I just bought a cat yesterday; the seller said she’s healthy, but this one-year-old female is all skin and bones on her back yet has a large belly that bulges to both sides, and she retches occasionally. She drank a lot of water after arriving home last night. What could be the cause?

A swollen belly in a cat can have several possible causes. One is ascites – fluid accumulation in the abdomen. This may stem from low protein levels causing liver-related fluid buildup, or from feline infectious peritonitis (FIP). The typical signs are a very thin back combined with a distended belly that feels wave-like or fluid-filled when lightly pressed, and the cat may show lethargy, loss of appetite, and difficulty breathing. These conditions require timely veterinary diagnosis and treatment.

Another common cause is pregnancy. If this unspayed female was mated while still at the seller’s, the belly enlargement is very likely a sign of pregnancy. A third possibility is constipation or gas and bloating, which often comes with retching, difficulty defecating, slow digestion, and a belly that feels firm when pressed.

Because an enlarged abdomen can indicate serious or even infectious disease, the best step is to take the cat to a veterinary hospital for imaging such as X-rays and ultrasound to determine the cause. If an infection or contagious disease is suspected, further blood tests or infectious-disease screening will be needed to confirm the diagnosis and guide medication.