Cystine Stone Formers Have Impaired Health-Related Quality of Life Compared with Noncystine Stone Formers: A Case-Referent Study Piloting the Wisconsin Stone Quality of Life Questionnaire Among Patients with Cystine Stones

Recurrent Urinary Stone Formers: Imaging Assessment and Endoscopic Treatment Strategies: A Systematic Search and Review

Background/Objectives: Nephrolithiasis is a heterogeneous disease with a high prevalence and recurrence rate. Although there has been much progress regarding the surgical treatment of stones, a standardized follow-up, especially in recurrent stone formers (SFs), has yet to be decided. This fact leads to the overuse of computed tomography (CT) scans and many reoperations in patients, thus increasing their morbidity and the financial burden on the health systems. This review systematically searched the literature for original articles regarding imaging strategies and endoscopic treatment for patients with recurrent urolithiasis, aiming to identify optimal strategies to deal with these patients. Methods: We systematically searched the Medline database (accessed on 1 April 2024) for articles regarding imaging modalities and endoscopic treatment for patients with recurrent urinary tract lithiasis. Results: No specific follow-up or endoscopic treatment strategy exists for patients with recurrent urolithiasis. CT scan was the imaging modality most used in the studies, followed by X-ray, ultrasonography, and digital tomosynthesis. A transparent algorithm could not be identified. Percutaneous nephrolithotomy (PCNL), retrograde intrarenal surgery (RIRS), and ureteroscopy (URS) were used in the studies for endoscopic treatment. PCNL showed the best stone-free (SFr) rate and lowest hazard ratio (HR) for reoperation. RIRS showed superiority over extracorporeal shockwave lithotripsy for recurrent SFs, but fragments over 4 mm increased the recurrent rate. URS has an increased HR for reoperation for bilateral stones. Conclusions: The heterogeneity of urolithiasis leaves urologists without a standardized plan for recurrent SFs. Thus, each patient's follow-up should be planned individually and holistically. Pre-stenting is not to be avoided, especially in high-risk patients, and SFr status needs to be the aim. Finally, CT scans should not be generally overused but should be part of a patient's treatment plan. Prospective studies are required to define SFr status, the size of significant residual fragments, and the modalities of intervention and follow-up.

Postoperative Recovery of Quality-of-Life Following Ureteroscopy for Nephrolithiasis: The Impact on Pain Intensity and Interference and the Ability to Participate in Social Roles

OBJECTIVE

To prospectively capture patient-reported outcomes to assess the recovery profile of ureteroscopy (URS).

MATERIALS AND METHODS

Adults undergoing URS for renal/ureteral stones were eligible for inclusion (11/2020-8/2022). Patients prospectively completed PROMIS - Pain Intensity, - Pain Interference, and - Ability to participate in social roles and activities in-person preoperatively (POD 0) and via email on POD 1, 7, 14, and 30. Scores are reported as T-scores (normalized to U.S. population, mean=50) with a change of 5 (0.5 SD) considered clinically significant.

RESULTS

One hundred and seventy-eight participants enrolled at POD 0 (POD 1 =87, POD 7 =83, POD 14 =70, POD30 =67). There was a worsening of quality of life from day 0 to day 1 and day 0 to 7. All dimensions then improved with an increase in scores from day 0 to day 14 and day 0 to day 30. On multivariable analysis, the presence of a preoperative ureteral stent (OR 0.14) and use of semirigid URS (OR 0.33) were associated with a reduced odds for severe pain interference at day 1. The use of semirigid URS (OR 0.20) was associated with a reduced odds for severe worsening in the ability to participate in social roles at day 1.

CONCLUSION

Ability to participate in social roles declines immediately postoperatively, while pain intensity and interference sharply increase. There is a gradual improvement until POD 30. Findings suggest preoperative stents may influence postoperative recovery. Results offer meaningful insight to assist in counseling and setting expectation for patients postoperatively.

