Eww, that's weird. Wish I new. I only once had a dog with impacted anal glands. He was on antibiotics for a couple of weeks and he was fine.
Is is possible he has a food allergy? Have to tried a corn-free food? I have also read that obesity can contribute to anal gland problems. Anal glands can be removed, but only as a last resort if the dog is in pain.
"And why do we fall, Bruce? So we can learn to pick ourselves up."