The pathogenesis and treatment of kidney stones

Is the "Pandemic Diet" Nonlithogenic?

Introduction and Objective: The COVID-19 pandemic and worldwide quarantine resulted in major changes in individual lifestyles. In New York State, March 16, 2020, marked the end of in-restaurant dining and a reported shift to more cooking at home. We investigated the 24-hour urine of patients with known history of nephrolithiasis to see if changes during COVID-19 pandemic altered the risk of stone disease. Methods: Retrospectively, patients with history of nephrolithiasis seen for an outpatient visit from April 1, 2020, to December 31, 2020, were studied. All patients had a 24-hour urine study "pre-COVID" defined as before March 16, 2020, "during-COVID" from March 16, 2020, to December 31, 2020; if available, "post-COVID" from January 1, 2021, to October 31, 2022, was also included. Mean study values were compared using paired, two-tailed t-tests. Results: Ninety-three patients (M = 54, F = 39) with a mean age of 60 years were evaluated. Twenty-four-hour urine revealed a significant reduction in urinary sodium (uNa) levels from pre-COVID (166.15 ± 7.51 mEq/L) compared with during-COVID (149.09 ± 7.55 mEq/L) (p = 0.015) and urinary calcium (uCa) levels from pre-COVID (214.18 ± 13.05 mg) compared with during-COVID (191.48 ± 13.03 mg) (p = 0.010). Post-COVID 24-hour urine (N = 73) levels for uNa (138.55 ± 6.83 mEq/L, p = 0.0035) and uCa (185.33 ± 12.61 mg, p = 0.012) remained significantly reduced compared with pre-COVID values, but with no difference compared with during-COVID values. Upon age stratification, this significance was found only in patients younger than 65. There were no significant differences in 24-hour urine total volume, magnesium, or citrate levels. Conclusions: During the COVID-19 lockdown, dietary choices limited to home-cooked meals allowed patients to better identify their food choices. This study demonstrates that home-cooked meals improved urinary parameters minimizing lithogenic risk factors for stone formation, including hypernatriuria and hypercalciuria. That these changes persisted into the post-COVID period may indicate improved dietary practices after the lockdown ended.

Understanding the role of zinc ions on struvite nucleation and growth in the context of infection urinary stones

Taking into account that in recent decades there has been an increase in the incidence of urinary stones, especially in highly developed countries, from a wide range of potentially harmful substances commonly available in such countries, we chose zinc for the research presented in this article, which is classified by some sources as a heavy metal. In this article, we present the results of research on the influence of Zn2+ ion on the nucleation and growth of struvite crystals-the main component of infection urinary stones. The tests were carried out in an artificial urine environment with and without the presence of Proteus mirabilis bacteria. In the latter case, the activity of bacterial urease was simulated chemically, by systematic addition of an aqueous ammonia solution. The obtained results indicate that Zn2+ ions compete with Mg2+ ions, which leads to the gradual replacement of Mg2+ ions in the struvite crystal lattice with Zn2+ ions to some extent. This means co-precipitation of Mg-struvite (MgNH4PO4·6H2O) and Znx-struvite (Mg1-xZnxNH4PO4·6H2O). Speciation analysis of chemical complexes showed that Znx-struvite precipitates at slightly lower pH values than Mg-struvite. This means that Zn2+ ions shift the nucleation point of crystalline solids towards a lower pH. Additionally, the conducted research shows that Zn2+ ions, in the range of tested concentrations, do not have a toxic effect on bacteria; on the contrary, it has a positive effect on cellular metabolism, enabling bacteria to develop better. It means that Zn2+ ions in artificial urine, in vitro, slightly increase the risk of developing infection urinary stones.

Understanding formation processes of calcareous nephrolithiasis in renal interstitium and tubule lumen

Kidney stone, one of the oldest known diseases, has plagued humans for centuries, consistently imposing a heavy burden on patients and healthcare systems worldwide due to their high incidence and recurrence rates. Advancements in endoscopy, imaging, genetics, molecular biology and bioinformatics have led to a deeper and more comprehensive understanding of the mechanism behind nephrolithiasis. Kidney stone formation is a complex, multi-step and long-term process involving the transformation of stone-forming salts from free ions into asymptomatic or symptomatic stones influenced by physical, chemical and biological factors. Among the various types of kidney stones observed in clinical practice, calcareous nephrolithiasis is currently the most common and exhibits the most intricate formation mechanism. Extensive research suggests that calcareous nephrolithiasis primarily originates from interstitial subepithelial calcified plaques and/or calcified blockages in the openings of collecting ducts. These calcified plaques and blockages eventually come into contact with urine in the renal pelvis, serving as a nidus for crystal formation and subsequent stone growth. Both pathways of stone formation share similar mechanisms, such as the drive of abnormal urine composition, involvement of oxidative stress and inflammation, and an imbalance of stone inhibitors and promoters. However, they also possess unique characteristics. Hence, this review aims to provide detailed description and present recent discoveries regarding the formation processes of calcareous nephrolithiasis from two distinct birthplaces: renal interstitium and tubule lumen.

Effect of Copper and Zinc Ions on Biochemical and Molecular Characteristics of Calcium Oxalate Renal Stones: a Controlled Clinical Study

Contradictory results are existed in the literature regarding the impact of trace elements on the pathogenesis of calcium oxalate (CaOx) stone patients. Therefore, the aim of our study was to investigate the effect of Cu and Zn on biochemical and molecular characteristics of CaOx stones. Plasma and urine concentrations of Cu and Zn in 30 CaOx stones patients and 20 controls were determined by flame atomic absorption spectrometry (FAAS). Urinary levels of citric acid and oxalate were measured by commercial spectrophotometric kits. Blood levels of glutathione reduced (GSH) and catalase (CAT) were determined as markers of antioxidant activity, while blood malondialdehyde (MDA) and urine level of nitric oxide (NO) were used to assess oxidative stress. Gene expression of MAPk pathway (ERK, P38, and JNK) were estimated. The plasma and urine levels of Cu were significantly increased in the patient group compared to those of controls, while the levels of Zn were decreased. Excessive urinary excretion of citric acid and oxalate were found among CaOx stone patients. The GSH and CAT concentration were significantly reduced in CaOx stones patients compared to healthy group. The plasma MDA and urine NO concentration were significantly increased in CaOx stones patients compared to control group. The expressions of the studied genes were significantly increased in CaOx stones patients. These findings suggest that alteration in Cu and Zn might contribute to pathogenesis of CaOx patients through oxidative stress and MAPK pathway genes (ERK, P38 and JNK).

Vascular calcification on the risk of kidney stone: a meta-analysis

BACKGROUND

The association between vascular calcification (VC) and kidney stone is still inconclusive. Therefore, we conducted a meta-analysis to estimate the risk of kidney stone disease in subjects with VC.

METHODS

To identify publications from related clinical studies, we performed a search on PubMed, Web of Science, Embase, and Cochrane Library databases from their inceptions until 1 September 2022. According to obvious heterogeneity, a random-effects model was used to calculate the odds ratios (ORs) and corresponding 95% confidence intervals (CIs). Subgroup analysis was conducted trying to dissect the effects of VC in different segments and population regions in predicting kidney stone risk.

RESULTS

Seven articles were included with a total number of 69,135 patients, of which 10,052 have vascular calcifications and 4728 have kidney stones. There was a significantly higher risk of kidney stone disease in participants with VC versus control (OR = 1.54, 95% CI: 1.13-2.10). Sensitivity analysis confirmed the stability of the results. VC can be separated into abdominal, coronary, carotid, and splenic aortic calcification while pooled analysis of abdominal aorta calcification did not indicate a significant higher kidney stone risk. An obvious higher risk of kidney stone was observed in Asian VC patients (OR = 1.68, 95% CI: 1.07-2.61).

CONCLUSION

Combined evidence of observational studies suggested patients with VC may be associated with an increased risk of kidney stone disease. Despite the predictive value was relatively low, it is still worth noting that patients with VC are under the threat of kidney stone disease.

Underdiagnosis of Hyperparathyroidism in Patients With Nephrolithiasis in a Community Setting

Objective Untreated primary hyperparathyroidism (PHPT) has wide-ranging multisystemic effects. Recent studies based in the US have shown a less than 25% screening rate for PHPT. Our study aims to detect whether similar deficiencies exist in our community healthcare system while quantifying the prevalence of PHPT underdiagnosis and inadequate surgical referrals. Study design This retrospective quantitative study enrolled patients aged ≥18 years with imaged-confirmed nephrolithiasis at our healthcare facilities from 2017 to the present (n=2021). Patients with documented calcium levels and kidney/ureter stones were included. Descriptive and univariate analyses were performed. Results A total of 2021 subjects met the criteria to be enrolled in the study. 26.6% (n=537) of patients with nephrolithiasis had elevated calcium levels on record. 13.6% (n=73) of hypercalcemic patients were screened for PHPT with an intact parathyroid hormone (PTH). A majority (63%, n=46) of patients with intact PTH had PHPT defined as PTH levels >55 pg/mL. Ultimately, only 19.6% (n=9) of patients with PHPT were referred for surgical intervention, and there was no significant difference in referral rate between patients with PHPT and those without (p=0.913). Conclusions PHPT is underdiagnosed in our community, leading to a significantly low rate of surgical referral and delay in management. Implementation of hospital protocols to aid in improving diagnosis and interventions could improve outcomes for PHPT patients.