Ureteroscopic management in cystinuric patients: long-term results from a tertiary care referral center

OBJECTIVE

To evaluate long-term surgical and functional outcomes of cystinuric patients exclusively treated with Ureteroscopy (URS).

METHODS

Data from patients treated for cystine stones at a single academic center were retrospectively analyzed. The management protocol consisted of (i) treating symptomatic or > 7 mm stones, (ii) multi-staged URS for voluminous stones, (iii) referring patients to a dedicated nephrological clinic. The eGFR was calculated according to the MDRD formula. CKD category was assessed according to the NKF classification. Relevant CKD was defined as CKD category ≥ 3a. Descriptive statistics were used to analyze the cohort data.

RESULTS

Data from 46 cystinuric patients treated with 332 URS were available. Median age at diagnosis and at first URS in our center were 18 and 32 years, respectively. Median follow-up was 101 months. Median number of URS and recurrences per patient were 6 and 2, respectively. The median interval between the first and the last available creatinine level was 64 months. Median first and last eGFR were 72 and 74 mL/min, respectively. Overall, 83% of patients had stable or improved renal function within the study period. Ureteral stricture occurred in 3 (6.5%) patients.

CONCLUSIONS

Cystinuria requires intensive endoscopic management. Most patients treated with URS have stable or improved renal function within a long-term follow-up. CKD is a not neglectable event that potentially occurs at an early stage of life. Current findings should be considered for the surgical management of cystinuric patients.

The impact of kidney stone disease on quality of life in high-risk stone formers

OBJECTIVE

To assess the impact of kidney stone disease (KSD) and its treatment on the health-related quality of life (HRQOL) of high-risk stone formers with hyperparathyroidism, renal tubular acidosis, malabsorptive disease, and medullary sponge kidney.

PATIENTS AND METHODS

The Wisconsin Stone Quality of Life questionnaire was used to evaluate HRQOL in 3301 patients with a history of KSD from 16 institutions in North America between 2014 and 2020. Baseline characteristics and medical history were collected from patients, while active KSD was confirmed through radiological imaging. The high-risk group was compared to the remaining patients (control group) using the Wilcoxon rank-sum test.

RESULTS

Of 1499 patients with active KSD included in the study, the high-risk group included 120 patients. The high-risk group had significantly lower HRQOL scores compared to the control group (P < 0.01). In the multivariable analyses, medullary sponge kidney disease and renal tubular acidosis were independent predictors of poorer HRQOL, while alkali therapy was an independent predictor of better HRQOL (all P < 0.01).

CONCLUSIONS

Among patients with active KSD, high-risk stone formers had impaired HRQOL with medullary sponge kidney disease and renal tubular acidosis being independent predictors of poorer HRQOL. Clinicians should seek to identify these patients earlier as they would benefit from prompt treatment and prevention.

Measuring quality of life in patients with kidney stone disease: is it the future in endourology?

PURPOSE OF REVIEW

Kidney stone disease is recognized to negatively impact quality of life. This pertains to acute episodes, surgical interventions and even during asymptomatic periods. Over time there has been increased attention towards assessing this subjective parameter, including as a determinant of treatment success. Our aim was to evaluate the current status and emerging trends in this field.

RECENT FINDINGS

Patient groups most affected appear to be recurrent stone formers, cystine stone formers, women, younger populations, non-Caucasians and low-income populations. Several stone specific patient reported outcome measures are now available of which, WISQol has been implemented the most in clinical research studies. More invasive interventions such as percutaneous nephrolithotomy impede quality of life to greater extent than alternatives such as shockwave lithotripsy.

SUMMARY

There are certain patient groups who are more vulnerable to the negative impact of kidney stone disease on their quality of life. Urologists can improve patient care by recognizing these particular populations as well as by implemented patient reported outcome measures in their routine clinical practice and when performing research.

