CT detection of retroperitoneal gas associated with gas in intervertebral disks

Beers, G. J.; Carter, A. P.; Leiter, B.; Shapiro, J. H.

Three cases are presented with computed tomographic evidence of gas in retroperitoneal soft tissues in association with the so-called "vacuum phenomenon" (Knutsson sign) in lumbar disks. We review the explanations of Knutsson sign and offer an explanation of how extradiscal gas can occur in association with it.