The definition of the mechanism of hypercalciuria is necessary for the treatment of recurrent stone formers

Impact of the adherence to medical treatment on the main urinary metabolic disorders in patients with kidney stones

Objective

To assess the effect of the adherence to medical treatment on urinary parameters in the 24-h metabolic study of patients with kidney stones.

Methods

A retrospective, longitudinal, descriptive, and observational study was carried out by reviewing the hospital electronic medical record from 2014 to 2018. The adherence to drug treatment was measured 6 months after its initiation, and the numerical values of the metabolic studies were compared. Wilcoxon tests were performed to compare the difference before and after treatment.

Results

Ninety patients were evaluated, with 73.3% of adherence. The 180-day overall adherence rate was 61.2% in patients treated with a single drug and 85.4% in patients treated with multiple drugs. There is a statistically significant increase in citrate levels in patients with good adherence in comparison with non-adherent patients (p=0.031 vs. p=0.528).

Conclusions

Medical treatment and dietary measures in patients with kidney stones have an initial impact at 6 months on the values of the main urinary metabolic alterations that predispose to calculi formation; the most significant is seen in those patients with adherence to medical treatment for hypocitraturia.

Effectiveness of thiazides on serum and urinary calcium levels and bone mineral density in patients with osteoporosis: a systematic review and meta-analysis

Objective

Osteoporosis is the most common metabolic bone disease and a major public health problem worldwide. Thiazides are widely used as antihypertensive agents with good tolerability and efficacy. Furthermore, thiazides have long been regarded as candidates for the prevention of postmenopausal bone loss. However, there is insufficient evidence that thiazides have a sustained beneficial effect on preserving bone mass and preventing osteoporosis to date.

Materials and methods

We searched the PubMed, the Cochrane Library, and Embase in June 2018 for randomized controlled trials on the use of thiazides to treat osteoporosis. Continuous outcomes are presented as the standardized mean difference (SMD) and 95% CI. Furthermore, P-values <0.05 were considered significant.

Results

Five trials with 756 patients were randomly assigned in the five trials included in this meta-analysis. Serum calcium level was higher in the thiazide group than in the control group (SMD 0.33, 95% CI [0.16, 0.50]), and urinary calcium level was significantly lower in the thiazide group (SMD −0.35, 95% CI [−0.52, −0.17]). There was no significant difference in bone mineral density between the two groups (SMD 0.19, 95% CI [−0.16, 0.54]).

Conclusion

Thiazides might play a role in preserving bone mass and be effective in the prevention and treatment of osteoporosis. Future high-quality trials are needed to confirm our findings in the future.

Role of scanning electron microscopy in identifying drugs used in medical practice

Several plant preparations are administered for treatment of stone disease without scientific basis. This paper presents the results of in vitro and animal experimental studies using scanning electron microscopy (SEM) in the identification of the therapeutic properties of trial drugs in medicine. In the first set of the study, urinary crystals namely calcium oxalate monohydrate and calcium oxalate dehydrate were grown in six sets of Hane's tubes in silica gel medium. Trial drugs namely scoparia dulcis Lynn, musa sapiens and dolicos biflorus were incorporated in the gel medium to identify the dopant effect of the trial drugs on the size and extent of crystal column growth. The changes in morphology of crystals were studied using SEM. In the second set, six male Wistar rats each were calculogenised by administering sodium oxalate and ethylene glycol and diabetised using streptozotocin. The SEM changes of calculogenisation were studied. The rats were administered trial drugs before calculogenisation or after. The kidneys of the rats studied under the scanning electron microscope showed changes in tissue morphology and crystal deposition produced by calculogenisation and alterations produced by addition of trial drugs. The trial drugs produced changes in the pattern of crystal growth and in the crystal morphology of both calcium oxalate monohydrate and calcium oxalate dihydrate grown in vitro. Elemental distribution analysis showed that the crystal purity was not altered by the trial drugs. Scoparia dulcis Lynn was found to be the most effective anticalculogenic agent. Musa sapiens and dolicos biflorus were found to have no significant effect in inhibiting crystal growth. The kidneys of rats on calculogenisation showed different grades of crystals in the glomerulus and interstitial tissues, extrusion of the crystals into the tubular lumen, collodisation and tissue inflammatory cell infiltration. Scoparia dulcis Lynn exhibited maximum protector effect against the changes of calculogenisation. Musa sapiens and dolicos biflorus had only minimal effect in preventing crystal deposition, inflammatory cell infiltration and other changes of calculogenisation. SEM was found to be effective in assessing the effect of drugs on crystal growth morphology and tissue histology.