Translation and validation of the Italian version of the Wisconsin Stone Quality of Life Questionnaire (I-WISQOL) for assessing quality of life in patients with urolithiasis

BACKGROUND

Urolithiasis is a chronic condition, and it has been associated with a significant negative impact on patients' health-related quality of life (HRQOL). Several tools to assess patients' HRQOL have been validated in Italian, however disease-specific HRQOL instruments are still lacking. We aimed to develop and validate the Italian version of the WISQOL (I-WISQOL) in patients with urolithiasis.

METHODS

The Italian version of the WISQOL was developed in a multistep process involving primary translation, back-translation, and pilot testing among a group of patients (N.=10). Patients presenting with urolithiasis were prospectively recruited from the outpatient stone clinics and completed both questionnaire WISQOL and SF-36. Demographic information, as well as medical and surgical data, were obtained through an interview. Internal consistency of the I-WISQOL was obtained with Cronbach's α. Correlation of total scores of the I-WISQOL and SF36 was assessed to determine convergent validity using Spearman Rho. Correlations between clinical variables and results from the I-WISQOL were analyzed to descriptively assess the association of interest.

RESULTS

A total of 93 participants were evaluated and completed the Italian version of the I-WISQOL. The I-WISQOL demonstrated excellent internal consistency (Cronbach's α 0.95) and good convergent validity with the validated SF-36 (Spearman Rho r=0.70, P<0.001). Using ANOVA analysis, a significant decline in WISQOL Score was noted with the increasing number of renal colics (P=0.0543), ER visits (P=0.037), number of inpatient hospitalization (P=0.025). At multivariate analysis, worse WISQOL total score was predicted by a greater number of renal colic events (ß=-4.92 [-8.81-1.04], P=0.014) and by a greater number inpatient hospitalization (ß=-7.31 [-14.35 -0.26], P=0.042).

CONCLUSIONS

The I-WISQOL is an internally consistent and valid instrument to assess HRQOL in Italian-speaking patients with kidney stones. Its use in clinical practice should be implemented in order to tailor the management of each patient.

Cystine Stones: Developments in Minimally Invasive Surgery and Their Impact on Morbidity and Stone Clearance

Cystinuria is a rare genetic condition that is responsible for cystine stones. Besides stone recurrence, patients with cystine stones have reduced health-related quality of life, increased rates of chronic kidney disease and hypertension. Although lifestyle measures, medical therapy and close follow up are essential to reduce and monitor cystine stone recurrences, surgical intervention is frequently needed for most cystinuria patients. Shock wave lithotripsy, ureteroscopy, percutaneous nephrolithotomy and active surveillance all have a role, and technological advances in endourology are vital in achieving a stone-free status and to prevent recurrences. The complexity of managing cystine stones necessitates a multidisciplinary team discussion, patient involvement and an individualised approach in a specialist centre for optimum management. Thulium fibre laser and virtual reality may have an increasing role in the future of cystine stone management.

Cystinuria: an update on pathophysiology, genetics, and clinical management

Cystinuria is the most common genetic cause of nephrolithiasis in children. It is considered a heritable aminoaciduria as the genetic defect affects the reabsorption of cystine and three other amino acids (ornithine, lysine, and arginine) in the renal proximal tubule. Patients affected by this condition have elevated excretion of cystine in the urine, and because of this amino acid's low solubility at normal urine pH, patients tend to form cystine calculi. To date, two genes have been identified as disease-causative: SLC3A1 and SLC7A9, encoding for the two subunits of the heterodimeric transporter. The clinical features of this condition are solely related to nephrolithiasis. The diagnosis is usually made during infancy or adolescence, but cases of late diagnosis are common. The goal of therapy is to reduce excretion and increase the solubility of cystine, through both modifications of dietary habits and pharmacological treatment. However, therapeutic interventions are not always sufficient, and patients often have to undergo several surgical procedures during their lives to treat recurrent nephrolithiasis. The goal of this literature review is to synthesize the available evidence on diagnosis and management of patients affected by cystinuria in order to provide physicians with a practical tool that can be used in daily clinical practice. This review also aims to shed some light on new therapy directions with the aim of ameliorating kidney outcomes while improving adherence to treatment and quality of life of cystinuric patients.

