraindications.