Is stone free status really necessary for metabolic evaluation following stone removal procedures?

OBJECTIVE

To evaluate the impact of stone free status on the outcomes of metabolic evaluation in recurrent stone formers after ureteroscopic stone removal.

PATIENTS AND METHODS

A total of 78 patients undergoing retrograde intrarenal surgery (RIRS) for renal stones were included and cases were divided into two groups after 4 weeks based on the NCCT findings. While cases in the Group 1 (n = 54) was completely stone free, cases in Group 2 (n = 24) had residual fragments in the kidney. A full 24-h urine analysis for relevant stone forming risk factors has been performed after 4 weeks following the fURS procedures in all patients of both groups. Outcomes of metabolic evaluation (24-h urine and serum) have been comparatively evaluated in both groups.

RESULTS

Evaluation of the preoperative serum and urine stone forming risk factors revelaed no statistical difference in both groups. Comparative evaluation of the 24-h urinary stone forming risk factors also revealed no statistically significant difference between preoperative and postoperative findings in cases of Group 2 with residual stones. Last but not least, no significant difference was observed between the mean preoperative and postoperative serum variables between two groups.

CONCLUSIONS

Our results show that in the light of the similar metabolic evaluation outcomes obtained in cases with and without residual fragments, 'stone free status' may not be an essential factor to perform a detailed metabolic evaluation (24-h urine analysis and serum parameters) after endourological stone removal procedures.

Patient compliance for metabolic evaluation and medical treatment (CoMET) in calcium-oxalate stone patients: prospective study by EULIS eCORE study group

PURPOSE

In this study, we aimed to identify the compliance rates of calcium-oxalate stone patients for metabolic evaluation, diet and medical treatment and also determine the factors that are associated with poor compliance rates.

METHODS

This study was conducted by the EULIS eCORE working group prospectively. In the initial visit, demographic and stone-related characteristics were recorded. Patients were suggested metabolic evaluation, dietary advices and medical treatment. Follow-up visit was performed after 3 months and compliance rates were recorded. Logistic regression analysis was performed to determine factors associated with poor compliance to metabolic evaluation, diet and medical treatment.

RESULTS

Data of 346 patients from nine centers were analyzed. Compliance rates were 71.7%, 65.3%, and 63.7% for metabolic evaluation, diet, and medical treatment, respectively. In multivariate analysis, level of education (p = 0.003), history of emergency department visit (p = 0.04), number of stone surgeries (p = 0.03), patient care in dedicated stone clinic (p = 0.03), and history of shock wave lithotripsy (p = 0.005) were detected as independent predictors of compliance to metabolic analysis. Level of education (p < 0.001) and history of emergency department visit (p = 0.01) were detected as independent predictors of patient compliance to diet. Number of stone episodes (p = 0.03), family history of stones (p = 0.02), and polypharmacy (p < 0.001) were detected as independent predictors of patient compliance to medical treatment.

CONCLUSIONS

Patient compliance to metabolic evaluation, diet, and medical therapy is important for successful management of urolithiasis. Dietary advices and medications should be personalized by taking in to account the factors associated with poor compliance.

Serum and 24-hour urinary tests cost-effectiveness in stone formers

OBJECTIVE

To assess the routine serum and 24-hour urine tests proficiency in diagnosing the baseline metabolic abnormality of kidney stone formers.

METHODS

This study analyzes the routine serum and 24-hour urine tests proficiency in diagnosing the baseline metabolic abnormality of kidney stone formers. The sensitivity and specificity, false positive, and negative results of the tests are extracted from diagnostic kits used in the laboratories of the target community. To accurately infer the results, a simulation based on 1000 people was used through 22 standard laboratory tests (Additional File 2), including calcium, oxalate, phosphate, uric acid, sulfate, potassium, sodium, citrate, and magnesium in 24-hour urine; and calcium, creatinine, Vit D, uric acid, and intact parathyroid hormone (PTH) in serum. The incremental cost-effectiveness ratio (ICER) was calculated and compared for each diagnostic test versus other diagnostic tests according to the incremental cost required for correct diagnoses of stone causes.

RESULTS

Urinary uric acid, citrate, and serum potassium constitute the cost-effectiveness boundary curve in this study. This means that other diagnostic tests are not cost-effective compared to these three tests in terms of indexing at least one item of cost and effectiveness. The ICER index for each correct diagnosis with the urinary uric acid test was $ 1.25 per diagnosis, the most cost-effective test compared to serum potassium and urinary citrate.

