This does not sound like a usual presentation for cancer, lymphoma or osteosarcoma to me.
If you are able to post your dogs complete blood (CBC and Complete Chemistry Profile run at the lab and urinalysis results including the urine specific gravity, I would be glad to offer specific thoughts and options to help resolve this for you.
If you dog has bladder stones that would likely be the issue to deal with. Bladder stones often lead to kidney issues which then leads to excess water consumptions and excessive urination. Compromised kidney function makes pets feel poorly as toxins accumulate in their body and lethargy would be expected.
Elevated and/or reduced blood values can have varying levels of significance depending on where and how the blood was run and handled which would be revealed on blood run at a laboratory.
Prior to any major treatment, for example surgery, ultrasound and endoscopy are both non invasive procedures that help to pinpoint exact health problems and can provide an exact diagnosis in most cases.
I am glad to discuss further, feel feel free to contact our veterinary office.
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