Causes and consequences of kidney loss in patients with nephrolithiasis

Association between Kidney Stones and CKD: A Bidirectional Mendelian Randomization Study

Background:

Kidney stones and CKD are common disorders with a substantial interaction. Although observational studies have suggested a potential for enhanced CKD risk after prior kidney stones, the exact relationship remains ambiguous.

Methods:

Shared comorbidities between two diseases were identified using unbiased screening. Genome-wide association study summary statistics were obtained from the UK Biobank (UKBB), FinnGen, and CKDGen, followed by genetic association analyses across various traits. Bidirectional Mendelian randomization (MR) analyses were performed to define causal links, complemented by multivariable MR that included the shared comorbidities including hypertension, diabetes, and obesity. Observational analyses were undertaken using cohorts from the Mayo Clinic and a UKBB subset.

Results:

Despite identifying a total of 123 conditions as shared comorbidities, there was no significant genetic correlation between kidney stones and CKD. Unadjusted MR analysis revealed no significant association between kidney stones and CKD risk (UKBB [exposure]/FinnGen [outcome]: OR=0.97, 95% CI: 0.88∼1.06; FinnGen/UKBB: OR=1.17, 95% CI:0.98∼1.39). Kidney stones did significantly associate with a higher urinary albumin-creatinine ratio (UACR) (β=0.014, 95% CI: 0.002∼0.025), but this association disappeared in the multivariable MR model (β=0.009, 95% CI: -0.003∼0.020). Furthermore, in a cross-sectional analysis limited to the UKBB cohort, a robust regression model did not detect an independent association between kidney stones and UACR (β=0.16, 95% CI: -0.04∼0.35) or eGFR (β=0.10, 95% CI: -0.07∼0.28). Conversely, CKD associated with a diminished risk of kidney stones in multivariable MR models (UKBB/FinnGen: OR=0.77, 95% CI: 0.69∼0.87; FinnGen/UKBB: OR=0.73, 95% CI: 0.66∼0.81). Furthermore, in the Mayo Clinic cohort with available urinary biochemistries, lower eGFR was associated with lower urinary calcium excretion and urinary calcium oxalate/phosphate supersaturation.

Conclusions:

In this study, kidney stones were not independently associated with CKD. Conversely, CKD was associated with a lower risk of calcium kidney stones likely via changes in key urinary traits, including lower calcium excretion.

Does age impact outcomes of retrograde intrarenal surgery in the elderly? Results from 366 patients from the FLEXible ureteroscopy outcomes registry (FLEXOR)

BACKGROUND

There has been a consistent increase in the last decades in prevalence of renal stones in elderly.

AIMS

To evaluate outcomes of retrograde intrarenal surgery (RIRS) for renal stones in elderly and factors associated with postoperative complications and residual fragments (RFs).

METHODS

Data from 12 centers were retrospectively reviewed.

INCLUSION CRITERIA

 ≥ 75 years, renal stones only, normal renal anatomy. Patients were divided into three groups; Group 1: patients aged 75-79 years; Group 2: age 80-84 years; Group 3: age ≥ 85 years. Multivariable logistic regression analyses were performed to assess factors associated with perioperative complications, sepsis, and RFs.

RESULTS

366 patients were included. There were 189 patients in Group 1, 113 in Group 2, and 64 in Group 3. There was no difference between groups regarding stone features and total surgical time. Median length of stay was significantly longer in Group 3 (6.0 days, vs 2.0 days in Group 2 vs 2.5 days in Group 1, p = 0.043). There was no significant difference in postoperative complications and RFs between the groups. At multivariable logistic regression analysis, female gender (OR 2.82) and maximum stone diameter (OR 1.14) were associated with higher odds of sepsis, while surgical time (OR 1.12) and the use of a reusable ureteroscope (OR 6.51) with overall complications. Stone size (OR 1.23) was associated with higher odds of RFs.

CONCLUSION

RIRS showed safety and efficacy for kidney stones in elderly patients. Surgical time should be kept as short as possible to avoid higher odds of postoperative complications, particularly in females.

Increased risk of chronic kidney disease in uric acid stone formers with high neutrophil-to-lymphocyte ratio

Urolithiasis is associated with an increased risk of chronic kidney disease (CKD), irrespective of stone compositions. Chronic inflammation is an important factor for CKD progression. Neutrophil-to-lymphocyte ratio (NLR) has been recognized as a reliable biomarker of inflammation, yet its use in predicting renal deterioration in patients with urolithiasis remains limited. We aimed to explore whether the combination of stone composition and NLR could be useful as a predictor for CKD risk. A total of 336 stone formers with at least one stone submission for analysis were enrolled in the retrospective study. Stones were classified into uric acid and calcium groups. Renal functions were assessed at least one month after stone treatment. Uric acid stone formers had significantly lower estimated glomerular filtration rate (eGFR) compared with calcium stone formers (p < 0.001). NLR was significantly higher in uric acid stone formers (p = 0.005), and a significantly negative correlation (p < 0.001) between NLR and eGFR had been observed only in uric acid stone group. Univariate and multivariate logistic regression analyses showed that higher proportion of uric acid stone composition and higher NLR were both significantly associated with CKD risks. A nomogram integrating independent predictors was generated for CKD prediction, yielding an AUC of 0.811 (0.764-0.858). In conclusion, our study demonstrated that stone formers with higher proportion of uric acid composition and higher NLR levels were associated with higher CKD risk.

Ureteroscopy in the elderly: safety and functional results

PURPOSE

To evaluate the effectiveness and safety of ureteroscopy (URS) for urinary stones treatment in patients ≥ 80 years of age.

METHODS

From 2012 to 2021, 96 patients ≥ 80 years underwent URS for urinary stone disease. Patients' demographics and surgical outcomes were examined.

RESULTS

The median length of follow-up was 25 months. Median age was 84 years. Half of the patients (53%) were ASA score 3 and 16% ASA 4. Mean stone diameter (SD) was 10.6 mm, and mean procedure time was 78 min. Eighty-three patients underwent follow-up imaging (ultrasonography or computed tomography) with a median time of 31 days. Stone-free rate was 73.9%. Twenty patients (20.7%) experienced a minor complication [Clavien-Dindo (CD) I-II] whereas five (5.7%) experienced a major complication (CD III-V). SD ≥ 10 mm predicted CD III-V complications (OR 1.25, 95% CI 1.01-1.55, p = 0.03). Urinary drainage prior the procedure with double J stent, nephroureteral stent or percutaneous nephrostomy tube had no impact on patients' SFR [74.6% in the drained group versus 64.0% in the undrained group (p = 0.44)] nor on major complications (OR 4.68, 95% CI 0.25-87.77, p = 0.30).

CONCLUSION

In elderly patients, URS for treatment of renal and ureteral stones is a relatively efficient and safe procedure. The risk of major complications is low, and the only associated risk factor found was SD ≥ 10 mm. Urinary drainage prior the procedure did not affect patients' outcomes.

Safety and efficacy of ureteroscopy for urolithiasis in octogenarians

OBJECTIVE

To examine the safety and efficacy of ureteroscopy (URS) for urolithiasis in octogenarians, and identify preoperative risk factors for the incidence of postoperative complications.

METHODS

The patients who underwent URS for urolithiasis were divided into octogenarians and younger patients (age: <80 years), and the groups were compared regarding their clinical characteristics, intraoperative and postoperative complications, and stone-free rate. The predictors of postoperative complications were evaluated using logistic regression models.

RESULTS

A total of 1207 patients were included, 166 in the octogenarian patient group and 1041 in the younger patient group. The proportion of female patients (p < 0.001), American Society of Anesthesiologists (ASA) score (p < 0.001), rate of preoperative pyelonephritis (p < 0.001), and diabetes mellitus (p = 0.003) were higher in the octogenarian group. No statistically significant differences were found between the two groups regarding stone size, location, and intraoperative complications. Postoperative complications, which reached a significant difference, were observed in 34 (20.5%) octogenarians and 117 (11.2%) younger patients (p = 0.002). However, age itself was not significantly associated with postoperative fever, the most frequent postoperative complication, in multivariate analysis. Female sex, ASA score of ≥3, history of diabetes mellitus, and prolonged operative time (≥120 min) were the significant predictors of fever. The stone-free rate in the octogenarian group was superior to that in the younger patient group (80.1% vs. 70.6%, respectively; p = 0.035).

