Hello.
A Perineal urethrostomy is a procedure done for cats who have a history of Urinary obstructions/blocking. We do not do this procedure on cats who are marking around the house.
When we see cats exhibiting the same behavior as your kitty, we go through a few steps to figure out why… We first check a urine to make sure there is no infection/stones. We often see this behavior in our stressed kitties that have something effecting their life in a negative way. Have you talked to your vet about behavior modification? Stress relievers? Often seen are people using feliway- a plug in diffuser to help ease the stress. There are medications that your vet can prescribe to try and limit this behavior. Please try these as next options for your feline friend.

Hope this helps and your kitty gets better!