Diagnosis and metaphylaxis of stone disease. Consensus concept of the National Working Committee on Stone Disease for the upcoming German Urolithiasis Guideline

Predictive role of ureteral wall thickness and patient characteristics in endoscopic treatment outcomes for ureteral stricture disease following stone surgery

PURPOSE

To evaluate the role of certain radiological parameters and patient characteristics in predicting the success of endoscopic treatment in ureteral stricture disease.

METHODS

Fifty one adult patients with ureteral stricture disease (< 1 cm) after developing due to upper ureteral stones with ureteroscopic laser disintegration were included and in addition to stone and patient parameters, radiological parameters including ureteral wall thickness (UWT) at the impacted stone site were also measured on computed tomography (CT) images. Patients were divided into two groups: Group 1: Patients with endoscopic treatment success and Group 2: Patients with endoscopic treatment failure. The possible relationship between the UWT values and other radiological parameter was comparatively evaluated.

RESULTS

Mean UWT value assessed at the treated stone site was significantly higher in cases unresponsive to endoscopic treatment with values of 2.77 ± 1.03 mm and 4.25 ± 1.32 mm in Group 1 and 2 respectively. A cut off value 3.55 mm for UWT was found to be highly predictive for endoscopic treatment failure.

CONCLUSIONS

Our current results indicated that assessment of UWT value at the obstructing stone could be helpful enough to predict the likelihood of failure following endoscopic management of strictures with high sensitivity and specificity. Evaluation of this particular parameter could let the endourologists to look for more rational treatment alternatives with necessary measures taken on time.

The Saudi urological association guidelines on urolithiasis

Aims

The Saudi Urolithiasis Guidelines are a set of recommendations for diagnosing, evaluating, and treating urolithiasis in the Saudi population. These guidelines are based on the latest evidence and expert consensus to improve patient outcomes and optimize care delivery. They cover the various aspects of urolithiasis, including risk factors, diagnosis, medical and surgical treatments, and prevention strategies. By following these guidelines, health-care professionals can improve care quality for individuals with urolithiasis in Saudi Arabia.

Panel

The Saudi Urolithiasis Guidelines Panel consists of urologists specialized in endourology with expertise in urolithiasis and consultation with a guideline methodologist. All panelists involved in this document have submitted statements disclosing any potential conflicts of interest.

Methods

The Saudi Guidelines on Urolithiasis were developed by relying primarily on established international guidelines to adopt or adapt the most appropriate guidance for the Saudi context. When necessary, the panel modified the phrasing of recommendations from different sources to ensure consistency within the document. To address areas less well covered in existing guidelines, the panel conducted a directed literature search for high quality evidence published in English, including meta analyses, randomized controlled trials, and prospective nonrandomized comparative studies. The panel also searched for locally relevant studies containing information unique to the Saudi Arabian population. The recommendations are formulated with a direction and strength of recommendation based on GRADE terminology and interpretation while relying on existing summaries of evidence from the existing guidelines.

Pediatric renal lithiasis in Spain: research, diagnostic and therapeutic challenges, and perspectives

Incidence and prevalence of urolithiasis is apparently increasing worldwide, also among children and adolescents. Nevertheless, robust data have only been obtained in a few countries. In Spain, a voluntary Registry for Pediatric Renal Lithiasis has been active since 2015. Irregular participation limits its applicability, as well as its limitation to patients with a stone available for morphocompositional study, to obtain data about incidence and prevalence. On the other hand, findings about typology of stones and clinical and analytical characteristics of these subjects have been communicated in several meetings. Other valuable efforts in this field are the elaboration of guidelines for the collection and processing of urine samples for the study of urolithiasis in pediatric patients with the consensus of the Spanish Society for Pediatric Nephrology (AENP) as well as the Spanish Society for Laboratory Medicine (SEQC), the collaborative network RenalTube for the diagnosis of primary tubulopathies and the registry of patients with Primary Hyperoxaluria (OxalSpain). In many hospitals from the public healthcare system, pediatric nephrologists are the specialists in charge of the management of children with kidney stones, but there is no formal regulation on this competence. Other specialists, such as urologists, pediatric surgeons or pediatric urologists, in many cases do not offer a complete insight into the etiopathogenic mechanisms and the consequent medical treatment. Access to medication according to standards of treatment is warranted, provided a correct diagnosis is achieved, but criteria for the reimbursement of certain therapies, such as RNAi drugs for primary hyperoxaluria, are arguable.

Neural Network Analysis of Crystalluria Content to Predict Urinary Stone Type

Purpose

To investigate the relationship between urinary stone type and the type of crystals in the urine.

Patients and Methods

This retrospective study involved 485 patients with urinary stones treated at King Saud University Medical City from May 2015 to June 2017. Clinical data were obtained from medical records. Different statistical analysis methods were applied, including basic contingency analysis, analysis of variance, logistic regression, discriminant analysis, partition modeling, and neural network evaluations.