Comparative Analysis of Surgical Outcomes of Flexible Ureteroscopy and Da Vinci Robotic Surgery in Community Patients with Renal Pelvic Stones Larger than 2 cm

Background and Objectives: This study evaluated and compared the surgical outcomes of retrograde intrarenal surgery (RIRS) lithotripsy versus robot-assisted laparoscopic pyelolithotomy (RAPL) in community patients with renal pelvic stones larger than 2 cm. Materials and Methods: A total of 77 patients who underwent RIRS (RIRS group, n = 50) or RAPL (RAPL group, n = 27) at our institution between December 2016 and July 2022 were recruited. A single surgeon performed all surgical operations. Preoperative, operative, and postoperative data were recorded. The study evaluated various clinical outcomes, namely, urinary tract infections, analgesic use, emergency room readmissions, stone clearance rates, surgical complications, and medical expenditures associated with the treatment courses, and compared them between the groups. Results: The RAPL group had a larger mean stone diameter and higher degree of hydronephrosis than the RIRS group did. The RIRS group had superior outcomes regarding operative time, length of postoperative hospital stay, surgical wound pain, and medical expenditures. Regarding postoperative outcomes, comparable rates of postoperative urinary tract infection, prolonged analgesic use, and emergency room readmissions were observed between the groups. However, the RAPL group had a higher stone clearance rate than the RIRS group did (81.5% vs. 52.0%, p = 0.014). Conclusions: For the surgical treatment of renal pelvis stones larger than 2 cm, RAPL has a superior stone clearance rate than RIRS; however, RIRS achieves superior outcomes in terms of medical expenditures, length of hospital stay, and surgical wound pain. Both procedures were equally safe.

The effectiveness of citrates and pyridoxine in the treatment of kidney stones

The prevalence of nephrolithiasis is increasing across all demographic groups. Apart from the morbidity associated with an acute occurrence, preventative treatment is essential for stone disease, which can become a long-term problem. Simple interventions like fluid intake optimization and dietary modification are effective for most stone types. However, patients with specific metabolic abnormalities may require pharmaceutical therapy if lifestyle changes are insufficient to reduce the risk of stone recurrence. The treatment of citrates and/or pyridoxines may help eliminate or prevent recurrences of kidney stones, especially when they are composed of uric acid, calcium oxalate, calcium phosphate, or the latter two together. In cases of struvite stones, which often necessitate a surgical approach, acetohydroxamic acid emerges as a valuable second-line treatment option. Thiol-binding agents may be needed for cystinuria, as well as lifestyle modifications. Successful treatment reduces stone recurrence and the need to remove stones surgically.

Dietary supplements and medicinal plants in urolithiasis: diet, prevention, and cure

BACKGROUND

Urolithiasis has been a major health concern for centuries, primarily owing to the limited treatment options in the physician's armamentarium. However, various studies have underscored a lesser incidence of urolithiasis in cohorts predominantly consuming fruits and vegetables. This article aims to review various dietary plants, medicinal herbs and phytochemicals in the prevention and management of urolithiasis.

METHODS

To provide context and evidence, relevant publications were identified on Google Scholar, PubMed and Science-Direct using keywords such as urolithiasis, nephrolithiasis, urolithiasis, renal stones, phytochemicals and dietary plants.

RESULTS

Growing bodies of evidence suggest the incorporation of plant-based foods, medicinal and herbal supplements, and crude drugs containing phytochemicals into the staple diet of people. The anti-urolithiatic activity of these plant bioactives can be attributed to their antioxidant, antispasmodic, diuretic, and inhibitory effect on the crystallization, nucleation and crystal aggregation effects. These mechanisms would help alleviate the events and symptoms that aid in the development and progression of renal calculi. In addition, it will also avoid the exacerbation of secondary disorders like inflammation and injury, which can initiate a vicious circle in turn worsening the disease progression.

CONCLUSION

In conclusion, the results presented in the review demonstrate the promising role of various dietary plants, medicinal and herbal supplements, and phytochemicals in preventing and managing the precipitation of uroliths. However, more conclusive and cogent evidence from preclinical and clinical studies is required to substantiate their safety, efficacy and toxicity profiles in humans.

An overview of global research landscape in etiology of urolithiasis based on bibliometric analysis

The high incidence, recurrence and treatment costs of urolithiasis have a serious impact on patients and society. For a long time, countless scholars have been working tirelessly on studies related to the etiology of urolithiasis. A comprehensive understanding of the current status will be beneficial to the development of this field. We collected all literature about the etiology of urolithiasis from 1990 to 2022 using the Web of Science (WoS) database. VOSviewer, Bibliometrix and CiteSpace software were used to quantitatively analyze and visualize the data as well. The query identified 3177 articles for final analysis, of which related to the etiology of urolithiasis. The annual number of publications related to urolithiasis research has steadily increased during the latest decade. United States (1106) and China (449) contributed the most publications. University of Chicago (92) and Indiana University (86) have the highest number of publications. Urolithiasis and Journal of Urology have published the most articles in the field. Coe FL is the most productive author (63 articles), whose articles have obtained the most citations in all (4141 times). The keyword, such as hypercalciuria, hyperoxaluria, citrate, oxidative stress, inflammation, Randall's plaque, are the most attractive targets for the researchers. Our review provides a global landscape of studies related to the etiology of urolithiasis, which can serve as a reference for future studies in this field.

A path analysis to investigate the interaction between serum, urinary and demographic factors influencing urine calcium in kidney stone formers

BACKGROUND

Hypercalciuria is one of the most important urinary risk factors in kidney stone formers. This study aimed to delineate the interaction of some demographic, serum, and urinary risk factors influencing 24-h urinary (24-U) calcium excretion.

METHODS

This study was secondary data analysis, using data from 593 kidney stone patients referred to the Labbafinejad kidney stone prevention clinic from March 2015 to May 2019. The study considered serum, urinary and demographic factors that interact to influence 24-U calcium using path analysis. In addition to the direct impact of predictors on the 24-U calcium, this analysis considered the effects of the predictors on the 24-U calcium transmitted by a mediating variable named indirect effects.

RESULTS

The results showed that age indirectly affected on 24-U calcium through 25-hydroxy vitamin D (25(OH)D), serum and 24-U creatinine. As well, weight had an indirect effect through 24-urine metabolites (creatinine, citrate, urea, and sodium). Among serum variables, PTH and creatinine significantly directly affected on 24-U calcium. In comparison, 25(OH)D and phosphorus appeared to influence 24-U calcium indirectly through serum parathormone. Regarding 24-U metabolites, sodium, urea, and citrate had a significant direct effect on 24-U calcium. Moreover, 24-U creatinine has a significant direct and indirect effect on 24-U calcium through citrate and urea as mediator variables.

CONCLUSION

Serum 25(OH)D and phosphorus, along with age and weight, indirectly affected urinary calcium through a third variable. Other variables (PTH, serum creatinine, and 24-U sodium, urea, and citrate) showed a direct effect on 24-U calcium excretion.

Machine learning based multi-label classification of single or mixed-composition urinary stones in in vivo spectral CT

BACKGROUND

Urinary stones comprise both single and mixed compositions. Knowledge of the stone composition helps the urologists choose appropriate medical interventions for patients. The parameters from the spectral computerized tomography (CT) analysis have potential values for identification of the urinary stone compositions.

PURPOSE

The present study aims to identify the compositions of urinary stones in vivo using parameters from spectral CT and machine learning, based on multi-label classification modeling.

METHODS

This retrospective study collected 252 urinary stone samples with single/mixed compositions (including carbapatite [CP], calcium oxalate monohydrate [COM], calcium oxalate dehydrate [COD], uric acid [UA], and struvite [STR]), which were confirmed by ex vivo infrared spectroscopy. Parameters were extracted from an energy spectrum analysis (ESA) of the spectral CT, including the effective atomic number (Z_eff ), Z_eff histogram, CT values at a given x-ray energy level, and material densities. These ESA parameters were utilized for composition analysis via a multi-label classification fusion framework, where 250 multi-label models were built and the classification decisions from the top performance models were integrated by a multi-criterion weighted fusion (MCWF) approach in order to reach a consensus prediction. An example-based metric A c c e x a m $Ac{c_{exam}}$ and label-based metric A c c l a b e l $Ac{c_{label}}$ were used for global and label-wise accuracy evaluations, respectively. The top-ranked parameters associated with discriminating the stone composition were also identified.

