Impact of body weight on urinary electrolytes in urinary stone formers

OBJECTIVES: Obesity increases the risk of developing chronic medical conditions such as diabetes mellitus, hypertension, and coronary artery disease. We performed a retrospective review of a large data base on urinary stones to determine if differences are found in urine and serum chemistries among obese and nonobese stone-forming patients. The effect of body weight on stone recurrence among urinary stone formers was also determined. METHODS: A national data base containing serum biochemical profiles, 24-hour urine specimens, and standardized questionnaires was retrospectively evaluated from 5942 consecutive patients with urinary stone disease. Stone-forming patients were classified by body weight: nonobese men, less than 100 kg and nonobese women, less than 85 kg; intermediate men, 100 to 120 kg and intermediate women, 85 to 100 kg; and obese men, more than 120 kg and obese women, more than 100 kg. RESULTS: Obese stone formers comprised 6.8% (n = 404) of the patient population. The mean weight in the nonobese and obese groups was 81 kg versus 134 kg, respectively, for men and 64 kg versus 112 kg, respectively, for women. Obese patients represented 3.8% of the male and 12.6% of the female population. Obese patients had increased urinary excretion of sodium, calcium, magnesium, citrate, sulfate, phosphate, oxalate, uric acid, and cystine; obesity was associated with increased urinary volumes and urine osmolality compared with the nonobese patients. Obese men had increased concentration of urinary sodium, oxalate, uric acid, sulfate, and phosphate when corrected for urinary volume. Obese women had increased concentrations of sodium, uric acid, sulfate, phosphate, and cystine. The mean number of stone episodes in nonobese versus obese men was similar (3.55 and 3.56), whereas mean stone episodes were 2.93 and 3.38 (P = 0.045) for nonobese versus obese women. CONCLUSIONS: Among known stone formers, obesity is associated with unique changes in both serum and urinary chemistries. These changes are associated with an increased incidence of urinary stone episodes in obese women but not in obese men.     

Ammonium acid urate calculi: a reevaluation of risk factors

PURPOSE: We reevaluate the demographic and metabolic risk factors for ammonium acid urate stones. MATERIALS AND METHODS: Since 1986, 23 women and 21 men ranging in age from 20 to 81 years (mean 48.7) were treated for stones partly composed of ammonium acid urate. Stone composition ranged from 2 to 60% ammonium acid urate (mean 24.1) of the total stone mass. No patient had a pure ammonium acid urate stone, although 11 (25%) had stones with ammonium acid urate as the predominant crystal. RESULTS: In the 44 patients 1 or more potential risk factors for ammonium acid urate were identified. Of the patients 11 (25%) had a history of inflammatory bowel disease with 10 (22.7%) having undergone ileostomy diversion, 6 (13.6%) admitted to a history of significant laxative use or abuse, 18 (40.9%) were morbidly obese, 16 (36.4%) had a history of recurrent urinary tract infections and 9 (20.5%) had a history of recurrent uric acid stones. CONCLUSIONS: Patients clearly at risk for stones with an ammonium acid urate component include those with a history of inflammatory bowel disease and ileostomy diversion or laxative abuse. Other factors that may potentially enhance ammonium acid urate stone formation include morbid obesity, recurrent uric acid calculi and recurrent urinary tract infection. A careful history followed by further metabolic evaluation is warranted in these patients.     

Increased urinary uric acid excretion: a finding in Indian stone formers

Many studies have been done to determine the risk factors associated with urolithiasis so that preventive measures can be undertaken to prevent stone formation. However the exact aetiology of urinary stones still remains elusive. A prospective control study of epidemiological factors that influence urinary stone formation was done to determine the aetiology of urinary stones. Patients with stone disease had a significantly higher body mass index. 24-h urine excretion of uric acid and phosphate was found to be significantly higher in stone patients as compared to controls. The intake of non-vegetarian food was significantly higher amongst stone formers. Stone patients had a significantly higher consumption of curd and cheese as compared to controls. There was a significant correlation noted between stone formation and a positive family and past history of stone disease. The results indicate that obese patients, especially those with a family history of stone disease, should be counselled on weight loss. Individuals with a past history of stone disease should be advised to reduce their dietary intake of foods rich in uric acid (meat, liver and beans).     

