Factors that predict relapse of calcium nephrolithiasis during treatment: a prospective study

Urinary volume, water and recurrences in idiopathic calcium nephrolithiasis: a 5-year randomized prospective study

PURPOSE

We define the role of urine volume as a stone risk factor in idiopathic calcium stone disease and test the actual preventive effectiveness of a high water intake.

MATERIALS AND METHODS

We studied 101 controls and 199 patients from the first idiopathic calcium stone episode. After a baseline study period the stone formers were divided by randomization into 2 groups (1 and 2) and they were followed prospectively for 5 years. Followup in group 1 only involved a high intake of water without any dietetic change, while followup in group 2 did not involve any treatment. Each year clinical, laboratory and radiological evaluation was obtained to determine urinary stone risk profile (including relative supersaturations of calcium oxalate, brushite and uric acid by Equil 2), recurrence rate and mean time to relapse.

RESULTS

The original urine volume was lower in male and female stone formers compared to controls (men with calcium oxalate stones 1,057 +/- 238 ml./24 hours versus normal men 1,401 +/- 562 ml./24 hours, p < 0.0001 and women calcium oxalate stones 990 +/- 230 ml./24 hours versus normal women 1,239 +/- 440 ml./24 hours, p < 0.001). During followup recurrences were noted within 5 years in 12 of 99 group 1 patients and in 27 of 100 group 2 patients (p = 0.008). The average interval for recurrences was 38.7 +/- 13.2 months in group 1 and 25.1 +/- 16.4 months in group 2 (p = 0.016). The relative supersaturations for calcium oxalate, brushite and uric acid were much greater in baseline urine of the stone patients in both groups compared to controls. During followup, baseline values decreased sharply only in group 1. Finally the baseline urine in patients with recurrences was characterized by a higher calcium excretion compared to urine of the patients without recurrences in both groups.

CONCLUSIONS

We conclude that urine volume is a real stone risk factor in nephrolithiasis and that a large intake of water is the initial therapy for prevention of stone recurrences. In cases of hypercalciuria it is suitable to prescribe adjuvant specific diets or drug therapy.

An increasing number of calcium oxalate stone events worsens treatment outcome

Current practice recommends metabolic evaluation of patients who have formed multiple renal stones, but not those with one stone or temporally remote stones. This presumes that recentness and recurrence imply greater risk of new future stones. We hypothesize that number of stones reflects how long patients are permitted to form stones untreated, and that forming more stones, itself, raises risk of future stones despite treatment. Our report is a retrospective analysis of 371 male patients selected from a comprehensive clinical and laboratory data base containing 2,527 patients with nephrolithiasis. Before treatment, number of stone events rises with time of observation, and rate of stone event occurrence is constant or falls. During treatment, relapse is correlated with number of pretreatment stones. Life table analysis showed increasing relapse for patients grouped into those with one, two, and three or more stones. Even though number of stones seems controlled by the interval of observation before treatment, more stones predict higher relapse during treatment. Perhaps by leaving nuclei of crystals as residues, stones appear to promote new stones, and the practice of waiting while patients declare themselves multiple stone formers may not always be the best.

Urinary calcium oxalate saturation in 'stone formers' and normal subjects: an application of the EQUIL2 program

OBJECTIVE

To produce an index of lithogenic risk which identifies patients at risk of stone recurrence and facilitates the monitoring of prophylactic treatments.

PATIENTS AND METHODS

The EQUIL2 program provides an evaluation of the state of urinary saturation, particularly of calcium oxalate, based on the pH and total concentrations (mmol/l) of sodium, potassium, calcium, magnesium, uric acid, chloride, ammonium, citrate, phosphate, sulphate, oxalate, pyrophosphate and carbon dioxide. The morning urinary calcium oxalate saturation coefficient was thus calculated for 30 stone-formers (Group 1) and 30 normal control subjects (Group 2).

RESULTS

Urine from the majority of individuals was saturated, with no significant difference between the two groups. There appeared to be a correlation between the state of saturation and the urinary calcium oxalate molar product in both stone-formers (r = 0.931) and controls (r = 0.914).

CONCLUSION

In future studies on urinary calcium oxalate saturation, it should be possible to supplement the sophisticated coefficient determined by the EQUIL2 program with the molar product, except in cases where monitoring therapies have little or no effect on urinary oxalate or urinary calcium levels.

Calcium phosphate: an important crystal phase in patients with recurrent calcium stone formation?