RESULTS

The multi-label classification fusion framework achieved an overall A c c e x a m $Ac{c_{exam}}$ of 81.2%, with A c c l a b e l $Ac{c_{label}}$ of 86.7% (CP), 90.6% (COM), 80.6% (COD), 95.0% (UA), and 94.4% (STR) for each composition on the independent testing cohort 1, and A c c e x a m $Ac{c_{exam}}$ of 76.4% with A c c l a b e l $Ac{c_{label}}$ of 80.5% (CP), 88.7% (COM), 74.9% (COD), 94.4% (UA), and 98.5% (STR) on the independent testing cohort 2.

CONCLUSION

The parameters extracted from the ESA on spectral CT can be utilized to characterize single or mixed stone compositions via multi-label classification modeling. The generalization capability of the proposed methodology still requires further verification.

Predictors for Distinguishing Renal Infarction From Urolithiasis in the Emergency Department: A Randomly Matched Retrospective Case-Control Study

BACKGROUND

Emergency department (ED) clinicians may misdiagnose renal infarction (RI) as urolithiasis because RI is a rare disease with presenting symptoms similar to the symptoms of urolithiasis. However, earlier diagnosis of RI can improve patient prognosis.

OBJECTIVES

We investigated potential predictors for distinguishing RI from urolithiasis based on clinical findings and laboratory results.

METHODS

This randomly matched retrospective case-control study included patients who had been diagnosed with acute RI or acute urolithiasis between January 2016 and March 2020. Patients were excluded if they were aged under 18 years, had a history of trauma, or had incomplete medical records. Using a matching ratio of 1:4, RI patients were randomly matched to urolithiasis patients. Multivariable logistic regression was performed to identify factors that could distinguish RI from urolithiasis.

RESULTS

In total, 48 patients were included in the RI group and 192 patients were included in the urolithiasis group. Multivariable logistic regression showed that age ≥ 65 years (odds ratio [OR] 6.155; p = 0.022), atrial fibrillation (OR 18.472; p = 0.045), current smoking (OR 17.070; p = 0.001), costovertebral angle tenderness (OR 0.179; p = 0.037), aspartate aminotransferase level ≥ 27.5 U/L (OR 6.932; p = 0.009), sodium level ≥ 138.5 mEq/L (OR 0.079; p = 0.004), and hematuria (OR 0.042; p = 0.001) were significant predictors that could distinguish RI from urolithiasis. Based on these results, a nomogram was constructed.

CONCLUSION

Age ≥ 65 years, atrial fibrillation, current smoking, absence of costovertebral angle tenderness, aspartate aminotransferase level ≥ 27.5 U/L, sodium level < 138.5 mEq/L, and absence of hematuria were predictors that can distinguish between RI and urolithiasis.

[Diagnostic values of urinary citrate for kidney stones in patients with primary gout]

OBJECTIVE

To evaluate the relationship between 24 h urinary ion content and kidney stones, and to explore the diagnostic values of kidney stone in primary gout patients.

METHODS

Patients diagnosed with primary gout had ultrasound scanning of both feet and kidneys in Peking University First Hospital from Jan. 2020 to May 2021. Their clinical characteristics were compared between the positive and negative kidney stone groups, and the relationship between kidney stone and urinary ion composition were analyzed. Risk factors of kidney stone were analyzed. The explored diagnostic values were evaluated for urinary oxalate and citrate according with uric acid kidney stones by dual-energy computed tomography (DECT).

RESULTS

Among the 100 gouty patients, 80 patients had uric acid crystal deposition in lower joints of extremity by ultrasonography, 61 patients had kidney stone, and 34 had kidney uric acid stones by DECT. All the multiple kidney stones were proved as uric acid kidney stones by DECT. Compared with patients without kidney stone group proved by ultrasonography, patients with kidney stone had longer gouty duration [(48.7±26.6) months vs. (84.0±30.6) months, P=0.01], higher 24 h urinary oxalate [(20.1±9.6) mg vs. (28.6±20.7) mg, P=0.001] and lower 24 h urinary citrate [(506.3±315.4) mg vs. (355.7±219.6) mg, P=0.001]. Compared with the patients without kidney stone by DECT, the patients with uric acid kidney stone also had longer disease duration [(49.1±28.4) months vs. (108.3±72.2) months, P=0.001], higher 24 h urinary oxalate [(23.6±16.9) mg vs. (28.5±18.8) mg, P < 0.05], lower 24 h urinary citrate [(556.0±316.3) mg vs. (391.7±261.2) mg, P < 0.05], higher serum uric acid [(466.2±134.5) μmol/L vs. (517.2±18.1) μmol/L, P < 0.05] and higher 24 h urinary uric acid [(1 518.1±893.4) mg vs. (1 684.2±812.1) mg, P < 0.05]. Logistic regression analysis showed long gout disease duration (OR=1.229, 95%CI: 1.062-1.522, P < 0.05), high serum uric acid level (OR=1.137, 95%CI: 1.001-1.213, P=0.01), low 24 h urinary citrate (OR=0.821, 95%CI: 0.659-0.952, P=0.01) were all risk factors of kidney stones by ultrasonography. Also, long gout disease duration (OR=1.201, 95%CI: 1.101-1.437, P=0.005), high serum creatine uric level (OR=1.145, 95%CI: 1.001-1.182, P=0.04), low 24 h urinary citrate (OR=0.837, 95%CI: 0.739-0.931, P=0.02) were all risk factors of kidney uric acid stones by DECT.

CONCLUSION

Long disease duration and low 24 h urinary citrate were risk factors for kidney stones.

Comparison of cat and human calcium oxalate monohydrate kidney stone matrix proteomes

Despite its critical nature, the role of matrix in calcium oxalate stone formation is poorly understood. The wide diversity of proteins comprising matrix has contributed to the ambiguity. This study compares the protein distributions measured by mass spectrometry in human calcium oxalate stone matrix to that observed in cat stone matrix, because cats share many clinical characteristics of their stone disease with humans. The observed protein distributions were analyzed in the context of a recent model based on the aggregation of strongly anionic and strongly cationic proteins which includes selective adsorption of other proteins based on total charge. Matrix protein distributions shared many common features between species, including enrichment of both strongly anionic and strongly cationic proteins, increased total charge in matrix proteins compared to urine proteins, and a high degree of similarity of prominent strongly anionic proteins in the matrix of both species. However, there was weaker overlap of the specific dominant proteins in other regions of the net charge distribution. Collectively, these observations support the conceptual model where the strongly anionic proteins associate most strongly with the calcium oxalate crystal surfaces, while the other proteins associate with the strongly anionic proteins through non-specific, charge interactions with each other to create stones. Also, cats appear to be the best animal model of human stone disease identified to date based on these similarities.

Observation and identification of autofluorescent urine crystals may be linked to a sign of urolithiasis

Urolithiasis is a common disease of the urinary system. Its recurrence rate is high and may increase medical expenses. Urine stones are composed of urine crystals and other impurities. We discovered the existence of autofluorescence in some of the urine crystals, especially in urolithiasis patients. The fluorescent molecule existed in urine crystals was verified and identified. We have applied micro-Raman and fluorescence microscopy to classify the urine crystals, used confocal laser scanning microscopy (CLSM) to examine the 3D images and spectra of autofluorescence in crystals, used Fourier-transform infrared spectroscopy (FTIR) and mass spectrometry (MS) to identify the type of fluorophore in the autofluorescent urine crystals in urine. Riboflavin was identified as one of the major fluorophores in these autofluorescent urine crystals. The prevalence rates of the autofluorescent crystals in urolithiasis patients and subjects without the history of urolithiasis were to gather statistics. We observed that 80% of urolithiasis patients had autofluorescent crystals. Contrastingly, such crystals existed in only 7% of subjects without the history of urolithiasis. The presence of autofluorescent urine crystals may be linked to a sign of urolithiasis.

The effects of drinking bicarbonate-rich mineral water in calcium oxalate stone formers: an open label prospective randomized controlled study in an Asian cohort

PURPOSE

To examine the effects of drinking bicarbonate-rich mineral water in patients with calcium oxalate stones.

MATERIALS AND METHODS

This was an open label prospective randomized controlled study comparing the effects of a bicarbonate-rich mineral water versus plain water on urine biochemistry in patients with calcium oxalate stones. The mineral water group were instructed to consume 1.25 L of mineral water per day at meal times, and supplemented by plain water. Their total intake was up to 3 L/day. Control group consumed only plain water up to 3 L/day. 24 h urine analyses were performed at baseline, 1, 4, 8 and 12 weeks after starting protocol.

