One of my ferrets, Eve, has the exact same thing: a large, distended belly with no discernible lumps and no pain. We took her to the vet, and x-rays showed no large masses, lots of fat around her kidneys, a slightly enlarged heart, but everything was relatively normal. The vet did an aspiration to see if there was fluid, and there was--a yellowish fluid (not urine). On the slide, though, there was only the occasional large cell, so she sent the sample in for a more thorough cytology. The cytology came back negative for cancer, some signs of white blood cells, but generally inconclusive. Eve is active, curious, and chipper. The Vet recommended that our next step be an ultrasound, which we are going to wait on for a while to see if her condition changes any over time. Without further tests, which if nothing shows on the ultrasound, would involve opening Eve up to see what it is (which we're not too thrilled about), her condition is pretty much undiagnosed. So, I can't really help, but I can empathise. -cobalt [Posted in FML issue 3475]