Urinary Volume, Water and Recurrences in Idiopathic Calcium Nephrolithiasis: A 5-year Randomized Prospective Study

Prevention and management of urinary stone

The prevalence of urolithiasis is increasing not only in South Korea but also around the world. Urolithiasis has a high recurrence rate, therefore, reducing it is very important in the quality of life for stone formers. For this purpose, dietary modifications and drug therapy can be performed through stone analysis and 24-hour urine collection. Stone analysis is recommended for all stone formers, and the 24-hour urine collection is usually recommended for recurrent stone formers or high-risk groups. A general dietary modification for all stone formers includes a sufficient fluid intake, low levels of sodium, sugar, and animal protein, a normal calcium diet, as well as a high amount of citrate intake. Drug therapy should be performed in cases such as the recurrence of stones or increase of the existing ones, even after the application of preservation therapy, such as dietary modification. The ideal drug therapy should prevent the occurrence of urolithiasis, have no side effects, and have a suitable patientsʼ compliance. Follow-up should be performed periodically, through 24-hour urine collections and imaging studies. For follow-up imaging studies, a lowdose non-enhanced computed tomography is recommended, and it can be performed once a year if the patient is in a stable state. To control various and complex metabolic abnormalities in recurrent stone formers, multiple approaches may be required through diet modifications, drug therapy, treatment of the metabolic syndrome, and lifestyle modifications.

Risk factors for urinary stone

Urolithiasis is one of the most common urologic diseases in Korea. The annual incidence of urolithiasis in Korea has increased over time. Understanding the epidemiology and risk factors for urolithiasis is essential for patient care and prevention. The purpose of this review was to summarize the recent literature regarding the risk factors for urolithiasis. The available Korean-population-based trials were enrolled in this study. The peak incidence age was the fifth to sixth decades in Korea. There has been a persistent male predominance in the prevalence and incidence of stone disease. The gender gap has continuously narrowed over the world. Climate and seasonal variations, such as temperature and humidity, have a profound effect on the development of urolithiasis. Various dietary factors, including calcium, sodium, animal protein, and oxalate, play an important role in the development of urolithiasis. Dehydration is a wellknown risk factor for stone disease. Many metabolic diseases can affect urolithiasis, including obesity, hypertension, diabetes, gout, and metabolic syndrome. The fast-moving super-aged society and global warming can increase stone disease burden in the near future. To prevent and reduce stone diseases, clinicians should understand the risk factors affecting stone formation.

Impact of dietary counseling on urinary stone risk parameters in recurrent stone formers

OBJECTIVES

The aim of this study was to investigate the current impact of dietary counseling on the risk for urolithiasis.

METHODS

A retrospective cohort study of the patients treated in our stone clinics from July 2007 to February 2009 was carried out. Patients' urinary risk factors for stone disease were evaluated with pre- and postintervention 24-hour urine collections. All patients received dietary recommendations from a registered dietician at each visit.

RESULTS

One hundred thirty-seven subjects were identified and managed initially with only dietary interventions to address their urinary stone risk parameters. Average follow-up for this group was 15.19 ± 13.7 months. Subjects showed significant changes in urine volume (71.1%, 1.68 ± 0.68 to 2.59 ± 0.80 L/day, p < 0.0001), urine sodium (58.1%, 229.68 ± 72.51 to 144.65 ± 52.70 mmol/day, p < 0.0001), urine calcium (43.8%, 314.33 ± 95.75 to 216.81 ± 80.90 mg/day, p < 0.0001), urinary uric acid (50%, 0.821 ± 0.210 to 0.622 ± 0.128 g/day, p < 0.0001), urinary citrate (50.7%, 583.19 ± 330.86 to 797.36 ± 412.31, p < 0.0001), and urine oxalate (55.5%, 46.28 ± 10.31 to 32.56 ± 9.02 mg/day, p < 0.0001). The supersaturation for calcium oxalate also decreased significantly from baseline (9.34-5.03, p < 0.0001).

CONCLUSION

Urolithiasis is a multifactorial disease requiring a multidisciplinary approach. Our results support the use of dietary counseling by a registered dietician in the management of urolithiasis.

Effect of potassium citrate therapy on stone recurrence and regrowth after extracorporeal shockwave lithotripsy in children

BACKGROUND AND PURPOSE

Stone disease in children may cause functional and morphologic changes in the urinary tract during longer-term follow-up. Prevention of stone recurrence will be possible only with careful metabolic evaluation and appropriate management. The possible preventive effects of potassium citrate therapy on true stone recurrence, as well as regrowth rates after shockwave lithotripsy (SWL), were evaluated in children treated for renal stones.

PATIENTS AND METHODS

Following assessment of the efficacy of SWL, 96 children (72 male, 53 female aged 4 to 14 years with a mean of 6.6 years) were evaluated for the effects of potassium citrate on residual fragments as well as true new stone formation during long-term follow-up. All children had calcium-containing stones with normal renal morphology and function without any urinary-tract infection. Depending on the outcome of treatment, patients with and without residual stones were allocated independently to Group I (N = 52) and Group II (N = 44), which were matched for sex and age. Group I was given oral potassium citrate 1 mEq/kg daily for 12 months; the remaining children served as controls. Follow-up ranged from 12 to 36.6 months, with a mean of 24.4 months. Follow-up results for at least a year with respect to the stone recurrence or stone growth rates were recorded in both groups.