Results

Of 485 patients, 47 had crystals detected by urinalysis. The most common type of crystal was calcium oxalate (n = 31), which had the highest association with calcium oxalate stones. Uric acid crystals (n = 8) were associated with uric acid stones. The neural network model used for determining the sensitivity and specificity showed an R-square value of 0.88, with an area under the curve of 0.94 for calcium oxalate, 0.94 for carbonate apatite, and 1.0 for uric acid.

Conclusion

The predictive algorithm developed in the present study may be used with a patient's clinical parameters to predict the stone type. This approach predicts the stone types associated with certain patient characteristics with a high sensitivity and specificity, indicating that the models may be a valuable clinical tool in the diagnosis, management, and monitoring of stone diseases.

Preliminary assessment of a portable Raman spectroscopy system for post-operative urinary stone analysis

PURPOSE

We aimed to evaluate the reliability of a portable device that applies Raman spectroscopy at an excitation wavelength of 1064 nm for the post-operative analysis of urinary stone composition.

MATERIALS AND METHODS

Urinary stone samples were obtained post-operatively from 300 patients. All samples were analyzed by the portable Raman spectroscopy system at an excitation wavelength of 1064 nm as well as by infrared spectroscopy (IR), and the results were compared.

RESULTS

Both Raman spectroscopy and IR could detect multiple stone components, including calcium oxalate monohydrate, calcium oxalate dihydrate, calcium phosphate, uric acid, cystine, and magnesium ammonium phosphate hexahydrate. The results from 1064-nm Raman analysis matched those from IR analysis for 96.0% (288/300) of cases. Although IR detected multiple components within samples more often than Raman analysis (239 vs 131), the Raman analysis required less time to complete than IR data acquisition (5 min vs 30 min).

CONCLUSIONS

These preliminary results indicate that 1064-nm Raman spectroscopy can be applied in a portable and automated analytical system for rapid detection of urinary stone composition in the post-operative clinical setting.

TRIAL REGISTRATION

Chinese Clinical Trail Register ID: ChiCTR2000039810 (approved WHO primary register) http://www.chictr.org.cn/showproj.aspx?proj=63662 .

Predictive value of ureteral wall thickness (UWT) assessment on the success of internal ureteral stent insertion in cases with obstructing ureteral calculi

To evaluate the possible role of ureteral wall thickness (UWT) assessment in the prediction of the success for stent placement in cases with obstructing ureteric stones. 227 adult patients with a single unilateral obstructing ureteral stone requiring internal ureteral stent placement were included. In addition to stone size, the ureteric wall thickness at the impacted stone site and the degree of hydronephrosis were also assigned on CT images. Patients were divided into two subgroups: Group 1: patients in whom internal ureteral stent could not be passed beyond the stone and Group 2: patients in whom an internal ureteral stent was passed successfully. The possible relationship between the UWT values and the success of stent placement, degree of hydronephrosis were comparatively evaluated. The majority of the stones were located in the proximal ureter in Group 1 and the degree of hydronephrosis was also higher in these cases. Moreover, while the mean value of UWT calculated on CT images was 4.3 ± 0.9 mm in Group 1, this value was noted to be 2.5 ± 0.8 mm in cases of group 2. A cutoff UWT value of 3.35 mm was highly predictive for the stent insertion and cases with higher values required additional procedures or percutaneous nephrostomy tube placement. UWT value calculated at the obstructing stone site was found to be predictive enough for the likelihood of internal ureteral stent passage with high sensitivity and specificity. This evaluation may enable the urologist to make the best decision for urinary diversion in such cases.

Clinical and Radiological Predictors of Early Intervention in Acute Ureteral Colic

PURPOSE

Acute ureteric colic (AUC) is generally one of the most common reasons for emergency department attendance. Expectant management is recommended in non-complicated ureteral calculi. However, data regarding the optimal duration of observation or indications of early intervention (EI) are not well understood. This article describes the clinical and radiological factors that promote EI in AUC.

PATIENTS AND METHODS

This was an observational and retrospective cohort study. Patients with AUC diagnosed based on non-contrast computerized tomography (NCCT) between 2019 and 2020 were enrolled in the study. These patients were classified into two main categories: spontaneous passage of stone (SSP) and EI. In addition, a comparative analysis was performed to identify clinical and radiological variables that promote EI.

RESULTS

One-hundred and sixty-one patients were included. High WBCs are associated with a significant increase in EI. Forty-three percent (n=37) of patients with serum WBCs higher than 10 had an EI, while 23% had SSP (n=17;p<0.001). High CRP level is also significantly associated with EI (n=36; 86%; p<0.001). Upper and middle ureteral calculi are statistically associated with EI (n=54; 62%) in comparison to the SSP cohort (n=22; 30%;p<0.001). EI is also linked to the maximal length of ureteric calculi (MCL) of 9 mm (6-13mm), and HU density of stone of 700 (430-990) H.U (p<0.001). Ureteric stone volume of 0.2 (0.06-0.3) cm³ is significantly associated with EI (p<0.001). Ureteral wall thickness of 3 (2-3 mm), the presence of extrarenal pelvis (n=20; 23%), and AP diameter of renal pelvis 18 (13-28 mm) are all significantly associated with a higher rate of EI (p<0.001). Multiple binary logistic regression analysis showed that MCL is the strongest predictor of EI.

