Guinea pig question

Question
I'm hoping you can answer a question about our guinea pig even though you
specialize in rabbits. He is 3 years-old and is energetic and verbal. Lately he
is no longer producing pellets. He has developed a large sack between his
hind legs and is discharging large "balls of poop" instead of regular pellets.
He seems very constipated. He always has plenty of water with a vitamin C
supplement and has a regular diet of guinea pig pellets. Other than this
problem he seems healthy. We're not sure what to do.  

Answer
Dear Paul,

Because I'm not a guinea pig expert, I will direct you to a veterinarian who can handle this problem, which could be serious.  It certainly does need veterinary attention, as it sounds like something similar to cecal dysbiosis in rabbits.  But your guinea pig vet will be the one to determine that.

You can find a vet for your GP here:

http://www.aracnet.com/cgi-usr/seagull/vetfinder.cgi

I hope this helps.

Dana