Epidemiology of nephrolithiasis in France

Nephrolithiasis is a frequent disease that affects about 10% of people in western countries. The prevalence of calcium oxalate stones has been constantly increasing during the past fifty years in France as well as in other industrialized countries. Stone composition varies depending to gender and age of patients and also underlines the role of other risk factors and associated pathologies such as body mass index and diabetes mellitus. The decrease in struvite frequency in female patients is the result of a significantly improved diagnostic and treatment of urinary tract infections by urea-splitting bacteria. In contrast, the increasing occurrence of weddellite calculi in stone forming women aged more than 50 years could be the consequence of post-menopausal therapy. A high prevalence of uric acid was found in overweight and obese stone formers and in diabetic ones as well. Another important finding was the increased occurrence with time of calcium oxalate stones formed from papillary Randall's plaques, especially in young patients. Nutritional risk factors for stone disease are well known: they include excessive consumption of animal proteins, sodium chloride and rapidly absorbed glucides, and insufficient dietary intake of fruits and potassium-rich vegetables, which provide an alkaline load. As a consequence, an excessive production of hydrogen ions may induce several urinary disorders including low urine pH, high urine calcium and uric acid excretion and low urine citrate excretion. Excess in calorie intake, high chocolate consumption inducing hyperoxaluria and low water intake are other factors, which favour excessive urine concentration of solutes. Restoring the dietary balance is the first advice to prevent stone recurrence. However, the striking increase of some types of calculi, such as calcium oxalate stones developed from Randall's plaque, should alert to peculiar lithogenetic risk factors and suggests that specific advices should be given to prevent stone formation.     

Diagnosis and metaphylaxis of stone disease

This review draws the recent state of the art in metabolic diagnosis and metaphylaxis of stone disease. It is the basis for the consensus approval with the other medical societies and institutions in Germany involved in the guideline process of the new "Urolithiasis Guideline". The German Working Committee on Stone Disease reviewed critically the current literature in the field of urolithiasis-including the existing German and EAU-Guidelines as well as the Conference Book of the First International Consultation on Stone Disease. As far as possible the references were rated according to the EBM criteria. On this basis the expert group discussed all pathways and statements regarding the management of stone disease. The present review coincides with the consented guideline draft of the German Working Committee on Stone Disease. Occurrence of stone disease in the western world increases seriously. Modern lifestyle, dietary habits and overweight-problems of the affluent societies-emerge to be the important promoters of the "stone-boom" in the new millennium. This even affects children, whose stone prevalence is otherwise significantly less than that of adults. Criteria for the high risk group of stone formers were clearly defined. A diagnostic standard is formulated for the basic and the elaborate metabolic evaluation of a stone patient. Approximately 75% of all stone patients could anticipate stone recurrence with elementary reorientation of their lifestyle and dietary habits, summarized as general metaphylaxis. About 25% of the stone formers require additional pharmacological intervention to normalize their individual biochemical risk, precisely compiled for each stone type as specific metaphylaxis.     

International comparison of cost effectiveness of medical management strategies for nephrolithiasis

