Etiology and management of cystine lithiasis

In Vivo Analysis of Urinary Stones With Dual-Energy Computed Tomography

OBJECTIVE

Formation mechanisms and treatment of the urinary stones are different, depending on their chemical structure. Therefore, determining the stone type plays a key role in planning treatment and preventive measures. Computed tomography (CT), with the use of dual-energy technology in recent years, has made it possible to do in vivo analysis of urinary stones. In this study, we aimed to evaluate the diagnostic efficacy of dual-energy CT (DECT) and compare its results with in vitro analysis, which is accepted as a gold standard for analysis of urinary stones.

MATERIALS AND METHODS

The DECT examinations were performed on 373 patients using 128-slice dual-source CT scanner. Analysis of attenuation ratios in the high and low kilovoltage peak values of the stone was performed at workstation, and stones were classified as hydroxyapatite, calcium oxalate, cystine, and uric acid. On follow-up, the stone was obtained in 35 patients as a result of surgery or passed spontaneously. The DECT analysis and in vitro analysis results were compared and statistically evaluated.

RESULTS

In all patients, 136 hydroxyapatite, 160 calcium oxalate, 57 uric acid, and 20 cystine stones were detected with DECT. In vitro analyses of the stones were performed in 35 patients, and 8 hydroxyapatite, 18 calcium oxalate, 6 uric acid, and 3 cystine stones were revealed. When DECT analysis results were compared with in vitro analysis results, stone types were detected correctly in 32 (91.4%) patients and incorrectly in 3 (8.6%) patients. Especially all uric acid and cystine stones were correctly detected with DECT.

CONCLUSIONS

With advanced postprocess analysis methods, DECT is able to analyze urinary stones. The DECT is found superior especially in detecting uric acid and cystine stones. Its success in detecting hydroxyapatite and calcium oxalate stones is also high. When in vivo analyses of the stones are performed with DECT, it will be possible to make a contribution to the personalization and optimization of the treatment.

Management of Clinically Insignificant Residual Fragments following Shock Wave Lithotripsy

Clinically insignificant residual fragments (CIRFs) are small fragments (less than 5 mm) that are present in upper urinary tract at the time of regular post-SWL followup. The term is controversial because they may remain silent and asymptomatic or become a risk factor for stone growth and recurrence, leading to symptomatic events, and need further urologic treatment. Although a stone-free state is the desired outcome of surgical treatment of urolithiasis, the authors believe that the presence of noninfected, nonobstructive, asymptomatic residual fragments can be managed metabolically in order to prevent stone growth and recurrence. Further urologic intervention is warranted if clinical indications for stone removal are present.

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.

Comparative study of pulsed dye laser and pneumatic lithotripters for transurethral ureterolithotripsy

BACKGROUND

Clinical effectiveness and safety of the Swiss Lithoclast (Lithoclast) and the Candela MDL-2000 (MDL) in the treatment of lower ureteral stone were examined retrospectively.

METHODS

Eighty-six stones from 66 patients and 26 stones from 20 patients were treated by Lithoclast and MDL, respectively.

RESULTS

The stone-free rate on 3-month follow-up was 97% and 95% for the Lithoclast and MDL, respectively (no significant difference). The operation time was significantly shorter for the Lithoclast than for the MDL (90.2+/-50.2 vs 120.4+/-55.1 min; P<0.05). Postoperative analgesics were required significantly less frequently in Lithoclast (10/66 vs 11/20; P<0.01). Postoperative hospital stay was significantly shorter for Lithoclast (8.7+/-5.1 vs 12.1+/-4.2 days; P<0.01).

CONCLUSIONS

Swiss Lithoclast is an effective and less invasive modality for endoscopic treatment of lower ureteral stones.

Management of residual stones

Stone-free status is highly dependent on selection of the appropriate surgical technique, which should be tailored according to the individual stone and patient parameters. Although a stone-free state is the desired outcome of surgical intervention of urolithiasis, the authors believe that the presence of noninfection, nonobstructive, asymptomatic postprocedural residual fragments can be managed metabolically in order to prevent stone growth adequately. Further surgical intervention in the case of residual fragments is warranted if the clinical indications that prompted the original surgery persist.

Acalculous cystinuria

We compared quantitative urinary cystine values in stone-forming family members and unaffected relatives based on an index stone-forming patient. A family pedigree of 39 members was identified. Quantitative urinalyses and serum biochemical profiles were collected with the subjects on similar diets over 72 hours. Detailed medical histories were obtained. Three family members are stone-forming cystinuric patients with a mean urinary cystine excretion of 496 mg/g of creatinine per day. Six persons without a history of stones (mean age 50) had a mean urinary cystine excretion of 364 mg/g of creatinine per day. Thirty-four family members had elevated urinary cystine concentrations (mean 151 mg/g of creatinine per day), and only two family members had normal urinary cystine excretion. Fifteen subjects with elevated urinary cystine values (> 150 mg/g of creatinine per day) had no history of urinary stones despite a mean age of 44 years. Urinary electrolytes and volumes were similar in the stone-forming and non-stone-forming groups. Thirty-nine per cent of the persons from this family pedigree had elevated quantitative urinary cystine concentrations and no history of urinary stones despite a mean age of 44 years. Acalculous cystinuria is an elevated urinary cystine concentration without evidence of urinary stone disease. Despite abnormal urinary cystine excretion, acalculous cystinuria does not necessarily culminate in clinical urinary stone disease.

Update on interventional uroradiology

From its humble beginnings as a method of expediently decompressing the obstructed kidney, the field of interventional uroradiology has evolved in the hands of urologists and interventional radiologists to a means of addressing myriad problems in the urinary tract and has changed the day-to-day practice of urology. The foundation of interventional uroradiology is the creation of an appropriate entry into the urinary system. After a review of this basic procedure, extensions of the technique and new applications of emerging technology are reviewed.

Percutaneous nephrostolithotomy. What is its role in 1997?

PNL is a challenging and satisfying part of endourologic practice. Although more invasive than SWL or ureteroscopy, it offers a high chance of success in many different situations. The selective and appropriate application of PNL requires the consideration of many factors, especially stone location and size, patient habitus, and the anatomy of the upper urinary tract (Table 5). For the urologic surgeon in the last decade of the twentieth century, complete stone therapy entails judgment and skill with myriad modalities: SWL, ureteroscopy, PNL, and open or laparoscopic stone surgery.