C.L.
I think it sounds like he's constipated and some stool is getting out. It's a fairly common problem. Call your doctor. They can do an abdominal x-ray if necessary to check for backed up stool and give you recommendations about temporary supplements like Miralax or mineral oil. My son deals with the constipation issue and stool getting out involuntarily, although not when he's sleeping. Good luck. Oh, constipation can cause bedwetting problems too so the issues are often related. It's also not unusual to still have nighttime wetness at age 8, although the doctor may be able to address that also.