RESULTS

Stone-free children undergoing no specific therapy had significant new stone formation compared with the group receiving potassium citrate on a regular basis (34.6% and 7.6%, respectively). Children with residual fragments receiving no specific preventive measure also showed significant new stone formation, along with enlargement of the fragments.

CONCLUSION

In addition to stone removal, treatment of pediatric urolithiasis requires a thorough metabolic evaluation. Depending on the abnormalities, each patient should be advised on adequate drinking to increase the urine volume in accordance with body size. Although children with hypocitraturia may well benefit from therapeutic agents that raise the urine citrate concentration, our results did clearly show that all children bearing residual fragments should be counseled on adequate fluid intake along potassium citrate treatment to prevent stone regrowth or formation during long-term follow-up.

Prevention of Stone Disease

In recent years stone disease has become more widespread in developed countries. At present the prevalence is 5.2 and 15% of men and 6% of women are affected. The increase is linked to changes in lifestyle, eating patterns and obesity which has become very common. The 'metabolic syndrome' includes all the diseases, e.g. hypertension, lipid imbalances, type 2 diabetes mellitus, gout and cardiovascular disease, which are concomitant in the majority of stone formers. Dietary patterns, besides leading to stone formation, also determine stone chemistry. With a diet that is rich in oxalates, calcium oxalate will constitute 75% of stones, struvite 10-20%, uric acid 5-6% and cystine 1%. As approximately 50% of patients with stones suffer recurrences, metabolic and/or pharmacological prophylaxis is recommended.

Lithiasis and Risk Factors

Nephrolithiasis is a worldwide disease with high clinical and economic costs. The increasing incidence in industrialized countries seems to be related to several risk factors, which are partly inherited and partly acquired. Although risk factors in urolithiasis are still under discussion, their identification would provide a notable gain for the patient in terms of stone episodes, and for the health service in terms of costs. This article presents an easy classification of risk factors based on clinical background.

Medical Therapy of Urolithiasis

Nephrolithiasis treatment has become easier and less invasive with the development of extracorporeal shockwave lithotripsy (SWL) and endourologic techniques. However, medical therapy represents a well-established and complementary approach that can improve the efficacy of SWL and endourology. During recent decades, pharmacologic intervention has become more effective in stone disease: drugs can control the pain of renal colic, interfere at various levels in lithogenesis, and contribute to the expulsion of stones. It is well known that lithogenesis is a multifactorial process influenced by environmental-nutritional factors (low urinary volume, diet rich in animal protein, etc) and metabolic alterations; i.e., hypercalciuria, hyperuricosuria, and deficiency of stone-inhibiting factors (citrate, magnesium, glycosaminoglycans [GAGs]). Specific drugs such as citrate, allopurinol, and thiazide represent highly effective treatments for the promoting factors. Furthermore, recent findings suggest an interesting role for a phytotherapeutic agent, Phillantus niruri, and its inhibitory action on calcium oxalate crystallization related to the higher incorporation of GAGs into the calculi. Another step forward in medical management of stone disease is expulsive therapy. Many studies have proven the efficacy of medical expulsive therapy with nifedipine and alpha-blockers: their specific action on ureteral smooth muscle in association with anti-edema drugs accounts for their efficacy in expelling ureteral stones. In this paper, we provide an update on the medical treatment of stone disease, focusing our attention on what is known and what is new in renal colic and litholithic and expulsive medical therapy.

Medical management of urinary stone disease

A variety of dietary and metabolic factors may contribute or cause stone formation in idiopathic calcium oxalate nephrolithiasis. Dietary factors include a high intake of animal proteins, oxalate and sodium, and a low intake of fluids and potassium-containing citrus products. Some of the metabolic causes of stones are hypercalciuria, hypocitraturia, gouty diathesis, hyperoxaluria, and hyperuricosuria. Dietary modification, to be applied in all patients with stones includes a high fluid intake, restriction of oxalate and sodium, and balanced diet with animal proteins complemented by adequate intake of fruits and vegetables. When dietary modification is ineffective in controlling stone formation or in the presence of severe metabolic derangements, a pharmacologic intervention may be necessary. In a simple approach, thiazide or indapamide with potassium citrate is recommended for patients with hypercalciuria, and potassium citrate alone for the remaining normocalciuric subjects.

Effects of dietary supplementation with sodium chloride on urinary relative supersaturation with calcium oxalate in healthy dogs

OBJECTIVE

To evaluate the effect of dietary supplementation with sodium chloride (NaCl) on urinary calcium excretion, urine calcium concentration, and urinary relative supersaturation (RSS) with calcium oxalate (CaOx).

ANIMALS

6 adult female healthy Beagles.