CONCLUSION

Our results suggest that URS for urolithiasis can be safely and effectively applied to octogenarians in selected cases.

Effect Modification of Hyperuricemia, Cardiovascular Risk, and Age on Chronic Kidney Disease in China: A Cross-Sectional Study Based on the China Health and Nutrition Survey Cohort

Introduction

The question of whether the increased burden of chronic kidney disease (CKD) is caused by the interaction of hyperuricemia and cardiovascular disease (CVD) risk factors or is accelerated by aging remains unresolved. The purpose of this study is to better understand the effect modification of hyperuricemia, cardiovascular risk, and age on CKD among the Chinese population.

Methods

This cross-sectional study of 8243 participants was derived from the China Health and Nutrition Survey (CHNS) in 2009. Inclusion criteria included age ≥18 years, non-pregnancy, and no history of high-protein diet prior to blood test. Demographics, comorbidities, health-related behaviors, and serum biomarkers were collected. Interaction association of hyperuricemia, CVD risk and age with CKD were analyzed using Logistic regression.

Results

CKD was detected in 359 (27.2%, 95% CI 24.8∼29.7%) of 1321 participants with hyperuricemia and 680 (9.8%, 95% CI 9.1∼10.5%) of 6,922 participants without hyperuricemia, and these patterns remained significant after controlling for age, gender, and Framingham risk score (adjusted odds ratio [aOR] 3.82, 95% CI 3.20∼4.57). We found a negative multiplicative interaction between hyperuricemia and CVD risk on CKD. The aOR in low-CVD risk groups was 5.51 (95% CI 4.03∼7.52), followed by medium-CVD risk groups (aOR: 3.64, 95% CI 2.61∼5.09) and high-CVD risk groups (aOR: 2.89, 95% CI 2.12∼3.96). CVD risk was less associated with CKD in hyperuricemia group (aOR: 0.92, 95% CI 0.68∼1.22) than in non-hyperuricemia group (aOR: 1.43, 95% CI 1.21∼1.70). Furthermore, hyperuricemia and age had a significant additive effect on CKD, with a synergy index of 2.26 (95% CI 1.45∼3.52). Coexisting with older age and hyperuricemia, the likelihood of developing CKD was higher than the sum of the two alone.

Conclusion

The link between hyperuricemia and CKD begins at a young age and becomes stronger in the low CVD risk group. For young adults, early detection of hyperuricemia, routine CVD risk assessment, and timely intervention of modifiable factors are warranted.

Efficacy and safety of percutaneous nephrolithotomy in patients with chronic kidney disease: Outcomes from a tertiary care center

BACKGROUND

The management of renal stone disease in the presence of chronic kidney disease is a challenging scenario, both in terms of surgical safety as well as perioperative outcomes. The aim of the present study is to study the efficacy, safety, and outcomes of percutaneous nephrolithotomy in patients with chronic kidney disease.

MATERIALS AND METHODS

A prospective study was conducted including adult patients with renal stone disease and a creatinine clearance of <90ml/min (Stage 2 CKD or more) who underwent percutaneous nephrolithotomy. Pre-operative and post-operative serum creatinine and glomerular filtration rates were compared. Patients were divided into CKD stages 1-5 having creatinine clearance >90ml/min, 60-90ml/min, 30-60ml/min, 15-30ml/min and <15ml/min respectively. Based on up migration or down migration of CKD stages, patients were classified as improved, deteriorated or stable. Peri-operative complications and outcomes were also compared.

RESULTS

A total of 185 patients with CKD stage less than or equal to 2 underwent PCNL. The mean age of the patients was 43.24+/-14.32 years. The mean preoperative estimated glomerular filtration rate was 62.88±23.42mL/min/1.73m2. Pre-operative CKD stage distribution was as follows: stage 2-121(65.4%), stage 3-34(18.4%), stage 4-24(13%) and stage 5-6(3.2%). On last follow-up of patients, the mean creatinine was 1.07±0.65 mg/dL and the mean eGFR was 82.75±31.22 mL/min/1.73m2. The median change in creatinine and mean change in GFR was 0.23 (0.16-0.27) g/dL and 19.87 ± 19.77 mL/min/1.73 m2 respectively. Improvement in kidney function with a stage down migration was seen in 115 cases(62.2%), slight improvement with no change in stage in 69 cases(37.3%) and deterioration of CKD stage was present in one case(0.5%).

CONCLUSION

Percutaneous nephrolithotomy is associated with favourable functional outcomes in chronic kidney disease patients including severe CKD(stage IV and V). Improvement or stabilization of CKD stage was seen in 99.5% patients post PCNL.

[Cystinuria]

Cystinuria is the most common monogenic nephrolithiasis disorder. Because of its poor solubility at a typical urine pH of less than 7, cystine excretion results in recurrent urinary cystine stone formation. A high prevalence of high blood pressure and of chronic kidney disease has been reported in these patients. Alkaline hyperdiuresis remains the cornerstone of the preventive medical treatment. To reach a urine pH between 7.5 and 8 and a urine specific gravity less than or equal to 1.005 should be the goal of medical treatment. D-penicillamine and tiopronin, two cysteine-binding thiol agents, should be considered as second line treatments with frequent adverse events that should be closely monitored.

Flexible ureteroscopy in extreme elderly patients (80 years of age and older) is feasible and safe

PURPOSE

To compare the safety and efficacy of RIRS in patients ≥ 80 years to a younger population.

METHODS

We retrospectively compared the data from patients ≥ 80 years of age undergoing RIRS with the data of a group of patients from 18 and < 80 years. Perioperative outcomes, complications and emergency department visits were compared between two groups.

RESULTS

A total of 173 patients were included in the study. Mean age was 44 (27-79) and 81 years-old (80-94), for younger and elderly group, respectively. Elderly patients had higher ASA scores (≥ 3) (28.6% vs 75.8%; p = 0.0001) and Charlson comorbidity index (1.99 vs 7.86; p = 0.0001), more diabetes (p = 0.006) and respiratory comorbidities (p = 0.002). No statistical difference was found between two groups in stone size (p = 0.614) and number (p = 0.152). Operative time (74.48 vs 102.96 min; p = 0.0001) and duration of hospitalisation (1.7 vs 2.9 days; p = 0.001) were longer for the elderly. Intraoperative complication rate did not show differences between the two groups (p = 0.166). Postoperative complications rates were similar between the cohorts (7.7% vs 9.5%; p = 0.682). The success rates were 67.5% in the younger group and 71.4% in the elderly group (p = 0.584). No difference was seen in stone recurrence (p = 0.73). A higher rate of visits to the emergency department was found in younger cohort (23.6% vs 11.6%; p = 0.046), mostly duo to stent-related symptoms.

CONCLUSIONS

Despite the higher rate of comorbidity in the elderly group, RIRS was a safe procedure with similar complication rate and outcomes at an expense of higher operative time and hospital stay.

Association of Chronic Kidney Disease Stage with 24-Hour Urine Values Among Patients with Nephrolithiasis

Introduction: Nephrolithiasis is a known risk factor for chronic kidney disease (CKD); however, it is unknown how CKD affects urinary parameters related to stone risk. The purpose of this study was to assess the relationship of diminishing glomerular filtration rate (GFR) and kidney stone-related 24-hour urine (24H urine) composition. Materials and Methods: A single-institution retrospective review of patients (n = 2057) who underwent 24H urine analysis was performed. The serum creatinine within 1 year of the first 24H urine was used to determine estimated GFR and stratify patients by CKD stage. We performed analysis of variance and multivariable linear regression to assess the relationship of GFR and urinary analytes. Results: Among all patients, there were 184 (8.9%), 1537 (74.7%), 245 (11.9%), 70 (3.4%), 17 (0.8%), and 4 (0.2%) in CKD stage I, II, IIIa, IIIb, IV, and V groups, respectively. On analysis of 24H urine composition, as CKD increased, changes in urinary parameters protective against crystallization included decreased calcium and uric acid (UA) (P < 0.001). In addition, parameters favoring crystallization included decreased citrate and magnesium (P = 0.002 and P < 0.001, respectively). The net effect with increasing GFR was decreasing supersaturation of calcium oxalate and phosphate. On linear regression, urinary excretion of calcium, oxalate, citrate, UA, phosphate, and ammonia all decreased with decreasing GFR (all P < 0.05). Conclusions: Higher CKD stage was associated with changes in urinary analytes that both promoted and inhibited stone formation, with the net effect of decreasing calcium oxalate and phosphate supersaturation. These patients may benefit from medical therapy that targets improving urinary citrate instead of lowering calcium or UA.

