A BUN of 38 isn't all that high. I was wondering if your vet told you what the Creatinine level was. Generally with a high BUN test with preop blood work the test should be repeated in a few months because the result may be high due to the pup being somewhat dehydrated by the time surgery is actually started. The Creatinine is the test for long term kidney disease. I would ask whether this reading was normal or not. Has your vet recommended anything to you regarding ongoing management for your pup?
I have actually gone through this with two six month old pups. My vet suggested that the blood work be repeated in three month intervals. Abnormal results can change to normal in some puppies. Maggie just had another high BUN and she is only just over a year. Our vet has put her on Hills KD aas of today and we will recheck her bloodwork in July again and see if this has made a difference. He said her bloodwork may still return to normal.
I hope your pup's blood work returns to normal too. | 