RESULTS

58 patients were recruited for the study. 51 patients were included in the final analysis. Baseline data were comparable between the two groups. Over the course of 12 weeks, compared to patients drinking plain water, those drinking mineral water had higher overall urinary volume (difference = 644.0 ml/24 h, 95% CI = (206.7, 1081.3)), higher overall urinary magnesium (difference = 1.894 mmol/24 h, 95% CI = (1.006, 2.782)), and pH (difference = 0.477, 95% CI = (0.149, 0.804)). However, there was no difference in urinary oxalate and Tiselius index. Mineral water group had net increase of urinary citrate (at each study point compared to baseline) which was sustained until week 12, whereas plain water group showed no significant change.

CONCLUSIONS

Drinking bicarbonate-rich mineral water in calcium oxalate stone formers increased stone inhibitors such as magnesium, citrate and moderate degree of urinary alkalinization compared to patients drinking plain water, but it did not alter Tiselius index or urinary oxalate after 12 weeks.

Medical Treatment and Prevention of Urinary Stone Disease

The pathophysiology underlying urinary stone formation remains an area of active investigation. There are many pharmacotherapies aimed at optimizing metabolic factors and reducing urinary supersaturation of stone components that play an important role in urinary stone prevention. In addition, medical expulsive therapy for ureteral stones and medical dissolution therapy for uric acid-based urinary stones are helpful treatment tools and are used alongside surgical treatments in the management of urinary stones.

A Case of Bilateral Infected Kidney Stones Presenting With Septic Shock and Acute Kidney Injury

The incidence of unilateral ureteral calculi has been reported at 20% in the literature; however, cases of bilateral kidney stones are not commonly reported in the urology, nephrology, and emergency medicine literature. Here, we present the case of a 31-year-old female who presented to the emergency department with septic shock and acute kidney injury. Acute kidney injury was initially thought to be prerenal secondary to septic shock but later found to have complete bilateral ureteral obstruction as a cause of septic shock and acute kidney injury. Urinary tract infection and sepsis secondary to bilateral obstructing ureteral stones are some of the few true urological emergencies. Anuria is the common presenting feature of complete urinary tract obstruction, and physicians should have a high index of suspicion for this diagnosis in anuric patients as rare as it is.

Innate Bacteriostatic Mechanisms Defend the Urinary Tract

Urinary tract infection (UTI) is the most common type of urogenital disease. UTI affects the urethra, bladder, ureter, and kidney. A total of 13.3% of women, 2.3% of men, and 3.4% of children in the United States will require treatment for UTI. Traditionally, bladder (cystitis) and kidney (pyelonephritis) infections are considered independently. However, both infections induce host defenses that are either shared or coordinated across the urinary tract. Here, we review the chemical and biophysical mechanisms of bacteriostasis, which limit the duration and severity of the illness. Urinary bacteria attempt to overcome each of these defenses, complicating description of the natural history of UTI.

Quantitative phase analysis and microstructural characterization of urinary tract calculi with X-ray diffraction Rietveld analysis on a Caribbean island

In the twin-island state of Trinidad and Tobago, urinary stone analysis is not routinely performed. This study investigates, via powder X-ray diffraction, 52 urinary tract calculi collected from hospitals in Trinidad. Of these, 46 stones were analysed with Rietveld refinement for quantitative analysis and materials characterization. Refined unit-cell, microstructural and weight fraction parameters were obtained, with the last being used for stone classification. The results revealed seven distinct mineralogical phases of varying frequency: calcium oxalate monohydrate (COM, 58%), calcium oxalate dihydrate (COD, 23%), carbonated apatite (APA, 48%), brushite (BRU, 6%), struvite (STR, 42%), uric acid (UA, 23%) and ammonium acid urate (AAU, 19%). The average refined crystallite sizes were 1352 ± 90 Å (COM), 1921 ± 285 Å (COD), 83 ± 5 Å (APA), 1172 ± 9 Å (BRU), 1843 ± 138 Å (STR), 981 ± 87 Å (UA) and 292 ± 83 Å (AAU). Subsequently, 36.5% of stones were categorized as phosphates, 34.6% as oxalates, 13.5% as uric acid/urates and 15.4% as mixed compositions. The study findings highlight the importance of stone analysis as a necessary step towards disease management of local patients, and endorse the application of Rietveld refinement as a natural extension to diffraction-based kidney stone investigations.

Removal of Large Urinary Stone Using Percutaneous Nephrolithotomy in a Patient with Crohn's Disease

Extraintestinal manifestation (EIM) of inflammatory bowel disease (IBD) is approximately 36%. Of genitourinary complications as an EIM of Crohn’s disease (CD), nephrolithiasis is the most common urinary complication in patients with CD. CD patients have been shown to have decreased urinary volume, pH, magnesium, and excretion of citrate, all of which are significant risk factors for nephrolithiasis. Genitourinary complications often occur in case of a severe longstanding disease and are associated with, the activity of bowel disease, especially in those who have undergone bowel surgery. As uncontrolled nephrolithiasis could impair renal function as well as adversely affect quality of life, proper monitoring, early detection, and prevention of the occurrence of urologic complications in CD is crucial. Few data are available about urolithiasis in patients with CD. Herein we report a case of a successful removal of a 2.7 cm calcium oxalate stone using percutaneous nephrolithotomy from a patient with long-standing CD with a previous surgery for small intestinal and colonic stricture.

Calcium and Vitamin D Supplementation and Their Association with Kidney Stone Disease: A Narrative Review

Kidney stone disease is a multifactorial condition influenced by both genetic predisposition and environmental factors such as lifestyle and dietary habits. Although different monogenic polymorphisms have been proposed as playing a causal role for calcium nephrolithiasis, the prevalence of these mutations in the general population and their complete pathogenetic pathway is yet to be determined. General dietary advice for kidney stone formers includes elevated fluid intake, dietary restriction of sodium and animal proteins, avoidance of a low calcium diet, maintenance of a normal body mass index, and elevated intake of vegetables and fibers. Thus, balanced calcium consumption protects against the risk for kidney stones by reducing intestinal oxalate availability and its urinary excretion. However, calcium supplementation given between meals might increase urinary calcium excretion without the beneficial effect on oxalate. In kidney stone formers, circulating active vitamin D has been found to be increased, whereas higher plasma 25-hydroxycholecalciferol seems to be present only in hypercalciuric patients. The association between nutritional vitamin D supplements and the risk for stone formation is currently not completely understood. However, taken together, available evidence might suggest that vitamin D administration worsens the risk for stone formation in patients predisposed to hypercalciuria. In this review, we analyzed and discussed available literature on the effect of calcium and vitamin D supplementation on the risk for kidney stone formation.

Recurrent Nephrolithiasis Due to Parathyroid Adenoma

Nephrolithiasis is a common urologic disorder affecting various age groups worldwide, in association with significant morbidity. The cause associated with renal stone varies, of which increased calcium level due to primary hyperparathyroidism (parathyroid adenoma) is one of the unique and rare causes associated. The case report we are presenting is a 35-year-old female with a history of recurrent renal stones in developing country settings. Upon detailed workup, parathyroid adenoma hence was identified to be the primary culprit. She underwent parathyroidectomy and has recovered well without any complications.

The controversial association of gut and urinary microbiota with kidney stone formation

Nephrolithiasis (kidney stones) is one of the most common chronic kidney diseases that are typically more common among adult men comparing to adult women. The prevalence of this disease is increasing which is influenced by genetic and environmental factors. Kidney stones are mainly composed of calcium oxalate and urinary oxalate which is considered a dangerous factor in their formation. Besides diverse leading reasons in the progression of nephrolithiasis, the gut and urinary microbiome has been recognized as a major player in the development or prevention of it. These microbes produce metabolites that have diverse effects on host biological functions. Therefore, Changes in the composition and structure of the microbiome (dysbiosis) have been implicated in various diseases. The present review focuses on the roles of gut and urinary in kidney stone formation.

Exploring the Molecular Level Interaction of Human Serum Albumin with Calcium Oxalate Monohydrate Crystals

BACKGROUND

Human serum albumin (HSA) is one of the most abundant proteins in the blood plasma, urine as well as in the organic matrix of renal calculi. Macromolecules present in the urine modulate kidney stone formation either by stimulating or inhibiting crystallization process.

OBJECTIVE

In the present study, effect of HSA protein on the growth of calcium oxalate monohydrate crystal (COM) was investigated.

METHODS

Crystal growth assay was used to measure oxalate depletion in the crystal seeded solution in the presence of HSA. HSA concentrations exhibiting effect on crystal growth were selected for FTIR and XRD analysis. In silico docking was performed on seven different binding sites of HSA.