Chronic kidney disease and kidney stones

PURPOSE OF REVIEW

Both chronic kidney disease (CKD) and kidney stones are major public health problems, which are closely interrelated. Recurrent kidney stones predispose to CKD although CKD seems to decrease risk of further kidney stone formation. Herein, we review new information of this interrelationship.

RECENT FINDINGS

Several epidemiological studies in the past have shown an association between history of kidney stones and risk for CKD and CKD progression. Recent literature supports this concept and it is reviewed in this article. The issue of whether CKD protects against new kidney stone formation remains unsettled and there is no recent literature addressing it. In relation to stone risk factors in CKD, there are several interesting new articles that discuss mechanisms of hypocitraturia in early CKD before overt metabolic acidosis. Since hypocitraturia is an important risk factor for kidney stone formation we addressed these new data in detail. There are also new data supporting urinary oxalate excretion as a predictor of CKD progression.

SUMMARY

It seems clear that recurrent kidney stones should be avoided not only because of their immediate clinical manifestations but also because of their long-term predisposition to CKD progression. Mechanisms leading to hypocitraturia in early CKD still remain controversial.

To study the incidence and preintervention factors associated with acute kidney injury in patients diagnosed with ureteric calculi

Aims and Objectives:

The study aims to evaluate the incidence and factors associated with acute kidney injury (AKI) among patients presenting with ureteric calculi. We also intend to study the impact of time delay since first symptom to presentation to our hospital among patients with ureteric calculi and its influence on AKI.

Material and Method:

The study is a prospective observational study and included all symptomatic ureteric calculi patients. AKI was defined as per the KDIGO guidelines. All the patients diagnosed with ureteric calculi were grouped into those having an episode of AKI and those without an episode on AKI.

Results:

The incidence of AKI in our study was 14.63% (18 patients) among 123 patients of ureteric calculi. Average time delay from time of diagnosis to presentation among patients with AKI was 31.7±6.2 days (mean ± S.D) as compared to 19.5±5.7 (mean ± S.D) days among all cases. Factors which were significantly associated with AKI in patients with ureteric calculi include time delay, diabetes mellitus, bilateral ureteric calculi, stone size greater than 10 mm, solitary functioning kidney and urine culture showing gram negative growth. Fifty percent of the AKI group eventual required nephrectomy of one renal unit.

Conclusion:

This study will help us streamline our resources predominantly towards those patients who present with factors associated with increased risk of AKI. As the time delay to presentation in patients with AKI with ureteric calculi is significantly higher, it is imperative to counsel patients with stone disease.

Vitamin K1 Inhibition of Renal Crystal Formation through Matrix Gla Protein in the Kidney

BACKGROUND AND OBJECTIVES

Vitamin K (VK) plays a major role in modifying the binding of calcium in bones and blood vessels. Understanding the effect of VK on crystal formation in the kidney would contribute to advancing the treatment and prevention of kidney stones.

METHODS

Rats were treated with vitamin K1 (VK1) for 8 weeks. VK1 levels were detected and crystal formation were observed. HK2 cells were exposed to calcium oxalate monohydrate crystals. Apoptosis and cell viability were detected. Crystal deposition was analyzed using atomic absorption assay. The adenovirus vectors expressing matrix Gla protein (MGP) and siMGP were constructed to elucidate the effect and mechanism of VK1 on crystal formation. MGP expression in vivo and in vitro was analyzed by Western blot. The mRNA levels of monocyte chemoattractant protein-1 (MCP-1) and collagen I was measured by semiquantitative RT-PCR.

RESULTS

The concentrations of VK1 in whole blood and kidney tissues rose under treatment with VK1. Crystal formation was inhibited from the second to the 6th week, the frequency and quality of crystal formation decreased significantly, and the location of crystal formation was limited to a greater extent in the rats treated by VK1 compared to the control group. Warfarin treatment in the crystals-exposed HK2 cells significantly increased the number of crystals adhering to cells and the number of apoptotic cells and reduced cell viability. VK1 treatment reversed warfarin's above influence. VK1 inhibited the upregulations of MCP-1 and collagen I in kidney tissues under crystal load. VK1 treatment increased MGP expression in vivo and in vitro, and MGP is necessary for VK1 to play a role in crystal deposition in cells.

CONCLUSIONS

VK1 treatment can inhibit the formation of renal crystals in vivo. VK1 increases MGP expression and functions through MGP to reduce crystal deposition in cells and provide cell protection. Our findings suggest that VK1 treatment could be a potential strategy for the treatment and prevention of nephrolithiasis.

Kidney Stones and Risk of Osteoporotic Fracture in Chronic Kidney Disease

Osteoporotic fracture associated with calcium dysregulation is more common in patients with kidney stones. However, little is known about the association of kidney stones and bone health status in patients with chronic kidney disease (CKD). This retrospective medical record-based study included 2282 patients with stable stage 3–4 CKD between 2007 and 2017. Of these, 113 patients were diagnosed with kidney stones. Propensity score matching for 226 patients with and without kidney stones showed that osteoporotic fracture occurred more often in patients with kidney stones (33, 29.2%) than in patients without kidney stones (16, 14.2%), resulting in rates of 5.56 and 2.63/100 patient-years, respectively (p < 0.01). In particular, Cox proportional hazard analysis revealed that kidney stones were significantly associated with osteoporotic fracture, even after adjusting for age, sex, body mass index, kidney stones, estimated glomerular filtration rate, excessive alcohol consumption, current smoking, and steroid use in patients with CKD stage 3–4 (hazard ratio, 2.32, 95% CI 1.24–4.34, p = 0.01). This study showed that the presence of kidney stones was a significant predictor for osteoporotic fracture in patients with CKD, suggesting that it should be considered as a clinical risk factor for osteoporotic fracture in them.

Living kidney donation from people at risk of nephrolithiasis, with a focus on the genetic forms

Deciding whether to accept a donor with nephrolithiasis is a multifaceted task because of the challenge of finding enough suitable donors while at the same time ensuring the safety of both donors and recipients. Until not long ago, donors with a history of renal stones or with stones emerging during screening on imaging were not considered ideal, but recent guidelines have adopted less stringent criteria for potential donors at risk of stones. This review goes through the problems that need to be approached to arrive at a wise clinical decision, balancing the safety of donors and recipients with the need to expand the organ pool. The risk of declining renal function and worsening stone formation is examined. Documents (consensus statements, guidelines, etc.) on this issue released by the most important medical societies and organizations are discussed and compared. Specific problems of living kidney donation associated with certain systemic (chronic hypercalcemia due to CYP24A1 gene mutations, primary hyperoxaluria, APRT deficiency) and renal (medullary sponge kidney, cystinuria, distal renal tubular acidosis, Dent's disease, Bartter syndrome, familial hypomagnesemia with hypercalciuria and nephrocalcinosis) Mendelian disorders that cause nephrolithiasis are also addressed.

Uric acid stones increase the risk of chronic kidney disease

The aim of this study was to compare the clinical characteristics of uric acid stones and their potential risk for chronic kidney disease (CKD). A total of 401 patients (196 with uric acid stone and 205 without) were enrolled from our database of patients with urolithiasis. We analyzed the clinical demographic features, stone location, urine chemistries, and renal function. There was a significant difference (p < 0.001) between the two groups in terms of age, with the higher mean age in the uric acid group. Patients with uric acid stones had much lower pH of urine (p < 0.001) and higher serum uric acid level (p = 0.002). Notably, those with uric acid stones had worse eGFR than those with non-uric acid stones. Multivariate analysis confirmed that age over 60 years (ORs = 9.19; 95% CI 3.5-24.3), female sex (ORs = 4.01; 95% CI 1.8-9.0), hyperuricemia (ORs = 8.47; 95% CI 1.6-43.5), and uric acid stone (OR = 2.86; 95% CI 1.2-6.7) were the independent predictors of poor prognoses in CKD. Therefore, an association exists between uric acid stones and higher prevalence of CKD. Patients with uric acid stones may need close monitoring of renal function during follow-up.

