Several underlying metabolic abnormalities may be present in patients with recurrent calcium calculus disease (RCCD). The aim of this study was to determine the prevalence of deficiencies of 2 well-known potent inhibitors of crystal formation and growth, citrate and pyrophosphate, in the various metabolic subgroups and as single defects. In 107 patients with RCCD, urinary citrate was significantly decreased in all metabolic subgroups with 49% of patients having hypocitraturia (2.53 ± 1.19 mmol/24 h) versus controls (3.44 ± 0.96 mmol/24 h; p < 0.001). Reduced pyrophosphate: creatinine ratios were present in all the patient subgroups, and 48% of all patients had reduced ratios (1.68 ± 1.68 vs. 3.10 ± 2.66 in controls; p < 0.01). There was no correlation between citrate and pyrophosphate concentration. Isolated hypocitraturia was found in 11.2%, reduced pyrophosphate: creatinine ratios as the single defect in 11.2% and a combination of both in 12.1% of patients. Thus inhibitor defects play an important role in patients with RCCD and frequently occur as isolated biochemical defects.

The presence of mild hyperoxaluria in recurrent calcium oxalate stone formers is controversial. The aim of this study was to identify recurrent stone formers with mild hyperoxaluria and to classify them further by assessing their response to a low oxalate diet. In addition, the prevalence of other risk factors for stone formation in this group of patients was investigated. A total of 207 consecutive patients with recurrent renal calculi were screened and 40 (19%) were found to have mild hyperoxaluria. Of these, 18 (45%) responded to dietary oxalate restriction by normalising their urinary oxalate. The remaining 22 patients were classified as having idiopathic hyperoxaluria and were subdivided into those in whom urinary oxalate excretion was consistently elevated in all specimens measured and those in whom the elevation was intermittent in nature. Dietary oxalate restriction had a partially beneficial effect in lowering oxalate excretion in the patients with persistent hyperoxaluria. No difference in urinary oxalate excretion was found after dietary restriction in the patients with intermittent hyperoxaluria. Other risk factors, including dietary, absorptive and renal hypercalciuria and hypocitraturia, were documented, the prevalence of which (65%) was not significantly different from that (62.5%) found in 40 age- and sex-matched calcium stone formers without hyperoxaluria. The prevalence of hyperuricosuria was significantly greater in patients with hyperoxaluria when compared with stone controls. Further studies are required to elucidate the underlying mechanisms of hyperoxaluria in recurrent stone formers.

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The effect of low density lipoproteins on esterification of cholesterol was studied in lymphocytes from patients with familial hypercholesterolaemia; results were compared with those obtained using cells from normal individuals. Freshly isolated lymphocytes were maintained in lipoprotein-deficient medium for 48 h and the rate of formation of [3H] cholesteryl oleate from [3H] oleate was then determined in the presence or absence of low density lipoproteins. In the absence of low density lipoproteins, incorporation of [3H] oleate was higher in heterozygote and homozygote cells than in normal lymphocytes. Incorporation in the presence of low density lipoproteins was increased relative to that measured in their absence for all of the subjects studied; heterozygotes and homozygotes showed marked changes in some cases but not in others.