RESULTS

Albumin is playing dual role in growth of calcium oxalate crystallization. FTIR and XRD studies further revealed HSA exerted strain over crystal thus affecting its structure by interacting with amino acids of its pocket 1. Docking results indicate that out of 7 binding pocket in protein, calcium oxalate interacts with Arg-186 and Lys-190 amino acids of pocket 1.

CONCLUSION

Our study confirms the role of HSA in calcium oxalate crystallization where acidic amino acids arginine and lysine are binding with COM crystals, revealing molecular interaction of macromolecule and crystal in urolithiasis.

Protein primary structure correlates with calcium oxalate stone matrix preference

Despite the apparent importance of matrix proteins in calcium oxalate kidney stone formation, the complexity of the protein mixture continues to elude explanation. Based on a series of experiments, we have proposed a model where protein aggregates formed from a mixture containing both strongly charged polyanions and strongly charged polycations could initiate calcium oxalate crystal formation and crystal aggregation to create a stone. These protein aggregates also preferentially adsorb many weakly charged proteins from the urine to create a complex protein mixture that mimics the protein distributions observed in patient samples. To verify essential details of this model and identify an explanation for phase selectivity observed in weakly charged proteins, we have examined primary structures of major proteins preferring either the matrix phase or the urine phase for their contents of aspartate, glutamate, lysine and arginine; amino acids that would represent fixed charges at normal urine pH of 6–7. We verified enrichment in stone matrix of proteins with a large number of charged residues exhibiting extreme isoelectric points, both low (pI<5) and high (pI>9). We found that the many proteins with intermediate isoelectric points exhibiting preference for stone matrix contained a smaller number of charge residues, though still more total charges than the intermediate isoelectric point proteins preferring the urine phase. While other sources of charge have yet to be considered, protein preference for stone matrix appears to correlate with high total charge content.

Diminishment of Nrf2 Antioxidative Defense Aggravates Nephrotoxicity of Melamine and Oxalate Coexposure

Chronic kidney disease (CKD) usually causes devastating healthy impacts on patients. However, the causes affecting the decline of kidney function are not fully revealed, especially the involvement of environmental pollutants. We have revealed that exposure to melamine, a ubiquitous chemical in daily life, is linked to adverse kidney outcomes. Hyperoxaluria that results from exposure to excessive oxalate, a potentially nephrotoxic terminal metabolite, is reportedly associated with CKD. Thus, we explored whether interaction of these two potential nephrotoxicants could enhance kidney injury. We established a renal proximal tubular HK-2 cell model and a Sprague-Dawley rat model of coexposure to melamine with sodium oxalate or hydroxy-L-proline to investigate the interacting adverse effects on kidneys. Melamine and oxalate coexposure enhanced the levels of reactive oxygen species, lipid peroxidation and oxidative DNA damage in the HK-2 cells and kidney tissues. The degrees of tubular cell apoptosis, tubular atrophy, and interstitial fibrosis were elevated under the coexposed condition, which may result from the diminishment of Nrf2 antioxidative capacity. To conclude, melamine and oxalate coexposure aggravates renal tubular injury via impairment of antioxidants. Accumulative harmful effects of exposure to multiple environmental nephrotoxicants should be carefully investigated in the etiology of CKD progression.

Cystinuria in Dogs and Cats: What Do We Know after Almost 200 Years?

The purpose of this review is to summarize current knowledge on canine and feline cystinuria from available scientific reports. Cystinuria is an inherited metabolic defect characterized by abnormal intestinal and renal amino acid transport in which cystine and the dibasic amino acids ornithine, lysine, and arginine are involved (COLA). At a normal urine pH, ornithine, lysine, and arginine are soluble, but cysteine forms a dimer, cystine, which is relatively insoluble, resulting in crystal precipitation. Mutations in genes coding COLA transporter and the mode of inheritance were identified only in some canine breeds. Cystinuric dogs may form uroliths (mostly in lower urinary tract) which are associated with typical clinical symptoms. The prevalence of cystine urolithiasis is much higher in European countries (up to 14% according to the recent reports) when compared to North America (United States and Canada) where it is approximately 1-3%. Cystinuria may be diagnosed by the detection of cystine urolithiasis, cystine crystalluria, assessment of amino aciduria, or using genetic tests. The management of cystinuria is aimed at urolith removal or dissolution which may be reached by dietary changes or medical treatment. In dogs with androgen-dependent cystinuria, castration will help. In cats, cystinuria occurs less frequently in comparison with dogs.

Association of urate-lowering drugs with the risk of future urolithiasis in patients with gout: A population-based nested case-control study

BACKGROUND

Patients with gout have an increased risk of urolithiasis and usually need urate-lowering therapy (ULT) for the prevention of disease progression. However, there is a paucity of clinical data regarding the risk of future urolithiasis in ULT users.

METHODS

This nested case-control study was performed using the Taiwan National Health Insurance Research Database. The aim of this study was to examine whether ULT (xanthine oxidase inhibitors [XOIs] or uricosuric agents) is associated with risk of future urolithiasis in patients with gout. Data were collected from January 2000 to December 2012.

RESULTS

This study included 2307 case patients and 2307 matched controls. Case patients had gout that developed into urolithiasis, and control patients had gout but were not diagnosed with urolithiasis during the study period. Patients had a mean age of 56.3 years at diagnosis of gout, and 83.2% were male patients. No association was detected between use of XOIs or uricosuric agents and risk of future urolithiasis. Furthermore, there was no significant difference in the risk of future urolithiasis in patients exposed to various cumulative days of XOI or uricosuric prescriptions.

CONCLUSION

The present study provides evidence that neither XOIs nor uricosuric agents are associated with risk of future urolithiasis in patients with gout. Before the availability of more clinical evidence, ensuring high fluid intake and prospective monitoring of urolithiasis development are still important for uricosuric agent users.

TRPV1 Hyperfunction Contributes to Renal Inflammation in Oxalate Nephropathy

Inflammation worsens oxalate nephropathy by exacerbating tubular damage. The transient receptor potential vanilloid 1 (TRPV1) channel is present in kidney and has a polymodal sensing ability. Here, we tested whether TRPV1 plays a role in hyperoxaluria-induced renal inflammation. In TRPV1-expressed proximal tubular cells LLC-PK₁, oxalate could induce cell damage in a time- and dose-dependent manner; this was associated with increased arachidonate 12-lipoxygenase (ALOX12) expression and synthesis of endovanilloid 12(S)-hydroxyeicosatetraenoic acid for TRPV1 activation. Inhibition of ALOX12 or TRPV1 attenuated oxalate-mediated cell damage. We further showed that increases in intracellular Ca²⁺ and protein kinase C α activation are downstream of TRPV1 for NADPH oxidase 4 upregulation and reactive oxygen species formation. These trigger tubular cell inflammation via increased NLR family pyrin domain-containing 3 expression, caspase-1 activation, and interleukin (IL)-1β release, and were alleviated by TRPV1 inhibition. Male hyperoxaluric rats demonstrated urinary supersaturation, tubular damage, and oxidative stress in a time-dependent manner. Chronic TRPV1 inhibition did not affect hyperoxaluria and urinary supersaturation, but markedly reduced tubular damage and calcium oxalate crystal deposition by lowering oxidative stress and inflammatory signaling. Taking all these results together, we conclude that TRPV1 hyperfunction contributes to oxalate-induced renal inflammation. Blunting TRPV1 function attenuates hyperoxaluric nephropathy.

Protective Effects of Quercetin on Oxidative Stress-Induced Tubular Epithelial Damage in the Experimental Rat Hyperoxaluria Model

Background and Objectives: The most common kidney stones are calcium stones and calcium oxalate (CaOx) stones are the most common type of calcium stones. Hyperoxaluria is an essential risk factor for the formation of these stones. Quercetin is a polyphenol with antioxidant, anti-inflammatory, and many other physiological effects. The aim of this study was to investigate the protective effect of quercetin in hyperoxaluria-induced nephrolithiasis. Materials and Methods: Male Wistar-Albino rats weighing 250–300 g (n = 24) were randomized into three groups: Control (n = 8), ethylene glycol (EG) (n = 8), and EG + quercetin (n = 8). One percent EG-water solution was given to all rats except for the control group as drinking water for five weeks. Quercetin-water solution was given to the EG + quercetin group by oral gavage at a dose of 10 mg/kg/day. Malondialdehyde (MDA), catalase (CAT), urea, calcium, and oxalate levels were analyzed in blood and urine samples. Histopathological assessments and immunohistochemical analyses for oxidative stress and inflammation indicators p38 mitogen-activated protein kinase (p38-MAPK) and nuclear factor kappa B (NF-kB) were performed on renal tissues. Results: The MDA levels were significantly lower in the quercetin-treated group than in the EG-treated group (p = 0.001). Although CAT levels were higher in the quercetin-treated group than the EG-administered group, they were not significantly different between these groups. The expression of p38 MAPK was significantly less in the quercetin-treated group than the EG group (p < 0.004). There was no statistically significant difference between the quercetin and EG groups in terms of NF-kB expression. Conclusions: We conclude that hyperoxaluria activated the signaling pathways, which facilitate the oxidative processes leading to oxalate stone formation in the kidneys. Our findings indicated that quercetin reduced damage due to hyperoxaluria. These results imply that quercetin can be considered a therapeutic agent for decreasing oxalate stone formation, especially in patients with recurrent stones due to hyperoxaluria.

