Kidney stones. Computer artwork showing a section through a human kidney containing kidney stones (yellowish, right). The ureter (tube) that carries urine from the kidney to the bladder (bottom centre) can also be seen with a stone having travelled over half way along its length. Kidney stones are solid accumulations of dissolved urinary minerals that have come out of solution and built up into hard stone-like objects. They typically leave the body without any symptoms when passing urine. However, if they grow to a sufficient size they may cause an obstruction in the urethra, leading to severe pain.