What this means
A belly can grow for very different reasons: gas, fluid, enlarged organs or fat. From the outside they cannot be told apart, so do not try to guess. What matters most is whether it appeared suddenly or grew gradually.
Sudden swelling, particularly in larger, deep-chested dogs, may mean the stomach has bloated and twisted. This is one of the most urgent conditions there is, and every minute counts. If the belly is tight like a drum, your dog is drooling and restless and tries to vomit without success, go at once.
If the belly grew over weeks or months, note whether your dog is also drinking and urinating more, coughing, tiring faster, whether the back and legs are getting thinner and whether appetite changed. This helps your vet decide where to begin looking.
Possible causes
These are things that can cause this sign. It is not a diagnosis, and they are not equally likely for your dog.
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Stomach bloat and twisting
The stomach fills with gas and may rotate. Typical signs are a suddenly swollen, hard belly, unproductive retching, drooling and restlessness. This is an emergency.
About the condition: Bloat (gastric dilatation-volvulus) -
A blood vessel abnormality around the liver
When blood bypasses the liver through an abnormal connection, a dog may grow poorly, seem dull or act strangely, and sometimes fluid collects in the belly.
About the condition: Liver shunt (portosystemic shunt) -
Heart disease
When the heart works less well, fluid can collect in the belly. The belly grows gradually, and your dog tires faster, coughs or breathes harder.
About the condition: Heart disease -
Cushing's disease
With an excess of certain hormones the belly can become round and pendulous, your dog drinks and urinates more, the coat thins and the muscles weaken.
About the condition: Cushing's disease -
Swallowing a lot of food or water
After very greedily eating a large meal or drinking a lot at once, the belly can swell for a while. If your dog is bright and the belly is soft this usually passes, but any doubt is a reason to phone your vet.
What else to watch for
These observations help your vet build the picture faster. Note down what you saw and when.
- Whether the belly swelled suddenly or grew gradually
- Whether it is hard or soft, and whether it hurts when touched
- Whether your dog drinks and urinates more
- Whether it coughs, tires faster or breathes harder
- Whether the back and legs look thinner, or the coat is thinning
- Whether appetite, eating or behaviour changed
When to book a routine visit
Book a visit if the belly is growing gradually, or if your dog also drinks more, coughs, tires faster or has changed shape. If any of the urgent signs above appear, go straight away rather than waiting for an appointment.
Related conditions
Conditions whose entries mention this sign. The list is somewhere to read on, not a way to reach a diagnosis.
- Bloat (gastric dilatation-volvulus) Digestion and liver This is a condition in which the stomach fills with gas and can twist around on itself, pinching off its blood vessels and cutting off circulation. It develops very quickly and is life-threatening, so the dog needs a vet immediately. Large, deep-chested dogs are known to be at risk, so it is worth noting the number of the nearest emergency clinic in advance.
- Liver shunt (portosystemic shunt) Digestion and liver A liver shunt is an abnormal blood vessel that carries blood from the intestines around the liver instead of through it. As a result, the liver cannot clear the toxic substances coming from the gut, and they enter the general circulation, affecting the brain and the whole body. A shunt can be present from birth or develop later because of other liver disease.
- Heart disease Heart This is an umbrella term for various conditions in which the heart muscle, the valves or the heart rhythm stop working as well, making it harder for the heart to pump blood around the body. Some are present from birth, others develop with age, and they can go a long time without any noticeable signs. During a check-up the vet listens to the heart and decides whether further tests are needed.
- Cushing's disease Hormones and metabolism Cushing's disease is a condition in which the body makes too much of a stress hormone. This hormone affects many of the body's processes, so an excess gradually changes a dog's appetite, skin, coat and muscles. The changes come on slowly, so they are easy to mistake for simple ageing.
- Pyometra General health Pyometra is a pus-filled infection of the womb that can develop in an unspayed bitch in the weeks after a season. Pus collects in the womb, and substances released by the bacteria harm the whole body. The condition can quickly become life-threatening, so the bitch needs a vet immediately.
Body systems: Digestion and liver Heart Hormones and metabolism General health