Stone Episodes Research Articles

Urinary Metabolic Evaluations in Solitary and Recurrent Stone Forming Children

We have previously reported a high rate of urinary metabolic abnormalities in stone forming children compared to normal controls. At our institution a 24-hour urine evaluation is initiated after the first stone episode in children, to measure stone risk indices. The purpose of this study was to determine which children are at the greatest risk for recurrent stone formation. A retrospective cohort study was performed to assess urinary metabolic profiles in children with urolithiasis. In all patients 24-hour urine collections were performed and evaluated elsewhere. Urine chemistry assessments such as calcium and citrate were adjusted for creatinine and weight. Calcium oxalate supersaturation was measured. Patients were stratified as solitary or recurrent stone formers based on review of the medical record. Univariate analysis between means was performed with a 2-tailed t test. A total of 148 samples from 88 solitary stone formers and 84 samples from 51 recurrent stone formers were evaluated. Age and gender were well matched between the 2 groups. Timed urinary calcium levels referenced to creatinine and citrate were significantly higher in patients with recurrent stones. Supersaturation levels of calcium oxalate were higher in recurrent stone formers but did not reach statistical significance. There are significant differences in 24-hour urinary calcium levels between solitary and recurrent calcium stone forming children. A patient with increased urinary calcium indices on a 24-hour specimen may benefit from more aggressive initial dietary and pharmacological treatment to prevent stone recurrence.

Determinants of Quality of Life for Patients With Kidney Stones

We evaluated various factors relating to quality of life in a population of patients with stones. A total of 155 patients seen at our urology clinic for stones between January and May 2007 were prospectively questioned regarding stone history and were administered the SF-36 questionnaire to assess quality of life. Age, body mass index, American Society of Anesthesiologists score, number of stone episodes, interval from the last stone episode, number of surgical procedures for stones and associated complications, missed days of work and long-term medical treatment were elicited from the patients. Individual SF-36 domains and composite scores were compared to those of the American general population. Univariate and multivariate regression analyses were performed to assess the impact of all covariates on quality of life scores. Patients with stones scored lower than the average American population in 5 of the 8 domains of the SF-36 as well as in the physical composite score. Multivariate regression modeling showed that increasing body mass index and age were the strongest predictors of decreased physical well-being. The number of stone episodes did not influence SF-36 scores, although the number of surgical procedures impacted physical and mental components. The number of ureteroscopy procedures and stent placements primarily impacted mental well-being. Medical therapy, particularly the use of potassium citrate, was associated with more favorable quality of life. Various factors impact quality of life in patients with urolithiasis but the most important are body mass index, age and the number of surgical procedures. Prospective longitudinal studies may further elucidate the determinants of quality of life and they might be used to optimize patient care.

What Radiation Exposure Can a Patient Expect During a Single Stone Episode?

There is increasing concern about the risks of radiation exposure with the advent of new, more complex imaging modalities. For example, computed tomography (CT), with its obvious advantages, is being more commonly used in the investigation of acute flank pain. The likely radiation exposure a patient can expect during a single complete urinary stone episode was studied. The hospital records of 60 consecutive unselected patients who had become or were rendered stone-free were studied. The effective radiation doses in milliSieverts (mSV) associated with diagnostic imaging modalities such as intravenous urogram studies and CT scans were calculated for St. George's Hospital. By combining these with the published effective doses for interventional examinations, the total effective dose over an entire stone episode was derived. There were a total of 60 patients with 68 stones (15 renal, 9 in the upper, 12 in the middle, and 32 in the lower ureter), with a median stone burden of 4 mm. Thirty-two patients had procedures performed, including extracorporeal shockwave lithotripsy SWL. Total effective doses ranged from 1.18 to 37.66 mSv (median 5.3 mSv; 95% CI of the median 4.13, 7.61). Renal and proximal ureteral stones resulted in the highest radiation exposures. In this study the median radiation dose per stone episode was calculated at 5.3 mSv, with higher doses in those with renal stones and those who required CT scans and other interventions. Monitoring and reduction of radiation exposure is advised for all patients presenting with urolithiasis.