CONCLUSION

The simplified blood and 24-hour urine metabolic evaluation, including urinary uric acid, citrate, and serum potassium, constitute the cost-effectiveness boundary curve. The most cost-effective test was urinary uric acid measurement.

Attitudes of urologists on metabolic evaluation for urolithiasis: outcomes of a global survey from 57 countries

Although stone disease is an important health problem with high incidence and recurrence rates, it is a preventable disease. Attitudes and practices of urologists regarding the prevention of recurrence continue to be a subject of debate. In this context, an online survey study was conducted involving 305 urologists from 57 different countries. The first 7 questions collected demographic data about the urologists and the remaining 23 questions were about the recurrence and metabolic evaluation, medical treatment, and follow-up of urinary stone disease. Most urologists (85.2%) thought that metabolic examination was important. Approximately one-third of the participants (34.1%) performed 24-hour urine analysis and stone analysis was ordered by 87.5% of the urologists. Metabolic analysis was performed for all patients by 14.7% of the participants. For pediatric patients this rate was 68.5%, and for adults with recurrence the rate was 81.6%. Reasons cited by the urologists for not performing metabolic analysis included not feeling confident doing so (18.3%), having limited facilities in their hospital (26.5%), having an excessive daily workload (31.8%), patient-related factors (27.5%), and referring patients to other departments for metabolic evaluation (20.9%). Although majority of the responding urologists do consider the metabolic analysis as vital important, they seemed not to be willing to perform these tests with the same degree of enthusiasm in their daily practice. Our results show that urologists need support in performing and interpreting 24-hour urine analysis, improving their knowledge levels, and communicating with patients. Urology residency training should focus more on the prevention of urinary stone recurrence in addition to the surgical training.

Acidification of 24-hour urine in urolithiasis risk testing: An obsolete relic?

BACKGROUND

Recommendations on the optimal preservation of 24 h urine for the metabolic work-up in urolithiasis patients are very heterogeneous. In case two such tests with different storage condition recommendations are being analysed, multiple collections would be needed, challenging especially elderly and very young patients. We therefore aimed to evaluate the stability of urine constituents under different storage conditions.

MATERIAL AND METHODS

We collected urine samples from ten healthy volunteers and prepared aliquots to be stored either at room temperature or 4 °C. Some aliquots were preserved using hydrochloric acid prior to storage, some thereafter, some using the BD Urine preservation tube and some were not preserved at all. Storage duration was 0, 24, 48 or 72 h. In all samples calcium, magnesium, phosphorus, creatinine, oxalate, citrate and uric acid were measured and compared to the according reference sample.

RESULTS

We could not find any significant deviation for any of the analytes and preanalytical treatment conditions compared to the associated reference sample.

CONCLUSION

Preservation of 24 h urine for the metabolic evaluation in stone formers might not be necessary for sample storage up to 72 h.

Three-channel ion chromatograph for improved metabolic evaluation of urolithiasis

Background

Urolithiasis is a multi-etiological disease resulting from a combination of environmental and genetic factors. One of the most challenging aspects of this disease is its high recurrence rate. For most patients, an in-depth metabolic evaluation may reveal the presence of urinary stones. The fact that different urinary stone-related compounds (USRCs) are measured by different methods renders the metabolic evaluation of urolithiasis quite tedious and complex.

Methods

A three-channel ion chromatograph (IC) that automatically measures the concentration of common metabolic indicators of urolithiasis in urine (i.e., oxalate, citrate, uric acid, calcium, and magnesium) was developed to improve the efficiency. To validate its precision and specificity, standard curves were prepared using working solution of these indicators. 100 standard solutions of these indicators were measured with our new IC and three other ICs as the control instruments; analyte concentrations in 100 24-h urine samples from volunteers and 135 calculi patients were also measured.

Results

All analytes had good linear relationships in concentration ranges of 0–10 mg/L. The precision experiments in the standard and urine samples showed that the measurement errors of the newly developed IC were all less than 5%. In urine, the recovery rate ranged from 99.6 to 100.4%, the coefficient of variation ranged from 1.39 to 2.99%, and the results matched between our newly developed IC and the control ICs. The results of the efficiency test showed that we can finish the analysis at the average number of 14 people per day with the new IC. While the average number in the control group is 3.85/day (p = 0.000).

