Diabetes Insipidus

Looking for some insight? This might be a bit long, so I apologize. Kingsland is an approximately 9y6m Am Staff Terr, SF. For the last 2 years, we have been struggling with PU/PD and it seems to be getting worse.   Kingsland used to NEVER have accidents inside until she got a UTI, however with 2 weeks of Amoxi/Clav, the UTI was gone (this was in 2021). Since then, she goes through these 'spells' where she is PU/PD and seems to be unable to hold her urine. These spells last about 2 weeks and then she's normal for 2-3 months, and then it starts back to PU/PD like clockwork.   We test her for a UTI and culture, both come back negative (meaning, out of all these PU/PD moments, she has only had 1 UTI and that was the initial one in 2021). We did throw antibiotics at her once or twice. She does have a HX of elevated liver values, but those have been stable for the last year (will attach most recent labs). We've done an ACTH and Low Dose Dex, both normal. She is on Hills C/D. Ultrasound showed significant gallbladder sludge, R kidney smaller than L, enlarged liver and a nodule on her spleen. Her kdiney values have always been normal. She has been on Ursodiol since November.   Last Monday, she started back PU/PD after an 11 week break of it. UA was clear. We are now trying Desmopressin to see if she possibly has Diabetes Insipidus and she's responding well.   What causes DI? How concerned should I be for a brain tumor?

Hello!  Diabetes Insipidus can be caused by a lack of a hormone called ADH - 'anti-diuretic hormone.'  ADH is literally, 'the hormone that stops you from weeing.'  It is part of the body's system for controling the amount of water 'weed out' in the urine vs the amount retained in the body.   When Anti-Diuretic hormone fails, the dog weeks more and less urine is retained. There are two methods of ADH 'failing':   1) Brain / gland related i.e. enough ADH isn't being made, or 2) the kidney is 'resistant' i.e. 'not listening' to the ADH, and carries right on filtering water out anyway.  Either way, the result is the same:  excessive, very dilute urine. Insufficient ADH can occur due to an abnormality at birth, brain damage (e.g. trauma such as a head injury, or a developmental problem) or e.g. a tumour or a cyst in the pituitary gland in the head, where ADH is made.  In a few of the cases associated with brain injury, it may get better once the swelling goes down.   Insufficient response to ADH by the kidney typically occurs in certain diseases, such as kidney disease or apparently some severe infections.  Dogs can also be born with this type of Diabetes Insipidus. To my understanding, genetic types are usually evident before a dog reaches 20 weeks old and up to 40% cases of Diabetes Inspipidus may involve a brain tumour.    Diabetes Insipidus itself can be treated; longevity is often linked to the underlying cause.  Your vet and / or their pathologist ought to be able to break the liklihood of different underlying causes down further for you, as applied to your own dog.  However, the cause in your dog won't necessarily be the most likely for their age / breed, so a 'full work up' with scans etc may well come highly reccommended.  I hope that something there helps.