CONCLUSION

MCL is an independent and robust predictor of EI in AUC. Biochemical variables and radiological characteristics can also act as an adjunct to promote EI.

Relationship between urine specific gravity and the prevalence rate of kidney stone

Background

The purpose of this study was to evaluate the relationship between urine specific gravity (USG) and the prevalence rate of kidney stone.

Methods

We conducted a cross-sectional study of adult participants (≥20 years) of the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2008. The USG was divided into three groups: <1.008, 1.008-1.020 and >1.020. Univariate and multivariate logistic regression analysis was used to determine the effect of USG on the prevalence rate of kidney stone.

Results

A total of 4,791 patients were included in this study, of which 464 (9.7%) reported a history of kidney stone. Univariate logistic regression analysis showed that age, gender, race, hypertension, diabetes, body mass index (BMI), estimated glomerular filtration rate (eGFR), USG and urine creatinine were closely related to the prevalence of kidney stones. After adjusting for known confounding factors, multivariate logistic regression showed that the prevalence rate of kidney stone increased with the increase of USG (1.008-1.020 vs. <1.008, OR =1.31, 95% CI, 0.09-1.91, P=0.155; >1.020 vs. <1.008, OR =1.71, 95% CI, 1.16-2.54, P=0.007).

Conclusions

The increase of USG was significantly correlated with self-reported kidney stone. This finding helps to identify risk factors for kidney stones as early as possible in the United States.

[Interpretation of the metabolic study in renal lithiasis and its treatment]

Urolithiasis is a common disease, and is an important health problem that is associated with a great economic burden. The nature of stone disease varies according by dietary and lifestyle factors, including, among others, climate variations. The majority of patients will suffer a new lithiasic episode at some point in their life, unless preventive measures, such as changing lifestyles and dietary habits, are put in place to avoid it. The risk factors involved in lithogenesis should be evaluated in order to reduce recurrences. In the majority of these patients, metabolic changes are observed in the urine that predispose lithogenesis. The kind of evaluation depends on stone composition and on the clinical presentation. A diagnosis of systemic and renal diseases of lithogenic nature can be diagnosed with these studies, and they also enable the adoption of precise prophylactic measures that achieve control of recurrence in a great number of patients.

Usefulness of Protocolized Point-of-Care Ultrasonography for Patients with Acute Renal Colic Who Visited Emergency Department: A Randomized Controlled Study

Background and Objectives: Ultrasonography is useful in evaluating patients with renal colic and it has high sensitivity and specificity for diagnosing ureter stones by revealing hydronephrosis. We evaluated the efficacy of point-of-care ultrasonography protocol in managing patients with acute renal colic who visited the emergency department (ED). Materials and Methods: Between March 2019 and July 2019, patients who visited the ED because of renal colic were randomly assigned by date of visit either to the conventional group (CG), who underwent routine diagnostic work-up without ultrasonography, or to the ultrasonography group (UG), who underwent bedside ultrasonography as an initial diagnostic testing. When hydronephrosis was detected in the UG group, a confirmatory non-contrast abdomen computed tomography scan was promptly performed. The ED length of stay, complications, and missed or delayed high-risk diagnosis were evaluated. Results: In total, 128 of 147 analyzed patients were confirmed to have ureter stones. The ED length of stay was significantly lower in the UG group than in the CG group (mean 172 min; 95% confidence interval (CI): 151–194 min vs. mean 234 min; 95% CI: 216–252 min). The medical cost was also remarkably lower in the UG group than in the CG group (259 USD vs. 319 USD; p < 0.001). The incidence of complications within 30 days after visiting ED and missed or delayed high-risk diagnosis were not significantly different between the two groups. Conclusions: We found that protocolized point-of-care ultrasonography in patients with acute renal colic who visited the ED can more effectively reduce the length of stay and medical cost without 30-day complication than usual clinical practice.

The Urological Association of Asia clinical guideline for urinary stone disease

The Urological Association of Asia, consisting of 25 member associations and one affiliated member since its foundation in 1990, has planned to develop Asian guidelines for all urological fields. The field of stone diseases is the third of its guideline projects. Because of the different climates, and social, economic and ethnic environments, the clinical practice for urinary stone diseases widely varies among the Asian countries. The committee members of the Urological Association of Asia on the clinical guidelines for urinary stone disease carried out a surveillance study to better understand the diversity of the treatment strategy among different regions and subsequent systematic literature review through PubMed and MEDLINE database between 1966 and 2017. Levels of evidence and grades of recommendation for each management were decided according to the relevant strategy. Each clinical question and answer were thoroughly reviewed and discussed by all committee members and their colleagues, with suggestions from expert representatives of the American Urological Association and European Association of Urology. However, we focused on the pragmatic care of patients and our own evidence throughout Asia, which included recent surgical trends, such as miniaturized percutaneous nephrolithotomy and endoscopic combined intrarenal surgery. This guideline covers all fields of stone diseases, from etiology to recurrence prevention. Here, we present a short summary of the first version of the guideline - consisting 43 clinical questions - and overview its key practical issues.