Conclusions

Overall, this multi-channel system significantly improves the efficiency of metabolic evaluation while retaining accuracy and precision.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12894-021-00914-4.

Metabolic Evaluation: Place of the Calcium Load Test: How, When, For Whom, and Why?

Most human urinary stones are calcium-based and are often associated with hypercalciuria. A simple test described in 1975 by Pak et al allows for pathogenic classification of hypercalciuria: the calcium load test (CLT). The CLT explores calcium homeostasis after a low-calcium diet and then a calcium load (typically oral administration of 1 g of elemental calcium). Only simple laboratory equipment is required. Inadequate calcium excretion after a calcium-free diet or a calcium load is suggestive of resorptive or absorptive hypercalciuria, respectively. The CLT is particularly valuable in diagnosing primary hyperparathyroidism, even in most early stages of this disease. PATIENT SUMMARY: Kidney stone formation can be linked to calcium metabolism. When high calcium levels are found in urine despite adequate diet changes, a calcium load test may help to understand the underlying mechanisms. Urine and blood levels are explored during a low-calcium diet phase, and after a calcium load phase in the test. The calcium load test is particularly advantageous for revealing abnormally high function of the parathyroid gland, which is called hyperparathyroidism.

Integration of exome sequencing and metabolic evaluation for the diagnosis of children with urolithiasis

PURPOSE

To investigate the prevalence of inherited causes in an early onset urolithiasis cohort and each metabolic subgroup.

METHODS

A retrospective analysis of both metabolic and genomic data was performed for the first 105 pediatric urolithiasis patients who underwent exome sequencing at our hospital from February 2016 to October 2018. Measurements included the diagnostic yield of exome sequencing in the entire cohort and each metabolic subgroup (hyperoxaluria, hypocitraturia, hypercalciuria, hyperuricosuria and cystine stone subgroups). The conformity between molecular diagnoses and metabolic evaluation was also evaluated.

RESULTS

The present study involved a cohort of 105 pediatric patients with urolithiasis, from which diagnostic variants were identified in 38 patients (36%), including 27 primary hyperoxaluria and 11 cystinuria. In the metabolic subgroup analyses, 41% hyperoxaluria cases were primary hyperoxaluria caused by monogenic defects, and 100% of the causes of cystine stones could be explained by monogenic defects. However, no appropriate inherited causes were identified for hypocitraturia, hypercalciuria, or hyperuricosuria in the cohort. A high conformity (100%) was obtained between the molecular diagnoses and metabolic evaluation.

CONCLUSION

Exome sequencing in a cohort of 105 pediatric patients with urolithiasis yielded a genetic diagnosis in 36% of cases and the molecular diagnostic yield varies substantially across different metabolic abnormalities.

[Establishment and primary clinical application of metabolic evaluation database of urolithiasis]

Objective: To establish the metabolic evaluation database of urolithiasis, perform metabolic evaluation, and provide instructions for treatment and prevention of urolithiasis. Methods: This metabolic evaluation database was developed by JAVA and was established by Oracle11g database and Browser/Server framework. We extracted the clinical data of all patients who had complete information, and analyzed their risk factors of stone formation, stone-related medical history, blood and urine tests results and 24-hour urine analysis. Results: A total of 360 patients diagnosed as urolithiasis were included in this research. Male to female ratio was 1.9∶1, and the urolithiasis was first diagnosed at (35.5±13.5) years old. Family history was positive in 39.7% of patients. Metabolic syndrome occurred in 35.0% of patients. Overweight or obesity occurred in 73.2% and 50.0% of male patients, respectively. Abdominal obesity in 62.3% and 56.1% of male and female patients, respectively. Among all patients, 67.5% had high urine sodium, 53.6% had hypercalciuria, 41.1% had hypocitraturia, 29.7% had hyperuricosuria, 22.5% had hypomagnesuria, 15.8% had hyperoxaluria, 11.7% had hyperphosphoraturia, and 36.4% had low urinary volume. Conclusions: The prevalence of overweight or obesity, abdominal obesity, hypertension, diabetes, and metabolic syndrome in stone patients were significantly higher than those in general population. The number of 24-hour urinary abnormalities was positively associated with body mass index. The interventions on high urinary sodium, low urinary volume, obesity and metabolic syndrome were important to the treatment of urolithiasis. This database would facilitate the metabolic evaluation, provide evidence for the treatment and prevention of urolithiasis, and lay foundation for finding important controllable risk factors of urinary stone.

