With the worsening cataracts and the increased water consumption I wonder if the insulin dose or kind of insulin is correct despite the recent curve results. I have not used, but there have been some who have used a Dexcom constant glucose monitor to get a better idea of glucose levels over time in diabetic.
Chasing down these types of problems that don't appear to have the "typical" causes are certainly frustrating, time consuming and costly.
Some questions I have: What are Urinalysis results, particularly SpGr, protein and glucose. What are elecrolyte values?
Depending on results, has anyone suggested a water deprivation test?
They checked for Cushing's, what about Addison's?
This is a pretty good article on diagnostic for PU/PD
VIN article