Hi,
This may sound an odd question - when you are handling her does the mass ever seem to move about - or even gurgle?
One of my females got blocked once and swelled up at the back end - though to be honest that was quite a quick change.
But as that mass was mainly comprised of held in pee it actually seemed to slosh about slightly when she was handled and never felt "firm".
Hope everything works out ok for you.
dr del