Metabolic evaluation and medical management of staghorn calculi

Staghorn renal calculi are large renal calculi that occupy nearly the entirety of the renal collecting system. They may be composed of metabolic or infection stone types. They are often associated with specific metabolic defects. Infection stones are associated with urease-producing bacterial urinary tract infections. The ideal treatment for staghorn calculi is maximal surgical removal. However, some patients are either unwilling or unable to proceed with that modality of treatment, and therefore other management must be used. One such technique is the metabolic evaluation with directed medical management. Based on contemporary evidence that the majority of staghorn stones are metabolic in etiology, and furthermore that even infection stones are usually associated with metabolic abnormalities, metabolic evaluation with directed medical management is recommended for all staghorn stone formers. The scientific basis of this recommendation is reviewed in the present work.

A preliminary survey of practice patterns across several European kidney stone centers and a call for action in developing shared practice

Currently an evidence-based approach to nephrolithiasis is hampered by a lack of randomized controlled trials. Thus, there is a need for common platforms for data sharing and recruitment of patients to interventional studies. A first step in achieving this objective would be to share practice methods and protocols for subsequent standardization in what is still a heterogeneous clinical field. Here, we present the results of a pilot survey performed across 24 European clinical kidney stone centers. The survey was distributed by a voluntary online questionnaire circulated between June 2017 and January 2018. About 46% of centers reported seeing on average 20 or more patients per month. Only 21% adopted any formal referral criteria. Centers were relatively heterogeneous in respect of the definition of an incident stone event. The majority (71%) adopted a formal follow-up scheme; of these, 65% included a follow-up visit at 3 and 12 months, and 41% more than 12 months. In 79% of centers some kind of imaging was performed systematically. 75% of all centers performed laboratory analyses on blood samples at baseline and during follow-up. All centers performed laboratory analyses on 24-h urine samples, the majority (96%) at baseline and during follow-up. There was good correspondence across centers for analyses performed on 24-h urine samples, although the methods of 24-h urine collection and analysis were relatively heterogeneous. Our survey among 24 European stone centers highlights areas of homogeneity and heterogeneity that will be investigated further. Our aim is the creation of a European network of stone centers sharing practice patterns and hosting a common database for research and guidance in clinical care.

Defining metabolic activity of nephrolithiasis - Appropriate evaluation and follow-up of stone formers

Considering the variation in metabolic evaluation and medical management of kidney stone disease, this consensus review was created to discuss the metabolic activity of nephrolithiasis, define the difference between single and recurrent stone formers, and develop a schema for metabolic and radiologic follow-up. A systematic review of the literature was performed to identify studies of metabolic evaluation and follow-up of patients with nephrolithiasis. Both single and recurrent stone formers share many similarities in metabolic profiles. The study group determined that based on an assessment of risk for stone recurrence and metabolic activity, single and recurrent stone formers should be evaluated comprehensively, including two 24 h urine studies on a random diet. Targeted medication and dietary recommendations are effective for many patients in reducing the risk of stone recurrence. Follow-up of those with stone disease should be obtained depending on the level of metabolic activity of the patient, the risk of chronic kidney disease and the risk of osteoporosis/osteopenia. A standard scheme includes a baseline metabolic profile, a repeat study 3-6 months after initiation of treatment, and then yearly when stable, with abdominal imaging obtained every 1-2 years.

