Keep in mind that the pet's stool should be small and firm. Most cases of constipation are temporary and due to dietary interruptions. Loose stools also are often temporary and can be due to dietary interruptions, as well as many other things, including an abrupt change in diet, overeating, parasites, medication, eating table scraps, viral or bacterial infections, and stress. If constipation or diarrhea persists, however, it is important to consult a veterinarian.