Bloat
In most literature and dog training, this is called a play bow or a stretch. However this style of bow, occurs when the abdomen is painful. Most people do not notice it since it can occur hidden. This dog, my dog, was under a table doing this.
The dog with upper GI pain is subdued, tail down and tucked under not playful.
The spittle image is just to show you the issue with bubbles in the upper GI that slows natural gas passage.
Many dogs clear this issue of GI pain with the vomiting spittle, or eating grass then vomiting, or some dogs panic, eat a sock or foreign object which now complicates the problem making it a foreign body requiring surgery.

But this can be followed by gagging, cough, and spittle / vomiting .

An x-ray at this level of pain, would show an enlarged stomach with gas density but no torsion/vulvulus.















