Polydipsia

Patient was polydipsic and passed urine every one to two hours, up to four leaters per day. Her urin osmalality was a hundred 75, with a serum osmalability of 308. She's more of a water diaresus than a solute diaresu right? So at this point in the case, we have confirmed that this patient truly is polyeric. Our options are: Are you just drinking too much water, or are your kidneys unable to hold on to free water? And if so, why is that? If it's central diabedes insipidus, then i don't see reliable evidence that h is