The technical name for bloat is "Gastric Dilatation-Volvulus" ("GDV"). Bloating of the stomach is often related to swallowed air (although food and fluid can also be present). It usually happens when there's an abnormal accumulation of air, fluid, and/or foam in the stomach ("gastric dilatation").
Order your Bloat Awareness Sticker
Beating Bloat In Dogs - from Morris Animal Foundation
GDV - What we know, and what we wish we knew! Elizabeth Rozanski, DVM, DACVIM, DACVECC