Stone and urine composition were analysed in 75 men and 40 women with recurrent calcium oxalate stone disease (group R) and in 48 men and 19 women who had formed only one calcium-oxalate-containing stone (group S). Patients who had developed stones with a large fraction of calcium phosphate were significantly more frequent in group R than in group S. There was furthermore a higher excretion of calcium and higher calcium oxalate supersaturation levels in patients with stones containing more than 25% calcium phosphate. It was concluded from these observations that the calcium phosphate content of renal stones might be a useful factor in predicting the future course of the disease.

Prophylaxis in idiopathic calcium urolithiasis

The most important measure in the prophylaxis of idiopathic calcium urolithiasis is dietary advice. Patients should be kept to a high-fluid intake, increasing their diuresis by at least 0.51. The mineral content of drinking water seems to be of minor importance, but the liquid should be low in carbohydrates and oxalate. The intake of animal proteins should be reduced to no more than five meals with meat, fish or poultry per week. Excesses of oxalate-rich food must be avoided. The daily intake of calcium in dairy products should be in the range of 800-1200 mg. Sodium and refined carbohydrates should be moderately restricted. Medical treatment is indicated only in cases of recurrence under the appropriate diet. Selective treatment according to urinary chemical composition is favoured; alkali citrate, thiazides, allopurinol, and pyridoxine are of major interest.

Urinary volume in children with urolithiasis

Urinary volume in 24-hour urine collections was examined in 50 children with hypercalciuria and urolithiasis or hematuria, 12 with idiopathic calcium oxalate urolithiasis and 36 healthy children. Urinary volume was 22.2 +/- 2.0 ml. per kg. per day in healthy children and 25.4 +/- 2.0 ml. per kg. per day in children with hypercalciuria, and it was similar in children with absorptive and renal hypercalciuria, and significantly lower in children with idiopathic calcium oxalate urolithiasis (12.2 +/- 1.4 ml. per kg. per day, p less than 0.001 from controls and children with hypercalciuria). Volume was not statistically different in hypercalciuric children with and without urolithiasis. Urinary sodium excretion in children with idiopathic calculi was not statistically different from controls. Urine osmolality was similar among the groups. Urinary volume represents a risk factor in children with idiopathic calcium oxalate urolithiasis, and increased fluid intake should be emphasized in such patients.

Does hyperuricosuria play a role in calcium oxalate lithiasis?

This review evaluates the epidemiologic, clinical and experimental evidence for an etiological link between urinary uric acid and the propensity to develop calcium oxalate calculi. While epidemiologic and laboratory studies provide only equivocal support for a synergistic relationship, several clinical trials with allopurinol have demonstrated a reduction in calculus recurrence. These beneficial effects are observed only when allopurinol is given to subjects with calcium oxalate calculi who have isolated hyperuricosuria. The specificity of this effect suggests that there is an important interaction between uric acid and calcium oxalate but the mechanism(s) remain to be elucidated.

Pattern of urolithiasis in a general hospital. A prospective study

Judging from the abundance of papers published in the medical journals there appears to be a global increase in the incidence of urolithiasis. Urinary excretion of various stone-forming salts in a 24-hour urine specimen is the mainstay of the metabolic workup done in stone-formers. According to the findings patients have been classified into neat categories depending on whether they were hypercalciuric, hyperuricosuric, etc. As a group their excretion of calcium, oxalate, and urate was not different from the controls. However, they excreted significantly more phosphate and had lower 24-hour urine volumes than the controls.

Specific gravity test strips used in monitoring urine concentrations of urolithiasis patients

Current therapy for urolithiasis patients includes instructions to increase water intake and 24-hour urine output. Previous studies have measured changes in the 24-hour urine volume to evaluate the efficacy of fluid therapy in each patient. We used paper test strips to monitor urine pH and specific gravity in 22 of our stone clinic patients: 10 were instructed to increase water intake just before the study (group 1) and 12 were not so instructed (group 2). Mean specific gravities of 1.0222 (1.0238 corrected for pH) for group 1 and 1.0197 (1.0220 corrected for pH) for group 2 did not differ significantly. Urine specific gravities also were compared for 3 intervals: 1 to 9 a.m., 9 a.m. to 5 p.m. and 5 p.m. to 1 a.m. Of the 22 patients 10 (3 from group 1 and 7 from group 2) had significant diurnal variations in the urine specific gravities, corrected and uncorrected, among these 3 periods. In addition, both groups had a significantly higher mean specific gravity from 1 to 9 a.m. (1.0234 uncorrected and 1.0248 corrected) than from 9 a.m. to 5 p.m. (1.0194 uncorrected and 1.0218 corrected). The 5 p.m. to 1 a.m. (mean of 1.0220 uncorrected and 1.0239 corrected) specific gravity did not differ significantly in either group. If 1.015 is the highest acceptable specific gravity of urine in stone patients, the findings suggest inadequate dilution of urine in these patients, whether or not they were instructed to increase water intake. Also, the significant diurnal variation in urine specific gravity would allow a nighttime triggering event at these hours of higher urine concentration.