Atomistic Assessment of Cystine Kidney Stone Behavior in a Mechanical Breakdown Process by Nanobiorobots through Classical Molecular Dynamics Simulations

Because cystine kidney stones are a more serious challenge for health-related quality of life than other types of kidney stones, the search for a new treatment for cystinuria is considered the main goal of this study. To achieve the defined goal, classical molecular dynamics simulations and quantum mechanics calculations were implemented in this study. Three nanodrills with different stiffnesses (i.e., silicon, silica, and silicon carbide) were selected to find the efficient nanodrill to break the kidney stones into smaller pieces. The related nanodrills under various forces from 20 to 100 eV/Å inclusive were exerted on the cystine kidney stones to determine the effect of the force magnitude on the rate of destruction. The exerted forces were modeled via a hypothetical spring force. To bring this investigation closer to reality, the urinary tract and the bulk of cystine kidney stones were modeled by simulation of the real blockage of the kidney stones. The obtained results from quantum mechanics calculations reveal the strong interaction (chemisorption) between the cystine stone components. Moreover, the molecular dynamics simulations show that an increase in force does not necessarily lead to more destruction of cystine kidney stones. The maximum rate of cystine kidney stone destruction occurs under forces of 80, 70, and 60 eV/Å for SiO₂, Si, and SiC nanodrills, which is about 19, 13, and 11%, respectively. In addition, the SiO₂ nanodrill has more crossing time and z-direction deformation than other nanodrills due to the attractive interaction between SiO₂ and stones, it shows less deformation during the process of kidney stone breaking because of repulsive interactions between the nanodrill and the kidney stone.

The impact of the number of lifetime stone events on quality of life: results from the North American Stone Quality of Life Consortium

To evaluate the impact of chronic stone recurrence on an individual's quality of life using the validated Wisconsin Stone Quality of Life (WISQOL) questionnaire. We collected cross-sectional data on patients with kidney stones from 14 institutions in North America. A stone event was defined as renal colic, stone-related procedure or emergency department visit. The regression analyses using general linear models and pairwise comparison determined the impact of the number of stone events on quality of life. The median number of stone events among the 2205 patients who completed the questionnaire was 3 (IQR 1-6). The mean total score was 107.4 ± 28.7 (max 140 points). The number of lifetime stone events was an independent predictor of lower quality of life (p < 0.001), specifically, score declined significantly beyond five events. Compared with patients who experienced a single stone event, there was a 0.4, 2.5, and 6.9 point decline in the adjusted mean WISQOL score after 2-5, 6-10, or > 10 events, respectively. The cumulative number of lifetime stone events was associated with a lower quality of life when more than five stone events were occurred. These findings underscore the importance of efforts to determine the underlying metabolic etiology of urolithiasis in the recurrent stone former, and the institution of a regimen to place their stone disease in remission.

Is Stone-free Status After Surgical Intervention for Kidney Stones Associated With Better Health-related Quality of Life? - A Multicenter Study From the North American Stone Quality of Life Consortium

OBJECTIVE

To compare the health-related quality of life (HRQOL) of patients with residual fragments after surgical intervention for kidney stones to patients that are stone-free using the disease-specific Wisconsin stone quality of life (WISQOL) questionnaire. Kidney stones contribute to impaired HRQOL, which is increasingly recognized as an important healthcare outcome measurement.

MATERIALS AND METHODS

With institutional review board approval, 313 adult patients who underwent surgical intervention for kidney stones at 4 sites completed a WISQOL questionnaire. We retrospectively collected surgical data including presence of residual fragments on post-operative imaging. We calculated standardized WISQOL total and domain scores (0-100), which included items related to social functioning (D1), emotional functioning (D2), stone-related impact (D3), and vitality (D4). Scores were compared between patients with residual fragments to those who were stone-free after surgical intervention.

