Kidney Stones
Kidney stones are formed when material that is normally excreted by the kidney precipitates, usually because of an increase in concentration, either due to an increase in secretion or a reduction in fluid intake causing relative dehydration. They may be small or large - large ones tend to stay within the kidney substance, causing loin pain or backache, while small ones may be passed into the tube between the kidney and the bladder (the ureter) causing severe pain and possibly obstruction. The most common stone is made up of calcium oxalate but others, made up of other constituents such as uric acid or phosphates, also occur. Stones are much more likely to form in patients who secrete high levels of calcium (called hypercalcuria) and who produce highly concentrated urine - a condition which may be familial, and promote recurrent stone formation. The likelihood may be reduced by high fluid intake together with attention to dietary factors (for example potassium citrate may help to reduce the incidence of stone formation).
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