Clinical results of allopurinol treatment in prevention of calcium oxalate stone formation

Allopurinol in a daily dose of 300 mg. was administered to 99 patients with calcium oxalate stone disease. Treatment was started irrespective of urine composition and was continued for up to 8 years. Only 43 per cent of the patients treated for 5 or more years remained free of further stone formation, a result not better than observations in untreated stone patients. When patients were subgrouped with respect to recurrent or nonrecurrent stone formation during treatment, the former group, besides being followed for longer intervals than the latter group, had a urine composition suggesting a higher crystallization risk. We concluded that with the possible exception of hyperuricosuria or hyperuricemia the indication for allopurinol treatment of recurrent calcium oxalate stone disease is weak. The results also demonstrate clearly the problems combined with evaluation of prophylactic medical therapy in patients with calcium stones. The necessity of long-term followup and analysis of the biochemical risk situation is emphasized.

A urinary calcium-citrate index for the evaluation of nephrolithiasis

We have performed a multivariate analysis of urine abnormalities in patients with calcium oxalate nephrolithiasis, in which effects of gender were also considered. The characteristic of patients that most clearly sets them apart from normal people is a high level of urine calcium for any given level of urine citrate. Other urine measurements cannot improve upon the separation between patients and normals provided by urine calcium and citrate, and their abnormal relationship to each other. Normal women have higher urine citrate and lower urine calcium than normal men or patients of either sex; normal men differ from stone forming men only moderately. Direct measurements of supersaturation are not helpful in distinguishing between patients and normals, once calcium and citrate have been considered. From our analysis, we have derived a new index for evaluating the significance of urine calcium and citrate levels that seems to offer a better basis for clinical diagnosis than criteria presently in use.

Investigation and treatment of renal calculi

We have investigated and treated 176 patients who were suffering from renal calculi. The stones contained calcium in 87% of patients, predominantly urate in 11%, and rarely contained magnesium ammonium phosphate or cystine. Of the patients with calcium stones, hypercalciuria was present in 75% and was identified in 57% by the measurement of the 24-hour urinary calcium excretion, and in a further 18% by a standardization calcium "fast-and-load" test. Nine patients were found to have primary hyperparathyroidism and were treated surgically. A further 21% were suspected to have normocalcaemic hyperparathyroidism, and metabolic studies are being developed to clarify this. The treatment of hypercalciuria included a low-calcium diet, and various combinations of a thiazide diuretic, phosphate supplements and sodium cellulose phosphate. Hypercalciuria was controlled in all compliant patients, and only two developed further stones. Hyperuricosuria was rarely the sole metabolic abnormality in patients with calcium stones, though this might reflect the referral pattern of the Unit. Uric acid stones were frequently, but not invariably, associated with hyperuricosuria and acid urine, and even large uric acid calculi dissolved with a combined therapy of high fluid intake, allopurinol and an alkalinizing agent. Surgical treatment was rarely required in these patients. A stone in the renal pelvis of one patient was removed percutaneously and did not require ultrasonic fragmentation. Modern methods of investigation and treatment have greatly improved the outlook for patients with recurrent renal calculi.

Allopurinol treatment of renal calcium stone disease

Thirty-one calcium stone patients were treated with 300 mg allopurinol daily during a mean follow-up period of 2 years. They were also given advice on diet and fluid intake. The effects on the recurrence rate of stones were compared with the effects on the recurrence rate in 43 calcium stone patients who were given similar advice on diet and fluid intake but were not treated with allopurinol. In both groups there was a reduction in the recurrence rate but no difference between patients treated with allopurinol and the control group. Some patients with only hyperuricosuria prior to treatment seemed to benefit from allopurinol treatment, whereas those with hypercalciuria continued to form stones with the same frequency. Allopurinol treatment in calcium stone disease appears less effective than treatment with thiazides, magnesium hydroxide or orthophosphate.