RESULTS

Demographics did not differ between groups, overall mean age 54.6 ± 13.5 and 55.4% female. There was no significant difference in total WISQOL score for patients with residual fragments (n = 124) compared to patients that were stone-free (n = 189), 110.5 ± 27.8 vs 115.4 ± 23.6 respectively, (P = .12). Interestingly, patients with residual fragments who underwent secondary surgery were found to have significantly lower total WISQOL score (88.4 ± 30.1 vs 116.6 ± 25.0, P <.0001).

CONCLUSION

Stone-free status after surgical intervention is not associated with better HRQOL when compared with patients whose surgeries left residual fragments. Indeed, further surgical intervention on residual fragments to achieve stone-free status may actually result in worse HRQOL.

A Longitudinal Cohort Study of Pain Intensity and Interference After Ureteroscopy for Nephrolithiasis Without Postoperative Opioids

OBJECTIVE

To better understand the degree and time to resolution of pain in the postoperative period, we captured patient-reported pain intensity and interference prospectively in patients following ureteroscopy for nephrolithiasis.

MATERIALS AND METHODS

Adults undergoing ureteroscopy for renal/ureteral stones from 11/2018 to 1/2020 were eligible for inclusion. All received nonopioid postoperative pain control. Patients prospectively completed Patient-Reported Outcome Measurement Information System-Pain Intensity and Patient-Reported Outcome Measurement Information System-Pain Interference instruments preoperatively on postoperative day (POD) 0 and via email on POD 1, 7, and 14. Scores are reported as T-scores (normalized to US population, mean = 50) with changes of 5 (0.5 standard deviation) considered clinically significant.

RESULTS

A total of 126 patients completed enrollment at POD 0 (POD 1 = 74, POD 7 = 61, POD 14 = 47). Compared to US means, intensity and interference were significantly different at all time point comparisons (Wilcoxon rank test; all P <.001) except intensity at POD 7 (P = .09) and interference at POD 14 (P = .12). For both, there was a significant difference at each time comparison (repeated measures ANOVA; all P <.05). Increasing age was predictive of lower intensity (Confidence Interval (CI): -0.31 to -0.04; P = .012) and interference (CI: -0.36 to -0.06; P =.01) at POD 1. The presence of a postoperative stent was predictive of higher intensity (CI: 0.68-10.81; P = .03) and interference (CI: 0.61-12.96; P = .03) at POD 7. Increasing age remained a predictor of lower interference at POD 1 on multivariable analysis (CI: -0.46 to -0.01; P = .03).

CONCLUSION

Pain intensity and interference are elevated immediately, but intensity normalizes by POD 7, while interference remains elevated until POD 14. Age and indwelling ureteral stent influence both intensity and interference.

Cystinuria: clinical practice recommendation

Cystinuria (OMIM 220100) is an autosomal recessive hereditary disorder in which high urinary cystine excretion leads to the formation of cystine stones because of the low solubility of cystine at normal urinary pH. We developed clinical practice recommendation for diagnosis, surgical and medical treatment, and follow-up of patients with cystinuria. Elaboration of these clinical practice recommendations spanned from June 2018 to December 2019 with a consensus conference in January 2019. Selected topic areas were chosen by the co-chairs of the conference. Working groups focusing on specific topics were formed. Group members performed systematic literature review using MEDLINE, drafted the statements, and discussed them. They included geneticists, medical biochemists, pediatric and adult nephrologists, pediatric and adult urologists experts in cystinuria, and the Metabolic Nephropathy Joint Working Group of the European Reference Network for Rare Kidney Diseases (ERKNet) and eUROGEN members. Overall 20 statements were produced to provide guidance on diagnosis, genetic analysis, imaging techniques, surgical treatment (indication and modalities), conservative treatment (hydration, dietetic, alkalinization, and cystine-binding drugs), follow-up, self-monitoring, complications (renal failure and hypertension), and impact on quality of life. Because of the rarity of the disease and the poor level of evidence in the literature, these statements could not be graded. This clinical practice recommendation provides guidance on all aspects of the management of both adults and children with cystinuria, including diagnosis, surgery, and medical treatment.