Although medical therapy is known to reduce the risk of kidney stone recurrence, the cost effectiveness of medical prophylaxis is controversial. We evaluated medical treatment strategies including dietary measures (conservative), empiric medical therapy (empiric) or directed medical therapy (directed) based on comprehensive metabolic evaluation (CME) for patients with recurrent kidney stones, and compared the costs of these strategies using cost data from ten different countries. We previously established rates of stone formation in recurrent stone-formers, risk reduction of medical therapy, sensitivity of CME and rates of spontaneous stone passage from a comprehensive literature search (Lotan et al. 2004 J Urol 172: 2275). The costs of medication, surgical therapy, emergency room visits and CME for ten different countries were obtained from a published report of an international cost survey (Chandhoke 2002 J Urol 168: 937) as well as from our own county hospital in the US. Medication costs in the US were obtained from two national pharmacy chains. A decision tree model was created to compare the costs of different treatment strategies assuming cost accrual for metabolic evaluation, medical therapy and surgery or emergency room visits. For medical therapy, we assumed the distribution of medication use described in the published report, consisting of potassium citrate (60%), thiazide (30%) and allopurinol (10%). A nearly 20-fold difference in the costs of shock-wave lithotripsy, ureteroscopy and medication was found among different countries. From the model (US dollars/patient/year), conservative therapy alone was the most cost effective approach followed by empiric and directed medical therapy in all countries except in the UK. In the UK, the cost of drug therapy (estimated at $29/patient/year) resulted in empiric therapy being the most cost effective strategy for recurrent stone formers. The low likelihood of surgical intervention, as well as the low relative cost of surgery to medication, contributed to the higher cost of empiric and directed medical therapy strategies. Of note, despite the higher cost, drug treatment strategies were associated with significantly lower stone recurrence rates. We found that drug treatment strategies are more costly than conservative treatment but produce good control of stone formation. In all but one country (UK), dietary therapy was the most cost effective approach due to the relatively low cost of surgery compared with medication. The differential resource allocation to different components of a healthcare system (i.e. subsidized medication versus surgical treatment) in different countries determines the cost effectiveness of various treatment strategies.     

10-year experience with extracorporeal shockwave lithotripsy in the state of Colorado

PURPOSE: To evaluate trends in the utilization of extracorporeal shockwave lithotripsy (SWL) and the potential need for medical prophylaxis of urolithaisis in the state of Colorado. MATERIALS AND METHODS: We examined patient and stone characteristics of individuals undergoing SWL for renal or upper-ureteral stones over a 10-year period (1987-1996) at the Kidney Stone Center of the Rocky Mountains. There were no significant changes in the in-state physician referral patterns nor SWL treatment criteria over this time interval. All patients were treated on the Dornier HM3 lithotripter. From September 1999 to December 1999, 198 consecutive patients undergoing SWL filled out a 10-point questionnaire regarding their interest in medical prophylaxis of urolithiasis. RESULTS: The number of patients from Colorado rose 32.5%: from 15.7 per 100,000 population in 1987 to 20.8 per 100,000 in 1996. Patient demographics such as sex, race, age, and history of nephrolithiasis did not change. Furthermore, there were no significant changes in the treated stone size or stone location. The overall increase in treatment numbers was attributable equally to increases in the number of upper ureteral and renal stones. Of the 198 patients questioned, 114 (58%) were recurrent stone formers, but only 52 (45%) of these had been offered a metabolic evaluation. CONCLUSIONS: Over the 10 years since the introduction of WSL in Colorado, there has been a gradual increase in its utilization. This higher utilization is probably multifactorial. Patients undergoing SWL have a strong desire to prevent future stone episodes and are very interested in medical prophylaxis of their stone disease.     

