Extracorporeal shock wave lithotripsy for treatment of ureterolithiasis in patients with cystinuria

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: 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.

Imaging and surgical utilization for pediatric cystinuria patients: A single-institution cohort study

OBJECTIVE

Although cystinuria is rare, its clinical manifestations are life-long. Little is known about healthcare utilization in this population.

STUDY DESIGN

Through billing records and chart review, we identified pediatric patients with cystinuria treated at our institution. Variables included demographics, gender, race, comorbidities, location of presentation, presenting symptoms, initial laboratory data, and stone characteristics. Outcomes included the number and type of imaging tests and procedures performed. Descriptive statistics were performed. Median annual frequencies of procedures and imaging were calculated.

RESULTS

Twenty-three patients who presented between 1995 and 2011 were identified. The median age at presentation was 12 years, 48% of our patients were male, and 91% were Caucasian. Median follow-up was 4.6 years. Over half were diagnosed in clinic (13/23), while 30% (7/23) presented to the ED. Pain was the most common presenting symptom (13/23), followed by nausea/vomiting (6/23), gross hematuria (5/23), and fevers (5/23). Only one patient presented with acute renal failure. Five patients were discovered by sibling screening. The median number of stones at presentation was two and median size of the largest stone was 9 mm, with three staghorn calculi. During follow-up, a total of 110 stone procedures were performed in 15 patients. Five patients underwent 13 PCNLs, 11 patients underwent 44 ureteroscopy procedures, and nine underwent open or robotic surgery, including one nephrectomy. Among patients identified by sibling screening, most (4/5) were managed with medical therapy alone. A total of 390 imaging procedures were performed. Radiation-associated imaging comprised half of all imaging tests.

DISCUSSION

The high rates of imaging and surgical utilization among pediatric cystinuria patients reflect the morbidity of this condition and the need for preventative management. By practicing the ALARA principle during urologic procedures, urologists can reduce radiation exposure. Multiple procedures are often required to render patients stone-free. URS/LL and PCNL are likely to be more effective than ESWL. In complex cases, robotic-assist lithotomy provides the advantage of a minimally invasive approach. Both sibling screening and transitional care represent long-term strategies with the potential to reduce life-long morbidity. The limitations of this study include its small sample size, retrospective nature, and single-center experience.

CONCLUSIONS

Our study demonstrates that the clinical impact of disease among pediatric patients presenting with cystinuria at our institution is considerable, with most requiring surgery. Our population also generates heavy utilization of diagnostic imaging. Given the lifelong nature of this disease, research on improved preventive therapies is urgently needed.

Cystinuria-a urologist's perspective

Cystinuria is a genetic disease that leads to frequent formation of stones. In patients with recurrent stone formation, particularly patients <30 years old or those who have siblings with stone disease, urologists should maintain a high index of suspicion of the diagnosis of cystinuria. Patients with cystinuria require frequent follow-up and a multidisciplinary approach to diagnosis, prevention and management. Patients have reported success in preventing stone episodes by maintaining dietary changes using a tailored review from a specialist dietician. For patients who do not respond to conservative lifestyle measures, medical therapy to alkalinize urine and thiol-binding drugs can help. A pre-emptive approach to the surgical management of cystine stones is recommended by treating smaller stones with minimally invasive techniques before they enlarge to a size that makes management difficult. However, a multimodal approach can be required for larger complex stones. Current cystinuria research is focused on methods of monitoring disease activity, novel drug therapies and genotype-phenotype studies. The future of research is collaboration at a national and international level, facilitated by groups such as the Rare Kidney Stone Consortium and the UK Registry of Rare Kidney Diseases.

Ureteroscopic management of recurrent renal cystine calculi

BACKGROUND AND PURPOSE

Patients with recurrent cystine nephrolithiasis oftentimes require multiple procedures for stone removal. As the majority of cystine stones are resistant to the effects of shockwave lithotripsy, repeat percutaneous surgery is often required and may cause renal damage. Moreover, repeat percutaneous access may become more difficult as perinephric fibrosis develops. Small-caliber ureteroscopes along with the holmium laser now enable routine intrarenal ureteroscopic access to symptomatic renal stones. Herein, we present our experience in managing recurrent renal cystine calculi using flexible ureterorenoscopy and assess whether such an approach may be used as an alternative to percutaneous surgery in selected patients.

PATIENTS AND METHODS

Three patients with large-volume (mean diameter 22 mm) renal cystine stones were managed with a 7.5F flexible ureterorenoscope combined with holmium laser lithotripsy to fragment the stones completely.

RESULTS

The mean treatment time was 97 minutes, with successful fragmentation in all cases. Two of the three patients were completely stone free on follow-up intravenous urography, with the third patient having only small-volume residual fragments in a lower pole calix. All patients are currently asymptomatic and are being maintained on high oral fluid intake, urinary alkalization with potassium citrate, and alpha-mercaptopropionylglycine to reduce urinary cystine excretion.

CONCLUSION

Flexible ureterorenoscopy with holmium laser lithotripsy provides a reasonable alternative for the management for recurrent cystine calculi in patients who are not candidates for repeat percutaneous procedures. Although it is time consuming, complete stone fragmentation, along with clearance of fragments, can be achieved in the majority of patients.

Contemporary urological intervention for cystinuric patients: immediate and long-term impact and implications

PURPOSE

We determined the immediate efficacy of contemporary urological intervention for cystine stones and the impact of such intervention on the subsequent rate of recurrent stone formation.

MATERIALS AND METHODS

A total of 31 cystinuric patients underwent selected intervention for 61 stone events. Patients were subsequently followed at 6 to 12-month intervals while being treated with standard medical therapy. Logistic regression models were used to correlate potential risk factors with the efficacy of the intervention in achieving a stone-free status. Kaplan-Meier estimates of the probability of recurrence-free survivals at 1 and 5 years were generated, and risk factors for stone recurrence were analyzed using the log rank test.

RESULTS

Overall stone-free rate was 86.9%, which was not significantly influenced by the initial stone burden or type of intervention selected. The probability of recurrence-free survival at 1 and 5 years was 0.73 and 0.27, respectively, and again this probability was independent of initial stone burden or type of intervention selected. Urinary cystine levels before intervention and post-procedure residual stone status also failed to impact significantly on the risk of recurrence. However, a stone-free result, in contrast to residual stones, prolonged the mean time to stone recurrence from 346 to 1,208 days.

CONCLUSIONS

While cystine stones are not amenable to all currently available minimally invasive therapeutic modalities, high stone-free rates can be achieved without the need for open surgery and as such cystinuric patients clearly benefit from contemporary intervention. When such intervention is used selectively, with consideration given primarily to stone burden and location, rates of recurrence will relate primarily to the natural history of the medically treated cystinuric patient, and not the type of intervention applied.