That was a well-crafted pun!
It’s not a pun:
https://en.m.wikipedia.org/wiki/Pun
It’s more creative than the usual one that translates to “something you find in the catbox”, though. I’ll give it that.
It’s rather insulting to dedicated family members who lovingly care for ill or elderly loved ones, though, and those suffering from medical conditions that require catheterization. I don’t mind it for my own sake — what’s another childish insult to me? I just consider the source. I do find it distasteful on their account, however.