A single center's experience in pediatric cystine stone disease management: what changed over time?

The authors aimed to evaluate the factors affecting clinical outcomes of cystine stone disease in children and to understand the change in disease management over time. Between January 1991 and September 2017, the demographic and clinical data of pediatric patients with documented cystine stone disease were retrospectively analyzed. Patients with at least 12-month follow-up were included. Disease management and clinical outcomes were compared between the first and second 35 patients managed during the study's time frame. A total of 70 patients were included. The female to male ratio was 30/40. The mean age and follow-up period was 29.8 ± 40.1 months and 106.5 ± 56 months, respectively. The mean initial procedure number to treat the first stone episode was 2.4 ± 1.6. Single stone and single affected site were significant predictors for stone clearance. Overall, patients underwent a mean of 5.5 procedure during their follow-up. Recurrence was detected in 71.4% (50/70) of patients. Residual fragments and non-compliance to medical treatment after the initial intervention were significant predictors for recurrence within shorter interval period. 31.4% (22/70) of patients had renal atrophy during follow-up. They were older at the initial diagnosis and had average urine pH lower than 7.5. The first 35 patients had more open procedures. Still, they had more recurrence rate and tend to have more renal atrophy. As a conclusion, cystine stone disease has a recurrent course in children. Stone and fragments entirely removed (SaFER) concept with all minimally invasive methods available and strict follow-up should be the basis for any management plan.

Tolvaptan treatment of cystine urolithiasis in a mouse model of cystinuria

INTRODUCTION

Cystinuria is an inherited disease characterized by increased urinary cystine excretion and recurrent cystine stones. Current treatment regimens have limited effectiveness in preventing stone recurrence and are often poorly tolerated. The aim of this study was to evaluate the effect of tolvaptan, a vasopressin receptor 2 (V2) antagonist, on cystine stone volume in mice with cystinuria.

MATERIALS AND METHODS

Tolvaptan (0.4 mg per mouse) or placebo was delivered by gavage daily for 30 days. Urinary amino acids and cystine stones were analyzed to assess drug efficacy in preventing L-cystine stone growth using several analytical methods. Data were entered into SPSS and analyzed by paired sample T test. p value < 0.05 was considered significant.

RESULTS

Compared with control group, the liquid intake and urine volume in tolvaptan-treated mice were significantly increased. The urinary cystine concentrations in group tolvaptan was lower than the baseline concentration before the experiment. After treatment, mice treated with tolvaptan had significantly delayed stone growth, exhibited lower overall stone volume accumulation, compared with control group. The increased stone volume of tolvaptan group was less than control group (8.00 ± 4.93 mm³ vs 27.90 ± 4.48 mm³, p < 0.001). The serum creatinine in the control group (11.75 ± 1.634 μmol/L) was higher than that in the tolvaptan group (7.625 ± 1.401 μmol/L) (p = 0.0759). In addition, tolvaptan significantly inhibited the formation and growth of stones in mice after cystolithotomy.

CONCLUSION

The present study indicated that tolvaptan's efficacy in preventing L-cystine stone growth through increased liquid intake and urine volume of cystinuric mice.