Excretion of urine extracellular vesicles bearing markers of activated immune cells and calcium/phosphorus physiology differ between calcium kidney stone formers and non-stone formers

BACKGROUNDS

Previous studies have demonstrated that excretion of urinary extracellular vesicles (EVs) from different nephron segments differs between kidney stone formers and non-stone formers (NSFs), and could reflect pathogenic mechanisms of urinary stone disease. In this study we quantified selected populations of specific urinary EVs carrying protein markers of immune cells and calcium/phosphorus physiology in calcium oxalate stone formers (CSFs) compared to non-stone formers (NSFs).

METHODS

Biobanked urine samples from CSFs (n = 24) undergoing stone removal surgery and age- and sex- matched NSFs (n = 21) were studied. Urinary EVs carrying proteins related to renal calcium/phosphorus physiology (phosphorus transporters (PiT1 and PiT2), Klotho, and fibroblast growth factor 23 (FGF23); markers associated with EV generation (anoctamin-4 (ANO4) and Huntington interacting protein 1 (HIP1)), and markers shed from activated immune cells were quantified by standardized and published method of digital flow cytometry.

RESULTS

Urine excretion of calcium, oxalate, phosphorus, and calcium oxalate supersaturation (SS) were significantly higher in CSFs compared to NSFs (P < 0.05). Urinary excretion of EVs with markers of total leukocytes (CD45), neutrophils (CD15), macrophages (CD68), Klotho, FGF23, PiT1, PiT2, and ANO4 were each markedly lower in CSFs than NSFs (P < 0.05) whereas excretion of those with markers of monocytes (CD14), T-Lymphocytes (CD3), B-Lymphocytes (CD19), plasma cells (CD138 plus CD319 positive) were not different between the groups. Urinary excretion of EVs expressing PiT1 and PiT2 negatively (P < 0.05) correlated with urinary phosphorus excretion, whereas excretion of EVs expressing FGF23 negatively (P < 0.05) correlated with both urinary calcium and phosphorus excretion. Urinary EVs with markers of HIP1 and ANO4 correlated negatively (P < 0.05) with clinical stone events and basement membrane calcifications on papillary tip biopsies.

CONCLUSIONS

Urinary excretion of EVs derived from specific types of activated immune cells and EVs with proteins related to calcium/phosphorus regulation differed between CSFs and NSFs. Further validation of these and other populations of urinary EVs in larger cohort could identify biomarkers that elucidate novel pathogenic mechanisms of calcium stone formation in specific subsets of patients.

Imaging of ureter: a primer for the emergency radiologist

In this review article, we will discuss the gamut of abnormalities involving the ureters. In the emergency department, ureterolithiasis is the most common indication for imaging abdomen and pelvis. However, spectrum of ureteral abnormalities including congenital, infectious and inflammatory, primary and secondary ureteral malignancies, retroperitoneal fibrosis rare described in this article may be encountered. Thus, we will describe acute subacute as well as chronic conditions that may affect ureter. Knowledge of common, as well as rare entities and their imaging features, is of utmost importance to enable appropriate management.

Risk of Hospital Encounters With Kidney Stones in Autosomal Dominant Polycystic Kidney Disease: A Cohort Study

Background:

There is a perception that patients with autosomal dominant polycystic kidney disease (ADPKD) are more likely to develop kidney stones than the general population.

Objective:

To compare the rate of hospital encounter with kidney stones and the rate of stone interventions between patients with and without ADPKD.

Design:

Retrospective cohort study.

Setting:

Ontario, Canada.

Patients:

Patients with and without ADPKD who had a prior hospital encounter between 2002 and 2016.

Measurements:

Rate of hospital encounter with kidney stones and rate of stone intervention.

Methods:

We used inverse probability exposure weighting based on propensity scores to balance baseline indicators of health between patients with and without ADPKD. We followed each patient until death, emigration, outcomes, or March 31, 2017. We used a Cox proportional hazards model to compare event rates between the two groups.

Results:

Patients with ADPKD were at higher risk of hospital encounter with stones compared with patients without ADPKD (81 patients of 2094 with ADPKD [3.8%] vs 60 patients of 1902 without ADPKD [3.2%]; 8.9 vs 5.1 events per 1000 person-years; hazard ratio 1.6 [95% CI, 1.3-2.1]). ADPKD was not associated with a higher risk of stone intervention (49 of 2094 [2.3%] vs 47 of 1902 [2.4%]; 5.3 vs 3.9 events per 1000 person-years; hazard ratio 1.2 [95% CI = 0.9-1.3]).

Limitations:

We did not have information on kidney stone events outside of the hospital. There is a possibility of residual confounding.

Conclusion:

ADPKD was a significant risk factor for hospital encounters with kidney stones.

Metabolic assessment in pure struvite stones formers: is it necessary?

BACKGROUND AND OBJECTIVE

Magnesium ammonium phosphate stones (MAP), also known as struvite stones, are associated with urinary infection and impairment of renal unit. The aim of this study is to evaluate the urinary metabolic risk factors for recurrence of renal calculi in patients submitted to nephrectomy due to MAP stones.

METHODS

We retrospectively reviewed the charts of patients > 18 years old submitted to total nephrectomy due to pure MAP stones and pure calcium oxalate (CaOx) stones from July 2006 to July 2016. Urinary metabolic parameters were assessed through 24-hour urine exams ≥ 3 months after nephrectomy. Urinary metabolic parameters and new event related to lithiasis were compared.

RESULTS

Twenty-eight and 39 patients were included in MAP and CaOx group, respectively. Abnormalities in 24-hour urine samples were similar between groups. Hypercalciuria occurred in 7.1 and 10.3% of patients in MAP and CaOx group, respectively (p = 0.66), whereas hypocitraturia was present in 65.2 and 59.0% of patients with MAP and CaOx group, respectively (p = 0.41). No significant difference in new events was found between MAP and CaOx groups (17.9 vs. 23.1%, respectively; p = 0.60).

CONCLUSION

A 24-hour urine evaluation should be offered to patients submitted to nephrectomy due to pure MAP stones in order to detect metabolic risk, improve treatment, and prevent stone recurrence.

Improvement of organisms by biomimetic mineralization: A material incorporation strategy for biological modification

Biomineralization, a bio-organism controlled mineral formation process, plays an important role in linking biological organisms and mineral materials in nature. Inspired by biomineralization, biomimetic mineralization is used as a bridge tool to integrate biological organisms and functional materials together, which can be beneficial for the development of diversified functional organism-material hybrids. In this review, recent progresses on the techniques of biomimetic mineralization for organism-material combinations are summarized and discussed. Based upon these techniques, the preparations and applications of virus-, prokaryotes-, and eukaryotes-material hybrids have been presented and they demonstrate the great potentials in the fields of vaccine improvement, cell protection, energy production, environmental and biomedical treatments, etc. We suggest that more researches about functional organism and material combination with more biocompatible techniques should be developed to improve the design and applications of specific organism-material hybrids. These rationally designed organism-material hybrids will shed light on the production of "live materials" with more advanced functions in future. STATEMENT OF SIGNIFICANCE: This review summaries the recent attempts on improving biological organisms by their integrations with functional materials, which can be achieved by biomimetic mineralization as the combination tool. The integrated materials, as the artificial shells or organelles, confer diversified functions on the enclosed organisms. The successful constructions of various virus-, prokaryotes-, and eukaryotes-material hybrids have demonstrated the great potentials of the material incorporation strategy in vaccine development, cancer treatment, biological photosynthesis and environment protection etc. The suggested challenges and perspectives indicate more inspirations for the future development of organism-material hybrids.

