Our (fixed female, 16 years old, indoor only) cat spent the entire night noisily licking herself. There's no nice way to put this, but she was licking her anus. When we tried to get her to stop, by talking and lightly petting her, she hissed, then continued licking. We looked at the area and didn't see anything that looked out of the ordinary. She did this ALL night!!! What could be the problem? Thank you!
Impacted anal sacs would be first on the list. However, there are other possibilities such as constipation, diarrhea, tapeworm, urinary tract infection, growths inside the rectum, other parasites, fleas, and so on. It is impossible to know without having her examined. If it continues to occur, she should definitely be taken to the vet.
She is older and although she appears to be healthy in the picture and QUITE beautiful, it's important not to wait too long before taking her to the vet anytime something unusual comes up.
Thank you for writing.