Five years of experience with selective therapy in recurrent calcium nephrolithiasis

We evaluated the efficacy of selective treatment in 126 patients with recurrent calcium urolithiasis who were chosen on the basis of ability to correct underlying physiochemical disturbances. Patients with hyperparathyroidism underwent an operation. Patients with renal hypercalciuria were treated with thiazide and those with absorptive hypercalciuria were given a low calcium, low oxalate diet with or without thiazide. The only treatment for normocalciuric patients was high fluid intake, which was suggested also to the other groups. A significant individual mean reduction in stone formation was observed in all groups after 5 years of treatment. However, only 48 per cent of the normocalciuric patients were in remission after 5 years of high fluid intake therapy and 45 per cent of those with absorptive hypercalciuria were free of recurrence with diet only. Thiazide treatment seemed to be effective despite the type of hypercalciuria. The effect of the treatment on stone formation was mediated through reduction of risk factors in the urine. Conversely, a high level of risk factors commonly predicted stone recurrence.

Clinical experience with long-term bendroflumethiazide treatment in calcium oxalate stone formers

Bendroflumethiazide was administered to 85 patients (62 men, 23 women) with recurrent calcium oxalate stone disease. Side effects leading to interrupted treatment were observed in 26 (31%) of the patients. Fifty-nine (40 men, 19 women) remained on treatment for a mean (+/- SD) period of 3.7 +/- 1.0 years, and 21 reported late side effects. Twenty patients were given 2.5 mg bendroflumethiazide daily (Group A), 27 were given 2.5 mg twice daily (Group B), and 12 were given 5 mg once daily (Group C). Eight patients (14%) formed new stones and another two demonstrated stone growth during treatment. A beneficial effect on stone formation was observed in Groups B and C but not in Group A. Patients who failed to respond to treatment had a pre-treatment stone formation rate of 0.74 stones per year compared with 0.22 in those who did not form new stones. Those with recurrence during treatment had a lower citrate excretion than other patients. No effect on urinary citrate was recorded during treatment, and long-term treatment with bendroflumethiazide did not affect oxalate excretion.

When should the stone patient be evaluated? Limited evaluation of single stone formers

The purpose of a metabolic stone evaluation is to provide information that will influence treatment. For stone formers who have not tried a conservative diet-fluid program, only a limited metabolic evaluation is indicated. An extensive metabolic evaluation is reserved for stone formers who actively grow calculi despite conservative treatment.

Medical evaluation and management of calcium nephrolithiasis

Stone disease is a common medical problem, frequently recurs, and is associated with significant morbidity. Because appropriate medical therapy significantly decreases stone recurrence, this disorder must not be ignored by nonurologists. Even the single stone-former should be offered a metabolic evaluation.

The stone clinic effect in patients with idiopathic calcium urolithiasis

The "stone clinic effect" refers to the effect of encouraging a high intake of fluid and avoiding dietary excesses on stone formation and growth in patients with urolithiasis. To determine the extent of this effect we reviewed the clinical courses of 108 patients with idiopathic calcium urolithiasis and indeterminant metabolic activity. There was no evidence of stone growth or new stone formation (metabolic inactivity) after a mean followup of 62.6 months in 63 of the 108 patients (58.3 per cent), including 12 of 17 (70.6 per cent) with hypercalciuria and 7 of 15 (46.7 per cent) with hyperuricosuria. Comparison of initial and followup 24-hour urine volumes demonstrated a significant increase in patients who were metabolically inactive at followup (p less than 0.0005), while no increase was detected in patients who were metabolically active at followup. We recommend that specific drug therapy should not be given to patients with idiopathic calcium urolithiasis until the stone clinic effect has been evaluated.

Pathogenesis and clinical course of mixed calcium oxalate and uric acid nephrolithiasis

By direct measurement, urine from patients who form calcium oxalate stones was supersaturated abnormally with respect to calcium oxalate monohydrate but not supersaturated with respect to undissociated uric acid. Urine from patients who form uric acid stones was supersaturated excessively with undissociated uric acid but not calcium oxalate. Patients who form both calcium oxalate and uric acid stones, however, produce urine that is supersaturated with respect to both solid phases. Low urine pH was the primary factor that increased supersaturation with respect to undissociated uric acid. The formation of both calcium oxalate and uric acid stones appears to be explained by a dual abnormality of urine supersaturation.