A caudal epidural steroid injection delivers anti-inflammatory medication into the lowest part of the spinal canal through a small opening near the tailbone called the sacral hiatus. It’s one of the most common procedures for treating lower back pain and leg pain caused by inflamed spinal nerves, and it typically takes 15 to 30 minutes to perform.
How the Injection Reaches Spinal Nerves
Your spine has a fluid-filled space surrounding the spinal cord and nerve roots called the epidural space. When discs bulge, the spinal canal narrows, or scar tissue builds up from surgery, nearby nerves can become compressed and inflamed. A caudal epidural targets this space from below rather than going between the vertebrae higher up on the back.
The entry point is the sacral hiatus, a natural gap at the base of the sacrum (the triangular bone above the tailbone). Two small bony bumps called the sacral cornua sit on either side, forming a gateway into the lowest end of the spinal canal. The doctor slides a needle through a ligament covering this opening and advances it just far enough to place the steroid medication near the affected nerve roots. The steroid reduces inflammation, which is the main driver of pain in most cases.
Conditions It Treats
Caudal epidurals are primarily used for pain originating in the lower lumbar spine and sacral region. The most common reasons include:
- Sciatica: pain radiating down the leg from a compressed nerve root, often caused by a herniated disc
- Lumbar spinal stenosis: narrowing of the spinal canal that squeezes nerves
- Failed back surgery syndrome: persistent pain after spinal surgery, where scar tissue may block access to the epidural space from higher approaches
- Degenerative disc disease: chronic lower back pain from worn-down discs
The caudal approach is especially useful when scar tissue from previous surgery makes it difficult to access the epidural space through the more common interlaminar route between the vertebrae. It also allows the medication to spread across multiple nerve levels at once, which can help when pain involves more than one segment of the lower spine.
What Happens During the Procedure
You’ll lie face down on a procedure table. The skin over your lower back and tailbone area is cleaned and numbed with a local anesthetic. Most providers use fluoroscopy (live X-ray) to guide the needle, though some use ultrasound.
With fluoroscopy, the doctor views the sacral hiatus from the side and watches the needle enter the canal in real time. Once the needle is positioned, a small amount of contrast dye is injected to confirm the medication will flow into the epidural space and not into a blood vessel or the fluid surrounding the spinal cord. After confirmation, the steroid and often a local anesthetic are injected.
With ultrasound guidance, the sacral cornua appear as two bright structures on the screen, with the sacral hiatus visible as a darker space between them. The needle is tracked as it pierces the ligament and enters the canal. Because ultrasound can’t see past a certain depth in this area, needle advancement is kept very limited, typically no more than 5 millimeters beyond the opening, to avoid puncturing the membrane (dura) that contains spinal fluid. The distance between the hiatus and the dura can be less than 6 millimeters in some people.
Without imaging guidance, the miss rate for hitting the correct space can be as high as 26%, even with experienced practitioners. This is why most modern protocols use fluoroscopy or ultrasound.
How Well It Works
Pain relief typically begins within two to three days, though it can take up to 10 days to notice a meaningful difference. The relief generally lasts weeks to months, and in some cases up to a year, though that’s uncommon.
A systematic review examining caudal epidurals for chronic low back and radicular pain found that the proportion of patients achieving at least 50% pain reduction ranged from 40 to 58% at three months, 25 to 67% at six months, and 58 to 61% at one year. Functional improvement varied more widely, from modest to substantial depending on the study. These numbers reflect a real-world picture: caudal epidurals help many people significantly, but they don’t work for everyone, and they’re generally more effective as part of a broader pain management plan that includes physical therapy and activity modification.
Risks and Side Effects
Most side effects are minor. The most commonly reported issues include a temporary increase in pain (about 1.1% of cases), soreness at the injection site (0.33%), and brief numbness (0.14%). Some people experience a temporary rise in blood sugar, particularly those with diabetes, because the steroid medication can affect glucose levels for several days.
Serious complications are rare but possible. Vascular penetration, where the needle enters a blood vessel, has been observed in about 7.4% of fluoroscopy-guided procedures in one large study, though this typically leads only to minor effects like light-headedness and doesn’t cause lasting harm. Dural puncture can cause a positional headache that worsens when standing and improves when lying down. Infection and epidural bleeding are very uncommon but represent the most serious risks.
Acute symptoms that occasionally appear within 72 hours include temporary drops in blood pressure, chest discomfort, and brief numbness or tingling in the extremities. These usually resolve quickly but should be reported.
Who Should Not Have the Procedure
Certain conditions rule out a caudal epidural entirely: active infection (either systemic or at the injection site), being on full-dose blood thinners, a known severe allergy to contrast dye, local anesthetics, or steroids, and the presence of a tumor at the injection site.
Some situations call for extra caution rather than outright avoidance. Uncontrolled diabetes is a relative concern because the steroid will temporarily raise blood sugar. Congestive heart failure can be worsened by the fluid volume injected. Pregnancy is a relative contraindication mainly due to the radiation exposure from fluoroscopy, though ultrasound-guided approaches may be an alternative in specific circumstances.
Recovery and Activity After the Injection
You should not drive yourself home. For the rest of the day, avoid operating machinery, making major decisions, signing contracts, or drinking alcohol. Light activities around the house are fine, but skip heavy lifting, strenuous exercise, and work for the remainder of the day.
You can resume your regular medications afterward, including blood thinners, unless your provider tells you otherwise. Most people return to normal activities the following day, though it’s worth easing back into physical demands gradually.
Contact your provider promptly if you develop worsening back pain, new numbness or weakness in your legs, loss of bowel or bladder control, or fever. Redness, swelling, increased pain, or discharge at the injection site may indicate infection and should also be reported. A headache that gets worse when you stand up and improves lying down suggests a dural puncture and needs evaluation.