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)

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.

Urological Guidelines for Kidney Stones: Overview and Comprehensive Update

BACKGROUND

Evidence-based guidelines are published by urological organisations for various conditions, including urolithiasis. In this paper, we provide guidance on the management of kidney stone disease (KSD) and compare the American Urological Association (AUA) and European Association of Urologists (EAU) guidelines.

METHODS

We evaluate and appraise the evidence and grade of recommendation provided by the AUA and EAU guidelines on urolithiasis (both surgical and medical management).

RESULTS

Both the AUA and EAU guidelines provide guidance on the type of imaging, treatment options, and medical therapies and advice on specific patient groups, such as in paediatrics and pregnancy. While the guidelines are generally aligned and based on evidence, some subtle differences exist in the recommendations, but both are generally unanimous for the majority of the principles of management.

CONCLUSIONS

We recommend that the guidelines should undergo regular updates based on recently published material, and while these guidelines provide a framework, treatment plans should still be personalised, respecting patient preferences, surgical expertise, and various other individual factors, to offer the best outcome for kidney stone patients.

Observation and comparison of gas formation during holmium:YAG laser lithotripsy of cystine, uric acid, and calcium oxalate stones: a chromatographic and electron microscopic analysis

The primary aim of the present in vitro study is to analyze the chemical content of the bubbles occurring during the fragmentation of cystine stones with both the high-power and low-power holmium:YAG (Ho:YAG) lasers. The secondary aim is to discuss their clinical importance. Three types of human renal calculi calcium oxalate monohydrate (COM), cystine, and uric acid were fragmented with both low-power and high-power Ho:YAG lasers in separate experimental setups at room temperature, during which time it was observed whether gas was produced. After laser lithotripsy, a cloudy white gas was obtained, after the fragmentation of cystine stones only. A qualitative gas content analysis was performed with a gas chromatography-mass spectrometry (GC-MS) device. The fragments in the aqueous cystine calculi setup were dried and taken to the laboratory to be examined by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) and X-ray diffraction analysis. No gas production was observed after fragmentation in the COM and uric acid stones. Free cystine, sulfur, thiophene, and hydrogen sulfide gas were produced by both low-power and high-power Ho:YAG laser lithotripsy of the cystine stones. In the SEM-EDX mapping analysis, a free cystine molecule containing 42.8% sulfur (S), 21% oxygen (O), 14.9% carbon (C), and 21% nitrogen (N) atoms was detected in the cystine stone experimental setup. The evidence obtained, which shows that hydrogen sulfide emerges in the gaseous environment during Ho:YAG laser fragmentation of cystine stones, indicates that caution is required to prevent the risk of in vivo production and toxicity.

Entering into 2.0 cystinuric management with a medical digital tool to monitor urine pH: a prospective, randomized study

BACKGROUND AND OBJECTIVES

Individuals with cystinuria can experiment recurrent lithiasis events due to the relative insolubility of cystine at physiological urine pH, resulting in renal function decline. The Lit-Control® pH Meter is a medical device that accurately allows urine pH self-monitoring. The main objective of this study was to compare the usability of the Lit-Control® pH Meter with the reactive strips for self-monitoring of urinary pH at home by patients with cystinuria, and their overall satisfaction with each tool.

PATIENTS AND METHODS

We included 28 patients (9 females and 19 males, age 19-76 years), who were randomly assigned to monitor their urine pH with reactive strips (n = 17) or the Lit-Control® pH-meter (n = 11).

RESULTS

After six months of use, the satisfaction with the two methods was similarly high, but the patients rated (0-10 scale) the pH meter better in terms of ease of learning (mean ± SD, 8.11 ± 0.60 vs. 7.06 ± 1.18; P = 0.038), ease to prepare (8.22 ± 0.67 vs. 7.25 ± 1.18; P = 0.034), and ease of use (8.22 ± 0.67 vs. 7.25 ± 1.39; P = 0.062). Overall, patients did not reach the alkalinization goals (pH between 7.0 and 8.0).

CONCLUSIONS

The Lit-Control® pH Meter demonstrated to be an easy-to-use device that can facilitate urinary pH control by cystinuric patients. A prospective study is warranted to assess the correlation between urine pH monitoring, a treat to target approach, and the recurrence of cystine stones.

