Does my cat have sinus problems....?

when i used to work as a med tech for a cat shelter there were a few cats that at first seemed to have a sinus infection/upper respiratory infection and after continued treatment and continued close observation noticed that they always sounded stuffed up and sneezed alot as well as snoring and came to find that they had a nasal polyp growing in the nose that caused irritation. The cats i seen with this had surgery to remove the polyp and the surgery was successfull .