Intended meaning of "urethra"

The uploader of [NSFW]>>2562199 used the keyword “inner pipe”, which seems to be used for something totally else, but I realized what he meant: the urethra that so well sticks outta the skin of the back of the stallion’s dick.
 
I entered “\*urethra\*” into the keyword search which didn’t bring up anything specific to just the pipe sticking outta the dick when not seeing the opening, to which “urethra” has been referring for as long as I’ve been on the site.
 
So, what should be done in this case ? And when that’s decided, it should be mentioned in the keyword’s description cuz ATM there’s nothing describing it.
 
To be fair, the pipe is more often than not sticking out like that when a horse dick is present.

@rautamiekka  
Uhh, you know the innertube is the round thing he’s floating on, right? :P

@LightningBolt  
Oh, I didn’t even notice that. My bad.
 
But the subject still stands.