Genetic basis of renal cellular dysfunction and the formation of kidney stones

Nephrolithiasis is a result of formation and retention of crystals within the kidneys. The driving force behind crystal formation is urinary supersaturation with respect to the stone-forming salts, which means that crystals form when the concentrations of participating ions are higher than the thermodynamic solubility for that salt. Levels of supersaturation are kept low and under control by proper functioning of a variety of cells including those that line the renal tubules. It is our hypothesis that crystal deposition, i.e., formation and retention in the kidneys, is a result of impaired cellular function, which may be intrinsic and inherent or triggered by external stimuli and challenges. Cellular impairment or dysfunction affects the supersaturation, by influencing the excretion of participating ions such as calcium, oxalate and citrate and causing hypercalciuria, hyperoxaluria or hypocitraturia. The production and excretion of macromolecular promoters and inhibitors of crystallization is also dependent upon proper functioning of the renal epithelial cells. Insufficient or ineffective crystallization modulators such as osteopontin, Tamm-Horsfall protein, bikunin, etc. are most likely produced by the impaired cells.

Genetic and dietary factors in urinary citrate excretion

BACKGROUND AND PURPOSE

Hypocitraturia, an important risk factor for calcium oxalate nephrolithiasis, is the result of numerous factors. We studied citrate excretion by patients with and without stones consuming normal and controlled formula diets.

SUBJECTS AND METHODS

Subjects with and without a history of calcium oxalate stones (N = 101 per group) provided two or three 24-hour urine specimens during consumption of self-selected diets. Data also were collected on subsets of subjects consuming formula (Ensure) diets. Citrate was determined using the citrate lyase method of Petrarulo and associates, and values for multiple specimens were averaged. The data were adjusted for creatinine excretion and examined on a per-day basis.

RESULTS

The mean citrate excretion of the non-stone formers was slightly but not significantly higher than that of the stone formers (442 +/- 217 versus 378 +/- 153 mg/g of creatinine). All statistical analyses revealed highly significant differences between, but not within, individuals, a result compatible with a genetic influence. In the normal population, 5% of subjects had a citrate excretion <200 mg/g of creatinine, whereas this result was seen in 34% of the stone-forming subjects. When the subjects consumed a formula diet, women in both groups had much higher citrate excretion than when on a self-selected diet, but little difference was seen in the men. The patterns of citrate recovery suggest low, intermediate, and high excretors. In the normal population, 15% of subjects excreted <340 mg/g of creatinine, whereas this was true of 43% of the stone-forming subjects. Analysis of six families suggested three excretor phenotypes, with a codominant pattern of inheritance.

CONCLUSION

These findings imply a genetic influence on citrate excretion, as has already been demonstrated for calcium excretion. Further studies of genetic influences on calcium oxalate stone formation are warranted.

Rapid Communication: relative effect of urinary calcium and oxalate on saturation of calcium oxalate

BACKGROUND

The study compared the effect of urinary calcium with that of oxalate on urinary saturation [relative saturation ratio (RSR)] of calcium oxalate.

METHODS

A retrospective data analysis was conducted on urinary stone risk analysis from 667 patients with predominantly calcium oxalate stones. Urinary RSR of calcium oxalate was individually calculated using Equil 2. A "theoretical" curve of the relationship between urinary RSR of calcium oxalate and concentration of calcium or oxalate was obtained at two stability constants for calcium oxalate complex, while varying calcium or oxalate and using group mean values for urinary constituents.

RESULTS

At the stability constant of 7.07 x 10(3), the increase in RSR of calcium oxalate was less marked with calcium than with oxalate. However, at the stability constant of 2.746 x 10(3) from the Equil 2 that is considered the "gold standard," calcium and oxalate were equally effective in increasing RSR of calcium oxalate. The above theoretical curves (relating RSR with calcium or oxalate) were closely approximated by the actual curves constructed with data from individual urine samples. Urinary saturation of calcium oxalate was equally dependent on urinary concentrations of calcium and oxalate (r= 0.75 unadjusted and 0.57 adjusted for variables, and P < 0.0001 for calcium; r= 0.73 unadjusted and 0.60 adjusted, P <0.0001 for oxalate).

