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To evaluate the efficacy of ultrasound-assisted monitoring during shock wave lithotripsy for kidney and proximal ureteral calculi.We retrospectively reviewed 535 patients who initially underwent shock wave lithotripsy for renal or proximal ureteral calculi between January 2012 and December 2021. The patients were divided into the X-ray group (n = 294) and ultrasound plus X-ray group (n = 241) based on the methods of targeting and monitoring calculi during shock wave lithotripsy. Because of differences in patient backgrounds, 1:1 propensity score-based matching was performed. The primary endpoint was the stone-free rate.In the final 1:1 matched cohort, 192 kidney stone cases and 162 proximal ureteral stone cases were analyzed. For patients with kidney calculi, the stone-free rate of the ultrasound plus X-ray group was significantly higher than that of the X-ray group (66.7% vs. 47.9%; P = 0.013). In the multivariate analysis, a large stone area (odds ratio 2.37), lower caliceal stones (odds ratio 3.37), and X-ray monitoring alone (odds ratio 0.49) were independently associated with shock wave lithotripsy failure. For patients with proximal ureteral stones, there was no significant difference in the stone-free rate between the ultrasound plus X-ray group and X-ray group (71.6% and 58.0%, respectively; P = 0.100). During the multivariate analysis, high computed tomography attenuation (odds ratio 2.31) and large stone area (odds ratio 2.18) were independent factors associated with residual stones after shock wave lithotripsy.Ultrasound-assisted monitoring may contribute to a higher stone-free rate for patients with kidney calculi, but not for those with proximal ureteral calculi.

BACKGROUND: This study aimed to evaluate the safety and efficacy of an inner ureteral access sheath (i-UAS) with a double-lumen channel used in ureteroscopic lithotripsy (URS) as a dilator for the percutaneous tract in endoscopic combined intrarenal surgery (ECIRS). METHODS: This was a single-center cohort study conducted from January 2016 to April 2020. We used an i-UAS as a dilator and a double-lumen catheter to insert a safety guidewire during the creation of the nephrostomy tract in ECIRS. Univariate and multivariate analyses were performed to assess the association between the perioperative parameters and the use of i-UAS. The primary endpoint was perioperative complications, and secondary endpoints were stone-free rate (SFR), operative time, fluoroscopy time, and duration of hospitalization. RESULTS: In total, 221 patients were enrolled during the study period. Patients were divided into an i-UAS dilation group (n=108) and a one-shot dilation group (n=113). No differences were observed between the two groups in terms of patient history. Univariate analyses indicated that, in the i-UAS dilation group, the operative time was shorter [105.50 (83.75–143.25) vs. 121.00 (90.00–155.00) min; P=0.02] and the modified Valdivia position was more frequently selected. Multivariate analyses showed no significant differences in the frequency of complications, such as urinary injury or postoperative pyelonephritis, but it showed a significantly shorter operative time as well as fewer tract creation troubles in the i-UAS dilation group. CONCLUSIONS: Using an i-UAS as a dilator and a double-lumen catheter to insert a safety guidewire during ECIRS is a convenient and safe technical method for creating a nephrostomy tract that can reduce the operative time.

We conducted a randomized, single-blind clinical trial comparing the surgical outcomes of robotic-assisted fluoroscopic-guided (RAF group) and ultrasound-guided (US group) renal access in mini-percutaneous nephrolithotomy (PCNL).We recruited patients who underwent mini-PCNL with ureteroscopic assistance for large renal stones between January 2020 and May 2021. Block randomization was performed using online software. Automated needle target with x-ray was used for fluoroscopic-guided renal access in the RAF group. PCNL was performed by residents using a pneumatic lithotripsy system with 16.5Fr/17.5Fr tracts. The primary outcome was single puncture success, and the secondary outcomes were stone-free rate, complication rate, parameters measured during renal access and fluoroscopy time.In total, 71 patients (35 in US group, 36 in RAF group) were enrolled. No difference was seen in the single puncture success rate between the US and RAF groups (34.3% and 50.0%, p=0.2). In 14.3% cases in the US group vs no cases in the RAF group, the resident was unable to obtain access due to difficult targeting (p=0.025). The mean number of needle punctures was significantly fewer, and the median duration of needle puncture was shorter in the RAF group (1.83 vs 2.51 times, p=0.025; 5.5 vs 8.0 minutes, p=0.049, respectively). The stone-free rate at 3 months after surgery was 83.3% and 70.6% in the RAF and US groups, respectively (p=0.26). Multivariate analysis revealed that RAF guidance reduced the mean number of needle punctures by 0.73 times (p=0.021).RAF renal access in mini-PCNL may have further potential applications in this field.

