Even though it's a bit uncomfortable, you can primarily address digestive problems easily recognizable in your dog's feces: Small amounts of hard or dry feces, feces with attached mucus, very soft feces, or even diarrhea are signs of digestive problems.
Even if your dog tries multiple times to defecate without success, or is doing its business very frequently and often, something is not right. Other symptoms may include Loss of appetite, fatigue, bloating, pressure sensitivity in the abdominal area as well as occasional vomiting.