CONCLUSION

Among calcium oxalate stone-formers, urinary calcium is equally effective as urinary oxalate in increasing RSR of calcium oxalate.

STONE FORMING RISK OF CALCIUM CITRATE SUPPLEMENTATION IN HEALTHY POSTMENOPAUSAL WOMEN

PURPOSE

We evaluated the effect of calcium citrate supplementation alone or in combination with potassium citrate on the stone forming propensity in healthy postmenopausal women.

MATERIALS AND METHODS

A total of 18 postmenopausal women without stones underwent a randomized trial of 4 phases comprised of 2 weeks of treatment with placebo, calcium citrate (400 mg calcium twice daily), potassium citrate (20 mEq twice daily), and calcium citrate and potassium citrate (at same doses). During the last 2 days of each phase urine was collected in 24-hour pools for complete stone risk analysis.

RESULTS

Compared to placebo, calcium citrate increased urinary calcium and citrate but decreased urinary oxalate and phosphate. Urinary saturation of calcium oxalate, brushite and undissociated uric acid did not change. Potassium citrate decreased urinary calcium, and increased urinary citrate and pH. It decreased urinary saturation of calcium oxalate and undissociated uric acid, and did not change the saturation of brushite. When calcium citrate was combined with potassium citrate, urinary calcium remained high, urinary citrate increased even further and urinary oxalate remained reduced from the calcium citrate alone, thereby marginally decreasing the urinary saturation of calcium oxalate. Urinary pH increased, decreasing urinary undissociated uric acid. The increase in pH increased the saturation of brushite despite the decrease in urinary phosphorus.

CONCLUSIONS

Calcium citrate supplementation does not increase the risk of stone formation in healthy postmenopausal women. The co-administered potassium citrate may provide additional protection against formation of uric acid and calcium oxalate stones.

Pathogenesis of hypercalciuric nephrolithiasis

The major contribution of hypercalciuria in raising urinary state of saturation with respect to calcium salts and subsequent risk of nephrolithiasis is appreciated. Derangements in the physiological mechanisms that regulate calcium homeostasis and contribute to hypercalciuria have also been identified. New avenues of research are beginning to explore the specific defects that may contribute to hypercalciuria. From such studies, an understanding of the role of certain dietary excesses as contributors to the development of hypercalciuria and, in some cases, attendant bone loss, is beginning. The contribution of genetics to hypercalciuria has provided a powerful means of identifying genes that contribute to the hypercalciuric phenotype in a number of hypercalciuric conditions. Such studies have disclosed that hypercalciuria is probably polygenic in nature and will require a concerted effort to better understand the defects while attempting to develop gene-specific countermeasures.

Medical therapy, calcium oxalate urolithiasis

The development of diagnostic protocols that identify specific risk factors for calcium oxalate nephrolithiasis has led to the formulation of directed medical regimens that are aimed at correcting the underlying metabolic disturbances. Initiation of these treatment programs has reduced markedly the rate of stone formation in the majority of patients who form stones. This article discusses the rationale that underlies the choice of medical therapy for the various pathophysiologic causes of calcium oxalate nephrolithiasis and the appropriate use of available medications.

Alterations in renal stone risk factors after space flight

Exposure to the microgravity environment of space produces a number of physiological changes of metabolic and environmental origin that could increase the potential for renal stone formation. Metabolic, environmental and physicochemical factors that influence renal stone risk potential were examined in 24-hour urine samples from astronauts 10 days before launch and on landing day to provide an immediate postflight assessment of these factors. In addition, comparisons were made between male and female crewmembers, and between crewmembers on missions of less than 6 days and those on 6 to 10-day missions. Results suggest that immediately after space flight the risk of calcium oxalate and uric acid stone formation is increased as a result of metabolic (hypercalciuria, hypocitraturia, pH) and environmental (lower urine volume) derangements, some of which could reflect residual effects of having been exposed to microgravity.