Could twinkling artifact be a parameter in predicting the success of shock wave lithotripsy? A prospective study

Introduction

It is important to predict success before the treatment of urolithiasis. We aimed to predict the success of shock wave lithotripsy (SWL) by comparing twinkling artifact (TA) revealed through colour Doppler ultrasonography (CDUS) with stone density in non-contrast computed tomography (NCCT).

Material and methods

Eighty patients who underwent SWL between January 2021 and January 2022 were included in the study. Patients with stones of 5-20 mm in the renal pelvis and proximal ureter at NCCT were included. Patients' demographics, Hounsfield units (HU) in NCCT, and TA grades in CDUS were recorded. The stone-free rate after SWL, additional treatments, overall success rates, and the association between TA and success rates were evaluated.

Results

The mean age was 47.41 ±15.08 years. The mean BMI was 24.49 ±3.67 kg/m2. Twenty-three (28.8%) patients were TA grade 0, 33 (41.2%) patients were grade 1, and 24 (30%) were grade 2. The mean HU of TA grades 0, 1, and 2 of stones were 628 ±107, 864 ±123, and 1166 ±292, respectively. The HU increased along with the increase in the TA grade of the stone (p <0.01). The mean number of SWL sessions was 2.26 ±0.75 in patients with TA grade 0, and 2.92 ±0.40 in patients with TA grade 2. The mean number of SWL sessions increased along with the increase in TA grade (p <0.01). The stone-free rate decreased as the TA grade increased. Stone diameter and TA were the only predictors of SWL success.

Conclusions

We think that TA may be useful in predicting SWL success.

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.

Can cystinuria decrease the effectiveness of RIRS with high-power ho:yag laser in children? Outcomes from a tertiary endourology referral center

Cystinuria, which is the cause of cystine urolithiasis, accounts for 2-6% of all urinary stones in children, has a low prevalence with a high recurrence rate, making this metabolic disorder a therapeutic challenge in pediatric population. The aim of this work is evaluate the efficacy and safety of retrograde intra-renal surgery (RIRS) in pediatric patients with cystinuria and kidney stones smaller than 2 cm. Prospective study of 64 stones treated in 22 retrograde intra-renal surgeries (RIRS) in cystinuric pediatric patients with renal or proximal ureteral stones less than 2 cm. Average age of 9.5 years. The following data were analyzed: demographics, stone characteristics and surgical data with intra- and postoperative complications. Location of the stones was 68.7% in the calyces, 20.3% in the renal pelvis, and 9.3% in the ureteropelvic junction; 41% of cases had multiple locations. The average cystinuria level before the procedure was 825 mg/dL. The anatomy of 73% of the interventions increased the difficulty of flexible ureteroscopy and decreased stone free rates, because distorted renal anatomy was present: sclerosis of the pelvis or infundibulum, abnormal calyceal dilations, or excluded calyces. Intraoperative complications occurred in 18.2% of the procedures. Reno-vesical ultrasound was performed in all patients in the first postoperative month, with an SFR of 59%. Cystinuric patients are a challenge for pediatric urologists, decreasing the effectiveness of RIRS. However, it could be better treatment than SWL and with fewer complications than PCNL in the pediatric population with this disease.

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 Long-Term Follow-Up of Patients with Cystine Stones: A Single-Center Experience for 13 Years

Introduction: Cystine stone development is relatively uncommon among patients with urolithiasis, and most studies have reported only on small sample sizes and short follow-up periods. We evaluated clinical courses and treatment outcomes of patients with cystine stones with long-term follow-up at our center. Methods: We retrospectively analyzed 22 patients diagnosed with cystine stones between January 1989 and May 2019. Results: The median follow-up was 160 (range 6–340) months, and the median patient age at diagnosis was 46 (range 12–82) years. All patients underwent surgical interventions at the first visit (4 extracorporeal shockwave lithotripsy, 5 ureteroscopy, and 13 percutaneous nephrolithotripsy). The median number of stone events and surgical interventions per year was 0.45 (range 0–2.6) and 0.19 (range 0–1.3) after initial surgical intervention. The median time to stone events and surgical intervention was 2 years and 3.25 years, respectively. There was a significant difference in time to stone events and second surgical intervention when patients were divided at 50 years of age at diagnosis (p = 0.02, 0.04, respectively). Conclusions: Only age at a diagnosis under 50 was significantly associated with recurrent stone events and intervention. Adequate follow-up and treatment are needed to manage patients with cystine stones safely.

