[Gpdd] rear end issues

[Renee]

Just the other day I noticed that my 5 year old guinea pig's rear end has 
become awfully filthy and swollen.  It was crusty and she obviously was not 
able to defecate so I let her soak in warm water to break up the crust.  
After, I easily wiped away at the area and made sure she would be able to poop 
normally, which she did.  Two days later, I noticed that the crust had been 
building up again and I tried to wipe it clean.  I know she is old but I am 
very worried and I need a solution fast.  Please help, I have never 
encountered this problem before.

Thankyou!!
Renee (neyski13 at mail.uri.edu)