Diet as culprit or therapy. Stone disease, chronic renal failure, and nephrotic syndrome

A number of renal disorders are amenable to dietary manipulation. This article reviews nutritional strategies for the management of renal stone disease, chronic renal failure, and nephrotic syndrome. The first portion discusses dietary factors that promote urolithiasis and dietary recommendations utilized in the medical management of stone disease. The second segment discusses the pathophysiology of the progression of renal disease and nutritional interventions to delay progression. Finally, the third portion examines losses of protein, vitamins, and minerals in the nephrotic syndrome and makes recommendations for replacement.

Inhibitory effect of potassium citrate on rat renal tumors induced by N-ethyl-N-hydroxyethylnitrosamine followed by potassium dibasic phosphate

Potassium dibasic phosphate (PDP) was administered at a concentration of 10% by weight in basal diet to unilaterally nephrectomized Wistar rats previously given 1000 ppm N-ethyl-N-hydroxyethyl-nitrosamine (EHEN) in the diet for 2 weeks. To study the effect of alkalinization on renal mineralization, some animals concomitantly received 5% potassium citrate (PC). Feeding PDP alone promoted adenomatous hyperplasias, which were regarded as preneoplastic lesions, as well as renal cell tumors in EHEN-initiated rats, whereas the addition of PC to PDP diets reduced the promoting effect. Histopathology, serum biochemistry and urinalysis indicated retardation of renal calcium crystallization by PC. Two other phosphate salts, sodium phosphate (SP) and calcium phosphate (CP), were also administered. SP showed a slight promoting effect on adenomatous hyperplasias and a 2-fold increase in the yield of renal cell tumors, while CP induced a clear reduction of both lesions, over EHEN alone. The promoting effects of both PDP and SP and the inhibitory effect of PC were somewhat correlated to 5-bromo-2'-deoxyuridine labeling indices, the degree of nephropathy, and mineralization in the kidney. Immunohistochemically, the nephropathy induced by phosphate salts was not linked to alpha 2u-globulin. A pathogenesis for renal carcinogenesis is suggested in which nephropathy associated with mineralization enhances the development of renal cell tumors.

Magnesium oxide administration and prevention of calcium oxalate nephrolithiasis

We studied the effect of oral administration of magnesium oxide (MgO) on calcium oxalate (CaOx) nephrolithiasis in rats. Nephrolithiasis was induced by administration of 1.0% ethylene glycol (EG) in drinking water. Magnesium oxide was given mixed with food at 500 mg./100 g. rat chow. Dispensation of MgO resulted in a significant increase of urinary pH and a modest increase in urinary excretion of citrate. Urinary excretion of oxalate started to decline by day 14 and was significantly reduced on days 21 and 28. All rats receiving EG displayed crystalluria. From the group receiving EG only, 3 of 4 rats sacrificed on day 15 and 2 of 4 rats sacrificed on day 29 had CaOx crystal deposits in their kidneys. None of the 8 rats who received both EG and MgO had CaOx nephrolithiasis. Thus our findings indicate that dispensation of magnesium as MgO can be beneficial against calcium oxalate nephrolithiasis.

Citrate and renal calculi: new insights and future directions

Citrate is pathogenetically important in stone formation, because it retards the crystallization of stone-forming calcium salts and because its level in urine is low in many patients with nephrolithiasis. Potassium citrate is useful therapeutically, because it can often restore normal urinary citrate. Hypocitraturia often results from dietary aberrations, including sodium excess, and exaggerated intake of animal proteins. Hypocitraturia is frequently accompanied by a low net gastrointestinal absorption of alkali. New drugs are under development as improvements or refinements of currently available potassium citrate. They are potassium citrate 10-mEq-tablet preparation, effervescent calcium citrate, and potassium-magnesium citrate.

Bioavailability of potassium and magnesium, and citraturic response from potassium-magnesium citrate