Assessment of health-related quality of life in patients with cystinuria on tiopronin therapy

Cystinuria comprises less than 1% of kidney stones and is associated with impaired health-related quality of life (HRQOL). Limited evidence is available regarding HRQOL of patients with cystinuria treated with tiopronin (Thiola^®). The objective of this study was to assess the HRQOL of patients with or without tiopronin treatment. For this cross-sectional survey, patients on tiopronin treatment were recruited through the “Thiola^® Total Care Hub,” a specialty pharmacy used to dispense tiopronin, and compared with patients not taking tiopronin (non-tiopronin group) who were identified from the Cystinuria Contact Registry at New York University School of Medicine. Consented patients responded to a survey that included questions about their experiences with kidney stones, the Wisconsin stone quality of life (WISQOL) (disease-specific) questionnaire, and the short form-36 version 2 (SF-36v2) (generic) HRQOL questionnaire. Statistical analyses included independent-sample t tests, one-way analysis of variance (ANOVA), and correlations. The survey was completed by 312 patients: 267 in the tiopronin group (144 male, 123 female; mean 49 years) and 45 in the non-tiopronin group (10 male, 35 female; mean 48 years). Both groups utilized pain medications similarly (24% overall). Patients on tiopronin had a significantly better HRQOL than patients not on tiopronin for all WISQOL domains (p < 0.001) and all but the physical functioning SF-36v2 domain (p < 0.001), where both groups approached the US normative mean, when controlling for the last stone event. Compared with patients in the non-tiopronin group, patients taking tiopronin reported better HRQOL on both the WISQOL and SF-36v2.

The effect of travel distance on health-related quality of life for patients with nephrolithiasis

INTRODUCTION

Urolithiasis causes a significant impact on health-related quality of life (HRQOL). Patients with kidney stones have high levels of stress and anxiety. Symptom resolution often requires treatment. Travel distance is a barrier to care but little is known about its effects on HRQOL. We hypothesize that increased distance to treatment site is associated with decreased HRQOL.

METHODS

Patients with a history of stones were enrolled at 11 tertiary centers as part of the QOL Stone Consortium of North America. HRQOL data were obtained using the Wisconsin Stone Quality of Life questionnaire (WISQOL). We calculated distance between patient and treatment site using national ZIP codes. We used linear models to evaluate the effect of distance on HRQOL, while also considering demographics data, stones/symptom status, and distance.

RESULTS

Of the 1676 enrolled patients, 52% were male, 86% non-Latino White, and the mean age was 53 years. Mean distance to treatment site was 63.3 km (range 0-3774), with 74% reporting current stones and 45% current symptoms. WISQOL score and distance were negatively correlated for patients reporting current stones and symptoms (p=0.0010). Linear modelling revealed decreased WISQOL scores for patients with symptoms as distance increased from treatment site (p=0.0001), with a 4.7-point decrease for every 100 km traveled.

CONCLUSIONS

Stone disease imposes significant burden on patients' HRQOL due to a variety of factors. Patients with active stone symptoms report worse HRQOL with increased distance to their treatment site. Possible etiologies include travel burden, increased disease burden, decreased healthcare use, and delays in care.

Cystinuria: genetic aspects, mouse models, and a new approach to therapy

Cystinuria, a genetic disorder of cystine transport, is characterized by excessive excretion of cystine in the urine and recurrent cystine stones in the kidneys and, to a lesser extent, in the bladder. Males generally are more severely affected than females. The disorder may lead to chronic kidney disease in many patients. The cystine transporter (b^0,+) is a heterodimer consisting of the rBAT (encoded by SLC3A1) and b^0,+AT (encoded by SLC7A9) subunits joined by a disulfide bridge. The molecular basis of cystinuria is known in great detail, and this information is now being used to define genotype-phenotype correlations. Current treatments for cystinuria include increased fluid intake to increase cystine solubility and the administration of thiol drugs for more severe cases. These drugs, however, have poor patient compliance due to adverse effects. Thus, there is a need to reduce or eliminate the risks associated with therapy for cystinuria. Four mouse models for cystinuria have been described and these models provide a resource for evaluating the safety and efficacy of new therapies for cystinuria. We are evaluating a new approach for the treatment of cystine stones based on the inhibition of cystine crystal growth by cystine analogs. Our ongoing studies indicate that cystine diamides are effective in preventing cystine stone formation in the Slc3a1 knockout mouse model for cystinuria. In addition to crystal growth, crystal aggregation is required for stone formation. Male and female mice with cystinuria have comparable levels of crystalluria, but very few female mice form stones. The identification of factors that inhibit cystine crystal aggregation in female mice may provide insight into the gender difference in disease severity in patients with cystinuria.

