The value of studying crystalluria in the management of the calcium-rich stone-formers

Abstract

The treatment of stone formation is made very difficult by certain unsolved problems. Firstly, although the recurrence rate of renal stones is high (Williams, 1963) it is extremely difficult to know whether a particular patient is in danger of stone formation at the time of investigation. Secondly it may be very difficult clearly to find out it a treatment given is effective in preventing stone formation. Thus, in considering the treatment of calcium oxalate (plus or minus phosphate) stone formation how are we to judge effectiveness of treatment with thiazides or cellulose phosphate? Although urinary calcium can be controlled by the used of these drugs (Rose and Harrison, 1974) and although such reduction in urinary calcium may reduce the incidence of stone formation, there are sometimes surprises with both treatments. Fig. 1–5 show the formation of a new calcium-rich kidney stone in a patient with idiopathic hypercalciuria whose urinary calcium had been well controlled continously for over eight years with Bendrofluazide. Clearly, simple measurement of urinary calcium was not adequate to predict stone recurrence. What is not clear is how this stone recurrence could have been predicted. It is of course possible to measure other ions in the urine and oxalate, citrate, phosphate and magnesium seem to be expecially important. We have been particularly concerned with the measurement of oxalate and have shown that thiazide raises urinary oxalate verly slightly and that cellulose phosphate raises it a lot, (Hallson, Kasidas and Rose, 1976). It has not been possible however, to devise a method of calculating whether or not a urine that is super-saturated with calcium oxalate will actually throw this salt out of solution. A better way to approach the problem might be to look at urine samples to see whether or not they contain crystals, i.e. simply to see whether in fact they have thrown calcium salts out of solution. We have therefore applied the crystal count method of Robertson (1969) to a series of patients with idiopathic hypercalciuria attending an out-patient’s clinic on a random follow-up basis. The results were reported by Hallson and Rose (1976) and are summarised in Table 1.