The bioavailability of potassium and magnesium, and the citraturic response were determined for the new compound, potassium-magnesium citrate, in 14 normal volunteers. Results were compared to those of potassium citrate and magnesium citrate. Each subject participated in 4 phases of study: potassium-magnesium citrate, potassium citrate, magnesium citrate and potassium chloride. After stabilization on a metabolic diet, each subject ingested a single load of a test medication followed by timed urine collections for the next 24 hours. Test loads included potassium-magnesium citrate (49 mEq. potassium, 24.5 mEq. magnesium and 73.5 mEq. citrate), potassium citrate (50 mEq.), potassium chloride (50 mEq.) and magnesium citrate (25 mEq.) Urinary potassium, magnesium and citrate were measured for each collection period. Potassium-magnesium citrate provided an equivalent potassium bioavailability as potassium citrate and potassium chloride, and a comparable magnesium bioavailability as magnesium citrate. However, it gave the highest citraturic response, since the cumulative increment in urinary citrate post-load was 129 mg. daily for potassium-magnesium citrate, 105 mg. daily for potassium citrate and 35 mg. daily for magnesium citrate. Thus, potassium-magnesium citrate gave an optimum citraturic response in addition to providing absorbable potassium and magnesium.

Effect of thiazide on rates of bone mineral loss: a longitudinal study

OBJECTIVE

To determine the effect of thiazide diuretic drugs on rates of bone mineral loss.

DESIGN

Longitudinal, observational study with a mean follow up of five years.

SETTING

Hawaii Osteoporosis Center, Honolulu.

SUBJECTS

1017 Japanese-American men born between 1900 and 1920, of whom 378 were treated for hypertension (study group) and 639 did not have hypertension (control group).

INTERVENTION

Thiazide diuretics were taken by 325 men for a mean of 11.9 years; 53 men took antihypertensive drugs other than thiazides.

MAIN OUTCOME MEASURE

Rate of bone loss estimated from serial photon absorptiometric scanning at three skeletal sites (calcaneus, distal radius, and proximal radius).

RESULTS

Rates of bone loss at all three sites were significantly reduced among thiazide users when compared with controls. The reductions in loss rate ranged from 28.8% (p = 0.02) (distal radius) to 49.2% (p = 0.0005) (calcaneus) relative to the controls. At all three sites the men taking other antihypertensive drugs had faster loss rates (22.6-43.1%) than those of the controls but the difference was significant only for the distal radius.

CONCLUSION

Thiazide diuretics slow the rate of bone loss in elderly men.

Direct tubular effect on calcium retention by hydrochlorothiazide

Previous studies with hydrochlorothiazide revealed a calcium retaining effect of this substance. The mechanism by what this is done is still matter of controverse discussion. Effects of hydrochlorothiazide on vitamin D metabolism have been reported as well as those on parathyroid function. To further clarify the calcium retaining potency of hydrochlorothiazide (HCTZ) we treated 10 healthy young volunteers for four weeks with 2 x 50 mg HCTZ. In all volunteers we observed a marked decrease in urinary calcium excretion as well as in calcium clearance. Furthermore, we found a slight rise in ionized serum calcium (6.7%) and in intact PTH, as well as a 36% drop in 1,25-(OH)2-D3-levels. These effects were reversible after discontinuation of the treatment. No change was observed in urinary cAMP, phosphate excretion, serum anorganic phosphate levels, serum calcitonin and magnesium levels. Data presented here suggest that treatment with HCTZ causes a persistent reduction in calcium excretion through direct tubular effects, inhibits hydroxylation of vitamin D, and does not affect parathyroid function.

Long-term use of thiazide diuretics and risk of hip fracture

To assess whether long-term thiazide use is associated with a decreased risk of hip fracture, a nested case-control study was done in the Canadian province of Saskatchewan between 1984 and 1985 among residents who were 65 years of age or older and who were not receiving other drugs thought to affect bone mass. There were 905 hip fractures identified from hospital discharge records and 5137 population controls matched for age, sex, and calendar year. Drug use was ascertained from computerised pharmacy records. Risk of hip fracture decreased significantly with increasing duration of current thiazide use: relative risk (95% confidence interval) of 1.2 (0.9-1.5) for less than 2 years use, 0.8 (0.7-1.0) for use of 2-5 years, and 0.5 (0.3-0.7) for 6 or more years. In contrast, there was no such trend for use of other antihypertensive-diuretic drugs (relative risk 0.9 [0.6-1.3] for use of 6 or more years). This protective effect was not altered by age, sex, nursing home residence, previous hospital admission, or use of other antihypertensive-diuretic drugs or psychotropic drugs. Medical record review for a sample of 235 cases suggested this finding was not due to confounding by body mass, ambulatory status, functional status, or dementia. These results support the hypothesis that thiazides protect against osteoporosis in elderly people.