Metabolic abnormalities associated with calyceal diverticular stones

OBJECTIVE: To review the metabolic analyses of patients with calyceal diverticular stones who had surgical treatment of their calculi and to examine the effect of selective medical therapy on stone recurrence, as recent reports suggest that metabolic abnormalities contribute to stone development. PATIENTS AND METHODS: In all, 37 patients who had endoscopic treatment of symptomatic calyceal diverticular calculi were retrospectively reviewed. Stone composition and initial 24-h urine collections (24-h urinary volumes, pH, calcium, sodium, uric acid, oxalate, citrate, and the number of abnormalities/patient per collection) were compared with 20 randomly selected stone-forming patients (controls) with no known anatomical abnormalities. Stone formation rates before and after the start of medical therapy were calculated in the patients available for follow-up. RESULTS: Twelve of the diverticulum patients (five men and seven women) had complete 24-h urine collections, all of whom had at least one metabolic abnormality. Seven patients had hypercalciuria, four had hyperuricosuria and three had mild hyperoxaluria. The most common abnormality was a low urine volume; 11 of the 12 patients had urine volumes of <2000 mL/day (range 350-1950). Ten patients had hypocitraturia in at least one of the two 24-h urine samples; seven had low urinary citrate levels (172-553 mg/day) on both samples. The findings were similar in the control group. The diverticulum patients had 3.1 abnormalities/patient, and the controls had 2.9 abnormalities/patient (P > 0.05). No patients had gouty diathesis and none developed cystine stones. Stone analyses were similar in the two groups; both developed either calcium oxalate or mixed calcium oxalate/calcium phosphate stones. Six patients were followed for a mean of 23.1 months while on selective medical therapy; only one passed any additional stones, thought to be existing calculi, for a remission rate of five of six (83%). CONCLUSIONS: All patients with symptomatic calyceal diverticular stones who had comprehensive metabolic evaluation had metabolic abnormalities. There were similar abnormalities in the control random stone-formers. The abnormalities were corrected with selective medical therapy, as shown by the high remission rate. We recommend that, for patients with symptomatic calyceal diverticular calculi, a metabolic evaluation should be considered to determine stone forming risk factors.     

Role of stone analysis in metabolic evaluation and medical treatment of nephrolithiasis

BACKGROUND AND PURPOSE: Comprehensive metabolic evaluation has become an important aspect of the management of recurrent nephrolithiasis, yet the role of stone analysis is often neglected or perhaps underestimated. The purpose of this study was to determine the role of stone analysis in medical decision making in patients with recurrent nephrolithiasis. MATERIALS AND METHODS: We evaluated 100 consecutive stone-forming patients who had undergone compositional stone analysis as well as comprehensive metabolic evaluation at our institution. An analysis of stone composition in relation to metabolic disturbances was performed. Patients were stratified into two groups: calcium and non-calcium stone formers. RESULTS: Patients having non-calcium stones were found to have a metabolic analysis reflecting specific metabolic disorders. Alternatively, patients with calcium stones were heterogeneous with regard to metabolic disorders, but there was a significant likelihood of renal tubular acidosis in those patients with calcium phosphate calculi. On the basis of these results, a simplified metabolic evaluation and nonselective medical therapy based on stone composition was formulated to facilitate assessment, management, and monitoring of stone disease. CONCLUSIONS: Compositional stone analysis should be an integral part of the metabolic evaluation of patients with nephrolithiasis. Moreover, stone analysis alone may provide guidance for therapeutic treatment and obviate a formal metabolic evaluation.     

Urolithiasis and obesity: metabolic and technical considerations

PURPOSE OF REVIEW: The increasing prevalence of obesity poses a challenge to urologists in the diagnosis and treatment of urolithiasis. This review summarizes the new evidence linking obesity and urolithiasis, and the technical considerations and modifications necessary in the diagnosis and treatment of stone disease in obese patients. RECENT FINDINGS: Recent studies have confirmed the epidemiological link between obesity and urolithiasis, and have provided some possible explanations for its underlying cause. New clinical series have demonstrated that flexible ureterorenoscopy and adapted percutaneous nephrolithotomy techniques can result in similar stone clearance rates and morbidity to the non-obese patient. New data, however, suggest that obesity may be an independent predictor of extracorporeal shock wave lithotripsy treatment failure for ureteric stones. Evidence of the efficacy of dietary modification and medical treatment of metabolic abnormalities has been reported in obese stone formers. SUMMARY: Urolithiasis can be safely and effectively managed in obese patients with minor modifications to the established surgical techniques. Increased understanding of the underlying metabolic abnormalities in obese patients with urolithiasis may improve prevention strategies in the future.     

