Renal or Urethral Stone
Most calculi are of unknown origin but four aetiologies need to be remembered.
Hypercalcaemia : Check serum calcium, vitamin D uric acid excess in urine cystinuria mixed “triple-phosphate” stones, often due to chronic, occult urine infections with gram-negative bacteria such as Proteus.
The reason for analysing calculi is to detect pure uric acid (5-10% of all stones) or cystine. In the case of uric acid stones, the causes of increased uric acid excretion need to be looked for.
Allopurinol is effective in preventing further stone formation. The remaining 90% of stones are composed of calcium oxalate or phosphate and in half of these there is hypercalciuria due to increased intestinal absorption of calcium. A 24-hr urine should be analysed for calcium, phosphate, urate and oxadate.
Referred test
21 days
Cannot be added on to an existing request
Dept of Clinical Chemistry,Birmingham City Hospital
Specimen Labelling Procedure
8210
