Doctors don't consider bed wetting to be a problem until children are above 7 years old.
So if the child is just wetting the bed from potty training until age 7 then it's likely that the child will just outgrow it by age 8 years old.
Between 7 to 8 years old is when some children stop wetting the bed but sometimes kids will continue to wet the bed until 15 and even 17 and in some rare cases bed wetting continues to happen all the persons life.
I wouldn't even consider taking the kid to the doctor for bed wetting until 7 or 8 years old and even then the doctor will likely just say it's due to the bladder not growing properly and the muscles in the bladder just being weak where the child is unable to hold the urine in at night.
If the bed wetting does continue past 7 years of age then taking the child to the doctor to have some tests done is a good idea just to make sure everything is okay.
You should however use a waterproof mattress cover or washable mattress cover on the child's bed to help keep it clean, dry and sanitary.
You can have the child wear some diapers for bed wetting or some pull ups.
The diapers that tape on will work much better at keeping the child dry at night though and not leak like the pull ups can.