Management of Cystinuric Patients: An Observational, Retrospective, Single-Centre Analysis

Objective: A critical appraisal of the management of patients with cystine stones treated in our unit in the past 6 years and to analyze the outcome of multimodality therapies. Study Design: An observational, single-centre retrospective study. Methods: We reviewed the records of all patients with stones referred to our centre over a 6-year period from 1998 to 2005. Data recorded included demographic details, medical therapies received/prescribed, compliance with medical therapies, mode of treatment, stone clearance and any recurrence during this period of study. Results: A total of 30 cystinuric patients were treated in our institution over the period of 6 years from 1998 to early 2005. Of these 16 were males and 14 females with an average age at last follow-up of 39 years (range 15–70). Two patients were successfully managed medically. The remaining patients (n = 28) underwent a total of 237 procedures (pre- and postreferral to our unit), with an average of 7.9 procedures per patient for 126 stone episodes (4.2 episodes/patient). The modes of treatment included extracorporeal shockwave lithotripsy (n = 143), ureterorenoscopy and intracorporeal lithotripsy (n = 50), percutaneous nephrolithotomy (n = 28) and open procedures (n = 16). Two patients needed open surgery at our unit. Prior to referral to our dedicated unit, patients had received treatment with extracorporeal shockwave lithotripsy (multiple sessions), ureteroscopy (n = 14), percutaneous nephrolithotomy (n = 4) and open stone removal (n = 14). Most of the stones at our unit were managed using minimally invasive therapies. Conclusion: Compliance of cystinuric patients with medical treatment is often poor and patients experience recurrent stone episodes requiring multiple interventions. Modern management of cystine calculi should be with staged minimally invasive procedures to avoid the complications of multiple open procedures wherever possible along with appropriate medical prophylaxis.

Fructose intake as a risk factor for kidney stone disease

Taylor and Curhan report that consumption of fructose is independently associated with an increased risk of incident kidney stones. What could be the mechanisms underlying the relation between fructose intake and stone risk? And how should we incorporate this finding into the dietary advice that we give to our patients to prevent kidney stone formation?

Multiple giant diverticula of the foregut causing upper gastrointestinal obstruction

Small bowel diverticulosis represents an uncommon disorder (except for Meckel diverticulum) often misdiagnosed since it causes non-specific gastrointestinal symptoms. Most of times the diagnosis is carried out in case of related complications, such as diverticulitis, hemorrhage, perforation or obstruction. Intestinal obstruction can be caused by inflammatory stenosis due to repeated episodes of diverticulitis, volvulus, intussusception or jejunal stones. Herein we report a case of multiple jejunal diverticula causing chronic gastrointestinal obstruction.

Impact of Obesity in Patients With Urolithiasis and its Prognostic Usefulness in Stone Recurrence

Recent studies have suggested an increased prevalence of urolithiasis and recurrence associated with obesity. We assessed the influence of obesity on stone risk factors as well as on stone recurrence. A database of patient history, body mass index, and serum and urine chemistry was analyzed for 704 consecutive stone formers (467 first time stone formers and 247 recurrent stone formers). Obesity was defined as body mass index greater than 25 kg/m(2). The effect of obesity on stone risk factors and recurrence were stratified according to stone episodes. Of these, 163 (23.2%) patients who had been followed for more than 36 months (median 54, range 5 to 148) were included in recurrence analysis. Obesity was significantly associated with stone episodes (p = 0.043). Obese stone formers excreted increased amounts of sodium, calcium, uric acid and citrate, while the urinary pH in a 24-hour urine sample was decreased compared to nonobese stone formers (p <0.05, respectively). Stone analysis revealed that uric acid stone was significantly more commonly found in the obese patients (p = 0.046). Multivariate Cox regression model stratified by stone episodes revealed that obesity (HR 2.572, 95% CI 1.376-4.807, p = 0.003) was the only strong predictor of stone recurrence in first time stone formers. No association between obesity and stone recurrence was detected in recurrent stone formers. Kaplan-Meier curves showed identical results. This study reveals that obesity is associated with metabolic alterations and urinary stone recurrence. Weight control may be considered one of the preventive modalities against recurrent stone formation, especially in first time stone formers.

Wie vermeidet man kalziumhaltige Nierensteine?

