In this cholangiogram, you see an extreme example of biliary ductal dilation. The normal caliber of intrahepatic bile ducts is similar to the ones seen at the inferior margin of the right hepatic lobe.
Highest on the differential diagnosis in a case like this is distal obstruction, either due to a stricture or compression by a mass. If you trace the dilated ducts distally, towards the common hepatic duct, you will notice the sudden disappearance of contrast. An extraluminal mass here (?Klatzkin tumor) could be compressing the common hepatic duct. Multiphasic CT or MRI should be performed to delineate any underlying, pathologic process.