Formation of struvite urinary stones and approaches towards the inhibition-A review

BACKGROUND

Struvite is one of the most common urinary/kidney stones, composed of magnesium ammonium phosphate (MgNHPO₄·H₂O). They are also termed as infection stones as these are associated with urinary tract infections. Numerous studies have been carried out to examine the growth and inhibition of struvite stones.

OBJECTIVE

This review summarizes various reports on the factors responsible for inducing struvite stones in the kidney and gives a detailed account of studies on inhibition of growth of struvite crystals.

RESULTS

The presence of urea-splitting bacteria such as Proteus mirabilis and alkaline pH plays a crucial role in struvite formation. In vitro inhibition of struvite stones by various chemical agents were examined mainly in artificial urine whereas inhibition by herbal extracts was studied in vitro by gel diffusion technique. Herbal extracts of curcumin, Boerhaavia diffusa Linn, Rotula aquatica and many other plants, as well as some chemicals like pyrophosphate, acetohydroxamic acid, disodium EDTA and trisodium citrate, were reported to successfully inhibit struvite formation.

CONCLUSION

The present review recapitulates various factors affecting the growth of struvite urinary stones and the inhibitory role of certain chemicals and herbal extracts. Most of the tested plants are edible hence can be easily consumed without any adverse effects whereas the side effects of chemicals are unknown due to lack of toxicity studies. Thus, the use of herbal extracts might serve as an alternate and safe therapy for prevention of struvite stones.

The Risk of Chronic Kidney Disease Associated with Urolithiasis and its Urological Treatments: A Review

PURPOSE

Urolithiasis can impair kidney function. This literature review focuses on the risk of kidney impairment in stone formers, the specific conditions associated with this risk and the impact of urological surgery.

MATERIALS AND METHODS

The PubMed® and Embase® databases were searched for publications on urolithiasis, its treatment, and the risk of chronic kidney disease, end stage renal disease and nephrectomy in stone formers.

RESULTS

In general, renal stone formers have twice the risk of chronic kidney disease or end stage renal disease, and for female and overweight stone formers the risk is even higher. Patients with frequent urinary tract infections, struvite stones, urinary malformations and diversions, malabsorptive bowel conditions and some monogenic disorders are at high risk for chronic kidney disease/end stage renal disease. Shock wave lithotripsy or minimally invasive urological interventions for stones do not adversely affect renal function. Declines in renal function generally occur in patients with preexisting chronic kidney disease or a large stone burden requiring repeated and/or complex surgery.

CONCLUSIONS

Although the effect size is modest, urolithiasis may cause chronic kidney disease and, thus, it is mandatory to assess patients with renal stones for the risk of chronic kidney disease/end stage renal disease. We suggest that all guidelines dealing with renal stone disease should include assessment of this risk.

Nephrolithiasis in elderly population; effect of demographic characteristics

Background

Kidney stone (nephrolithiasis) is one of the most common diseases. During the past several decades, its prevalence and incidence have increased markedly in elderly population.

Objectives

This study was conducted to evaluate the risk factors for nephrolithiasis in elderly population.

Patients and Methods

This study was based on the Amirkola Health and Ageing Project (AHAP). Elderly people with kidney stones in every size, type and number were considered to be the case group and other subjects without a history of kidney stones served as control group. Demographic and anthropometric data, smoking, diabetes and metabolic syndrome (MetS), calcium (Ca), vitamin D, parathyroid hormone (PTH), uric acid and urine pH were compared in both groups.

Results

In this study, 1390 elderly people with the mean age of 69.37 ± 7.42 years were evaluated which 202 (14.53%) cases had renal stones. The patients with nephrolithiasis were younger (P = 0.010) and had higher uric acid and body mass index (BMI) levels (P = 0.041 and P = 0.006, respectively). Age <75 years, male gender and BMI ≥30 kg/m² had a significant association with stone formation. The prevalence of diabetes, MetS and smoking in the patients with nephrolithiasis was lower than the subjects without it.

Conclusions

This study suggests that male gender, obesity and age <75 years might be independent risk factors for the development of nephrolithiasis. Hence, low animal protein intake and weight reduction should be included as part of the counseling of senior stone-formers.

Predictors of renal recovery in renal failure secondary to bilateral obstructive urolithiasis

Objectives

To identify factors predicting renal recovery in patients presenting with renal failure secondary to bilateral obstructing urolithiasis.

Patients and methods

Data from electronic records of consecutive adult patients presenting with bilateral obstructing urolithiasis between January 2007 and April 2011 were retrieved. Ultrasonography of the abdomen, and kidney, ureter, bladder (KUB study) X-ray or abdominal non-contrast computed tomography confirmed the diagnosis. Interventional radiologists placed bilateral nephrostomies. Definitive intervention was planned after reaching nadir creatinine. Renal recovery was defined as nadir creatinine of ⩽2 mg/dL.

Results

In all, 53 patients were assessed, 50 (94.3%) were male, and 18 (33.9%) were aged ⩽40 years. Renal recovery was achieved in 20 patients (37.7%). A symptom duration of ⩽25 days (P < 0.01), absence of hypertension (P = 0.018), maximum renal parenchymal thickness of >16.5 mm (P = 0.001), and haemoglobin >9.85 g/dL (P < 0.01) were significant on unadjusted analysis. Symptom duration of ⩽25 days alone remained significant after adjusted analysis. Symptom duration of ⩽25 days (hazard ratio (HR) 13.83, 95% confidence interval (CI) 4.52–42.26; P < 0.01), parenchymal thickness of ⩾16.5 mm (HR 5.91, 95% CI 1.94–17.99; P = 0.002), and absence of hypertension (HR 9.99, CI 95% 1.32–75.37; P = 0.026) were significantly related to time to nadir creatinine. Symptom duration of ⩽25 days (HR 17.44, 95% CI 2.48–122.79; P = 0.004) alone remained significant after adjusted analysis. A symptom duration of ⩽25 days (P = 0.007) was 22-times more likely to indicate renal recovery.

Conclusions

Shorter symptom duration (⩽25 days) is predictive of renal recovery in renal failure secondary to bilateral obstructive urolithiasis.

[Nephrolithiasis of adult: From mechanisms to preventive medical treatment]

Nephrolithiasis is a very common (prevalence around 10 to 12% in France) and recurrent disorder. Nephrolithiasis is associated to chronic kidney disease and is responsible for 2 to 3% of cases of end-stage renal disease, mainly if it is associated to nephrocalcinosis or to a monogenic disorder (1.6% of nephrolithiasis in adults, among them 1% of cystinuria). To understand the underlying pathophysiological processes, stone analysis (morphology and using infrared spectrophotometry) as well as minimal biological assessment including urine crystal research are required. The calcic nephrolithiasis is the more frequent subtype (>80%). Its medical treatment relies on simple dietary rules: non-alkaline hyperdiuresis>2 liters/day, calcium intake normalization (1 gram per day divided between the three principal meals), normalization of sodium (6 to 7 grams per day) and protein intake (1g/kg of theoretical body weight/day), and eviction of foods rich in oxalate. In case of persistent hypercalciuria (>0.1mmol/kg of theoretical body weight/day on free diet), a thiazide diuretic can be started while being aware to correct iatrogenic decrease in plasma potassium and urine citrate excretion. Measurement of bone mineral density must systematically be performed in patients with high 24 h-urinary calcium excretion. The medical treatment of uric acid nephrolithiasis relies on alkaline hyperdiuresis (goal of urine pH: 6.2 to 6.8). The use of allopurinol is justified only if urine uric acid is over 4mmol/day. Thanks to a well-managed preventive medical treatment, one can expect to stop the activity of nephrolithiasis in more than 80% of cases, making it one of the most accessible renal pathologies to preventive medical treatment.

Do kidney stone formers have a kidney disease?

