Nontraumatic Pneumorrhachis and Intraforaminal Gas, Presumed Intravascular, Is Occasionally Detected in Dogs Undergoing Computed Tomography Angiography Without Immediate Complications

Pneumorrhachis is a rare condition in human and veterinary medicine, defined as gas within the vertebral canal. Iatrogenic causes are the most common source of nontraumatic PR reported in humans. PR has been recognized in dogs undergoing routine CT. This study aims to identify the cause, prevalence, and distribution of PR and intraforaminal gas in dogs undergoing CT and identify any immediate post-CT complications. The medical records of dogs who underwent CT of the thorax, abdomen, and pelvis were retrospectively reviewed. Dogs were excluded if they presented with a history of trauma, neurologic deficits, recent surgery, or epidural injection. PR and intraforaminal gas were identified as present or absent and quantified subjectively. Patient positioning, intravenous catheter location, and complications in the 24 h following CT were recorded. 50/263 (19%) dogs with PR met the inclusion criteria. All dogs with PR had CT performed in sternal recumbency. Catheters were evenly distributed in laterality of placement, yet PR was predominantly right-sided (74%). The volume of gas identified was mild (87%) or moderate (13%). An increase in the amount of PR in postcontrast images was documented in 13 cases (20%). Intraforaminal gas was identified in 16.3% of dogs, and 88.4% had right-sided intraforaminal gas. No dogs developed neurologic deficits 24 h post-CT. The prevalence of PR and intraforaminal gas in this study was significantly higher than previously documented. Intravascular right-sided gas is proposed to be secondary to the ipsilateral location of the azygous vein and of no clinical significance.