Do you have a urostomy or colostomy? I have a urostomy and use coloplast sun suri mio one piece as well as overnight bag. Periodically my bags balloon also. It especially balloons while flying. I disconnected the two bags to let the air out if the overnight bag is ballooning or just emptied the ballooning bag. I have attended other support groups and find it rare for urostomy patients to have this problem. I have been told that it is food related but my diet is fairly consistent and can’t figure out what is causing it.