Nephrolithiasis is a highly prevalent disorder affecting approximately one in eleven people and is associated with multiple complications including hypertension, cardiovascular disease, and chronic kidney disease. Significant epidemiologic associations with chronic kidney disease and ESRD have been noted and are reviewed herein, but debate persists in the literature as to whether kidney stone formation is a pathogenic process contributing to kidney disease. Corroborating evidence supporting the presence of kidney disease in stone formers includes the variability of renal function by stone type, the positive association of stone size with renal dysfunction, the presence of markers of renal injury in the urine of even asymptomatic stone formers, and direct evidence of renal tissue injury on histopathology. Proposed pathogenic mechanisms include recurrent obstruction and comorbid conditions such as recurrent urinary tract infections and structural abnormalities. Recent work evaluating the renal histopathology of different groups of stone formers adds further granularity, suggesting variability in mechanisms of renal injury by stone type and confirming the pathogenic effects of crystal formation. Genetic abnormalities leading to stone formation including cystinuria and primary hyperoxaluria, among others, contribute to the burden of disease in the stone-forming population.

Studies on the effect of phyllanthus emblica extract on the growth of urinary type struvite crystals invitro

Background

Struvite also called as infection stones occur in the urinary system of humans particularly the women community. The present work was aimed to grow struvite crystals in-vitro using single diffusion gel growth technique and to understand the effect of phyllanthus emblica on its growth.

Methods

Sodium metasilicate gel of density 1.03 g/cc was used as the medium for growing the struvite crystals; The phyllanthus emblica extract of 5 % M/V concentration was used to understand its effect on struvite crystal crystal nucleation and growth. The well grown crystal samples were characterized by powder XRD, FTIR, UV–vis, Microhardness, SEM and Thermal analysis.

Results

The grown struvite crystals had dendritic morphology in both the control and phyllanthus emblica extract added systems. However, it was observed that the nucleation was controlled in the phyllanthus emblica added system when compared to the control system.

Conclusions

The result showed that phyllanthus emblica reduces nucleation of struvite crystals.

Urine proteomic analysis in cystinuric children with renal stones

INTRODUCTION

The gene mutations responsible for cystinuria do not fully explain kidney stone activity, suggesting that specific proteins may serve as promoters of cystine precipitation, aggregation or epithelial adherence. In this study we assessed (1) the differences in the urinary proteins between children with cystinuria and kidney stones (CYS) and healthy controls (HC), with particular attention to the fibrosis-related proteins, and (2) the presence of diagnostic biomarkers for CYS.

MATERIAL AND METHODS

We conducted a pilot study comparing individual urinary proteomes of 2 newly diagnosed children with CYS and 2 age- and gender-matched HC, using liquid chromatography-mass spectrometry. Relative protein abundance was estimated using spectral counting. Proteins of interest in both CYS and HC were selected using the following criteria: i) ≥5 spectral counts; ii) ≥2-fold difference in spectral counts; and iii) ≤0.05 p-value for the Fisher's Exact Test.

DISCUSSION

This study demonstrates a different urinary polypeptide profile in two children with CYS compared to two HC. Of the 623 proteins identified by proteomic analysis, 180 exhibited at least a 2-fold increased relative abundance in CYS compared to HC. Of these, 39 were involved in response to stress, 26 in response to wounding, 21 in inflammatory response, 18 in immune response, and 4 in cellular response to oxidative stress. 133 proteins were found only in children with CYS, 33 of which met the selection criteria. Of these 33 unique proteins, six are known to be associated with fibrosis pathways (Table). The major limitation of this study is the small number of samples that were analyzed. Validation using highly specific methods such as ELISA is needed.

CONCLUSION

We provide proteomic evidence of oxidative injury, inflammation, wound healing and fibrosis in two children with CYS. We speculate that oxidative stress and inflammation may cause remodeling via actin and vimentin pathways, leading to fibrosis. Additionally, we identified ITIH and MMP-9 as potential diagnostic biomarkers and novel therapeutic targets in CYS. These proteins merit further investigation.

Incidence and Risk Factors for Urolithiasis in Patients with Crohn's Disease

BACKGROUND

The incidence of urinary tract calculi is thought to be higher in patients with inflammatory bowel disease (IBD) than that in the general population. However, few data are available about urolithiasis in patients with Crohn's disease (CD). We investigated the incidence of urolithiasis and the risk factors for urolithiasis in patients with CD.

METHODS

We examined the records of 387 patients with CD followed at Samsung Medical Center from July 2011 to June 2013. Evidence for the presence of calculi was obtained from radiologic findings (plain films, ultrasonography, or computed tomography), urinary colic symptoms, or a treatment history of urolithiasis after diagnosis of CD. Demographic variables, phenotype, concurrent medications, and previous CD-related surgery were analyzed.

RESULTS

Urinary tract calculi were found in 18 (4.7%) patients, which developed after the CD diagnosis. The incidence of urolithiasis in CD was 706 per 100,000 patient-years. Cox models with a time-dependent covariate showed that azathioprine (AZA)/6-mercaptopurine (6-MP) treatment (hazard ratio = 0.963; 95% CI: 0.931, 0.996; p = 0.030) was negatively associated with urolithiasis.

CONCLUSIONS

The annual incidence rate of urolithiasis in patients with CD was 0.7%. AZA/6-MP therapy was associated with a low risk of urolithiasis in these patients.

CKD and Its Risk Factors among Patients with Cystinuria

BACKGROUND AND OBJECTIVES

Cystinuria is an autosomal recessive disorder affecting renal cystine reabsorption; it causes 1% and 8% of stones in adults and children, respectively. This study aimed to determine epidemiologic and clinical characteristics as well as comorbidities among cystinuric patients, focusing on CKD and high BP.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This retrospective study was conducted in France, and involved 47 adult and pediatric nephrology and urology centers from April 2010 to January 2012. Data were collected from 442 cystinuric patients.

RESULTS

Median age at onset of symptoms was 16.7 (minimum to maximum, 0.3-72.1) years and median diagnosis delay was 1.3 (0-45.7) years. Urinary alkalinization and cystine-binding thiol were prescribed for 88.8% and 52.2% of patients, respectively, and 81.8% had at least one urological procedure. Five patients (1.1%, n=4 men) had to be treated by dialysis at a median age of 35.0 years (11.8-70.7). Among the 314 patients aged ≥16 years, using the last available plasma creatinine, 22.5% had an eGFR≥90 ml/min per 1.73 m(2) (calculated by the Modification of Diet in Renal Disease equation), whereas 50.6%, 15.6%, 7.6%, 2.9%, and 0.6% had an eGFR of 60-89, 45-59, 30-44, 15-29, and <15, respectively. Among these 314 patients, 28.6% had high BP. In multivariate analysis, CKD was associated with age (odds ratio, 1.05 [95% confidence interval, 1.03 to 1.07]; P<0.001), hypertension (3.30 [1.54 to 7.10]; P=0.002), and severe damage of renal parenchyma defined as a past history of partial or total nephrectomy, a solitary congenital kidney, or at least one kidney with a size <10 cm in patients aged ≥16 years (4.39 [2.00 to 9.62]; P<0.001), whereas hypertension was associated with age (1.06 [1.04 to 1.08]; P<0.001), male sex (2.3 [1.3 to 4.1]; P=0.003), and an eGFR<60 ml/min per 1.73 m(2) (2.7 [1.5 to 5.1]; P=0.001).

CONCLUSIONS

CKD and high BP occur frequently in patients with cystinuria and should be routinely screened.

Effect of renal insufficiency on stone recurrence in patients with urolithiasis

The study was designed to assess the relationship between glomerular filtration rate (GFR) and urinary stone-forming constituents, and to assess the effect of renal insufficiency on stone recurrence risk in first stone formers (SF). Baseline serum creatinine levels were obtained, and renal insufficiency was defined as creatinine clearance ≤60 mL/min (Cockroft-Gault). This retrospective case-control study consists of 342 first SF; 171 SF with normal renal function were selected with 1:1 propensity scores matched to 171 SF with renal insufficiency. Urinary metabolic evaluation was compared to renal function. GFR was positively correlated with urinary calcium, uric acid, and citrate excretion. Subjects with renal insufficiency had significantly lower urinary calcium, uric acid, and citrate excretion than those with normal renal function, but not urine volume. With regard to urinary metabolic abnormalities, similar results were obtained. SF with renal insufficiency had lower calcium oxalate supersaturation indexes and stone recurrence rates than SF with normal renal function. Kaplan-Meier curves showed similar results. In conclusion, GFR correlates positively with urinary excretion of stone-forming constituents in SF. This finding implies that renal insufficiency is not a risk factor for stone recurrence.

