Chandana Chandra explains: The kidneys filter out excess water and waste products from blood to form urine, which is excreted to maintain the level of toxic materials in the body. But several reasons like intake of small quantity of water or having calcium rich food often lead to the super saturation of urine.

“The super saturation of these solutes (minerals and acids) produces crystals within the kidneys (nephrons ? kidney cells). These crystals act as a nucleus on which further deposition of solutes occurs, leading to the formation of kidney stones. But the presence of inhibitors like muco protein and citrate solution in our body prevents the growth of these crystals. Thus stones can not be formed in the kidney,” says urologist Dr Dilip Karmakar, the head of the department of Chittaranjan Medical College, Calcutta.

However, the concentration of urine results in the super saturation of solutes which results in the formation of stones in the urinary bladder or the kidney. But this happens in people who lack the inhibitors mentioned above.“Usually crystals are produced due to the super saturation of urine or the presence of any obstruction in the urinary passage. Once the crystals are obstructed in the passage, it leads to the continuous deposition of solutes or crystals over the nucleus (the first crystal obstructed) thereby leading to stone formation,” he adds.

The question was sent by Jayanti Guha via email