adopted guinea pig had been losing weight steadily. A blood test and X-ray had not revealed the cause, so the next step was an ultrasound exam. (We had decided that if six-year-old Pumpkin had cancer, it would be time to say goodbye.) The images showed that she had a couple of small (6mm) ovarian cysts. They were not malignant but could diminish appetite. The vet proposed spaying, a riskier procedure on an older pig but one which we will consider if the weight loss continues.
We have written before about the financial and time commitment involved in taking care of pocket pets. They're cute, but know what you're getting into.