Causes of abdominal swelling can range from mild chronic causes, to life threatening emergencies. Several, such as obesity, Cushing’s Disease, intestinal parasites and constipation are generally not considered to be emergencies and can be discussed with your veterinarian at a regularly scheduled appointment. These are not conditions that will likely resolve on its own, so you should still contact your veterinarian at your convenience.
That being said, acute abdominal swelling that is accompanied by signs of pain or general restlessness could be caused by stomach bloat, ruptured abdominal tumors, an infected uterus, and advanced heart failure and need to be treated as an emergency.
If you notice an enlarged abdomen accompanied by panting, pacing, restless behavior, or collapse, please contact your veterinary clinic immediately.