Dog getting impacted anal glands after neutering?

I got my male dog spayed, he had some tumorous tissue on his testicle and they had to be removed, after that vets said he wil be fine and he was, but when he recovered from the surgery his anal glands got impacted, we took him to the vet and he got treatmen an then he was fine for about a week, after a week his... show more I got my male dog spayed, he had some tumorous tissue on his testicle and they had to be removed, after that vets said he wil be fine and he was, but when he recovered from the surgery his anal glands got impacted, we took him to the vet and he got treatmen an then he was fine for about a week, after a week his glands got impacted again, and everytime we take him to the vet he gets better for a week or two and then it gets impacted again. Does anybody know whats wrong, is it connected wit his surgery, I am going to take him to the vet again but until then can somebody explain why is this happening, he is 3 years old and never had anal gland issues until his surgery.
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