What Causes Elevated Levels Of ALT And Gamma GT?

I have suspected cancer of my pancreas. My ALT is 275, Gamma GT over 1000,Bilirubin 70. These have all increased dramatically within the past 3 weeks after I had complained of a back ache & severe indigestion & pain in the base of my sternum.I have had a CT scan which showed that the 1st 10mm of my interpancreatic duct is abruptly & dramatically decreased in calibers. I have all the usual signs - white float stools, severe itching, yellow eyes etc. I am waiting for an ERCP. Can they install a shunt at the same time? If this is not done ASAP how long before I loose my cognitive abilities?