LITHORISK.COM: the novel version of a software for calculating and visualizing the risk of renal stone

Estimation of state of saturation with stone-forming salt represents a reliable tool to assess the overall risk. The available methods are based on computer-assisted ab initio calculations. Our earlier method URSUS was subsequently substituted by Lithorisk®, a software including visualization of risk profiles. Unfortunately, Lithorisk does not adapt to new versions of Windows® and Macintosh® Apple, neither runs on smartphones or tablets. We propose a novel version of the software which can be directly used online on any device equipped by different operating systems. Upon online connection and after registration, the software is ready for unlimited accesses, in either Italian, English or French. After digiting input variables (urea and creatinine also included) in a fixed dashboard, state of saturation is promptly given. In addition to state of saturation (ß) with calcium oxalate, brushite and uric acid, ß struvite and cystine are available. Both input variables and ß results are graphically depicted as green or red horizontal bars to indicate recommended values. The software was implemented with equations allowing to omit sulphate and ammonium excretion for users with difficult access to these measurements. This simplified version, tested for ßCaOx and ßBsh on 100 urine samples showed close correlation with the full version. The software gives a list of total and free concentrations and soluble complex species distribution. Results can be printed or saved as PDF. So, we propose an easily accessible software to estimate state of saturation usable on any operating system and personal device.

Complications in Patients With Autosomal Dominant Polycystic Kidney Disease Undergoing Ureteroscopy: A Cohort Study

BACKGROUND

Ureteroscopy is a minimally invasive treatment option for upper tract stones. The distorted kidney anatomy in patients with autosomal dominant polycystic kidney disease (ADPKD) may place them at higher risk for ureteroscopic complications.

OBJECTIVE

To compare the 30-day risk of ureteroscopic complications between patients with and without ADPKD.

DESIGN

Retrospective cohort study.

SETTING

Ontario, Canada.

PATIENTS

Seventy three patients with ADPKD and 81 445 patients without ADPKD who underwent ureteroscopy for upper urinary tract stones between April 1, 2002, and March 1, 2018.

MEASUREMENTS

A 30-day risk of (1) hospital presentation with ureteroscopic complications (which was a composite outcome of either emergency department visit or hospital admission with acute kidney injury, urinary tract infection, or sepsis); (2) all-cause hospital presentation; (3) all-cause hospital admission; and (4) all-cause emergency department visit.

METHODS

We regressed outcomes on demographic variables, health care use in the prior 1-year, various procedures and comorbidities related to the outcome in the prior 5 years, and prescribed medications filled in the past 120 days using modified Poisson regression to compare the risk ratio (RR) of each outcome between patients with and without ADPKD.

RESULTS

The median (interquartile, IQR) age was 44 (38-60 years) in the ADPKD group and 53 (42-64) in the control group. About 40% were women in both groups. The risk of ureteroscopic complications was not significantly different in patients with versus without ADPKD (8.2% vs 4.3%; adjusted RR = 1.5, 95% confidence interval [CI] = 0.7-3.2). Patients with versus without ADPKD were more likely to present to hospital after their procedure (35.6% vs. 20.0%; adjusted RR = 1.6, 95% CI = 1.2-2.2), which included a statistically significant increase in the risk of presenting to the emergency department (32.9% vs. 19.0%; adjusted RR = 1.6, 95% CI = 1.1-2.2) but not hospital admissions (10.9% vs. 5.0%; adjusted RR = 1.8, 95% CI = 0.9-3.4).

LIMITATIONS

The low numbers of events led to imprecision around the estimates.

CONCLUSION

Patients with ADPKD have a higher risk of return to the hospital within 30 days of ureteroscopy for stone disease.

TRIAL REGISTRATION

We did not register this study.

Relationship of spot urine oxalate to creatinine ratio and 24 hours urinary oxalate excretion in patients with urolithiasis

Background

The evaluation of 24 h urinary oxalate excretion is the gold standard for diagnosing hyperoxaluria in patients with recurrent urolithiasis. However, 24 h urine sample collection is cumbersome. Therefore we aim to see if oxalate to creatinine ratio in random urine sample can be used as an alternative.

Materials and methods

A cross-sectional study was conducted at Section of Chemical Pathology, Department of Pathology and Laboratory Medicine Aga Khan University Karachi from 1st February to December 31, 2019. A total of 62 adult patients, 18–60 years of age with history of kidney stones presenting to the clinical laboratory for 24 h urine oxalate estimation were invited to participate in the study after informed consent. Clinical details were recorded on a structured questionnaire and patients were guided to submit 24 h urine and a random spot urine sample. Urinary oxalate was measured on Micro lab 300 using a kit based on oxalate oxidase principle by Trinity Biotech plc, Wicklow, Ireland following standard operating procedures. Urinary creatinine was measured on ADVIA 1800 by Siemens, US using kinetic Jaffe reaction according to the manufacturer's instructions. The data was analyzed on SPSS.

Results

In a period of ten months, a total of 62 subjects were recruited; mean age was 32.4 ± 2.6 years. Males were 49 (79.0%) and females were 13 (20.9%). Correlation was found to be (r = 0.289) by Spearman correlation (p value < 0.005). Taking 24 h urinary oxalate as gold standard the sensitivity, specificity, positive predictive value and negative predictive value of spot oxalate to creatinine ratio was 83.3%, 17.8%, 9.8% and 90.9% respectively.

Conclusion

The random spot urine test cannot replace the 24 h urinary oxalate estimation in patients with urolithiasis.

•

Oxalate to creatinine ratio is proposed as an alternative to 24 h urine.

•

Sensitivity & specificity of spot ox:cr ratio was 83.3% and 17.8% respectively.

•

PPV and NPV of spot ox:cr ratio was 9.8% and 90.9% respectively.

•

Studies taking diet and molecular testing into consideration are needed.

Urinary Calculi: A Microbiological and Biochemical Analysis at a Tertiary Care Hospital in Eastern Nepal

Background

The occurrence of urinary tract infection in presence of urolithiasis is frequently noted; however, microbial agents of urolithiasis and their antimicrobial susceptibility patterns remain underinvestigated. This study aimed to identify the microorganisms isolated from urine and stone matrices to determine their antimicrobial susceptibility, to find the association between the pathogens of urine and stone matrices, and to perform the biochemical analysis of stones.

Methods

A total of 88 cases of urolithiasis admitted for elective stone removal at Department of surgery, B.P. Koirala Institute of Health Sciences (BPKIHS), were enrolled. Preoperative urine culture and postoperative stone culture were performed. Isolation, identification, and AST were done by the standard microbiological technique. Further qualitative biochemical analysis of stones was also attempted.

Result

Among 88 stone formers recruited, culture of urine, whole stone, and nidus yielded the growth of bacteria 44, 32, and 30, respectively. Bacteria isolated from urine culture correlated with those from stone matrices with a sensitivity of 90%, specificity of 79.69%, PPV of 63.64%, and NPV of 95.45%. Escherichia coli (46.7%) was the most common bacteria followed by Klebsiella pneumoniae (16.7%) and Proteus mirabilis (13.3%) from urine and stone cultures. Almost all the uropathogens isolated were susceptible to commonly used antibiotics. Calcium oxalate (84.1%) was common biochemical constituent found in stone formers followed by calcium oxalate + phosphate (8%).

Conclusions

The association of microorganism isolated from urine and nidus culture was significant that can predict the source of infective stone; however, in some cases, microorganisms and the antimicrobial susceptibility pattern from urine and nidus were different. This study emphasizes the use of appropriate antimicrobial agents to prevent the regrowth of residual stones and minimize the risk of infectious complications after surgical removal of stones.

Urolithiasis in complicated inflammatory bowel disease: a comprehensive analysis of urine profile and stone composition

PURPOSE

To evaluate the impact of extensive surgery on urine profile, serum exams and stone composition of complicated IBD patients.

METHODS

Patients with IBD and a history of total proctocolectomy (TPC) with fecal diversion (end ileostomy or ileal pouch anal anastomosis-IPAA) were selected. Only patients with at least one complete 24-h urine profile were included. A case-control study was performed selecting patients with kidney stone disease in a random way who had also at least on complete 24-h urine profile. Case and controls were matched for age, gender, and body mass index (BMI). Groups were compared to urine profile, serum exams and stone composition.

RESULTS

Sixty-eight patients were enrolled in this study, 34 patients with IBD who underwent TPC and had diagnosis of kidney stones and 34 matched patients with only kidney stones. IBD patients had a significantly lower urine volume, urine citrate and urine sodium. Regarding serum exams, only serum bicarbonate was statistically significant lower. In both groups, calcium oxalate stone was the most common.

CONCLUSION

Patients with IBD with TPC and kidney stones have a low urine volume and low urine citrate as main risk factors for kidney stone formation. As seen in the general population, calcium oxalate is the most common stone composition.

The association of Dietary Approaches to Stop Hypertension-style diet with urinary risk factors of kidney stones formation in men with nephrolithiasis

OBJECTIVE

The relation of the Dietary Approaches to Stop Hypertension (DASH)-style diet to urinary lithogenic factors is unclear. This study aimed to assess the association between adherence to the DASH diet and urinary risk factors of kidney stones formation.

