Sorry to hear this.
Do you know whereabouts the swollen glands are situated? e.g. Near the bladder, somewhere else such as the neck or are they all swollen?
If she were my piggie I would be discussing with y vet getting A biopsy and microbial culture done as it would diagnose lymphoma and if it is an infection instead then provide an idea of the bug concerned and its sensitivity to antibiotics.
If it is lymphoma, then a course of steroids is often recommended to slow the spread...(that was what my Willow was prescribed) However it can leave a piggie sensitive to other infections. Reference her bladder issues etc - has a urine culture been done at any time? Marbocyl belongs to the same family of antibiotics as baytril - there are an increasing number of bugs that infect guinea pigs that are developing resistance to baytril/marbocyl/septrin ........so other alternative drugs often have to be considered at such as doxycycline, azithromycin....hence why my vet now cultures for any URI/UTI my piggies have before choosing what to prescribe. One of my bladder pigs (Maple) had no stones or kidney issues yet his bleeding was often cause for concern as he bled so much he had to be given Vit K injections. On post-mortem we were expecting to find a tumour but all they found was a thickened inflamed bladder wall where the cells had grown round tiny particles of grit.
I've been doing quite a bit of research into bladder pigs as I have quite a few. For one pig, Carson, we found his !squeaky wee! symptoms were alleviated by a bladder flush and he is still, two years on, doing very well. The protein in his urine is high suggesting his kidneys are involved in some way, and his wee has chalky deposits but i think bladder flushing can in some cases help prevent the build up of grit/sludge that leads to the chronic inflammation. Carson is also on a restricted diet where he gets no leafy veg - just celery, cucuber, carrot and baby corn (and grass and dandelions when in season) as we found every time he ate the fresh green veggies the squeaky wees returned the following day.
HTH
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