Renal stone composition does not affect the outcome of percutaneous nephrolithotomy in children

PURPOSE

We sought to investigate the association between renal stone composition and percutaneous nephrolithotomy outcomes in pediatric patients and define the characterization of the stone composition.

METHODS

The data of 1157 children who underwent percutaneous nephrolithotomy between 1991 and 2012 were retrieved from the multicenter database of the Turkish Pediatric Urology Society. The study population comprised 359 children (160 girls, 199 boys) with stone analyses. Patients were divided into five groups according to the stone composition [group 1: calcium oxalate; group 2: calcium phosphate; group 3: infection stones (magnesium ammonium phosphate, ammonium urate); group 4: cystine; group 5: uric acid, xanthine stones].

RESULTS

Patient characteristics, perioperative, postoperative, and stone characteristics were compared considering the stone composition. There were no significant differences between the groups concerning age, sex, side involved, preoperative hematocrit levels, and solitary renal unit. Patients with cystine stones were more likely to have a history of stone treatment. Groups 2 and 5 had mostly solitary stones. However, group 3 had staghorn stone more often, and group 4 frequently had multiple stones. Overall stone-free rate (79.4%) was similar among the groups. Although stone composition was related to blood transfusion and prolonged operative and fluoroscopy screening times on univariate analysis, it was not a significant predictor of them on multivariate analysis.

CONCLUSIONS

Stone composition was not a predictor of outcomes of pediatric percutaneous nephrolithotomy. However, cystine and infection stones, which are larger and filled multiple calyxes due to the nature of stone forming, were more challenging cases that need multiple tracts.

Anti-Transforming Growth Factor β IgG Elicits a Dual Effect on Calcium Oxalate Crystallization and Progressive Nephrocalcinosis-Related Chronic Kidney Disease

Crystallopathies are a heterogeneous group of diseases caused by intrinsic or environmental microparticles or crystals, promoting tissue inflammation and scarring. Certain proteins interfere with crystal formation and growth, e.g., with intrarenal calcium oxalate (CaOx) crystal formation, a common cause of kidney stone disease or nephrocalcinosis-related chronic kidney disease (CKD). We hypothesized that immunoglobulins can modulate CaOx microcrystal formation and crystal growth and that therefore, biological IgG-based drugs designed to specifically target disease modifying proteins would elicit a dual effect on the outcome of CaOx-related crystallopathies. Indeed, both the anti-transforming growth factor (TGF)β IgG and control IgG1 antibody impaired CaOx crystallization in vitro, and decreased intrarenal CaOx crystal deposition and subsequent CKD in mice on an oxalate-rich diet compared to oxalate-fed control mice. However, the TGFβ-specific IgG antibody showed nephroprotective effects beyond those of control IgG1 and substantially reduced interstitial fibrosis as indicated by magnetic resonance imaging, silver and α-smooth muscle actin staining, RT-qPCR, and flow cytometry for pro-fibrotic macrophages. Suppressing interstitial fibrosis slowed the decline of glomerular filtration rate (GFR) compared to treatment with control IgG1 [slope of m = −8.9 vs. m = −14.5 μl/min/100 g body weight (BW)/day, Δ = 38.3%], an increased GFR at the end of the study (120.4 vs. 42.6 μl/min/100 g BW, Δ = 64.6%), and prolonged end stage renal disease (ESRD)-free renal survival by 10 days (Δ = 38.5%). Delayed onset of anti-TGFβ IgG from day 7 was no longer effective. Our results suggest that biological drugs can elicit dual therapeutic effects on intrinsic crystallopathies, such as anti-TGFβ IgG antibody treatment inhibits CaOx crystallization as well as interstitial fibrosis in nephrocalcinosis-related CKD.

Evaluation of ureteral jet dynamics in pediatric kidney stone formers: A cross-sectional study

INTRODUCTION

The risk of kidney stone formation increases with urinary stasis, which is associated with decreased peristaltism. The relationship between nonobstructive kidney stone formation and ureteral jet dynamics, which can be measured with Doppler ultrasonography (US) and provide information about ureteral peristaltism, has been demonstrated in adults.

OBJECTIVE

To investigate the relationship between ureteral jet dynamics, which provide information about ureteral peristaltism, and stone formation in children.

STUDY DESIGN

Children admitted to Dokuz Eylul University Hospital with flank pain, and asymptomatic age-matched children for the control group, were prospectively enrolled and underwent Doppler US for diagnostic reasons and bilateral ureteral jet flow measurements. Children diagnosed with unilateral nonobstructive lower pole kidney stones formed Group 1, and the control group, without any evidence of stone disease, formed Group 2. Ureteral jet dynamics were compared between the affected renal units in Group 1, and healthy renal units in Group 1 and Group 2.

RESULTS

A total of 32 children were included for each group. The mean average jet flow-rate (JETave (cm/second)) in affected renal units in Group 1 was found to be significantly lower than in the healthy renal units in Group 1 and left and right healthy renal units in Group 2 (P < 0.05). The continuous JETpattern rate in affected renal units in Group 1 was found to be significantly higher compared with healthy renal units in Groups 1 and 2 (P = 0.012) (Table). The odds ratio for kidney stone formation was 5.6 for renal units with JETave <9.5 cm/s when compared with renal units with JETave ≥9.5 cm/s.