Acute and chronic kidney injury in nephrolithiasis

PURPOSE OF REVIEW

Nephrolithiasis is a common systemic disease associated with both acute kidney injury (AKI) and chronic kidney disease (CKD). The purpose of this review is to discuss recent publications regarding nephrolithiasis-associated kidney damage, with an emphasis on AKI.

RECENT FINDINGS

Nephrolithiasis is not a common cause of adult AKI (1-2% of cases), although it may be a more important factor in young children (up to 30%). The primary mechanism of nephrolithiasis-associated AKI is obstructive nephropathy, and factors on presentation with obstructive uropathy predict the likelihood of long-term renal recovery. Crystalline nephropathy is another potential pathway in certain circumstances that is often associated with a worse outcome. Recent studies have elucidated additional pathways whereby calcium oxalate crystals can cause acute injury, implicating innate immunity and intracellular inflammasome pathways. Several large cohort studies have demonstrated an independent association of nephrolithiasis with CKD and end-stage renal disease, although the effect size is modest. Urologic comorbidities, urinary infection, and shared underlying risk factors (e.g., diabetes, hypertension) all impact nephrolithiasis-associated CKD risk.

SUMMARY

Obstructive nephropathy and crystalline nephropathy both contribute to nephrolithiasis-associated AKI, although the latter appears to have a worse prognosis. Nephrolithiasis is an independent, albeit small, risk factor for CKD. Further study is needed to clarify the incidence and mechanisms of nephrolithiasis-associated AKI, and the relationship between nephrolithiasis-associated AKI and CKD.

Renal deterioration index: preoperative prognostic model for renal functional outcome after treatment of bilateral obstructive urolithiasis in patients with chronic kidney disease

BACKGROUND AND PURPOSE

Patients who present with varying severity of obstructive urolithiasis behave differently after the treatment. Some patients recover with improved renal function while others progress to renal failure. Our objective was to objectively quantify which patients would progress to renal failure after treatment for obstructive urolithiasis.

PATIENTS AND METHODS

A prospective analysis of 167 patients with renal failure from bilateral obstructive urolithiasis who were treated and subsequently followed for at least 1 year was performed. Failure was defined as glomerular filtration rate (GFR) values less than 15 mL/min at 1 year follow-up. All patients had preoperative placement of a percutaneous nephrostomy tube for at least 5 days before treatment with either ureteroscopy or percutaneous nephrolithotomy. Multiple logistic regression analysis of affecting parameters was performed. A renal deterioration index (RDI) was constructed based on scores assigned to varying severity of multivariate significant factors and the receiver operating characteristic (ROC) curve was analyzed.

RESULTS

There were 48(28.7%) patients who progressed to CKD stage V at 1-year follow-up. Combined cortical width (≤ 0.001), proteinuria (0.01), positive urine culture (0.004), and nadir preoperative GFR postbilateral percutaneous nephrostomy (0.016) were statistically significant factors affecting renal deterioration on multivariate analysis. RDI has a high ROC curve (AUC=0.90) for predicting renal functional outcome. Combining these parameters in a prediction table yielded a RDI score ≥ 12 being associated with high odds risk (odds ratio=11.2) of treatment failure.

CONCLUSION

RDI ≥ 12 is associated with renal deterioration after appropriate treatment of bilateral obstructive urolithiasis.

Nephrolithiasis in patients with inflammatory bowel disease in the community

Background

Inflammatory bowel disease (IBD) has been associated with renal stone formation. The objective of this study was to determine prospectively the prevalence of nephrolithiasis in a community-based population of patients with IBD and to analyze factors associated with renal calculus formation.

Methods

Screening renal ultrasound was performed in a well characterized cohort of patients seen between 2009 and 2012 at an IBD clinic. We enrolled 168 patients, including 93 with Crohn’s disease and 75 with ulcerative colitis. Clinical and phenotypic variables associated with asymptomatic nephrolithiasis were determined.

Results

Nephrolithiasis was detected in 36 patients with Crohn’s disease and in 28 patients with ulcerative colitis (38% for both). Although none of the patients had been previously hospitalized for symptomatic nephrolithiasis, nine with Crohn’s disease and five with ulcerative colitis had recurrent urinary tract infections or hydronephrosis. In patients with Crohn’s disease, ileocolonic (L3) disease was associated with a greater risk of nephrolithiasis than was ileal (L1) or colonic (L2) disease (odds ratio [OR] 2.3, 95% confidence interval [CI] 1.8–7). Active ulcerative colitis (regardless of severity) represented a significant risk factor for formation of renal calculi (OR 4.2, 95% CI 1.1–15, P = 0.02).

Conclusion

In surgery-naïve patients with IBD in the community, asymptomatic nephrolithiasis is common and should be considered when renal dysfunction or infection is detected.

Impact of stone disease: chronic kidney disease and quality of life

This article reviews the impact of stone disease on chronic kidney disease and renal function; evaluating the natural progression of disease as well as the impact of surgical interventions. The impact of stone disease, medical therapy, and surgical therapy for stones on quality of life is discussed.

Association between chronic kidney disease and urinary calculus by stone location: a population-based study

Study Type--Disease prevalence study (cohort design) Level of Evidence 2a. What's known on the subject? and What does the study add? Several studies have estimated the potential association of urinary calculus (UC) with chronic kidney disease (CKD). However, previous literature focusing on this issue tended to evaluate the impact of kidney stones alone on incident CKD, with no studies having been conducted investigating the association between CKD and stone formation in other portions of the urological system. We found that patients with CKD were consistently more likely than comparison subjects to have been previously diagnosed with kidney calculus (odds ratio [OR] 2.10, 95% confidence interval [CI] 1.95-2.27), ureter calculus (OR 1.68, 95% CI 1.51-1.85), bladder calculus (OR 1.49, 95% CI 1.13-1.98), and unspecified calculus (OR 1.89, 95% CI 1.74-2.06). We concluded that there was an association between CKD and UC regardless of stone location.

OBJECTIVE

• To explore the association of chronic kidney disease (CKD) with prior kidney calculus, ureter calculus, and bladder calculus using a population-based dataset in Taiwan. Several studies have estimated the potential association of urinary calculus (UC) with CKD. However, previous literature focusing on this issue tended to evaluate the impact of kidney stones alone on incident CKD, with no studies having been conducted investigating the association between CKD and stone formation in other portions of the urological system.

PATIENTS AND METHODS

• We identified 21,474 patients who received their first-time diagnosis of CKD between 2001 and 2009. • The 21,474 controls were frequency-matched with cases for sex, age group, and index year. • We used conditional logistic regression analyses to compute the odds ratio (OR) and corresponding 95% confidence interval (CI) as an estimation of association between CKD and having been previously diagnosed with UC.

RESULTS

• The results show that compared with controls, the OR of prior UC for cases was 1.91 (95% CI 1.81-2.01, P < 0.001) after adjusting for potential confounders. • Furthermore, cases were consistently more likely than controls to have been previously diagnosed with kidney calculus (OR 2.10, 95% CI 1.95-2.27), ureter calculus (OR 1.68, 95% CI 1.51-1.85), bladder calculus (OR 1.49, 95% CI 1.13-1.98), and unspecified UC (OR 1.89, 95% CI 1.74-2.06).

CONCLUSION

• We concluded that there was an association between ckd and UC regardless of stone location.

Percutaneous nephrolithotomy and chronic kidney disease: results from the CROES PCNL Global Study

PURPOSE

We compared the characteristics and outcomes of patients treated with percutaneous nephrolithotomy in the CROES (Clinical Research Office of the Endourological Society) Global Study according to preoperative renal function.

