Congenital lumbar spinal stenosis is an uncommon condition that is often asymptomatic in young adults. Herein, we document the first reported occurrence of acute radicular back pain and associated congenital lumbar spinal stenosis in a healthy 24-year-old woman undergoing an epidural blood patch for treatment of a post-dural puncture headache related to an accidental dural puncture sustained during placement of a labor epidural catheter. The acute pain symptoms were elicited twice with injection of less than 1 mL of fluid into the epidural space during the fluoroscopically assisted epidural blood patch. Subsequent magnetic resonance imaging of the lumbar spine demonstrated shortened pedicle length consistent with severe congenital lumbar spinal stenosis and prominent epidural fat. We speculate that the transient increase in pressure within the epidural compartment following injection of a small amount of fluid could have compressed neural structures resulting in severe radicular pain. The prominent epidural fat could have prevented rapid disbursement of the injected fluid which could have further served to propagate the pressure increase throughout the epidural compartment. The unique radiographic features of congenital spinal stenosis could predispose some patients with this unrecognized condition to develop acute pain upon injection of a small amount of fluid into the epidural compartment. Unrecognized congenital lumbar spinal stenosis is an important addition to the differential diagnosis of acute radicular pain elicited during an epidural blood patch in previously asymptomatic patients. Key words: Epidural blood patch, congenital spinal stenosis, epidural lipomatosis, acute spinal pain