Normal urine output for an adult is about 1.5-2 L/day, and intake of fluids should be about 2 L. If you're urinary output is greater than 2 L, please mention it to the doctor when you go for the urodynamics, and ask about tests for osmolarity or osmolality ( checks for how well the kidneys concentrate the wastes in the urine).
If, like many of us, you are one of the "non-sweaters" the urine output may be increased to balance the absence of that form of fluid loss, but it still shouldn't exceed intake. "Insensible losses" include perspiration, respiratory secretions, fluid in stool, and whatever other "moisture" is excreted, and are usually around 800 ml/day (0.8 L). Since SjS bodies don't have the same pathways of insensible loss, that may account for a small amount of urinary increase (that isn't an established medical theory, just something my doctor and I have discussed)
Sometimes when measuring intake, only actual "drinks" are measured, and there can be significant fluid intake from food as well...in hospital foods like puddings, soups, hot cereals and gelled desserts are partially included in fluid intake.
By all means bring this up to the urologist, although that may only mean a referral to a nephrologist...it is something that should be looked into.