Kidney stones or calculi develop as a result of various metabloic disorders which affect the fate of calcium and other mineral elements in the body. Stones may be formed in the kidney, urinary bladder and lumens of ureter and urethra.
Kidney stones are solid structures made up of mainly uric acid, calcium oxalate, triple phosphate or cystine. Based on their composition four kinds of stones are identified-
1. calcium stones 2. uric acid stones 3. cystine stones and 4. struvite stones. Stones are formed when the urinary salts in amorphous form are bound to a colloid matrix. These are deposited surrounding a nucleus of organic origin.
Mechanism of stone formation is poorly understood. Calcium stones are formed due to excess secretion of calcium in the urine. Other causes of stone formation include- low urinary output, hypoglycemia followed by hypercalcularia hyper parathyrodism, bone tumours etc.
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Symptoms of renal stones include extreme pain in the ureter or abdomen. If the stone gets stuck in the ureter urine is blocked leading to dilatation of the kidney. Sometimes small stones may come out along with urine. Clinically renal stones can be detected by X-ray, ultrasound scan and magnetic resonance image techniques.
Structure of the stones
1. Uric acid stones:
These are composed of uric acid with sodium and ammonium urates. Stones appear smooth, hard; light or dark brown in colour.
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2. Oxalate stones:
These are found in pure form and extremely hard with prickly outline. The stones are dark coloured due to coating of blood which again is due to injury caused by the spiny exterior (of the stone).
3. Phosphate stones:
These may occur in pure form or in combination with others. These stones are white, smooth and often look like a stag horn hence the name stag horn calculi.
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Treatment:
It is both medical and surgical. Heat fermentation, analgesic drugs etc may reduce pain. Surgery is the best method when stones are larger than lc.m.
A recent technique of stone removal does not involve surgery for stones not larger than 3 c.m. This technique called Extra corporeal shock wave lithotrypsy (ESWL) sends shock waves over the kidney to pulverize the stones completely and the powdered particles come out along the urine. This is a safe method (though costly) and surgery is avoided. Patients (even after removal of the stones) should take lots of liquids including tender coconut, fruit juices (tomato or citrus juice should be avoided) etc., to prevent formation of stones again.