You cat might not ever face any of the issues presented in this question. But there is something we can all learn from here, that has nothing to do with the choice of treatment or even the financial cost’s involved in making these decisions.  There is something here that goes beyond whether you agree or not with a particular type of treatment or course of action.  

Very often, I will see a cat come into the clinic, and within 5 minutes, I know the cat has little to no chance. So then I go into “here are your options mode”. Where I have to emotionally detach myself from the situation, and give impartial “options of care”.  I take my opinion out of it. I take my personal will for this cat to survive and suppress and swallow it down. Why do I have to do this? Not so much because of anything to do with the cat curiously looking up at the two people talking. Not because of what this kitty could be facing medically. Very often it has nothing to do with money. It’s the psychology of the person who owns the cat. Because within the first 5 minutes, the person has “stacked the deck”.

So despite all the problems going on with this kitty, why does he still look like this:

Which is pretty damn good given everything going on.

To begin with, the person who cares for this cat has not “stacked the deck”.

People who stack the deck are much less likely to have success with their pets, regardless of the issue their cats face. Stacking the deck means that every problem is additive, and so under the weight multiple problems, the person may be overwhelmed, feels like they are losing control, or has simply given up before they walked into the exam room.
I am not making a moral judgment here. I have no idea what other pressures they are facing in their lives. I don’t know what role this little cat plays in their lives. Im am just identifying a very real and common type of psychological response when more than one problem occurs. You can be a veterinarian and stack the deck as well. Any of us can think this way.   

When we stack the deck, even normal everyday issues are an extra burden we don’t want to deal with. Age (typically any age above 8 or 9), arthritis (regardless how how significant it is), deafness (even though the pet doesn't care about that), cataracts (even though the pet can still see), sanitary issues (he pooped outside of the box) or unrelated issues that happened to a entirely different pet 5 years ago are all brought up for discussion, often in succession. We have stacked the deck, such that we rapidly narrow our vision to what is possible.

This rarely leads to choices that will work for this particular cat.

The alternative to stacking the deck is to think about the body and it’s domino effect. Very often, when you focus on the most important issues, the body becomes stronger, and other issues often stabilize on their own. Very often, a few key treatments will aid multiple issues all at the same time. And often is the case that instead of ramping up, our treatments ramp down over time. And as long as kitty is responding, and we are giving these treatments in a way that does not violate the trust we have formed with this pet, things have the potential to go well. We can truly determine the potential for health in this situation.  

So for the person who submitted this question: thank you for not stacking the deck against this kitty. You had every reason in the world to do it - yet you chose different.

So back to the question. How often does prednisolone (a steroid) cause diabetes in cats when used at a higher dose over many months? Answer: Prednisolone can act directly on the pancreas where insulin is produced and depress how much insulin you make. Steroids can act on the liver, pushing up the production of blood sugar, which in and of itself your pancreas will get fed up with. Steroids can make you gain weight, and if you are already fat, you can become more resistant to insulin.

So with all that potential badness, how often have I seen steroid induced diabetes? I have seen it about four times in over ten years. And I do use steroids judiciously in practice on a weekly basis. Which is my I have killer deltoids and biceps and avoid urine tests. Ha ha...nerd vet humour.  So, the statistics are on your side. I would say side effects to pred are dosage dependent, and it is rare I have then on very high doses past one month. Very often dosage decreases occur with the benefits intact - but chemo regimens are quite precise so you would need to make sure your not  messing it up by doing so!  Yes to the ultrasound - it can be an objective indicator of what to do with your medication regimen.  

Hope that helps,