Calcium containing renal stones represent a common medical problem and show a high rate of recurrence. Therefore, besides the treatment of acute stone episodes, also the prevention of new stone episodes is of crucial importance in the medical care of stone formers. To avoid stone recurrences, medical as well as dietary measures should be established based on the results of a thorough evaluation and the elaboration of an individual risk profile. This review article describes and discusses the currently established treatment options for the prophylaxis of calcium-containing renal stones.

AUTHOR INDEX

To investigate the effect of the vitamin D receptor (VDR) FokI polymorphism on the clinical presentation of calcium urolithiasis, as a FokI polymorphism in the VDR gene was recently reported to be associated with calcium metabolism disorders. In all, 235 patients with calcium urolithiasis and 231 age- and sex-matched healthy controls were recruited from Kaohsiung Medical University Hospital between June 2003 and February 2005. Clinical information on the age at first onset, stone episodes, stone severity and presence of family history were collected from patients with stones. Any VDR FokI polymorphism was detected using polymerase chain reaction-based restriction analysis. The frequency of VDR FokI genotypes between the patients and the healthy controls was not significantly different. However, among patients, those with the FF genotype had a significantly higher risk of having more stone episodes (adjusted odds ratio 2.15, 95% confidence interval 1.02-4.54, P = 0.044) and were younger at the first onset (3.23, 1.08-9.63, P = 0.036) than those with the ff genotype. The VDR FokI polymorphism might be important in the clinical presentation of patients with calcium urolithiasis, especially for the frequency of stone episodes and age at first onset, although it is not associated with the formation of stones.

Predicting Factors for Recurrence in First-time Stone Formers

Purpose: The purpose of the present study was to determine the risk factors for predicting the recurrence in first-time urinary stone formers. Materials and Methods: A total of 121 patients, who presented at our hospital with first-time urinary stone episodes, between 1996 and 2005, and followed up for at least 3 years, were retrospectively evaluated. Of these, 65 patients (41 males, 24 females) recurred (R group) and 56 (38 males, 18 females) not (NR group) during the follow-up period. The blood chemistry and urinary analytes values, as well as the clinical characteristics between the NR and R groups were compared by gender. p-values less than 0.05 were used to indicate statistical significance. Results: There were no differences in the clinical characteristics between the NR and R groups. A comparison of the blood chemistry showed differences in the phosphate and calcium in men and women (p=0.047 and 0.034), respectively. Greater urinary excretion of phosphates were found in the R group than in the NR group (p=0.018), but was more prominent in men (p=0.006). No significant differences were found between the two groups with regard to metabolic abnormalities. A multivariate analysis revealed that urinary phosphates excretion was the sole predictor for stone recurrence (Exp β=8.347, p=0.033). Conclusions: Our results suggested that the increased excretion of urinary phosphates was a significant risk factor for stone recurrence, which might be useful as a prognostic marker. (Korean J Urol 2007;48:176-182)

Urinary Metabolic Evaluations in Normal and Stone Forming Children

Urinary stone disease is relatively rare in children and urinary metabolic evaluations have been the standard in our practice. We have previously reported a high rate of urinary metabolic abnormalities in stone forming children. We compared urinary chemistry values in normal and stone forming children. A prospective study was performed to assess urinary metabolic profiles in children with no history or a family history of urinary calculi. The 24-hour urine collections were performed and evaluated at an outside central laboratory. Urine chemistry studies were adjusted for creatinine. The data were compared to those on a historical cohort of calcium stone forming children. A total of 58 samples from normal children and 142 from stone forming children were evaluated. Mean age was 10 years in normal children and 12 years in stone forming children. of the normal and stone forming children 45% and 51%, respectively, were female. Supersaturation levels of calcium oxalate as well as calcium to creatinine levels were significantly higher in children with stones. No data confounding by age or sex was identified by stratification. There are significant differences in urinary metabolic evaluations between normal and stone forming children. This may allow more precise treatment to prevent recurrent stone episodes. We continue to perform metabolic evaluations in all children with documented urolithiasis.

Is prevention of stone recurrence financially worthwhile?

