I am sorry to say, but this does sound Liver related. Either Liver Shunt or MVD....But please try to relax, this is not a death sentence. If she has a Liver Shunt, the success rate for surgery to close the shunt is very high ~ then she just needs to be managed with a special low, but quality protein diet (Rx kibble) and special liver aiding meds and supplements. And if this is MVD, no surgery can be done, only managed with special diet / supplements...Honey, she is going to be ok, she is at the Vet being taken care of, the proper tests are being done
Here is some info on the Protein C test. Print it out and give it to your Vet. IMO this should be done before you get the Ultrasound ~ it is a good guide for LS and MVD
Comparative Coagulation -- NYS Animal Health Diagnostic Center