I've seen this surgery many times. i don't know how your vet is doing this but it sounds like he's going thru the belly and then through the back end? you said this surgery is in two parts. can you explain? i've never heard of this being done, or the use of mesh, or bandaging for that matter. The only thing i can think of for two surgeries is if its a bilateral perineal hernia. Then we only do one side at a time.
I'm sure jack will do well with whatever your vet does. Just remember to give him metamucil for the next month to make things easier to come out.