This review shows that the cost of relying solely on minimally-invasive urological procedures for removing stones when patients return with recurrent stones is considerable and is significantly greater that that incurred by screening already proven recurrent stone-formers to identify the risk factors that are causing their stones and then instituting prophylactic measures to prevent stone recurrence. In the UK, at 1998 prices (when the original survey was carried out) for every stone episode prevented, there is a potential saving of almost 2,000 pound to the local Health Authority concerned. In spite of this, many Health Authorities have taken the liberty to discontinue comprehensive stone screening within the past 20 years under the mistaken supposition that minimally-invasive techniques for removing stones have "solved the stone problem". At UCLH in London where such a comprehensive scheme has been in place for the past 8 years, savings of up to 250,000 pound per year can be made by identifying the particular lifestyle as well as the epidemiological, metabolic and nutritional risk factors involved in a given patient and then instituting appropriate measures to prevent further stones.

Epidemiological trends in urolithiasis: impact on our health care systems

The progressive increase of the social cost for treating urolithiasis could be related to an increased incidence of the disease and/or to an increase of costs for diagnosing and treating renal stones. In the course of the last century, the incidence of renal stones has progressively increased in Europe, North America, and other industrialised countries. This has been explained in terms of changing social conditions and the consequent changes in eating habits. In contrast, renal stones were less frequent than in developing countries of the world but in the last 20 years investigators began to report high incidences of upper urinary stone disease also from some areas of the Third World concurring with the changing of economic and social conditions. Each stone episode involves the costs for emergency visits, diagnostic work up, and medical or surgical treatment. Furthermore, we have to consider the costs of follow-up visits and the costs of testing and drugs for stone prevention. In adjunct of direct costs for diagnosis and treatment, we should also take into account the indirect individual and social cost of workdays lost. Finally, we should estimate the costs of complications and outcomes of treatment with particular attention to the costs of chronic renal failure secondary to stone disease. The strategy of treatment of each stone centre involves different costs for the treatment of each single stone episode. On the other hand the choice of treatment can be driven by National Health Systems and insurance companies by their policy of reimbursement for different procedures. The trends of renal stone incidence will have different impact on health care systems in different countries. In Europe and North America, the peak of incidence has been probably reached but the increase of costs for diagnosing and treating each single stone episode will still increase the social cost for managing stone disease. For this reason the actual objective should be to optimise protocols avoiding redundant or expensive diagnostic procedures or inappropriate treatments. In developing countries, the incidence of stone disease is still increasing and it could reach peaks even higher as a consequence of hot climate in some geographical areas. In those countries the demand for treatment of symptomatic stones could dramatically increase involving a huge financial outlay.

Structural Basis for Activation of the Thiamin Diphosphate-dependent Enzyme Oxalyl-CoA Decarboxylase by Adenosine Diphosphate

Oxalyl-coenzyme A decarboxylase is a thiamin diphosphate-dependent enzyme that plays an important role in the catabolism of the highly toxic compound oxalate. We have determined the crystal structure of the enzyme from Oxalobacter formigenes from a hemihedrally twinned crystal to 1.73 A resolution and characterized the steady-state kinetic behavior of the decarboxylase. The monomer of the tetrameric enzyme consists of three alpha/beta-type domains, commonly seen in this class of enzymes, and the thiamin diphosphate-binding site is located at the expected subunit-subunit interface between two of the domains with the cofactor bound in the conserved V-conformation. Although oxalyl-CoA decarboxylase is structurally homologous to acetohydroxyacid synthase, a molecule of ADP is bound in a region that is cognate to the FAD-binding site observed in acetohydroxyacid synthase and presumably fulfils a similar role in stabilizing the protein structure. This difference between the two enzymes may have physiological importance since oxalyl-CoA decarboxylation is an essential step in ATP generation in O. formigenes, and the decarboxylase activity is stimulated by exogenous ADP. Despite the significant degree of structural conservation between the two homologous enzymes and the similarity in catalytic mechanism to other thiamin diphosphate-dependent enzymes, the active site residues of oxalyl-CoA decarboxylase are unique. A suggestion for the reaction mechanism of the enzyme is presented.

The etiology of urolithiasis in HIV infected patients.

