Hi @michalbajer, I used Google translate to read your post. I don't speak Polish, unfortunately. Perhaps you can use Google translate to read my message as well. https://translate.google.com/

It sounds as though your son had a a radical mastoidectomy. Members like @mgarthwait12 @squaredancer @imallears @lioness @johnbishop may be familiar with the surgery as well as the cholesteatoma accumulation you described and the need to remove it every 3 months. They may have some experience with this operation to share or be aware of others who have had this and have input to offer.

What was his diagnosis prior to the mastoidectomy?