Nephrolithiasis in children

Similar to adults, stone disease in the pediatric patient may present clinically as flank/abdominal pain or hematuria. Unlike in adults, pediatric stone disease is less frequent and is often associated with an underlying metabolic disorder. Because of the 50% likelihood of finding an underlying metabolic cause for stone formation in younger children, a metabolic workup is recommended for all children with stone disease, including first-time stone formers. Stone analysis, when available, can be very helpful in determining an underlying cause. If needed, all modalities of minimally invasive surgical treatment are possible for children with stones. Surgical approaches may be needed to achieve the goal of nephron preservation. Aggressive fluid intake is the mainstay of prevention for all forms of stone disease, but specific therapy targeted to the most likely underlying metabolic abnormality is often used. Newer data are now linking stone disease to CKD, thereby emphasizing the need for a better understanding and potentially more aggressive treatment approach. With increasing frequency of stone disease in the pediatric patient and increasing survival of these patients into adulthood, the adult caregiver must become familiar with different causes and treatment approaches to stone disease in young adult patients in whom disease onset began in childhood.     

Metabolic risk factors in pediatric and adult calcium oxalate urinary stone formers: is there any difference?

OBJECTIVES: Urolithiasis in children is recognized with an increasing frequency, while exact etiological factors remain to be determined. The aim of this study is to compare the metabolic risk factors and saturation of urine in pediatric and adult calcium oxalate (Ca-Ox) stone formers. METHODS: A total of 33 pediatric (mean age: 6.8 +/- 3.1 years) and 120 adult patients (mean age: 39.7 +/- 5.7 years), with documented Ca-Ox urinary stone disease, underwent a comprehensive metabolic evaluation at our institution. Beside a broad serum analysis, concentrations of calcium, oxalate, magnesium, uric acid and citrate were measured in 24-hour collected urine. Saturation of urine was calculated by Marshall-Robertson's nomograms. RESULTS: Hypocitraturia, observed in 60.6%, and hypomagnesuria, detected in 39.4%, but not hypercalciuria, were the most common metabolic risk factors in the pediatric group. In adults, hypercalciuria still represented one of the major metabolic risk factors, detected in 44.1%, although hypocitraturia, observed in 45.8%, was the most prevalent metabolic risk factor, as it was in the pediatric group. Pediatric cases had significantly (p < 0.05) higher prevalence of hypocitraturia, hypomagnesuria and supersaturated urine when compared to adults. Metabolic abnormalities could be detected in a high percentage (82%) of primary and recurrent pediatric Ca-Ox stone formers, but not in primary adult stone formers. CONCLUSIONS: Metabolic risk factors significantly differ in pediatric and adult Ca-Ox stone formers. Hypocitraturia and hypomagnesuria seem to play a major role in stone formation, and metabolic abnormalities can be detected in a significant percentage of both primary and recurrent pediatric stone formers. Thus, a comprehensive metabolic evaluation is of utmost importance for all children with Ca-Ox stones.     

Effect of medical management on recurrent stone formation following percutaneous nephrolithotomy

PURPOSE: Percutaneous nephrolithotomy is a commonly used procedure for treatment of large or complex renal calculi. In some instances postoperative residual stone fragments are an unavoidable result. Yet to our knowledge no study has examined the impact of medical management on stone formation in patients with or without residual fragments following percutaneous nephrolithotomy. Thus, we have conducted the first investigation of aggressive medical management following percutaneous nephrolithotomy and its impact on stone formation rates in patients with and without residual fragments. MATERIALS AND METHODS: A total of 70 patients who underwent percutaneous nephrolithotomy and received counseling regarding selective medical management following a comprehensive metabolic evaluation, were identified. Patients were placed into 4 groups following percutaneous nephrolithotomy, that is stone-free or residual fragments, who underwent or did not undergo medical therapy. New stone formation was assessed by spontaneous stone passage in the absence of residual stone fragments, stone passage without change in the number of residual fragments, surgical removal of newly formed stones, or appearance of new stones or increase in size of stone or fragments on abdominal radiographs. Stone remission rates were also calculated. RESULTS: Selective medical therapy significantly decreased stone formation rates in the stone-free (0.67 stones per patient per year vs 0.02) and residual fragment groups (0.67 stones per patient per year vs 0.02) as determined by the Wilcoxon signed rank test (p<0.0001). Moreover, remission was observed in a higher proportion of patients in the medically treated stone-free and residual fragment groups (87% and 77%) when compared to the same groups without medical therapy (29% and 21%, chi-square test p<0.0001). CONCLUSIONS: Our findings suggest that comprehensive metabolic evaluation and aggressive medical management can control active stone formation and growth in patients with or without residual stone fragments after percutaneous nephrolithotomy. Given the inherent morbidity and increased costs attendant with repeat procedures, medical management should be instituted in patients following percutaneous nephrolithotomy without regard to stone-free status.     