DISCUSSION

In a recent study, it was demonstrated in adults that low ureteral jet flow-rate and continuous JETpattern were significantly higher in affected renal units. The findings in children were also similar to adults: the mean JETave was significantly lower and determination rate of continuous flow pattern was significantly higher in affected renal units.

CONCLUSIONS

Children with low JETave and continuous JETpattern as a sign of decreased ureteral peristaltism are at an increased risk of kidney stone formation. However, it is vital that further studies are conducted to elaborate on this topic.

The Modern Metabolic Stone Evaluation in Children

OBJECTIVE

To evaluate metabolic abnormalities in a contemporary pediatric population after their first stone episode. The incidence of pediatric nephrolithiasis is increasing and therefore the etiologies contributing to today's pediatric stone formation may also be changing.

MATERIALS AND METHODS

A retrospective review of all consecutive children presenting after their first kidney stone between 2000 and 2014 was performed. We compared demographic data, serum chemistry results, and 24-hour urine results and treatments.

RESULTS

One hundred thirteen children with a mean age of 11 years (5 months to 18 years) who presented with their first kidney stone episode between 2000 and 2014 were evaluated. Sixteen patients (14%) were found to have an underlying genetic or systemic disease. Overall, there was a low rate of serum chemistry abnormalities. The most common abnormalities found within the 24-hour urine evaluation included low urine volume (89%) and hypocitraturia (68%). Hypercalciuria occurred rarely (11%).

CONCLUSION

We identified a low rate of underlying genetic or systemic diseases contributing to modern pediatric stone presentation and an increased proportion of idiopathic stones. Our study differs from historical findings by identifying a low rate of hypercalciuria and a high rate of low urine volume and hypocitraturia, suggestive of changing metabolic abnormalities contributing to modern pediatric stone disease.

Urolithiasis--an interdisciplinary diagnostic, therapeutic and secondary preventive challenge

BACKGROUND

The prevalence of urolithiasis in Germany is 4.7%; its incidence has trebled in the last three decades. The risk of recurrence is 50-80%, depending on the type of stone, unless secondary prevention is instituted. Risk-adapted secondary prevention lowers this risk to 10-15%.

METHODS

This review is based on publications retrieved by a selective search in PubMed using the key words "urolithiasis," "urinary stones," "epidemiology," "lithogenesis," "biominerals," "risk factors," and "diagnosis, therapy, metaphylaxis." These publications were evaluated with the aid of the urolithiasis guideline of the European Association of Urology.

RESULTS

Acute renal colic can usually be diagnosed without sophisticated equipment. Stones can be dealt with by a variety of techniques depending on their size and location, including extracorporeal shock-wave lithotripsy, ureterorenoscopy, percutaneous nephrolitholapaxy, and open surgery. Most ureteric stones of diameter up to 5 mm pass spontaneously. 75% of patients have no complications. The basic evaluation needed for secondary prevention can be carried out by any physician on an ambulatory basis. In the 25% of patients who have complications, a more extensive interdisciplinary evaluation of metabolic parameters should be performed in a clinical center for urinary stones.

CONCLUSION

Urolithiasis has many causes and can be treated in many different ways. An extensive metabolic work-up is often necessary for secondary prevention. The various treatment options must be considered for their suitability in each individual patient. Robust data are now available on surgical and interventional methods, but there are as yet no high-quality trials of secondary prevention. Further research should concentrate on the etiology and pathogenesis of urolithiasis.

Should we modify the principles of risk evaluation and recurrence preventive treatment of patients with calcium oxalate stone disease in view of the etiologic importance of calcium phosphate?

Prevention of recurrent calcium oxalate (CaOx) stone formation in the urinary tract is important to avoid negative effects on renal function, patient suffering and to reduce health care cost. Present shortcomings in this regard can be explained both by insufficient understanding of the mechanisms of stone formation and by poor patient compliance to those regimens that nevertheless have proven effective. During the past years, we have got increased insights in the nature of CaOx stone formation and it is suggested that the improved understanding of this process can be used for a more dynamic risk evaluation and treatment regimen directed to specific risk periods that can be identified in the individual patients. Some of the possibilities with regard to the important role of calcium phosphate are discussed in this article.

Current medical treatment in pediatric urolithiasis

Although the prevalence of urolithiasis is nearly 2-3% in childhood, the risk of recurrence may range from 6.5-54%. There has been an increase in urinary stone disease among pediatric age groups, and stone disease has a multifactorial etiology. After the diagnosis, detailed metabolic evaluation is required. High recurrence rates, therapeutic irregularities and deficiency in diagnosis may lead to comorbidities such as loss of kidney function. Following diagnosis, the requirement for surgery, such as stone extraction and correction of anatomical anomalies, is determined. Medical and supportive treatments are also needed to prevent recurrence and urinary tract infections and to preserve renal function. Supportive care includes increased fluid intake and dietary modifications. Medical treatment is dependent on the cause of the urinary stone disease. The morbidities associated with pediatric urolithiasis can be prevented by early diagnosis, detailed metabolic analysis, regular follow-up and medical treatment protocols.