Background Patients with urolithiasis have a lower bone mineral density (BMD) than those without stones, suggesting a potential correlation between calcium stone formation and bone resorption disorders, including osteopenia and osteoporosis. Methods To investigate the influence of BMD on clinical outcomes in urolithiasis, we performed a single-center retrospective cohort study to analyze patients with urolithiasis who underwent both BMD examination and 24-h urine collection between 2006 and 2015. Data from the national cross-sectional surveillance of the Japanese Society on Urolithiasis Research in 2015 were utilized, and additional data related to urinary tract stones were obtained from medical records. The primary outcome was the development of stone-related symptoms and recurrences during follow-up. A total of 370 patients were included in this 10-year study period. Results Half of the patients had recurrent stones, and the two-thirds were symptomatic stone formers. While only 9% of patients had hypercalciuria, 27% and 55% had hyperoxaluria and hypocitraturia, respectively. There was a positive correlation between T-scores and urinary citrate excretion. Both univariate and multivariate analyses demonstrated that female sex was associated with recurrences (odds ratio = 0.44, p = 0.007), whereas a T-score p = 0.037; odds ratio = 0.45, p = 0.01; respectively). Conclusion These results revealed that low T-scores might cause symptoms in patients with urolithiasis, suggesting the importance of BMD examination for high-risk Japanese patients with urolithiasis having hypocitraturia.

Difficulty in performing ureteroscopic lithotripsy (URSL) depends on endoscopic findings surrounding calculi. In this multicentre prospective cohort study of 185 patients with a single ureteral stone who underwent ureteroscopic lithotripsy registered in the SMART study between January 2014 and February 2017, we established a classification of endoscopic findings and analysed risk factors for ureteral changes. We evaluated endoscopic findings (oedema, polyps, ureteral mucosa-stone adherence, and distal ureteric tightness) based on the SMART classification. Operative time and ureteral injuries were significantly correlated with endoscopic finding grades. Multivariate analyses revealed that mucosa-stone adherence (MSA) was strongly affected by hydronephrosis grade (odds ratio, 12.4; p = 0.022) and the interval before surgery (odds ratio, 1.10; p = 0.012). The cutoff value for MSA was 98 days, with a predictive accuracy of 0.78. Risk factors for distal ureteric tightness were age (odds ratio, 0.96; p = 0.004) and early intervention (odds ratio, 0.90; p = 0.023). The cutoff value was 34 days, with a predictive accuracy of 0.72. In conclusion, appropriate intervention around 34 days (limited to 98 days) after symptom onset is necessary for treating ureteral calculi. Even if intervention passed 98 days post-symptom onset, staged URSL, alternative procedures, and detailed informed consent should be planned in advance, assuming strong MSA.

This prospective ex vivo study investigated microdamage to single-use flexible ureteroscopes (fURS) after ureteroscopy and endoscopic combined intrarenal surgery (ECIRS). The performance of 30 WiScope devices (OTU Medical, San Jose, CA, USA) was examined immediately after use, dividing them into three equal groups: ureteroscopy and ECIRS in the prone and supine positions. The overall scope microdamage assessment included the scope deflection, bending radius, resolution, and water flow rate. Additionally, we analyzed the association between scope status and surgical parameters. The deflection, bending radius, and resolution remained similarly above the thresholds in all groups. However, the water flow rate was below the threshold in seven scopes (70%) in the ureteroscopy group and none in the ECIRS groups (P = 0.001). Univariate and multivariable logistic regression analyses demonstrated that basket wire catheter use was associated with an increased risk for overall scope microdamage (odds ratio [OR], 22.70; P = 0.006 and OR, 22.40; P = 0.019, respectively). Stone size, total laser energy, and surgical position were not associated with a risk for scope microdamage. In conclusion, ureteroscopy was more closely associated with scope damage than ECIRS, and basket wire catheter use seemed to inflict more damage to the fURS.