MATERIALS AND METHODS

Prospective data on consecutive patients treated with percutaneous nephrolithotomy in a 1-year period were collected from 96 participating centers. The glomerular filtration rate was estimated using the Modification of Diet in Renal Disease formula based on preoperative serum creatinine measurement. Patients were divided into 3 groups by glomerular filtration rate, including chronic kidney disease stages 0/I/II-greater than 60, stage III-30 to 59 and stages IV/V-less than 30 ml/minute/1.73 m(2). Patient characteristics, operative characteristics, outcomes and morbidity were assessed.

RESULTS

Estimated glomerular filtration rate data were available on 5,644 patients, including 4,436 with chronic kidney disease stages 0/I/II, 994 with stage III and 214 with stages IV/V. A clinically significant minority of patients with nephrolithiasis presented with severe chronic kidney disease. A greater number of patients with stages IV/V previously underwent percutaneous nephrolithotomy, ureteroscopy or nephrostomy and had positive urine cultures than less severely affected patients, consistent with the higher incidence of staghorn stones in these patients. Patients with chronic kidney disease stages IV/V had statistically significantly worse postoperative outcomes than those in the other chronic kidney disease groups.

CONCLUSIONS

Poor renal function negatively impacts the post-percutaneous nephrolithotomy outcome. By more aggressive removal of kidney stones, particularly staghorn stones, at first presentation and more vigilantly attempting to prevent recurrence through infection control, pharmacological or other interventions, the progression of chronic kidney disease due to nephrolithiasis may be mitigated.

Urolithiasis and the risk of ESRD

BACKGROUND AND OBJECTIVES

The contribution of urolithiasis, if any, to the development of ESRD is unclear.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

All stone formers in Olmsted County, Minnesota, first diagnosed between 1984 and 2008 were identified by diagnostic codes with up to four controls matched on age and sex. Charts were reviewed to validate symptomatic stone formers in a random subset. Incident ESRD events were identified by the US Renal Data System.

RESULTS

Altogether, 51 stone formers and 75 controls developed ESRD among 6926 stone formers and 24,620 matched controls followed for a mean of 9 years. Stone formers had an increased risk of ESRD after adjusting for diabetes, hypertension, dyslipidemia, gout, and CKD (hazard ratio: 2.09; 95% confidence interval: 1.45-3.01). This increased risk of ESRD remained in the subset of 2457 validated symptomatic stone formers (hazard ratio: 1.95; 95% confidence interval: 1.09-3.49). The attributable risk of ESRD from symptomatic urolithiasis was 5.1% based on a prevalence of 5.4% for stone formers. For stone formers versus controls who developed ESRD, there was an increased likelihood of past hydronephrosis (44% versus 4%), recurrent urinary tract infections (26% versus 4%), acquired single kidney (15% versus 3%), neurogenic bladder (12% versus 1%), and ileal conduit (9% versus 0%), but not diabetes (32% versus 49%) or hypertension (44% versus 52%).

CONCLUSIONS

Symptomatic stone formers are at increased risk for ESRD independent of several cardiovascular risk factors. Other urological disease is relatively common among stone formers who develop ESRD.

Expanded Criteria Living Donors: How Far Can We Go?

In an effort to expand the deceased donor pool, transplant centers have accepted expanded criteria donors as appropriate for many of the patients in the deceased donor pool. Translating this into the living donor pool is more complex. One must consider not only the quality of the organ procured but the consequences that the nephrectomy might have on the living donors for the rest of their lives. This review examines the available data on higher risk donors and the appropriateness, or lack thereof, of accepting them as kidney donors.

Relationship between glomerular filtration rate and 24-hour urine composition in patients with nephrolithiasis

OBJECTIVE

To examine the relationship between GFR and 24-hour urine composition in patients with nephrolithiasis to understand how renal function may affect stone risk. Alterations in glomerular filtration rate (GFR) are associated with a number of physiological changes.

METHODS

A retrospective, institutional review board-approved review of patients from 2 metabolic stone clinics was performed. One-way analysis of variance and multivariate linear regression models were used to evaluate the relationship between GFR quintile and 24-hour urine composition.

RESULTS

A total of 403 patients (241 male, 162 female) with a mean age of 52.6 ± 14.2 years were included in the study. On univariate analysis, decreasing GFR by quintile was associated with significant reductions in urine calcium, citrate, supersaturation of calcium oxalate, and supersaturation of calcium phosphate (P < .05 for each). In multivariate linear regression models, decreasing GFR by quintile was associated with significant decreases in urine calcium (β = -11.2, 95% CI = -18.3 to 4.01), urine citrate (β = -32.4, 95% CI = -54.1 to 10.8), oxalate (β = -1.83, 95% CI = -2.85 to 0.81), supersaturation of calcium oxalate (β = -0.58, 95% CI = 0.84 to 0.33) and supersaturation of calcium phosphate (β = -0.09, 95% CI = 0.17 to 0.02), as well as an increase in urine magnesium (β = 3.40, 95% CI = 0.7 to 6.1).

CONCLUSION

Reduction in GFR is associated with decreased urine calcium, oxalate, and citrate, and increased urine magnesium. These findings have implications for treatment of patients with stone disease and impaired renal function.

Evaluation of the medically complex living kidney donor

Due to organ shortage and difficulties for availability of cadaveric donors, living donor transplantation is an important choice for having allograft. Live donor surgery is elective and easier to organize prior to starting dialysis thereby permitting preemptive transplantation as compared to cadaveric transplantation. Because of superior results with living kidney transplantation, efforts including the usage of “Medically complex living donors” are made to increase the availability of organs for donation. The term “Complex living donor” is probably preferred for all suboptimal donors where decision-making is a problem due to lack of sound medical data or consensus guidelines. Donors with advanced age, obesity, asymptomatic microhematuria, proteinuria, hypertension, renal stone disease, history of malignancy and with chronic viral infections consist of this complex living donors. This medical complex living donors requires careful evaluation for future renal risk. In this review we would like to present the major issues in the evaluation process of medically complex living kidney donor.

Nephrectomy as a cause of chronic kidney disease in the treatment of urolithiasis: a case-control study

OBJECTIVE

To analyze the clinical course of nephrectomized patients due to complications related to nephrolithiasis and ascertain the prevalence of chronic kidney disease (CKD) in this population.

METHODS

From 2005 to 2010, 658 patients were treated with urolithiasis. Among these, 30 (4.6%) were nephrectomized. For each case, a control was selected and matched to the case by age, sex and disease duration. All data were collected from medical records, which contained the clinical, laboratory evaluation and diagnostic imaging.

RESULTS

Age of the study group was 51.5 ± 10.4 years and the control group 47.1 ± 5.2 years. There were 17 (85%) women and three men in each group. Patients from the study group reported 3 (range, 1-5) episodes of acute renal colic before nephrectomy. Urinary tract infection and hematuria was detected in 70% of cases before surgery. In addition, half of the patients had at least one previous urological procedure. The control group showed higher urinary levels of calcium (216.1 ± 114.3 vs. 130.9 ± 72.2), uric acid (530.2 ± 197.4 vs. 424 ± 75.2) and citrate (755 ± 533 vs. 380.2 ± 260.7), p < 0.01, 0.03 and 0.01, respectively. The creatinine clearance was lower in the study group, 52.5 ± 18.8 ml/min vs. 92.9 ± 24.2 ml/min in the control group (p < 0.001).

CONCLUSIONS

There was a decrease in kidney function in nephrectomized patients compared to a control group of stone-forming patients with both kidneys. Prospective studies are needed to assess the incidence of CKD in patients with nephrolithiasis submitted to nephrectomy.

Metabolic assessment of elderly men with urolithiasis

OBJECTIVE

To assess the presence of metabolic disorders in elderly men with urolithiasis.

METHODS

We performed a case-control study. The inclusion criteria were as follows: (1) men older than 60 years of age and either (2) antecedent renal colic or an incidental diagnosis of urinary lithiasis after age 60 (case arm) or (3) no antecedent renal colic or incidental diagnosis of urolithiasis (control arm). Each individual underwent an interview, and those who were selected underwent all clinical protocol examinations: serum levels of total and ionized calcium, uric acid, phosphorus, glucose, urea, creatinine and parathyroid hormone, urine culture, and analysis of 24-hour urine samples (levels of calcium, citrate, creatinine, uric acid and sodium, pH and urine volume). Each case arm patient underwent two complete metabolic urinary investigations, whereas each control arm individual underwent one examination. ClinicalTrials.gov: NCT01246531.

