Just to add more to the conversation, I did an experiment yesterday where I kept track of my intake and measured my urine output. It certainly wasn't scientifically accurate, but not way off. My intake of fluids (all water other than 16 oz of black tea in the morning) was ~4600ml. My output was ~2725ml. Those numbers are WAY off and show that even though I urinate frequently, I'm not removing what I put in. I will continue the experiment for a few more days to see if the numbers are consistent. I plan to ask my neuro for a referral to a urologist to see if there is anything that can help this. Thanks folks for you thoughts and experience.