Strictly speaking, stones do not form in the kidney itself, but only in the collecting basin at the end of the kidney tubules, called the “pelvis of the kidney.” We have here the conditions favorable for the formation of a stone, i. e., a body cavity where fluid holding minerals in solution may be held stationary.
Also in the pelvis of the kidney there may be the other determining factor for the formation of a stonethat is to say, a foreign body around which the minerals can crystallize.
The famous theory of Rainey about kidney stones was that in the kidney pelvis a colloid substance, which desquamates from the cells of the kidney or the kidney pelvis, is the starting point of kidney stones. This desquamation may be due to infection, with the production of pus and shreds of mucus. Such infection occurs frequently in the pelvis from transfer of infectious material from the nearby large intestine. Many cases are, however, not so easily explained.
The chemical structure of kidney stones is derived from the salts in solution in the urine. The commonest of these is uric acid, and most kidney stones are of this character. Next come lime and phosphate stones.
What influence diet has upon the production of these structures has been widely discussed. It is often said that the consumption of too much sugar will tend to produce stones. A vegetable diet is recommended as a preventive. Nitrogenous foods, such as meat and other protein foods, are considered by many to be favorable to the formation of stones. Alcoholic excesses are sometimes blamed. Yet in contradiction to this is the experience of surgeons in India, where kidney stones are particularly common, occurring in patients who for religious reasons are total abstainers from alcoholic drinks and are also strict vegetarians.
After there is evidence the stone has formed, or when the discharge of small grains of stone gives indication that there is a tendency in that direction, much can be done to prevent further damage by the use of alkaline waters and a vegetable diet, and a life of abstinence, and careful regulation of the bowels.
The consequences and dangers of a kidney stone depend on circumstances. Such stones may vary in size from a grain of sand to one reported by Shields of one and one-half pounds. The smaller stones are liable to give the most trouble in the way of painful symptomsrenal colicbut are less liable to affect the general health. When the presence of a large stone causes obstruction to the flow of kidney secretion and extensive infection results, surgical removal should be seriously considered. The prospect need cause no alarm as in skilled hands today it is remarkably safe.