if you can hear its heart the animal is okay but if you really hear its insides take it to a vet
Most likely what you hear is food digesting. Many kids like to lay their head on a sleeping dog while playing or resting and are concerned about the sounds emanating from the dogs mid section. Digestion is a continual process even when the dog has not eaten for a while. Digestive juices are still present and making rumbling/gurgling sounds.