We have tried to get choledocho-cho1ecysto graphy by direct injection of "Urografin, into a biliary tract on occasion of the surgery. In order to get a better choledocho-cholecystography, we researched on the human simulating model with gallstones. The results we obtained were as follows : (1) Minimal ga1lstone shadow recognigable on the film depends on the correlation between the R-kVp and the concentration of urografin. (2) When a large stone and small stones were overlapped eachother in the medium of "60%-Urografin., the shadow of large stone disappeared on the film and, on the contrary, the shadow which may have been accepted as the small stone, became visual. (3) We obtained theoretically following conclusion : in a certain latitude of cncentration of Urografin, the higher concentrated urografin we used, the smaller became the stone shadow to smaller stone shadow than original stone. We analysed theoretieally these phenomena and obtained some findings. The results may be applied not only to the choledocho-cholecystography at the surgical operation, ie, percutneous trans hepatic choleangiography or endoscopic retrograde choleangiography.