Kidney stones: an update on current pharmacological management and future directions

INTRODUCTION

Kidney stones are a common problem worldwide with substantial morbidities and economic costs. Medical therapy reduces stone recurrence significantly. Much progress has been made in the last several decades in improving therapy of stone disease.

AREAS COVERED

This review discusses i) the effect of medical expulsive therapy on spontaneous stone passage, ii) pharmacotherapy in the prevention of stone recurrence and iii) future directions in the treatment of kidney stone disease.

EXPERT OPINION

Fluid intake to promote urine volume of at least 2.5 L each day is essential to prevent stone formation. Dietary recommendations should be adjusted based on individual metabolic abnormalities. Properly dosed thiazide treatment is the standard therapy for calcium stone formers with idiopathic hypercalciuria. Potassium alkali therapy is considered for hypocitraturia, but caution should be taken to prevent potential risk of calcium phosphate stone formation. For absorptive hyperoxaluria, low oxalate diet and increased dietary calcium intake are recommended. Pyridoxine has been shown effective in some cases of primary hyperoxaluria type I. Allopurinol is used in calcium oxalate stone formers with hyperuricosuria. Treatment of cystine stones remains challenging. Tiopronin can be used if urinary alkalinization and adequate fluid intake are insufficient. For struvite stones, complete surgical removal coupled with appropriate antibiotic therapy is necessary.

Improving the compliance of the recurrent stone-former

Objective

To provide an overview of aspects of compliance by the recurrent stone-former, and to give recommendations for its improvement. About half of all stone-formers have one recurrence during their lifetime. To avoid recurrent stone formation it is necessary to use metaphylaxis, based on individual risks. However, all general and specific efforts are meaningless if patients are not willing or are incapable of following the proposed therapy in the long-term.

Methods

PubMed was searched for articles on urolithiasis, metaphylaxis, compliance and adherence, and relevant papers were reviewed.

Results

Compliance is a multidimensional phenomenon which is determined by the interaction of different factors, i.e. social and economic, therapy-related, patient-related, condition-related, and healthcare team and system-related factors. Subsequently there are several different interventional possibilities at the urologist’s disposal to effect better compliance by the patient.

Conclusions

The treatment and metaphylaxis of the recurrent stone-former present a particularly pertinent challenge. Patient compliance has an immense influence on the success of the treatment with respect to metaphylaxis, which is the decisive factor for preventing stone recurrence.

Methods for diagnosing the risk factors of stone formation

OBJECTIVE

To compare various systems for assessing the risk of recurrent stones, based on the composition of urine.

METHODS

The relative supersaturation (RSS) of urine, the Tiselius Indices, the Robertson Risk Factor Algorithms (RRFA) and the BONN-Risk Index were compared in terms of the numbers of variables required to be measured, the ease of use of the system and the value of the information obtained.

RESULTS

The RSS methods require up to 14 analyses in every urine sample but measure the RSS of all the main constituents of kidney stones. The Tiselius Indices and the RRFA require only seven analyses. The Tiselius Indices yield information on the crystallisation potentials (CP) of calcium oxalate and calcium phosphate; the RRFA also provide information on the CP of uric acid. Both methods provide details on the particular urinary abnormalities that lead to the abnormal CP of that urine. The BONN-Risk Index requires two measurements in each urine sample but only provides information on the CP of calcium oxalate. Additional measurements in urine have to be made to identify the cause of any abnormality.

CONCLUSIONS

The methods that are based on measuring RSS are work-intensive and unsuitable for the routine screening of patients. The Tiselius Indices and the RRFA are equally good at predicting the risk of a patient forming further stones. The BONN-Risk Index provides no additional information about the causative factors for any abnormality detected.

Metaphylaxis, diet and lifestyle in stone disease

Objective

The most common urinary stones (calcium salts, uric acid) form due to genetic factors and lifestyle. This review describes why, if and how medication and lifestyle changes can reduce the risk of formation.

Methods

Previous reports were reviewed to obtain information on three aspects of urolithiasis, i.e. epidemiology, mechanisms linking lifestyle and urolithiasis and lifestyle intervention for preventing urolithiasis.

Results

Epidemiological evidence links the prevalence of urinary stone formation to general lifestyle factors. Detailed analysis has identified individual lifestyle elements that affect the risk of urinary stone formation. Currently there are several concepts that explain the mechanism of stone formation. Urinary markers like calcium, oxalate, phosphate, uric acid and urinary pH are involved in all these concepts. Many studies show that changing (combinations of) specific lifestyle elements has a favourable effect on these urinary markers. Based on this evidence, protocols have been developed that use a combination of these lifestyle changes and medication to prevent stone formation. In well-controlled studies where patients are optimally informed and continuously motivated, these protocols clearly reduce the stone formation rate. In general practice the result is less clear, because the time and tools are insufficient to maintain long-term patient compliance in the use of medication and lifestyle advice.

