Predinsone doesn't work for some people. Also, it sounds as if he could have an infection. We are especially susceptible to clostridium difficile (c. diff) colitis because the UC tends to kill off the healthy bacteria in our colons.
Call his doctor again (I assume he's being followed by a GI?) and tell him what's going on. In the meantime, try to get him to drink a lot of fluids. Sports drinks are okay, but he shouldn't be drinking all sports drinks; be sure he drinks a variety of things. Water is really good.
He also may want to start on a good probiotic such as VSL #3, Primadophilus Reuteri or Culturelle. There are also good choices at any health food store. These contain good bacteria to re-colonize the colon.
Moderate to severe left-sided UC diagnosed 2001.
Flared for 5 years, finally in remission with Remicade since March 2006.
Avascular necrosis in both shoulders is my "forever" gift from steroids.
Colazal, Remicade, Nature's Way Primadophilus Reuteri.
"My life is an ongoing medical adventure"