Recurrent Calcium Stone Formers Research Articles

Inhibitors of urinary stone formation in 40 recurrent stone formers.

The excretion of four inhibitors of urinary stone formation (zinc, magnesium, citrates and glycosaminoglycans (GAG) was studied in 20 normal controls and 40 recurrent calcium stone formers who were placed on a fixed diet restricted in calcium, oxalates and purines. We were unable to show any abnormality in the excretion of Zn, Mg or GAG. In 11 patients, a low level of urinary citrate was a significant feature that was associated in most cases with a urinary pH value above 6. Citrate concentration (per litre) and output (per 24 h) were found to be lower than in the controls in 19 and 33% respectively of the determinations. The overall ratio of average urinary citrate concentration in patients and controls was 0.56, a figure in agreement with previous data.

A possible etiological role for ascorbate in calculi formation.

Studies of recurrent stone formers indicated that they have significantly increased urinary oxalate and decreased ascorbate excretions. Results of oral and intravenous administration of ascorbate indicate an enhanced production of oxalate from ascorbate in recurrent calcium stone formers as compared with normal persons and that most of this oxalate is generated in the gut.

Correlation between causes and composition of urinary stones.

On the basis of routine clinical and laboratory investigations, one or more probable or possible causes of stone formation were established in 27% of upper urinary tract and 98% of bladder stone patients. In the upper urinary tract, causes were usually found for triple phosphate and pure calcium phosphate stones and rarely for pure calcium oxalate stones. Except for cystine stones and largely for triple phosphate stones there was no definite correlation between the composition of stone and causes. Uric acid and urate stones were often not associated with obvious causes, but their demonstration should lead to further investigations. In a small group of recurrent calcium stone formers examined for hypercalciuria, hyperoxaluria, hyperuricosuria, and renal tubular acidosis, positive findings were noted for 65%, but there was no consistent correlation between these findings and the types of stone. Stone analysis is most useful in so far as it identifies or excludes triple phosphate, cystine, and uric acid/urate stones. This may be done by simple chemical analysis. Certain rare components may, however, be overlooked, as will details of stone structure, unless crystallographic methods are employed.

Renal handling of urate in patients with calcium stone disease.

The renal handling of urate was investigated in 28 recurrent calcium stone formers and 12 healthy controls. 12 patients were hyperuricosuric and 16 patients had incomplete proximal or distal acidification defects. Measurements of the glomerular filtration and the tubular reabsorption of filtered urate were made through the pyrazinamide (PZA)-suppression test of urate secretion. Hyperuricosuria could not be explained by defects in the renal handling of urate. Patients with proximal acidification defects had a higher tubular reabsorption of filtered urate than the other subjects. Tubular reabsorption of filtered urate was inversely correlated, and filtered urate escaping reabsorption positively correlated to the 24-hour excretion of urate. In contrast, the PZA-suppressible fraction of urate excretion, which is the net effect of tubular secretion and post-secretory reabsorption and thought to be the main regulator of urate excretion, was not correlated to the 24-hour excretion of urate. It is concluded that the renal handling of urate is basically normal in calcium stone disease, whereas minor deviations may co-exist with renal tubular acidification dysfunction.

Phosphate treatment of recurrent calcium stone disease.

A group of 38 male recurrent idiopathic calcium stone formers were treated with oral supplements of orthophosphate (1 g phosphorus extra in the diet per day) and followed at intervals up to 4 years. The urinary excretion of calcium decreased (p less than 0.001) and that of inorganic phosphate increased (p less than 0.001) during treatment. These changes resulted in a small decrease in the supersaturation of urine with respect to calcium oxalate, sufficient to reduce the percentage of urines which exceeded the upper limit of solubility of that salt, and a small increase in the supersaturation of urine with respect to calcium phosphate. The stone episode rate on treatment fell in 35 of the 38 patients from a mean pretreatment value of 0.66 episodes/year to 0.22 episodes/year. The 3 initially most prolific stone formers increased their rate of stone formation during treatment. Plasma biochemistry showed no evidence of parathyroid stimulation.

The mechanisms of hypercalciuria are unnecessary for treatment of recurrent renal calcium stone formers.

The mechanisms of hypercalciuria are unnecessary for treatment of recurrent renal calcium stone formers.

Some characteristics of recurrent calcium stone formers in Puerto Rico

We have studied 83 patients with recurrent calcium stone formation in an attempt to determine an approximate incidence of metabolic disturbances associated with stone disease. Male veterans (n=42), male non-veterans (n=13), and women (n=28) composed the group. We divided the groups in such fashion because they represented generally two distinct socioeconomic groups. Primary hyperparathyroidism was present in 19 per cent of the subjects; a marked predominance of women ( 15 16 ) was noted. Hypercalciuria of renal or intestinal origin was present in 23 per cent of the group. Of interest was a group of male veterans ( 17 83 ) in whom normocalciuria, normocalcemia, and normal serum phosphate were associated with high values of immunoreactive parathyroid hormone. These subjects had low urine phosphate. This set of findings indicates that these patients may be a new subgroup of stone forming patients. Metabolic abnormalities could not be detected in 38 per cent of the patients. Classification of stone subjects is essential for rational management.