Accuracy in 24-hour Urine Collection at a Tertiary Center

There is a paucity of studies addressing the accuracy of 24-hour urine collection for assessing stone risk parameters. Collection accuracy is thought to be essential for assigning optimal therapy for stone prevention. The objective of this study was to determine factors associated with accurate and inaccurate collections. During a 2-year period (2015-2016), 241 stone formers completed 24-hour urine collections. They were divided into accurate collectors (AC), defined as at least one accurate urine collection, and inaccurate collectors (IC). Accuracy was assessed by 24-hour urine creatinine (Cr) excretion indexed to body weight (normal: males, 20-25 mg Cr/kg; females, 15-20 mg Cr/kg). Demographic data analyzed included age, gender, race, insurance status, partner status, income, and education. Statistical analysis methods included the chi-square test, Fisher's exact test, and the two-group t-test. Average age was 50.7 years at the time of collection; 50.2% were men, 86% were white, and 14% were black. Overall, 51.0% of collections were inaccurate. There was no statistical significance between AC and IC for gender (P = 0.85), race (P = 0.90), insurance status (P = 0.85), recurrence (P = 0.87), stone type (P = 0.57), education (P = 0.35), income (P 5 0.42), or poverty (P = 0.35). Older age (P = 0.017) and having a partner (P = 0.022) were significantly associated with AC. The high rate of inaccurate 24-hour urine collections is a concern. The only factors we identified as influencing collection accuracy were age and partner status. These results underscore the importance of developing methods to improve the accuracy of collecting 24-hour urine samples.

Renal stone clinic survey: calcium stone formers' self-declared understanding of and adherence to physician's recommendations

Nothing is known about how well stone formers understand physician's explanations of stone formation, and a few data are available on adherence to provided recommendations. In this study, two groups of recurrent calcium stone formers (RCSFs) were compared. Group 1: 153 consecutive RCSF (118 men, 35 women) referred 1/2011-6/2014. At least 3 months after a 60-75 min consultation explaining metabolic evaluation and therapeutic measures, RCSF received a questionnaire by mail, regarding understanding of stone formation and adherence to therapeutic recommendations (diet, lifestyle, drug treatment). Response rate was 62 %. Group 2 (control): 81 consecutive RCSFs referred 7/2014-3/2016 (60 men, 21 women) were asked to answer the same questionnaire in the stone center while waiting for their follow-up consultation 3 months after starting prevention; response rate was 100 %. Alkali citrate was prescribed in 45 %. Answer sheets were analyzed anonymously, and frequencies of answers were compared by Chi-square test.

RESULTS

67 % (group 1) and 62 % (group 2) indicated >80 % understanding of the given information (NS). Over 80 % adherence to recommendations occurred in 26 and 30 % (NS). Most frequent changes in dietary/lifestyle habits were increases in calcium (93 vs. 89 %) and fluid intakes (81 vs. 78 %); lowering psychosocial stress (23 vs. 24 %) was least popular. Adherence to 100 % on 6-7 days/week was significantly more frequent for medication than for dietary/lifestyle interventions, both in group 1 (84 vs. 24 %, p < 0.001) and group 2 (91 vs. 28 %, p < 0.001).

CONCLUSIONS

(1) results do not differ whether RCSFs are voluntarily participating by mail or asked to answer questionnaires in the stone clinic; (2) pathophysiologic explanations of stone disease are understood to >80 % by 2/3 of RCSFs; (3) after 3 months, perfect adherence to recommended treatment is more frequent on alkali citrate than on dietary/lifestyle measures; and (4) increasing calcium and fluid intake are the most popular dietary measures.

Frequency of metabolic abnormalities in urinary stones patients

OBJECTIVE

To determine the frequency of metabolic abnormalities in the serum and urine of patients with urinary stones disease.

METHODS

Two hundred patients with either multiple or recurrent urolithiasis diagnosed on ultrasonography and intravenous urography were included in this study. 24 hour urine sample were collected from each patient and sent for PH, specific gravity, Creatinine, uric acid, calcium, phosphate, oxalate, citrate and magnesium. In addition, blood sample of each patient was also sent for serum levels of urea, creatinine, uric acid, phosphate and calcium.

RESULTS

Mean age of patients was 38 ± 7.75 years with male to female ratio of 2:1. The main presenting complaint was lumber pain and 82.5% patients were found to have calcium oxalate stones on chemical analysis. Metabolic abnormalities were found in 90.5% patients, whereas there were no metabolic abnormalities in 19 (9.5%) patients. Forty patients (21.5%) only had one metabolic abnormality and 157 (78.5%) patients had multiple metabolic abnormalities. Hyperoxaluria was the most commonly observed metabolic abnormality and was found in 64.5% patients. Other significant metabolic abnormalities were hypercalciuria, Hypercalcemia, hypocitraturia and hyperuricemia.

CONCLUSION

This study concludes that frequency of metabolic abnormalities is very high in patients with urolithiasis and hyperoxaluria, hypercalciuria and hypocitraturia are the most important metabolic abnormalities observed in these patients.