Sorry for my late reply. I'm not a doctor and can't tell you what to do, but I can tell you what I did when I had a budgie in a similar situation:
Our budgie Rayleigh was limping and our primary vet recommended we take her the veterinary school in our area because they could do a CT scan. The veterinary school ER did a CT scan, and found a mass in Rayleigh's abdomen so large they could not tell if it was renal or ovarian. The mass was starting to put pressure on her lungs, making breathing somewhat challenging for her. The tumor likely explained why Rayleigh's left leg became limp.
We never knew 100% if Rayleigh was female or male, so the team at the veterinary school could not rule out an ovarian mass. I was told at the veterinary school ER that the color of her cere could not be a sole tool to identify gender for the reason that when male budgies have testicular cancer, their cere turns brown (much like the color of a female's cere).
They gave us the following options:
- If we felt Rayleigh still had a good quality of life, do not treat the day of. Take Rayleigh home and bring her back for euthanization when her breathing becomes too difficult.
- Try aspirating the mass with a needle. The color of the fluid would identify the tumor as renal or ovarian. If the tumor was renal, not much could be done and euthanization was recommended. If the tumor was ovarian, they could try an injection of Lupron. It would not shrink the tumor but the tumor would hopefully stop growing. It would be a short gap measure and prolong her life somewhat, but how much of a life extension was unknown.
- Do not aspirate the mass, but try giving a Lupron injection in the event this tumor was ovarian. Monitor Rayleigh for improvement. If no improvement, euthanization recommended.
- No further testing or treatment, and end her life through euthanization.
We chose to end Rayleigh's life that night in the ER because we felt the alternatives could have given her some time, but the quality of that time would be poor. She already had trouble walking and trouble breathing. We also didn't want her to suffocate as the mass continued to impinged on her lungs. We also were not sure how much pain she was in, as prey birds tend to mask their symptoms.
I think if we were to do it all over again, we would have made the same choice, given we didn't want to unnecessarily prolong her life if her life wasn't going to be enjoyable (she did play sometimes at that point, but her mobility kept her from playing as much as she used to).
We certainly miss her still. When we look back at her short time with us, I remember we tried giving her the best life that we could.