PROCEDURE

By use of a crossover study design, a canned diet designed to decrease CaOx urolith recurrence with and without supplemental NaCl (i.e., 1.2% and 0.24% sodium on a dry-matter basis, respectively) was fed to dogs for 6 weeks. Every 14 days, 24-hour urine samples were collected. Concentrations of lithogenic substances and urine pH were used to calculate values of urinary RSS with CaOx.

RESULTS

When dogs consumed a diet supplemented with NaCl, 24-hour urine volume and 24-hour urine calcium excretion increased. Dietary supplementation with NaCl was not associated with a change in urine calcium concentration. However, urine oxalate acid concentrations and values of urinary RSS with CaOx were significantly lower after feeding the NaCI-supplemented diet for 28 days.

CONCLUSIONS AND CLINICAL RELEVANCE

Dietary supplementation with NaCl in a urolith-prevention diet decreased the propensity for CaOx crystallization in the urine of healthy adult Beagles. However, until long-term studies evaluating the efficacy and safety of dietary supplementation with NaCl in dogs with CaOx urolithiasis are preformed, we suggest that dietary supplementation with NaCl be used cautiously.

Role of Nutrition in the Formation of Calcium-Containing Kidney Stones

Diet plays an important role in the pathogenesis of calcium-containing kidney stones. Although much work has demonstrated that specific dietary components alter urinary composition and supersaturation, relatively few studies link the ingestion of these components with actual nephrolithiasis. This article reviews the dietary factors thought to promote or inhibit the formation of calcium stones and discusses the current controversies in the field of nutrition and nephrolithiasis. Special attention is paid to the roles of dietary calcium, supplemental calcium, oxalate, phytate, and n-3 fatty acids. We offer dietary recommendations to individuals who have suffered from a calcium-containing kidney stone, and emphasize that a patient's 24-hour urine chemistries should be used to help guide dietary intervention.

Risk factor analysis and relative supersaturation as tools for identifying calcium oxalate stone-forming dogs

Twenty-four hour urine samples were collected from 17 calcium oxalate (CaOx) stone-forming (SF) dogs and 17 normal (N), age-, breed- and sex-matched dogs. Urinary CaOx relative supersaturation (RSS) was calculated and found to be significantly higher in the SF group than the N group. RSS measurement is not readily applicable to veterinary practice; thus, alternatives were explored. Discriminant analysis failed to identify key factors differentiating most SF from N dogs. Urinary calcium, oxalate and uric acid, which differed between the SF and N animals, were combined into a measure of relative probability of CaOx stone formation (PSF) to establish whether this approach could be used to assess the risk of CaOx stone formation in dogs. Although there was good correlation between the techniques, RSS more clearly discriminated between SF and N dogs. These data suggest that neither PSF nor discriminant analysis is preferable to RSS for assessing the risk of CaOx stone formation in dogs.

Effects of dietary potassium citrate supplementation on urine pH and urinary relative supersaturation of calcium oxalate and struvite in healthy dogs

OBJECTIVE

To assess the effect of dietary potassium citrate supplementation on the urinary pH, relative supersaturation of calcium oxalate and struvite (defined as the activity product/solubility product of the substance), and concentrations of magnesium, ammonium, phosphate, citrate, calcium, and oxalate in dogs.

ANIMALS

12 healthy adult dogs.

PROCEDURE

Canned dog food was fed to dogs for 37 days. Dogs were randomly allocated to 3 groups and fed test diets for a period of 8 days. Study periods were separated by 6-day intervals. During each study period the dogs were fed either standard diet solus (control) or standard diet plus 1 of 2 types of potassium citrate supplements (150 mg potassium citrate/kg of body weight/d) twice daily. Urinary pH, volume and specific gravity, relative supersaturation of calcium oxalate and struvite, and concentrations of magnesium, ammonium, phosphate, calcium, oxalate, and citrate were assessed for each treatment.

RESULTS

Mean urine pH was not significantly affected by dietary potassium citrate supplementation, although urine pH did increase by 0.2 pH units with supplementation. Diets containing potassium citrate maintained a higher urine pH for a longer part of the day than control diet. Three Miniature Schnauzers had a significantly lower urinary relative calcium oxalate supersaturation when fed a diet supplemented with potassium citrate, compared with control diet.

CONCLUSIONS AND CLINICAL RELEVANCE

Dietary potassium citrate supplementation has limited effects on urinary variables in most healthy dogs, although supplementation results in maintenance of a higher urine pH later in the day. Consequently, if supplementation is introduced, dogs should be fed twice daily and potassium citrate should be given with both meals or with the evening meal only.

Calcium oxalate urolithiasis in cats

Urolithiasis has long been recognized as a cause of irritative voiding in cats. Before the late 1980s, sterile struvite was the most common urolith; today, however, 40% of feline uroliths are of calcium oxalate. This change may be partly attributable to the change to urine-acidifying, magnesium-restricted diets that were introduced to reduce the formation of struvite. However, it is possible that the diet modifications made by cat food manufacturers simply exposed a population of cats predisposed to calcium oxalate stone formation. Urolithiasis in cats appears to be diet sensitive rather than diet induced. As in humans, water is crucial in the prevention and treatment of feline stones.