Rapid Systemic Absorption of Epidural Iodinated Contrast: Observations from Multilevel Blood Patching

Though systemic absorption from the spinal epidural space is a known physiologic process, it remains underexplored in the context of iodinated contrast. To evaluate systemic absorption from the epidural space, we performed CT imaging of the renal collecting system as part of CT-guided multilevel nontargeted dorsal interlaminar epidural blood patching.

Patients undergoing nontargeted multilevel blood patching without an identified CSF leak or fistula were included for analysis. Patients underwent dorsal epidural contrast injections with undiluted Omnipaque 300 at 2-4 levels followed by blood patching. Two board-certified neuroradiologists performed the procedures and assessed contrast presence qualitatively. Imaging, including the renal pelvis, was obtained pre- and post-epidural contrast and post-blood patching, with the presence of renal contrast at each time point assessed.

Seventeen patients (mean age 44 years, SD 14.4; 82% women) underwent epidural blood patching and renal imaging. No patient had contrast visible on initial imaging. Contrast appeared in the renal collecting systems in 100% of patients within the procedure period, on average 23 minutes following the first contrast injection.

Systemic contrast absorption from an epidural injection is consistently observed in patients within 30 minutes. This finding provides imaging evidence of the relatively fast uptake from the epidural space and could provide a new understanding of the systemic effects of medication or contrast injected into the epidural space during percutaneous spine procedures. Specifically, this systemic absorption should not be confused with pathology or as a stand-alone indirect marker of a CSF leak in the context of myelography.