Contrast is used to verify epidural location and to indicate the distribution of injectate. Some physicians use contrast as a volume expander while others prefer saline for this use. The contrast is typically nonionic and lowosmolar. In patients with contrast allergies gadolinium can be safely used in most lumbar procedures. 30,31,52,53 If using gadolinium, the amount should be just enough to document epidural injection. Gadolinium should not be used as a substitute for volume expander. The typical amount of contrast or contrastsaline mixture used for either cervical or lumbar interlaminar epidurography is 4 cc to 5 cc (less in nerve blocks; see below). A smaller amount will not provide sufficient contrast for an epidurogram to evaluate for adhesions or distribution of injectate. For coding purposes, an epidurogram is considered to have been performed when approximately 4 cc to 5 cc of contrast is injected regardless of the route (transforaminal or interlaminar). The report, CPT code, and amount billed must be adjusted if an epidurogram is not performed. The amount of contrast injected may be reduced in spinal stenosis. Many patients will feel pressure or leg cramping from almost any volume, no matter how small. Patients undergoing first-time injections may confuse this with pain. Careful questioning and reassurance that pressure is normal will be adequate in most cases. The injectate volume should be reduced if significant pain is experienced.
Very rarely the prolapse disc may press on the central area of nerves known as the cauda equina. The patient may experience sciatica down both legs, which may be associated with numbness of both legs. The condition is particularly urgent if there is numbness around the anus and/or genital area, indicating potential or actual damage to control of the bladder and/or bowel. Cauda equina syndrome is a surgical emergency and if patients have any concerns about this they should consult their doctor without delay, as emergency surgery may be required.