Thank you for your question. My name is***** I have been a small animal veterinarian for 13 years and I'd like to help with your question.
There could be one of several things going on with Shaddy..... the first thing would be to determine whether this is a behavior/break in potty training problem or a medical problem. Some older dogs with have mobility or senility problems that cause them to have problems with potty training. In these cases everything else is normal (appetite, drinking, weight), they just end up having accidents int he house. The fact that you are seeing an increase in drinking and appetite suggest that there is actually something medical going on.
Increases in appetite, changes in weight, increases in thirst, and accidents in the house all suggest a hormonal problem. There are a few... diabetes is one. Diabetic dogs are usually very hungry, very thirsty, but often will loose weight despite eating well. Cushing is another. Dogs with cushings will have similar symptoms as dogs with diabetes, but they are often overweight and gain weight. A few other imbalances, such as thyroid disease, can also cause similar problems.
You will need a basic blood panel and urinalysis to get an idea of what is going on, and maybe some additional testing if this is cushings. However, all these conditions are treatable so you may be able to get things back on track with treatment. I hope this helps, but if you have additional questions please let me know.