Conclusion

The risk of stone formation can be reduced in general practice when the patient’s compliance is optimised by providing individualised advice, continuous information, and feedback and incorporation of the advice into a regular lifestyle. The use of ‘e-tools’ might enable this without increasing the time required from the physician.

[Recurrence prevention of kidney stone disease]

In each urolithiasis patient the individual risk for recurrence determines the need for specific medical treatment. Therefore, a brief evaluation of the risk status after stone passage is mandatory to define patients at high risk for recurrence. Only one quarter of all urolithiasis patients are at high risk or suffer from severe metabolic disorders, which both demand further metabolic work-up prior to medical therapy. However, the other three quarters benefit sufficiently from general preventive measures, such as high fluid intake, well-balanced mixed diet and lifestyle changes. This article summarizes the recent recommendations for stone-specific recurrence prevention, discusses the different pharmacological treatment options and sketches the follow-up concept for high risk patients with ongoing medication.

[Why and how we must analyse urinary calculi]

CONTEXT

There is heterogeneity of criteria on the utility of urinary stone analysis as well as on which is the most suitable methodology. This review presents the analysis of the lithiasis using the morphoconstitutional analysis technique based on the combination of the stereoscopic microscopy (SM) with infrared study (IRS).

SUMMARY OF THE EVIDENCE

There are many techniques to analyze the stone: chemical analysis, electron microscopy, X-ray diffraction, SM and IRS. Reviewing each one of these techniques and through the study of several clinical cases, this review shows the usefulness of stone analysis and the pros and cons of each one of the mentioned techniques. Furthermore, it can be clearly seen how the morphoconstitutional analysis is the one that offers the most useful clinical information to the urologist. In addition, classification of the lithiasis based on this method and its clinical correlation with patients is presented.

CONCLUSIONS

Using the morphoconstitutional study to analyze the stone offers more information than the other techniques and it makes it possible to establish a stone classification of important clinical and diagnostic utility.

Pediatric urolithiasis: the current surgical management

Children represent about 1% of all patients with urolithiasis, but 100% of these children are considered high risk for recurrent stone formation, and it is crucial for them to receive a therapy that will render them stone free. In addition, a metabolic workup is necessary to ensure a tailored metaphylaxis to prevent or delay recurrence. The appropriate therapy depends on localization, size, and composition of the calculus, as well as on the anatomy of the urinary tract. In specialized centers, the whole range of extracorporeal shock-wave lithotripsy (ESWL), ureterorenoscopy (URS), and percutaneous nephrolithotomy (PCNL) are available for children, with the same efficiency and safety as in adults.

Using Computed Tomography to Predict in Vivo Stone Chemical Composition

Objectives

Several authors hypothesized the usefulness of the non-contrast helical computed tomography (NCHCT) with the determination of stone Hounsfield Unit (HU) values in order to predict urinary stone compositions. Preoperative knowledge of stone composition might be interesting in pre-operative decision-making process. The aim of this study was to evaluate the possible correlation between stone chemical composition and correspondent stone HU value in an in-vivo experience.

Methods

Forty patients with urinary stones were preoperatively studied with abdominal NCHCT, where stone HU values were reported. Stone chemical composition was obtained in each patient, using the colorimetric method. The HU value of each stone was compared with the correspondent chemical analysis.

Results

The median HU values of calcium oxalate (n=10), mixed calcium oxalate and phosphate (n=19), calcium phosphate (n=2), uric acid (n=6) and mixed uric acid and calcium oxalate (n=3) stones were 1060 HU [interquartile range (IQR) 743.75–1222.5]; 900 HU (IQR 588.5–1108.5); 774 HU (range 720–828); 371 HU (IQR 361.25–436.25) and 532 HU (range 476–626), respectively.

Conclusions

Our results confirmed a statistically significant difference of the HU values between calcium and pure uric acid calculi, suggesting a correlation between stone chemical composition and CT-density. Hounsfield unit

Relevance of the BONN Risk Index for metabolic monitoring of patients with calcium oxalate urolithiasis: a clinical application study of the Urolizer

The BONN Risk Index (BRI) successfully determines the calcium oxalate (CaOx) crystallization risk from urine samples. The BRI is based on a standardized crystallization test performed on native urine. A BRI-measuring device, the "Urolizer", has been developed, operating automatically and requiring only a minimum of preparative efforts. In this study, the Urolizer is evaluated regarding its analytical and diagnostic practicability for metaphylaxis control in the framework of the daily routine of a stone surgery. From 51 CaOx recurrent stone-formers, 24 h urines were collected at the beginning and after 3 months of metaphylaxis. As much as 27 patients were indicated to suffer from "mild hypercalciuria", low urinary pH or hypocitraturia, and 24 patients from "hypercalciuria". The former were treated with alkaline citrate (AC), and the latter with hydrochlorothiazide (HCT). Analyses of urines collected before and during treatment, BRI using the Urolizer, and urinalysis-based risk indices were evaluated. In both patient groups, BRI decreased significantly, while metaphylaxis (P<0.001) in the AC group decreased from 1.08 (+/-0.58) to 0.56 (+/-0.39) L(-1) and in the HCT-group from 3.30 (+/-1.15) to 1.60 (+/-0.52) L(-1). In most patients, urinary parameters changed as desired and related risk indices decreased appropriately. The clinical utility of the easy-to-determine BRI is demonstrated. By quantifying the "overall" therapy effect within 15 min, the innovative analysis device may be especially suited for practitioners specializing in urolithiasis treatment.

