RENAL AND ABSORPTIVE HYPERCALCIURIA - A METABOLIC DISTURBANCE WITH VARYING AND INTERCHANGING MODES OF EXPRESSION

Background. In previous studies, the oral calcium loading and deprivat ion test has been used to distinguish between children with renal (fas ting) hypercalciuria (RH) and absorptive hypercalciuria (AH). Objectiv e. We evaluated the long-term clinical course of 30 children with idio pathic hypercalciuria and investigated the influence of urinary sodium excretion, as a reflection of its intake, on urinary calcium excretio n. Methods. Thirty normocalcemic, normophosphatemic children (21 boys and 9 girls) with urinary calcium to creatinine ratios greater than 0. 57 mmol/L/mmol/L (>0.21 mg/dL/mg/dL) on three consecutive examinations participated in this study. They were divided according to their resp onses to calcium deprivation and loading into AH (16 patients) and RH (14 patients). Results. When restudied 3 to 7 years later, 6 of the 16 children with AH were normocalciuric and three demonstrated character istics compatible with RH. The remaining seven patients maintained the ir initial AH pattern. Of the 14 children with RH, four were normocalc iuric and four demonstrated AH. The remaining six children maintained their initial RH pattern. A significant positive correlation was obser ved between urine sodium and calcium excretion in children with AH or RH. Children who were normocalciuric at the second study had significa ntly lower values of urine sodium excretion when compared with those i n whom hypercalciuria persisted. Conclusions. We suggest that AH and R H constitute a continuum. The change in characteristics observed durin g the second study suggests that any attempt to divide these patients into two physiologically distinct-subtypes may be artificial. The main factor influencing urinary excretion of calcium in our patients seeme d to be sodium intake.