Serum phosphate in stone formers: what does a low serum phosphate level mean?

PURPOSE: Metabolic evaluation is indicated in stone formers to identify and subsequently modify risk factors for nephrolithiasis. Some believe that serum phosphate may be an important indicator of nephrolithiasis risk. We determined whether serum phosphate is an independent risk factor for recurrent calcium stone formation and whether it may be used as an early marker for occult disease, such as hyperparathyroidism. MATERIALS AND METHODS: The charts of all patients with regular long-term stone clinic followup were reviewed. Initial serum phosphate levels were compared with stone recurrence, complications due to stones, initial visit urinary laboratory values and the medical diagnoses made during followup. Unpaired 2-sample t tests, and correlation and logistic regression analyses were performed with statistical significance at p <0.05. RESULTS: Data were available on 51 men and 25 women 22 to 74 years old (mean age 52). Of the patients 50 were recurrent and 26 were single stone formers. Serum phosphate levels were lower in women than in men. No consistent associations existed between initial or future serum phosphate levels and stone recurrence, complications from stones, urinary values or other medical diagnoses made during followup. CONCLUSIONS: Serum phosphate does not appear to be an independent risk factor for urinary tract stone recurrence or complications, or a reliable early predictor of occult disease.     

Metaphylaxis of nephrolithiasis

The introduction of extracorporeal shockwave lithotripsy (ESWL), with its noninvasive removal of stones and considerable reduction in the morbidity of stone disease, has revolutionized the therapy of urolithiasis. Unfortunately the propensity for stone recurrence is not altered by removal of stones with ESWL and stone recurrence is still about 50%. Progress in medical treatment has shown how different therapies can prevent the stone recurrence, even though it is often difficult to predict which patient will go on to become a recurrent stone former. With the right evaluation, however, the cause of calculi formation can be treated in 97% of the patients. Primary prevention of urolithiasis includes general prophylaxis in a no-risk population that has never been affected by urinary tract stones, is without familial predisposition, metabolic or genetic alterations, or urinary tract abnormalities or infections and who live in a geographical area that is at risk. Secondary prevention or metaphylaxis of stone disease is aimed at the population at risk, that is patients already affected by the stone disease, with familial predisposition, with urinary tract alterations, with metabolic or genetic alterations (gout, bone or bowel diseases) and urinary infection.     

The efficacy of dietary intervention on urinary risk factors for stone formation in recurrent calcium oxalate stone patients