It is commonly thought that urinary lithiasis in HIV infected patients on protease inhibitor therapy is composed primarily of the protease inhibitor itself. Since many HIV infected patients on protease inhibitors presenting to our institution had nonprotease inhibitor stones, we investigated potential underlying metabolic abnormalities that may account for the lithogenesis. We retrospectively reviewed all HIV infected patients on protease inhibitors with renal colic and evidence of nephrolithiasis who presented to our institution between June 1996 and January 2001. Patients were evaluated for stone composition and metabolic abnormalities of blood and urine when possible. A total of 24 patients were identified, and all were or had been on protease inhibitors (indinavir 14, ritonavir 3, nelfnavir 2, unspecified 5). Of the 14 patients on indinavir only 4 (28.6%) had indinavir containing stones. The remaining stones in this group and in those not on indinavir contained various amounts of calcium oxalate monohydrate and dihydrate, ammonium acid urate and uric acid. Of 10 patients who underwent 24-hour urine collection for metabolic evaluation 8 (80%) had abnormalities, including hypocitraturia in 5, hyperoxaluria in 4, hypomagnesuria in 4, hypercalciuria in 3, increased supersaturation of calcium oxalate in 3 and hyperuricosuria in 2. Abnormalities in the levels of urinary phosphate and sodium were also observed. HIV infected patients form many types of stones, which probably are attributable to underlying metabolic abnormalities rather than the use of protease inhibitors. A complete metabolic evaluation is warranted in these patients, as a means of guiding treatment to prevent future stone episodes, while avoiding the need to alter antiretroviral regimens.

High incidence of kidney stones in Icelandic children

All children less than 18 years of age who were diagnosed with a first episode of kidney stones at pediatric referral centers in Iceland during the years 1995-2000 were studied retrospectively. The diagnosis was based on clinical features and results of imaging studies. Patients were invited for evaluation at the end of the study period. Twenty-six patients (15 females, 11 males), median age 9.4 (range 0.2-14.9) years, experienced 34 episodes of kidney stones. The annual incidence was 5.6 and 6.3 per 100,000 children less than 18 and 16 years of age, respectively. Abdominal pain was the most common symptom (N=17; 69%) and urinalysis revealed hematuria in 21 patients (80.8%), sterile pyuria in 17 (65%), and 2,8-dihydroxyadeninuria in two. Six patients (23%) had positive urine cultures at the time of diagnosis and five (20%) had urinary tract anomalies. Family history of kidney stones was positive in one third of patients. Metabolic risk factors for stone formation were identified in 22 of 23 patients (96%) who underwent evaluation. Hypercalciuria, the most common metabolic risk factor, was identified in 18 patients (78%). Stones passed spontaneously in nine patients (35%) and six patients had recurrent stone episodes. The incidence of kidney stones in Icelandic children is high compared with other Western populations, affecting females more than males. Underlying metabolic risk factors were identified in most patients.

High kidney stone risk in men working in steel industry at hot temperatures

Objectives To study the incidence of urinary lithiasis and metabolic alterations among male employees from a steel industry who were exposed to high temperatures in the work environment. Methods A retrospective cross-sectional study was performed and consisted of two stages. First, the incidence of urolithiasis among the industry’s 10,326 employees was assessed. These employees were divided into two group’s: group 1 (n = 1289) consisted of the hot-area workers (temperature greater than 45°C) and group 2 (n = 9037) consisted of those working in areas at room temperature. In the second stage, 59 workers without urolithiasis who underwent a metabolic evaluation were divided into two group’s: group 3 (n = 34) consisted of hot-area workers and group 4 (n = 25) consisted of those working in areas at room temperature. Evaluations were made of calcium, creatinine, and uric acid in serum; in the 24-hour urine samples, we assessed the volume, calcium, uric acid, citrate, and oxalate. Results Of the 10,326 workers, 181 (1.75%) had presented with at least one episode of urinary stones. Of these, 103 were among the hot-area workers (8.0%) and 78 among the room-temperature workers (0.9%; P <0.001). The metabolic evaluation showed that the hot-area group (group 3), compared with the room-temperature group (group 4), presented more frequently with hypocitraturia (55.8% versus 28%, P = 0.03) and low urinary volume (79.4% versus 48%, P = 0.01). Conclusions Workers exposed to high temperatures presented with a ninefold risk of lithiasis. Hypocitraturia and low urine volumes were the metabolic alterations observed.