Conversion from Cystine to Noncystine Stones: Incidence and Associated Factors

PURPOSE

Patients with cystinuria are often treated with medical alkalization and shock wave lithotripsy, although each treatment is hypothesized to increase the risk of calcium phosphate stones. We performed a multicenter retrospective review to evaluate whether stones of another composition develop in patients with cystinuria and with what frequency.

MATERIALS AND METHODS

We retrospectively reviewed the records of a multi-institutional cohort of patients with cystinuria. We assessed medications, stone analyses, 24-hour urinalyses and types of procedures. We compared patients who formed only cystine stones vs those with noncystine stones.

RESULTS

We identified 125 patients from a total of 5 institutions who were followed a mean of 5.2 years (range 0 to 26). Stones with noncystine components were submitted by 37 patients (29.6%). Potassium citrate medication was not associated with a noncystine composition (p = 0.1877). Regarding surgical management 18 patients (13%) underwent at least 1 shock wave lithotripsy session (range 0 to 9) and 79 (63%) underwent percutaneous nephrolithotomy at least once (range 0 to 10). When stratified based on pure cystine vs converted stones, the average total number of shock wave lithotripsy and percutaneous nephrolithotomy procedures was higher in the group with cystine and subsequent noncystine stone compositions (0.94 vs 0.10, p <0.0001, and 1.7 vs 1.5, p = 0.0053, respectively). On logistic regression male gender (OR 3.1, p = 0.0280) and the number of shock wave lithotripsy sessions (OR 3.0, p = 0.0170) were associated with an increased likelihood of the development of stones with a noncystine composition.

CONCLUSIONS

Stones with noncystine components develop in more than 25% of patients with cystinuria, underscoring the importance of continued stone analysis. In this study prior shock wave lithotripsy was associated with conversion to a noncystine stone composition while urinary alkalization therapy was not associated.

Journey of a cystinuric patient with a long-term follow-up from a medical stone clinic: necessity to be SaFER (stone and fragments entirely removed)

There is a lack of studies looking at the longitudinal follow-up of patients with cystine stones. We wanted to assess the journey of cystinuric patients through our specialist metabolic stone clinic to improve the understanding of episodes, interventions and current outcomes in this patient cohort. After ethical approval, all patients who attended our metabolic stone clinic from 1994 to 2014 with at least one cystine stone episode were included in our study. Data were retrospectively analysed for patient demographics, stone episodes or intervention, clinical parameters and patient compliance. Over a period of 21 years, 16 patients with a median age of 15.5 years underwent a mean follow-up of 8.6 years (1–21 years). The mean number of surgical interventions was 3.1 (1–8/patient), but patients who were stone free after their first treatment had lower recurrences (p = 0.91) and lower number of interventions during their follow-up (2.7/patient, compared to those who were not stone free at 4/patient). During their follow-up period, patients with < 3 interventions had a significantly better renal function than those with ≥ 3 surgical interventions (p = 0.04). Additionally, linear regression analysis showed that eGFR was demonstrated to decline with increasing numbers of stone episodes (r² = 0.169). It was also noted that patients who began early medical management remained stone free during follow-up compared to those who had medical management after ≥ 2 stone episodes, of whom all had a recurrent episode. Our long-term longitudinal study of cystine stone formers highlights that patients who are stone free and receive early metabolic stone screening and medical management after their initial presentation have the lowest recurrence rates and tend to preserve their renal function. Hence, prompt referral for metabolic assessment, and the stone and fragments entirely removed (SaFER) principles are key to preventing stone episodes and improving long-term function.