Beers G J, Carter A P, Leiter B, Shapiro J H
J Comput Assist Tomogr. 1984 Apr;8(2):232-6.
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.