Replying to Kathryn B. 11/10/2022 - 21:02
Hello.
Great to hear from you. Thanks for the great question, I agree, these can be really frustrating cases!
Despite the normal total calcium in this case, I would still measure an ionised calcium, especially in cases when you are not finding anything else. An SDMA would be a good shout. I am less convinced these early cases present so much with obvious signs of PUPD, but again, in cases where you are not finding anything else, I would.
You are right about the USG. When the urine is hyposthenuric, the urine is more dilute than plasma and therefore there must be renal tubular function. Central and nephrogenic diabetes insipidus are differentials as are conditions that interfere with the concentration of urine such as hypercalcemia, sepsis (e.g., pyometra, pyelonephritis), hepatic disorders, hypoadrenocorticism, hyperadrenocorticism and psychogenic polydipsia.
Nothing is totally ruled out by the level of USG that a patient falls in to.
1. I would want to see multiple morning urine samples from this dog to assess ability to concentrate.
2. I would defiantly get the owners to quantify intake.
3. Ionised calcium and SDMA as mentioned.
4. I have seen some weird cases of cPSS present in later life just with PUPD. A bile acid stimulation test would not be a ridiculous shout.
5. I would tend to them image these patients next. There are some other weird things that could be to blame like splenic haemangiosarcoma and pheochromocytoma.
6. If all else fails then you could then consider DDAVP trial.
I hope that helps. Let me know how you get on with this one.
Scott 🙂