Medical management of nephrolithiasis in Dallas: update 1987

With available medical treatment programs a remission of stone disease could be achieved in more than 80 per cent of the patients and a decrease in individual stone formation rate obtained in greater than 90 per cent. The need for stone removal may be reduced dramatically by an effective prophylactic program. There is some evidence that certain stones (even calcareous types) may undergo dissolution in vivo with appropriate therapy. Moreover, properly applied medical treatments may be capable of overcoming nonrenal manifestations as well as preventing new stone formation. Thus, the potential development of bone disease in patients with renal tubular acidosis may be averted by potassium citrate therapy. Despite these advantages it is clear that the medical treatment approach cannot provide total control of the disease. Stone disease generally presents with a surgical problem related to an already formed stone before medical diagnosis and selective treatment may be applied. Some patients, albeit a minority, are recalcitrant to medical treatment no matter how heroic. A satisfactory response to medical treatment requires continued compliance by the patient to the recommended treatment program and a commitment by the physician to provide long-term followup care. There is no cure, only prophylaxis. The increasing ease and decreasing cost of new approaches to stone removal, particularly with the advent of second generation extracorporeal lithotripsy, will undoubtedly cast a continuing uncertainty on the need for medical diagnosis and treatment. Several factors might influence the choice between surgical and medical approaches. One factor is the severity of stone disease. Patients with repeated episodes of stone formation might be more likely to adopt preventive therapy, whereas those with infrequent stone episodes may elect simply to have them removed upon their occurrence without medical treatment between episodes. Also, the possibility that lithotripsy may cause long-term hazards (for example development of hypertension) must be clarified. Another factor is the occurrence of extrarenal manifestations. In patients suffering from systemic disorders in which nephrolithiasis is only 1 manifestation (for example distal renal tubular acidosis) a medical approach may be justified exclusive of effects on stone formation. Finally, one must consider the relative practicality and cost between stone removal and a medical approach. It is likely that improvements and reductions in costs will occur with both approaches. It is hoped that urologists and internists work jointly to find an appropriate balance between the 2 approaches.(ABSTRACT TRUNCATED AT 400 WORDS)

Alkali action on the urinary crystallization of calcium salts: contrasting responses to sodium citrate and potassium citrate

Alkali therapy is used commonly to prevent recurrent stone formation in patients with distal renal tubular acidosis. We compared the effects of potassium citrate to those of sodium citrate in 6 well defined cases of incomplete distal renal tubular acidosis. The patients were studied during a control phase, during potassium citrate treatment (80 mEq. per day) and during sodium citrate treatment (80 mEq. per day) chosen in random order. Potassium citrate caused a decrease in urinary calcium and a significant increase in urinary citrate that resulted in a significant decrease in the urinary saturation of calcium oxalate. It did not alter the saturation of brushite and sodium urate. However, while sodium citrate also was able to increase the urinary citrate level, there was no decrease in the urinary calcium (owing to the increased sodium load). Thus, the urinary saturation of calcium oxalate did not decrease as much as with potassium citrate and the saturation of brushite increased significantly. Moreover, the urinary saturation of sodium urate increased significantly owing to the enhanced sodium excretion. The results suggest that potassium citrate therapy may retard the crystallization of calcium oxalate and may not cause calcium phosphate crystallization. In contrast, sodium citrate may have no effect or it sometimes may accentuate the crystallization of calcium salts. Thus, our study supports the potential clinical advantage of potassium citrate therapy over sodium alkali treatment in patients with incomplete distal renal tubular acidosis and recurrent calcium nephrolithiasis.

Graphic display of urinary risk factors for renal stone formation

From the analysis of various urinary constituents and the estimation of urinary saturation of stone-forming salts, it is now possible to identify risk factors responsible for or contributing to stone formation. Metabolic factors included calcium, oxalate, uric acid, citrate and pH. Environmental factors were total volume, sodium, sulfate, phosphate and magnesium. Physicochemical factors represented saturation of calcium oxalate, brushite, monosodium urate, struvite and uric acid. A scheme for graphic display of risk factors was developed to allow ready visual recognition of important risk factors presumed to cause stone formation. This graphic display had diagnostic use as well as practical value in following response to treatment. For example, a low urinary pH and high urinary concentration of undissociated uric acid could be discerned readily in cases of uric acid lithiasis, as were high urinary pH and exaggerated urinary supersaturation of struvite in cases of infection lithiasis. In a patient with absorptive hypercalciuria and hypocitraturia treatment with thiazide and potassium citrate could be shown to abolish high risks (hypercalciuria, hypocitraturia and relative supersaturation of calcium oxalate) displayed before treatment.