METHODS

A total of 264 men apparently with nephrolithiasis, aged 18-89 years, participated in this cross-sectional study. The food item-based DASH diet based on 8 components (nuts and legumes, red and processed meat, low-fat dairy products, sweetened beverages, fruits, vegetables, sodium, and whole grains) and nutrient-based DASH score based on 9 target nutrients (protein, fiber, total fat, saturated fat, cholesterol, sodium, calcium, potassium, and magnesium) were calculated using a food frequency questionnaire. Urine analysis was performed to measure hypercalciuria, hypocitraturia, hyperoxaluria, hyperuricosuria, and hypercreatinuria as study outcomes. Multivariate logistic regression analysis was used to evaluate the relation of DASH diet to urinary factors.

RESULTS

After multivariate adjustment, high adherence to the food-based or nutrient-based DASH dietary patterns was significantly associated with lower odds for hypercreatininuria, hypocitraturia, and hypercalciuria. Higher nutrient-based DASH diet scores were related to lower odds of hyperuricosuria and moderate adherence to the food-based DASH score increased odds for hyperoxaluria. Moreover, expect for "Nuts and legumes" and sodium, other components of DASH diet were significantly related to urinary lithogenic factors.

CONCLUSION

Adherence to the DASH diet may be a strong preventive approach to decrease urinary risk factors of kidney stone formation.

Efficacy and Safety of Surgical Kidney Stone Interventions in Autosomal Dominant Polycystic Kidney Disease: A Systematic Review

BACKGROUND

Reduced kidney function and distorted kidney anatomy in patients with autosomal dominant polycystic kidney disease (ADPKD) may complicate stone interventions more compared with the general population.

OBJECTIVES

To review studies describing the safety and efficacy of the 3 main stone interventions in adults with ADPKD: shock wave lithotripsy (SWL), ureteroscopy, and percutaneous nephrolithotomy (PCNL).

DESIGN

Systematic review.

SETTING

Any country of origin.

PATIENTS

Adults with ADPKD who underwent SWL, ureteroscopy, or PCNL.

MEASUREMENTS

Being stone free after the intervention and postoperative complications as reported by each study, which included pain, bleeding, and fever.

METHODS

Relevant studies published until February 2019 were identified through a comprehensive search of MEDLINE, EMBASE, Web of Science, BIOSIS PREVIEW, and CINAHL. Studies were eligible for review if they reported at least one outcome following SWL, ureteroscopy, and/or PCNL in adults with ADPKD. We then abstracted information on study characteristics, patient characteristics, intervention details, and postintervention outcomes and assessed the methodological quality of each study using a modified Downs and Black checklist.

RESULTS

We screened 221 citations from which we identified 24 studies that met our review criteria. We identified an additional article when manually reviewing the reference list of an included article, yielding a total of 25 studies describing 311 patients (32 SWL, 42 ureteroscopy, and 237 PCNL). The percentage of patients who were stone free after 1 session ranged from 0% to 69% after SWL, 73% to 100% after ureteroscopy, and 45% to 100% after PCNL. The percentage of patients with ADPKD that experienced at least one postoperative complication ranged from 0% to 33% for SWL, 0% to 27% for ureteroscopy, and 0% to 100% for PCNL.

LIMITATIONS

The number and quality of studies published to date are limited.

CONCLUSIONS

The efficacy and safety of stone interventions in patients with ADPKD remains uncertain, with wide-ranging estimates reported in the literature.

TRIAL REGISTRATION

We did not register the protocol of this systematic review.

Hexametaphosphate as a potential therapy for the dissolution and prevention of kidney stones

The incidence of kidney stones is increasing worldwide, and recurrence is common (50% within 5 years). Citrate, the current gold standard therapy, which is usually given as potassium or sodium salts, is used because it raises urine pH and chelates calcium, the primary component of up to 94% of stones. In this study hexametaphosphate (HMP), a potent calcium chelator, was found to be 12 times more effective at dissolving calcium oxalate, the primary component of kidney stones, than citrate. HMP was also observed to be effective against other common kidney stone components, namely calcium phosphate and struvite (magnesium ammonium phosphate). Interestingly, HMP was capable of raising the zeta potential of calcium oxalate particles from -15.4 to -34.6 mV, which may prevent stone growth by aggregation, the most rapid growth mechanism, and thus avert occlusion. Notably, HMP was shown to be up to 16 times as effective as citrate at dissolving human kidney stones under simulated physiological conditions. It may thus be concluded that HMP is a promising potential therapy for calcium and struvite kidney stones.

Preliminary analysis of serum electrolytes and body mass index in patients with and without urolithiasis

OBJECTIVES

To compare body mass index (BMI); serum parameters; and urine parameters between patients with and without urolithiasis.

METHODS

Data from 1164 patients admitted to our Department of Urology from January 2011 to July 2013 were retrospectively reviewed; 714 patients (age, 5-87 years; male:female ratio, 1.8:1) exhibited urolithiasis, and 450 patients (age, 12-94 years; male:female ratio, 3.8:1) did not. Blood and urine were collected from patients the morning after hospital admission. Serum and urine parameters were checked by an automatic biochemistry analyzer. Statistical analysis included the Mann-Whitney U test and binary logistic regression.

RESULTS

Serum sodium, potassium, chloride, calcium, phosphorus, and carbon dioxide combining power significantly differed between groups. In male patients, serum sodium, calcium, and phosphorus levels were higher in the urolithiasis group, whereas serum potassium and urine pH levels were lower. In female patients, serum sodium was higher in the urolithiasis group. BMI was higher in the urolithiasis group in all patients, male and female. Respective β-values of serum sodium and BMI in male patients were 0.077 and 0.084; in female patients, these values were 0.119 and 0.102.

CONCLUSIONS

Changes in serum sodium and BMI may be involved in the pathogenesis and treatment of urolithiasis.

Dietary Oxalate Induces Urinary Nanocrystals in Humans

Introduction

Crystalluria is thought to be associated with kidney stone formation and can occur when urine becomes supersaturated with calcium, oxalate, and phosphate. The principal method used to identify urinary crystals is microscopy, with or without a polarized light source. This method can detect crystals above 1 μm in diameter (microcrystals). However, analyses of calcium oxalate kidney stones have indicated that crystallite components in these calculi are 50–100 nm in diameter. Recent studies have suggested that nanocrystals (<200 nm) elicit more injury to renal cells compared to microcrystals. The purpose of this study was to determine whether (i) urinary nanocrystals can be detected and quantified by nanoparticle tracking analysis (NTA, a high-resolution imaging technology), (ii) early-void urine samples from healthy subjects contain calcium nanocrystals, and (iii) a dietary oxalate load increases urinary nanocrystal formation.

Methods

Healthy subjects consumed a controlled low-oxalate diet for 3 days before a dietary oxalate load. Urinary crystals were isolated by centrifugation and assessed using NTA before and 5 hours after the oxalate load. The morphology and chemical composition of crystals was assessed using electron microscopy, Fourier-transform infrared spectroscopy (FTIR), and ion chromatography-mass spectrometry (IC–MS).

Results

Urinary calcium oxalate nanocrystals were detected in pre-load samples and increased substantially following the oxalate load.

Conclusion

These findings indicate that NTA can quantify urinary nanocrystals and that meals rich in oxalate can promote nanocrystalluria. NTA should provide valuable insight about the role of nanocrystals in kidney stone formation.

Risk of Kidney Stones: Influence of Dietary Factors, Dietary Patterns, and Vegetarian-Vegan Diets

Nephrolithiasis is a common medical condition influenced by multiple environmental factors, including diet. Since nutritional habits play a relevant role in the genesis and recurrence of kidney stones disease, dietary manipulation has become a fundamental tool for the medical management of nephrolithiasis. Dietary advice aims to reduce the majority of lithogenic risk factors, reducing the supersaturation of urine, mainly for calcium oxalate, calcium phosphate, and uric acid. For this purpose, current guidelines recommend increasing fluid intake, maintaining a balanced calcium intake, reducing dietary intake of sodium and animal proteins, and increasing intake of fruits and fibers. In this review, we analyzed the effects of each dietary factor on nephrolithiasis incidence and recurrence rate. Available scientific evidence agrees on the harmful effects of high meat/animal protein intake and low calcium diets, whereas high content of fruits and vegetables associated with a balanced intake of low-fat dairy products carries the lowest risk for incident kidney stones. Furthermore, a balanced vegetarian diet with dairy products seems to be the most protective diet for kidney stone patients. Since no study prospectively examined the effects of vegan diets on nephrolithiasis risk factors, more scientific work should be made to define the best diet for different kidney stone phenotypes.