PURPOSE: Nutrition is suggested to be the major environmental risk factor in idiopathic calcium oxalate stone disease. The study was designed to evaluate the effect of dietary intervention on urinary risk factors for recurrence in calcium oxalate stone formers. MATERIALS AND METHODS: A total of 76 men and 31 women with idiopathic calcium oxalate stone disease collected 24-hour urine on their habitual, self-selected diets and after 7 days on a balanced standardized diet according to the recommendations for calcium oxalate stone formers. RESULTS: On the usual diet, a urine volume of less than 2.0 l per 24 hours was present in 57.9%, hypercalciuria in 25.2%, hypomagnesuria in 18.7%, hyperoxaluria in 14.0%, hyperuricosuria in 41.3% and hypocitraturia in 57.0% of patients. The frequency of metabolic abnormalities and the risk of calcium oxalate stone formation decreased significantly on the ingestion of the balanced diet, due to the significant increase in urinary volume, pH and citrate excretion and the significant decrease in urinary calcium and uric acid excretion. No change occurred in urinary oxalate and magnesium excretion. CONCLUSIONS: The evaluation of urinary risk profiles of the patients on their usual dietary habits revealed a high risk for calcium oxalate stone formation. A low fluid intake and an increased intake of protein and alcohol were identified as the most important dietary risk factors. The shift to a nutritionally balanced diet according to the recommendations for calcium oxalate stone formers significantly reduced the stone forming potential.     

Factors influencing the course of calcium oxalate stone disease.

OBJECTIVE: To assess the influence of previous stone formation, urine and stone composition on the further course of the disease in recurrent calcium stone formers without pharmacological treatment. METHOD: The course of the disease was analysed during a prospective follow-up period by means of Kaplan-Meier estimates. At the start of follow-up the patients were subgrouped with regard to their previous history of stone formation expressed as stone age index (SAI = 100 x number of stones/age), urine composition, stone composition, and sex. In 223 of the patients was it possible to calculate AP(CaOx) index(s), a standardized estimate of the ion-activity product of calcium oxalate. RESULTS: The 446 patients (329 men, 117 women) who were considered representative of an average population of recurrent calcium stone formers, had a 5-year recurrence risk of approximately 50%. Patients with an SAI <2 had a lower recurrence risk than those with an SAI >2 and a corresponding difference was recorded between patients with SAI levels <5 and >5. Furthermore, female patients had a lower risk of new stone formation than male patients. Patients with an AP(CaOx) index(s) of 1.5 or more had a significantly higher recurrence risk than those with a lower index, a difference that was most pronounced in female stone formers. A slightly higher risk of recurrent stone formation during the follow-up period could also be related to the presence of calcium phosphate in the stone, a high AP(CaP) index(s) (a standardized estimate of the ion-activity product of calcium phosphate) and a low concentration of citrate. CONCLUSION: AP(CaOx) index(s) and SAI were the most obvious predictors of the recurrence risk and these two variables, together with information on the sex distribution, might be useful for deriving an expected recurrence risk at a defined point of time in a group of recurrent stone formers. Such an estimate can be valuable for conclusions on the efficacy of different stone-preventive treatments when an appropriate control group is lacking.     

5-year-follow-up of patients with clinically insignificant residual fragments after extracorporeal shockwave lithotripsy

OBJECTIVES: After SWL treatment, many patients have residual fragments in the kidney or ureter. Fragments 2 stones episodes. These patients and their referring urologist received follow-up questionnaires which contained questions about stone clearance, late complications, auxillary measures and dietary or drug metaphylaxis. RESULTS: Most residual stone fragments were located within the lower calyx (17%) and the renal pyelon (14%). Stone analysis was available in 142 patients with CIRF and revealed calciumoxalate calculi in 93.6% of the cases. In 78.6%, CIRF cleared spontaneously within few weeks and did not recur within 5 years. However, residual stones led to stone recurrence and need of re-treatment in 21.4%. Renal pyelon (23%) and calices showed comparable growth of former CIRF (lower calices 26.5%, middle calices 27%, upper calices 26%). Only 48% of the patients with recurrent stone formation followed dietary metaphylaxis. However, a significant correlation between a general or specific metaphylaxis and stone growth of CIRF could not be demonstrated. CONCLUSIONS: Most of the CIRF after SWL pass spontaneously without any complications. But considering that one fifth of the patients developed new stones at the side of residual fragments, it is obvious that close follow-up is required. Although we could not demonstrate a relation between metaphylaxis and stone re-growth, it is conceivable that adequate metaphylaxis can reduce stone recurrences.     

