causes for swelling in the belly
1 Heart failure can also cause swelling in your abdomen. Sometimes it can cause fluid to accumulate in your lungs (pulmonary edema), which can lead to shortness of breath.  Cirrhosis. Fluid may accumulate in your abdominal cavity (ascites) and in your legs as a result of liver damage (cirrhosis).
Some causes of stomach swelling in dogs include: Bloat / Gastric Dilation Volvulus. Called the mother of all emergencies, untreated gastric dilatation and volvulus (GDV) can be fatal to a dog within hours. Bloat happens when gas or food stretch a dog's stomach.