TIME TO RECURRENT STONE FORMATION IN PATIENTS WITH BLADDER OR CONTINENT RESERVOIR RECONSTRUCTION: FRAGMENTATION VERSUS INTACT EXTRACTION

Stone formation following bladder or continent reservoir reconstruction in children is a major source of long-term morbidity. We determine whether the method of stone removal (fragmentation or intact extraction) affected the time to stone recurrence in children after bladder reconstruction. Medical records from 1993 to 2003 were examined to identify patients with urinary reconstruction subsequently treated for bladder calculi at our institution. Retrospective review of the medical records was performed to determine the type of urinary reconstruction, time to stone recurrence, method of stone removal and length of followup. Kaplan-Meier analysis was performed with each stone episode considered as an individual event. Time to recurrence was measured in months from stone removal to identification of recurrent stones. A total of 60 patients with bladder or continent reservoir reconstructions had undergone 103 stone removal procedures (range 1 to 8 procedures per patient). Patients were rendered stone-free after each procedure. Stones recurred following 42.4% of intact and 43.9% of fragmented extractions at a mean of 27.0 (SD 31.3) and 27.6 (SD 21.8) months, respectively. Kaplan-Meier survival analysis curves for intact and fragmented extractions were not statistically different. Time to stone recurrence in patients with bladder or continent reservoir reconstruction is not altered by the method of stone removal (fragmented versus intact extraction). Since recurrence remains a frequent problem in children after bladder augmentation and/or reconstruction, use of the least invasive modality should be the initial management recommendation.

The role of overweight and obesity in calcium oxalate stone formation.

The aim of the study was to assess the influence of overweight and obesity on the risk of calcium oxalate stone formation. BMI, 24-hour urine, and serum parameters were evaluated in idiopathic calcium oxalate stone formers (363 men and 164 women) without medical or dietetic pretreatment. Overweight and obesity were present in 59.2% of the men and in 43.9% of the women in the study population. Multiple linear regression analysis revealed a significant positive relationship between BMI and urinary uric acid, sodium, ammonium, and phosphate excretion and an inverse correlation between BMI and urinary pH in both men and women, whereas BMI was associated with urinary oxalate excretion only among women and with urinary calcium excretion only among men. Serum uric acid and creatinine concentrations were correlated with BMI in both genders. Because no association was established between BMI and urinary volume, magnesium, and citrate excretion, inhibitors of calcium oxalate stone formation, the risk of stone formation increased significantly with increasing BMI among both men and women with urolithiasis (p = 0.015). The risk of calcium oxalate stone formation, median number of stone episodes, and frequency of diet-related diseases were highest in overweight and obese men. Overweight and obesity are strongly associated with an elevated risk of stone formation in both genders due to an increased urinary excretion of promoters but not inhibitors of calcium oxalate stone formation. Overweight and obese men are more prone to stone formation than overweight women.

Conversion of Calcium Oxalate to Calcium Phosphate With Recurrent Stone Episodes

We have extended our previous observation that the percent occurrence of calcium oxalate stones decreased while that of calcium phosphate stones increased with each new stone event. The National VA Crystal Identification Center has analyzed veteran patient urinary tract stones from VA hospitals throughout the United States since 1983. We reviewed the composition of 33,198 stones with emphasis on the changes in composition. More than 11,786 stones came from 5,088 recurrent stone formers. Stones were analyzed using high resolution x-ray powder diffraction and Fourier transform infrared spectroscopic techniques. When the stones were investigated as a function of time, it was determined that there was greater variability when samples were more than 30 days apart. The percent occurrence of whewellite, weddelite, apatite, brushite and uric acid in stones increased between 1.0% and 5.9% since our previous study. The percent occurrence of struvite decreased by 2.6%. The percent of calcium oxalate stones decreased while that of calcium phosphate stones increased with each new event. However, the total percent occurrence of all calcium containing stones did not significantly change with recurrent stone events. Our study suggests a strong trend for the conversion of stone disease from calcium oxalate to calcium phosphate containing stones, which could influence the progression and severity of disease.