0:39 The waste products and excess fluid become urine.
0:44 It travels through two narrow tubes called the ureters to the bladder,
0:50 and leaves the body through the urethra.
0:53 If there is an imbalance in the waste chemicals in the urine,
0:58 crystals can form, which may build up into stone-like lumps.
1:03 These are known as kidney stones.
1:07 This can happen for a number of reasons,
1:10 including not drinking enough water,
1:13 a diet high in protein,
1:16 or health conditions, such as kidney disease.
1:20 If kidney stones are small, they usually leave the body when you pass urine.
1:28 However, larger stones can get stuck in the kidneys
1:31 or pass down the ureter, causing irritation
1:35 and blocking the flow of urine.