RESULTS

A total of 51 subjects completed the clinical investigation: 25 in the case arm and 26 in the control arm. In total, 56% of the case arm patients had hypocitraturia (vs. 15.4% in the control arm; p = 0.002). Hypernatriuria was detected in 64% of the case arm patients and in 30.8% of the controls (p = 0.017).

CONCLUSION

Hypocitraturia and hypernatriuria are the main metabolic disorders in elderly men with urolithiasis.

Practice patterns in evaluation of living kidney donors in United Network for Organ Sharing-approved kidney transplant centers

INTRODUCTION

The current pattern of evaluation for living kidney donors was investigated.

METHODS

We designed a 37-question electronic survey to collect information about living kidney donor evaluation. Of the 181 United Network for Organ Sharing (UNOS)-approved centers, 72 responded. Survey responses were coded and downloaded into SPSS. Data was expressed as means and standard deviations or the percentage of centers with specific responses.

RESULTS

66% of the centers used a cut-off of <80 ml/min for exclusion of living kidney donors. 24-hour urine measuring creatinine clearance (CrCl) was the most common screening method for glomerular filtration rate (GFR) assessment in potential living donors. 56% of the centers excluded donors with blood pressure (BP) >140/90, whereas 22.7 and 7.1% excluded patients with pre-hypertension with a cut-off BP of 130/85 and 120/80, respectively. 66% of the centers used 24-hour urine creatinine to assess for proteinuria. 20% of the centers accepted living kidney donors with microalbuminuria and 84% accepted patients with a history of nephrolithiasis. 24% of the centers reported use of formal cognitive testing of potential living donors.

DISCUSSION

There were significant variations in exclusion criteria based on GFR, history of kidney stones, body mass index, BP and donors with urinary abnormalities. The definitions for hematuria and proteinuria were variable. There is a need for uniformity in selection and for a living donor registry. We also recommend raising the cut-off for estimated GFR to 90 ml/min to account for 10-15% overestimation when CrCl is used.

Genetic determinants of urolithiasis

Urolithiasis affects approximately 10% of individuals in Western societies by the seventh decade of life. The most common form, idiopathic calcium oxalate urolithiasis, results from the interaction of multiple genes and their interplay with dietary and environmental factors. To date, considerable progress has been made in identifying the metabolic risk factors that predispose to this complex trait, among which hypercalciuria predominates. The specific genetic and epigenetic factors involved in urolithiasis have remained less clear, partly owing to the candidate gene and linkage methods that have been available until now, being inherently low in their power of resolution and in assessing modest effects in complex traits. However, together with investigations of rare, Mendelian forms of urolithiasis associated with various metabolic risk factors, these methods have afforded insights into biological pathways that seem to underlie the development of stones in the urinary tract. Monogenic diseases account for a greater proportion of stone formers in children and adolescents than in adults. Early diagnosis of monogenic forms of urolithiasis is of importance owing to associated renal injury and other potentially treatable disease manifestations, but diagnosis is often delayed because of a lack of familiarity with these rare disorders. In this Review, we will discuss advances in the understanding of the genetics underlying polygenic and monogenic forms of urolithiasis.

Nephrolithiasis in children

Similar to adults, stone disease in the pediatric patient may present clinically as flank/abdominal pain or hematuria. Unlike in adults, pediatric stone disease is less frequent and is often associated with an underlying metabolic disorder. Because of the 50% likelihood of finding an underlying metabolic cause for stone formation in younger children, a metabolic workup is recommended for all children with stone disease, including first-time stone formers. Stone analysis, when available, can be very helpful in determining an underlying cause. If needed, all modalities of minimally invasive surgical treatment are possible for children with stones. Surgical approaches may be needed to achieve the goal of nephron preservation. Aggressive fluid intake is the mainstay of prevention for all forms of stone disease, but specific therapy targeted to the most likely underlying metabolic abnormality is often used. Newer data are now linking stone disease to CKD, thereby emphasizing the need for a better understanding and potentially more aggressive treatment approach. With increasing frequency of stone disease in the pediatric patient and increasing survival of these patients into adulthood, the adult caregiver must become familiar with different causes and treatment approaches to stone disease in young adult patients in whom disease onset began in childhood.

Chronic kidney disease in kidney stone formers

Recent population studies have found symptomatic kidney stone formers to be at increased risk for chronic kidney disease (CKD). Although kidney stones are not commonly identified as the primary cause of ESRD, they still may be important contributing factors. Paradoxically, CKD can be protective against forming kidney stones because of the substantial reduction in urine calcium excretion. Among stone formers, those with rare hereditary diseases (cystinuria, primary hyperoxaluria, Dent disease, and 2,8 dihydroxyadenine stones), recurrent urinary tract infections, struvite stones, hypertension, and diabetes seem to be at highest risk for CKD. The primary mechanism for CKD from kidney stones is usually attributed to an obstructive uropathy or pyelonephritis, but crystal plugs at the ducts of Bellini and parenchymal injury from shockwave lithotripsy may also contribute. The historical shift to less invasive surgical management of kidney stones has likely had a beneficial impact on the risk for CKD. Among potential kidney donors, past symptomatic kidney stones but not radiographic stones found on computed tomography scans were associated with albuminuria. Kidney stones detected by ultrasound screening have also been associated with CKD in the general population. Further studies that better classify CKD, better characterize stone formers, more thoroughly address potential confounding by comorbidities, and have active instead of passive follow-up to avoid detection bias are needed.

Renal function in patients with urinary stones of varying compositions

Kidney stones are a potential risk factor for chronic kidney disease. The impact of different urinary stone components on renal function is unknown. In this study, we retrospectively reviewed 1,918 medical records of patients with urolithiasis. The renal function was evaluated as estimated glomerular filtration rate. All the stones were analyzed by Fourier transform infrared spectroscopy. The patients were divided into five groups according to the stone components. Statistical analysis was performed with analysis of variance. All the patients with stones had Stage 2-3 chronic kidney disease. The patients with uric acid and struvite stones had significantly lower estimated glomerular filtration rate compared with those having other stone components (p<0.01). Furthermore, the patients with calcium-containing stones (calcium oxalate and calcium phosphate) had significantly better renal function than those with non-calcium-containing stones (struvite and uric acid, p<0.01). Patients with urolithiasis had decreased renal function, and the impact of renal function varied depending on the stone components. We conclude that stone analysis is important in predicting the change in renal function in patients with urolithiasis. Moreover, the patients with non-calcium-containing stones, such as struvite and uric acid stones, should be carefully evaluated and treated to preserve their renal function.

Analysis of 24-hour urine parameters as it relates to age of onset of cystine stone formation

INTRODUCTION

Cystinuria is an inherited disorder characterized by the impaired reabsorption of the dibasic amino acid, cystine, in the proximal tubule of the nephron. Cystine stones most frequently occur in the first through third decades of life with a decreased incidence in old age. We hypothesize that patients presenting with first stone event at an older age would have more favorable 24-hour urine parameters compared with those patients who present early.

PATIENTS

This is a retrospective review of 94 patients with cystinuria and cystine stones who underwent a 24-hour urine test. The patients were divided into four groups based on age at first clinical stone event: group 1, children aged <18 years (n = 37); group 2, 18 to 32 years (n = 19); group 3, 33 to 50 years (n = 19); and group 4, >50 years (n = 19). All 24-hour urines were collected prior to any medical therapy. Statistical analysis was performed using analysis of variance and Tukey pairwise comparison test.

RESULTS

There was a significant increase in cystine supersaturation (SS) for the young adults (group 2) as opposed to older adults (groups 3 and 4) though cystine excretion was not different among the groups. A higher urine volume appeared to account for the lower cystine SS in the older adults. The children were found to have cystine SS similar to the young adults.

DISCUSSION

In this retrospective study, a correlation was found between the age of onset of cystine stones and 24-hour urine parameters. Cystinuric patients presenting with first stone event at an older age have lower cystine SS and increased urinary volume compared with patients presenting earlier, likely conferring a protective effect.