Light micrograph section through a human gallbladder showing gallbladder cancer. The gallbladder is a small, pear-shaped organ on the right side of the abdomen, just beneath the liver. This stores bile, a digestive fluid produced by the liver. Gallbladder cancer is an abnormal growth of cells that begins in the gallbladder, although it's generally uncommon. Gallstones are the most common risk factor for gallbladder cancer. These pebble-like collections of cholesterol and other substances that form in the gallbladder can cause chronic inflammation.