Rectal Discharge is normally a clear discharge that doesn’t smell. Some people also pass an occasional whitish bowel motion from there rectum after colostomy surgery. This is normal and is a mixture of mucus mixed with dead cells from the lining of the rectum and lower bowel.
The lining of the bowel and rectum makes a mucus lubricant. This is to keep the lining of the bowel lubricated and help the passage of stools without causing any damage to the bowel.
The rectum can make quite a lot of mucus, after colostomy surgery the rectal tissue still makes mucus even though no stools are passing through, this can leak from the rectum and cause distress / shock the first time it happens, be assured it is quite normal.
If this becomes a problem your GP can prescribe steroid suppositories that can reduce the amount of mucus made.
If the leakage is green or yellowish and smells strongly, then you should contact your GP as you may have an infection that needs treating in the lower part of the remaining bowel / rectum. If this continues you could have surgery to remove the remaining part of the rectum but is only used as a last resort. Your surgeon would advise you if this is an option.