Hi,

I agree to what Carlos said. But, if we are indeed talking about an ADF (not an ACF), 12-13 years is a really, really good age as already said. Usually, they live for about 5-8 years, even in good environmental conditions. It´s still sad that your frog is sick, but maybe it´s still giving you comfort.
Some frogs can live on for quite a long time with dropsy, though. So if your keeping conditions are ok, I wouldn´t bother too much with treating efforts.