Prospective study on the efficacy of a selective treatment and risk factors for relapse in recurrent calcium oxalate stone patients

OBJECTIVE: The present study was performed to examine the efficacy of a selective treatment according to the guidelines for the prevention of recurrence in calcium oxalate stone patients and to assess risk factors for stone recurrence. METHODS: To investigate the effect of specific diagnostic and therapeutic measures, 134 recurrent calcium oxalate stone formers participated in a prospective study for two years with regular follow-ups of at least every six months. Depending on the results of analysis of 24-hour urine, nutrition record and metabolic situation, selective recommendations were given concerning diet and medication. RESULTS: Throughout the follow-up period, 57 (43%) of the patients experienced relapses. In recurrence-free patients, the significant increase in urinary volume, as well as urinary pH, potassium and citrate excretion, three indexes of compliance with alkalization, resulted in a significant decrease in the calculated risk of calcium oxalate stone formation. In patients with recurrences during follow-up, the relative supersaturation with calcium oxalate increased significantly, mainly due to the significant rise in urinary oxalate excretion exceeding the significant increases in urinary volume, pH, potassium and citrate excretion. Multiple logistic regression analysis revealed previous ESWL treatment and a history of multiple stones as independent predictors of the risk for recurrence. CONCLUSIONS: The results indicate that compliance with drinking advice and alkalization therapy was highest among both, patients with and without recurrences, compared with all other therapeutic measures. The increase in oxalate excretion is identified as the major urinary risk factor for relapse during follow-up in recurrent calcium oxalate stone disease.     

Metabolic abnormalities associated with renal calculi in patients with horseshoe kidneys

BACKGROUND AND PURPOSE: Horseshoe kidneys are a complex anatomic variant of fused kidneys, with a 20% reported incidence of associated calculi. Anatomic causes such as high insertion of the ureter on the renal pelvis and obstruction of the ureteropelvic junction are thought to contribute to stone formation via impaired drainage, with urinary stasis, and an increased incidence of infection. In this multi-institutional study, we evaluated whether metabolic factors contributed to stone development in patients with horseshoe kidneys. PATIENTS AND METHODS: A retrospective review of 37 patients with horseshoe kidneys was performed to determine if these patients had metabolic derangements that might have contributed to calculus formation. Stone compositions as well as 24-hour urine collections were examined. Specific data points of interest were total urine volume; urine pH; urine concentrations of calcium, sodium, uric acid, oxalate, and citrate; and number of abnormalities per patient per 24-hour urine collection. These data were compared with those of a group of 13 patients with stones in caliceal diverticula as well as 24 age-, race-, and sex-matched controls with stones in anatomically normal kidneys. RESULTS: Eleven (9 men and 2 women) of the 37 patients (30%) with renal calculi in horseshoe kidneys had complete metabolic evaluations available for review. All patients were noted to have at least one abnormality, with an average of 2.68 abnormalities per 24-hour urine collection (range 1-4). One patient had primary hyperparathyroidism and underwent a parathyroidectomy. Low urine volumes were noted in eight patients on at least one of the two specimens (range 350-1640 mL/day). Hypercalciuria, hyperoxaluria, hyperuricosuria, and hypocitraturia were noted in seven, three, six, and six patients, respectively. No patients were found to have gouty diathesis or developed cystine stones. Comparative metabolic analyses of patients with renal calculi in caliceal diverticula or normal kidneys revealed a distinct profile in patients with horseshoe kidneys, with a higher incidence of hypocitraturia. CONCLUSIONS: All patients with renal calculi in horseshoe kidneys were noted to have metabolic abnormalities predisposing to stone formation. In this initial series of 11 patients, hypovolemia, hypercalcuria and hypocitraturia were most common metabolic defects. These findings suggest that metabolic derangements play a role in stone formation in patients with a horseshoe kidney. Patients with calculi in anatomically abnormal kidneys should be considered for a metabolic evaluation to identify their stone-forming risk factors in order to initiate preventative selective medical therapy and reduce the risk of recurrent calculus formation.