Correction of hypocitraturia and prevention of stone formation by combined thiazide and potassium citrate therapy in thiazide-unresponsive hypercalciuric nephrolithiasis

Thirteen patients with hypercalciuric calcium nephrolithiasis continued to form calcium stones when treated with thiazide (4.69 +/- 6.62 [mean +/- SD] stones per patient-year to 5.12 +/- 10.87 stones per patient-year), despite adequate hypocalciuric response (a reduction in urinary calcium levels from 303 +/- 119 mg per day to 193 +/- 88 mg per day, p less than 0.01). Because they had hypocitraturia (250 +/- 86 mg per day versus 643 +/- 236 mg per day in normal subjects, p less than 0.001), potassium citrate (10 to 20 meq three times per day) was added to the ongoing treatment program. During combined treatment with thiazide and potassium citrate, urinary pH significantly rose, and normal levels of urinary citrate were restored. Ten patients stopped forming new stones and all 13 had reduced stone formation rate. Thus, potassium citrate supplementation should be considered in patients requiring thiazide therapy for the control of hypercalciuric nephrolithiasis, especially if they have concurrent hypocitraturia or if it develops during thiazide therapy.

New drug therapy for kidney stones: a review of cellulose sodium phosphate, acetohydroxamic acid, and potassium citrate

Kidney stones have an overall incidence of two to three percent in western countries. In many patients, the disease process is difficult to control and recurrence rates are high: 20 to 50 percent over the subsequent ten years. The pathogenesis and standard methods of treatment for the five major types of stones (i.e., calcium oxalate, struvite, calcium phosphate, uric acid, and cystine) are reviewed. Three new drugs are reviewed in the context of their roles in the selective treatment of kidney stones. Cellulose sodium phosphate (Calcibind) is a nonabsorbable ion-exchange resin with a limited indication for the treatment of calcium stones associated with absorptive hypercalciuria Type I. Acetohydroxamic acid (Lithostat) is an urease-inhibitor that is indicated as adjunctive therapy in patients with chronic urea-splitting urinary tract infections and struvite stones. Potassium citrate (Urocit) is an investigational agent that has clinical efficacy in patients with calcium oxalate and calcium phosphate stones who are hypocitraturic. In addition, potassium citrate is an alkalinizing agent that can be used in patients with uric acid stones.

Long-term treatment of calcium nephrolithiasis with potassium citrate

The long-term effects of potassium citrate therapy (usually 20 mEq. 3 times daily during 1 to 4.33 years) were examined in 89 patients with hypocitraturic calcium nephrolithiasis or uric acid lithiasis, with or without calcium nephrolithiasis. Hypocitraturia caused by renal tubular acidosis or chronic diarrheal syndrome was associated with other metabolic abnormalities, such as hypercalciuria or hyperuricosuria, or occurred alone. Potassium citrate therapy caused a sustained increase in urinary pH and potassium, and restored urinary citrate to normal levels. No substantial or significant changes occurred in urinary uric acid, oxalate, sodium or phosphorus levels, or total volume. Owing to these physiological changes, uric acid solubility increased, urinary saturation of calcium oxalate decreased and the propensity for spontaneous nucleation of calcium oxalate was reduced to normal. Therefore, the physicochemical environment of urine following treatment became less conducive to the crystallization of calcium oxalate or uric acid, since it stimulated that of normal subjects without stones. Commensurate with the aforementioned physiological and physicochemical changes the treatment produced clinical improvement, since individual stone formation decreased in 97.8 per cent of the patients, remission was obtained in 79.8 per cent and the need for surgical treatment of newly formed stones was eliminated. In patients with relapse after other treatment, such as thiazide, the addition of potassium citrate induced clinical improvement. Thus, our study provides physiological, physicochemical and clinical validation for the use of potassium citrate in the treatment of hypocitraturic calcium nephrolithiasis and uric acid lithiasis with or without calcium nephrolithiasis.