gallstones

/G AA1 L S T OW0 N Z/
noun
  1. 1

    A small, hard object, in the shape of a pebble, that sometimes forms in the gallbladder or bile duct; composed of cholesterol, bile pigments and calcium salts.

Source: https://en.wiktionary.org/wiki/gallstone, https://en.wiktionary.org/wiki/gallstones