This is Dr. David
it is up to you
you can try with very small anal dildos if you want to try anal stimulation.
what is your diagnosis of O.P.?
anal stimulation and penitration can irritate your large prostate but if you have a urine catheter, that is not a big deal.
make sure you use plenty of water based lubricants if you are trying a new anal dildo
and make sure you wash your dildo and your hands with antibacterial soap before and after use.
let me know if you have questions.