Shockwave lithotripsy and endourological management of urinary calculi in children: a single-center 10-year experience

PURPOSE

Shock wave lithotripsy (SWL) and endourological techniques revolutionized the management of pediatric urolithiasis. We sought to assess the impact of new technology and local practice in the treatment of pediatric urolithiasis during a 10-year period.

MATERIALS AND METHODS

Between 1997 and 2006, 125 children (90 boys and 35 girls), aged 18 months to 15 years, were managed in our department for urolithiasis. Stone localization, stone composition, presence of anatomic abnormalities, and treatment modality were evaluated retrospectively.

RESULTS

In 102 children, the stone was located in renal pelvis (0.5-45-mm diameter), in eight in the renal pelvis and one in the calyx; three had staghorn calculi; and 12 had ureteral stone (4-12-mm diameter). Ninety-three of 125 children underwent a total of 108 SWL sessions. Stone size ranged from 0.5 to 35 mm. The stone-free rates were 86%, 92%, and 96% after first, second, and third SWL session, respectively. Ureteroscopy was performed in 12/125 children, and 10/12 (83.5%) were rendered stone free. Nine of 125 children underwent percutaneous nephrolithotomy, and four of nine were stone free (44.5%), although five of the nine children (55.5%) required SWL for residual stone fragments. Open surgery was performed as initial procedure in 11 (9%) children. In 9 of 11 children, ureteropelvic junction obstruction was corrected simultaneously. Open surgery was followed by SWL in 3 of 11 patients. Two of three patients with staghorn calculi underwent nephrolithotomy and SWL and one of three with cysteinuria was managed with SWL.

CONCLUSIONS

SWL and endourological techniques are safe and effective in managing urolithiasis in pediatric patients. These minimally invasive methods reduced dramatically the cases of open surgery, which should be undertaken mainly in coexisting anatomic abnormalities.

[Qualitative and quantitative analysis of urolithiasis with the Rietveld method (x-ray diffraction)]

BACKGROUND

The Rietveld method is one of the most innovative and most important applications in x-ray diffraction and has now, for the first time, been applied to standard-free precise quantitative crystallographic analysis of urinary stones.

MATERIAL AND METHODS

The capability of the Rietveld method was demonstrated by analysis of a synthetic mixture of five typical urinary stones: whewellite, hydroxylapatite, brushite, struvite, and uric acid, with 20 weight % for each pure component.

RESULTS

The quantitative phase analysis (Rietveld method) yielded a mean absolute error of only 1.6% for the weight fractions of the single urinary stone components. The largest error in weight fraction, 2.3%, occurred with hydroxylapatite, caused by the typical insufficient crystallinity.

CONCLUSION

Crystallographic analysis of complex urinary stones with the aid of x-ray diffraction, in combination with a Rietveld structure refinement, is the method of first choice for qualitative and quantitative phase analysis. With this tool, significant changes in weight fractions for recurrent urinary stones can be precisely detected, with therapeutic consequences.

[Urolithiasis in children--rational diagnosis, therapy, and metaphylaxis]

With a proportion of 1-5%, children constitute only a small number of all patients with urolithiasis. Nevertheless, pediatric stone disease is an important health care problem because of the high recurrence rate and the threat of progredient renal function impairment with consecutive loss of quality of life. Modern therapies, especially extracorporeal shock wave lithotripsy (ESWL), ureteroscopy (URS), and percutaneous nephrolithotomy (PCNL), have caused a revolution in the operative treatment spectrum. Open surgery is required for stone removal only rarely, such as for the simultaneous repair of urinary tract anomalies. The minimally invasive modalities of modern stone therapy - mainly ESWL as the treatment of first choice - have led to widespread disregard of stone metaphylaxis. The important principle that says an urinary stone is just a symptom and not the cause of the disease is often forgotten. So it must be noted that despite the high standard of care in Germany, not all problems regarding urinary stone disease are being resolved, particularly in childhood. This article presents the current knowledge of the most important aspects of stone therapy and the methods of treatment in children.

Urolithiasis in an acute lymphoblastic leukemia child during induction chemotherapy

An 11-year-old acute lymphoblastic leukemia patient suddenly developed severe abdominal flank pain and hematuria caused by renal stone during induction chemotherapy. The patient was treated with forced hydration, and the pain was relieved after the renal stone passed through. The renal stone was composed of calcium phosphate. The patient is currently in continuous complete remission, has had no recurrence of the urolithiasis, and is on consolidation chemotherapy. Although urolithiasis is extremely rare in childhood acute lymphoblastic leukemia, it should be considered in patients who complain of abdominal flank pain or back pain during chemotherapy.