BIHYDRATED CALCIUM HYDROPHOSPHATE CALCULI - CLINICAL, AND RADIOLOGICAL FEATURES, LABORATORY FINDINGS, CLINICAL COURSE AND THERAPY

Seventeen cases of urinary calculi analyzed by infrared spectrophotome try were found to be composed entirely or nearly entirely of bihydrate d calcium hydrophosphate. The observations are summarized here. This t ype of stone occurs with a frequency of about 1 % (0.85 % in our exper ience) of all urinary calculi, pre dominantly in men (14 of our 17 cas es). Diagnosis is based on the physical and chemical analysis of the s tone and on infrared spectrophotometry. Most of these stones are pure or nearly pure compounds. The macroscopic aspect of the stones or frag ments of stones can guide diagnosis. These stones are cream coloured s tones with a smooth regular outer surface. Broken fragments show the s ame cream colour, sometimes with strips radiating from the centre of t he fracture surface. Radiologically, these stones are homogeneously ra dio-opaque, often oval-sahped with a regular outline. Blood tests can demonstrate suspected or proven hyperparathyroidism (4 out of 10 cases in our 17 observations) with hypercalcemia, hypophosphatemia and hype rcalciuria. Complementary examinations may be needed to search for a p arathyroid adenoma. With or without hyperparathyroidism, 24-h urinalys is usually shows hypercalciuria up to ro over 500 to 600 mg/24 h. Crys tallization usually occurs in the upper urinary tract, in the bladder or in indwelling catheters. These stones are extremely hard and are di fficult to break in vitro. To be successful, lithotripsy requires prol onged treatment : up to 3000 to 6000 shockwaves at 22-23 kv with the D ornier apparatus. Despite the notion of hypercalciuria, the pathogenes is of bihydrated calcium hydrophosphate calculi remains to be elucidat ed.