The most severe included one patient being treated for abdominal tumors who developed vomiting that required hospitalization. (uchospitals.edu)
It may be related to something as simple as diet or it may be due to a serious abdominal tumor. (catbreedsjunction.com)
Some internal abdominal tumors can eventually cause a visible swelling of the abdomen, as well, so have that checked out right away if you notice it. (doghealth.com)