What causes swollen feet and ankles after binge at bar?

Consider liver . Agree that sodium may cause swelling but usually alcohol causes volume depletion. If swelling occurs after alcohol binge some sort of liver abnormality should be ruled out.
Fluid. Just the increased in fluid whil binging could cause swelling, but most likely it is the increased sodium.
Need a check up. Binge denotes lots of fluid intake. If you have congestive heart failure this will happen. Note dangling feet in the bar for hours will make the swelling more apparent since water runs downhill. History of alcohol intake could be associated with heart failure called alcoholic cardiomyopathy. Other causes like liver disease for the same exact reasons are possible. Kidneys also need checked.