Extracorporeal Shockwave Lithotripsy for Cystine Stones in Children: An Observational, Retrospective, Single-Center Analysis

Purpose: Cystinuria is a genetic disorder characterized by a defective reabsorption of cystine and dibasic amino acids leading to development of urinary tract calculi from childhood onward. Cystine lithiasis is known to be resistant to fragmentation. The aim was to evaluate our long-term experience with extracorporeal shockwave lithotripsy (ESWL) used as first-line urological treatment to treat cystine stones in children. Methods: We retrospectively reviewed the charts of all children who underwent ESWL for cystine stone. We assessed the 3-month stone-free rate, according to age, younger (group 1) or older (group 2) than 2 years old. Results: Between 2003 and 2016, 15 patients with a median (IQR) age at first treatment of 48 (15-108) months underwent ESWL in monotherapy. Median age was, respectively, 15 and 108 months in each group. The median (IQR) stone burden was 2,620 (1,202-8,265) mm³ in group I and 4,588 (2,039-5,427) mm³ in group II (p = 0.96). Eleven patients had bilateral calculi. ESWL was repeated on average 2.4 times, with a maximum of 4 for patients of group I, and 4.8 times, with a maximum of 9 for group II (p > 0.05). ESWL in monotherapy was significantly more efficient to reach stone-free status for children under 2 years of age: 83% vs. 6.2% (p = 0.040). The median (IQR) follow-up of the study was 69 (42-111) months. Conclusion: ESWL appears as a valid urological option for the treatment of cystine stones, in young children. Even if cystine stones are known to be resistant to fragmentation, we report 83% of stone-free status at 3 months with ESWL used in monotherapy in children under 2 years old with cystinuria. In older children, the success rate is too low to recommend ESWL as a first line approach.

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.

Update on cystine stones: current and future concepts in treatment

Cystine stones are relatively uncommon compared with other stone compositions, constituting just 1% to 2% of adult urinary tract stone diseases, and accounting for up to 10% of pediatric stone diseases. Two responsible genes of cystinuria have been identified, the SLC3A1 and the SLC7A9. Cystinuria is diagnosed by family history, stone analysis, or by measurement of urine cystine excretion. Current treatments for cystinuria include increased fluid intake to increase cystine solubility by maintaining daily urine volume of greater than 3 Liter (L). Limiting sodium and protein intake can decrease cystine excretion. When conservative therapy fails, then pharmacologic therapy may be effective. Alkaline urine pH in the 7.0-7.5 range will reduce cystine solubility and can be achieved by the addition of alkali therapy. If these measures fail, cystine-binding thiol drugs such as tiopronin and D-penicillamine are considered. These compounds bind cysteine and prevent the formation of less soluble cystine. These drugs, however, have poor patient compliance due to adverse effects. Captopril can be useful in the treatment of cystine stones but the drug has not been tested in rigorous clinical trials. Novel potential therapies such as alpha-lipoic acid and crystal growth inhibitors (L-cystine dimethyl ester (L-CDME) and L-cystine methyl ester (L-CME)) were developed and tested in animals. Those therapies showed promising results. Compliance with treatment was associated with a lower rate of cystine stone formation.

Outcomes and Long-term Follow-up of Patients with Cystine Stones: a Systematic Review

PURPOSE OF REVIEW

Cystine stone patients can be difficult to manage with frequent recurrences. We performed a systematic review with a view to assessing interventions, compliance and their long-term outcomes.

RECENT FINDINGS

Ten retrospective observational studies (253 patients) assessed the outcomes and long-term follow-up of cystine stone patients. The mean length of follow-up was 9.6 years (range 3.5-21.8 years). The overall mean number of surgical procedures/patient was 5.7 (range 2-9.8/patient) with the overall mean number of surgical procedures/patient/year at 0.59 (range 0.22-1.32/patient/year). While open surgery has decreased over the last decade and PCNL has been stable, there seems to be a rise of RIRS during this period. Patients with cystine stones need periodic interventions for stone recurrences despite medical management, with limited data showing the impact on renal function. While the management is individualised, wide variability exists with often poor and incomplete patient data.

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.