Objectives: To evaluate the feasibility of robot-assisted fluoroscopy-guided (RAG) puncture and to compare RAG puncture, utilizing a novel robot system for percutaneous renal access, with ultrasoun...

INTRODUCTION AND OBJECTIVE:Brown adipocytes consume energy and are known to improve metabolic syndrome. In previous studies using mice that brown adipocytes could prevent the formation of urinary s...

INTRODUCTION AND OBJECTIVE:Renal access during PCNL is the most critical step in achieving effective stone clearance and mitigating unfavorable complications. There are two types of renal access ap...

INTRODUCTION AND OBJECTIVE:Ureteral stents are commonly used in endoscopic surgery for urinary calculi but are frequently associated with stent encrustation and stent-related infections. New biomat...

To investigate factors determining the outcomes of endoscopic management for stone-related ureteral stricture.Data of patients who underwent endoscopic surgery for ureteral stricture due to stones from January 2016 to April 2020 were retrospectively analyzed. We compared cases successfully treated with endoscopic surgery with cases that resulted in failure. We focused on factors associated with treatment success, including cause and length of stricture, methods of stricture treatment, surgical time, and duration of hydronephrosis before the treatment. Treatment success was defined as improvement in hydronephrosis status.Nineteen patients were treated for stone-related ureteral stricture. Hydronephrosis was successfully improved in 12 patients (63.2%). Seven patients with failed endoscopic management had ureteroscopic lithotripsy- related stricture, whereas 3/12 (25.0%) patients with ureteroscopic lithotripsy-related stricture and 7/12 (58.3%) patients with impacted stone-related stricture were successfully treated by endoscopic management (P = .004). The prevalence of stricture length15 mm was significantly higher in the patients with failed management than in the patients with successful management (71.4 vs 16.6%, P = .046). Intraoperative endoscopic observation demonstrated that the mucosa of the ureteroscopic lithotripsy-related stricture had ischemic appearance with relatively long stricture length (P = 0.13) compared to the impacted stone-related stricture. No association was observed between treatment outcome and method of endoscopic management, including laser incision, balloon dilation, or both.Ureteroscopic lithotripsy as a cause and stricture length15 mm could affect the success rate of endoscopic management of ureteral stricture. In such cases, reconstructive management should probably be considered in the early stages.

According to recent studies, kidney stones are associated with metabolic syndrome. We focused on brown adipocytes and β3-stimulant-induced brown-like adipocytes to investigate how these adipocytes influence kidney stone disease. For the interscapular brown adipose tissue (iBAT) removal experiment, mice were subjected to either iBAT removal or sham operation (X-BAT group or sham group), and, after 3 wk, renal crystal deposition was induced by intra-abdominal injection of glyoxylate (GOX) for 6 days. For the β3-stimulant experiment, mice were administered intra-abdominal injections of the β3-stimulant (β3-group) or saline (control group) for 6 days. Thereafter, renal crystal deposition was induced by intra-abdominal injection of GOX for 6 days. iBAT removal decreased the expression of Sod1 and increased that of chemokine (C-C motif) ligand 2 ( Ccl2), EGF module-containing mucin-like receptor 1 ( Emr1), and tumor necrosis factor ( Tnf) in the kidneys. Renal crystal deposition was 2.06-fold higher in the X-BAT group than in the sham group. The β3-stimulant caused differentiation of white adipocytes into brown-like adipocytes. In the kidneys of the β3-group, the expression of Ccl2 and Emr1 decreased and that of Sod1 increased. Renal crystal deposition was 0.17-fold lower in the β3-group than in the control group. In summary, iBAT removal promoted kidney inflammation and renal crystal formation. β3-Stimulant-induced brown-like adipocytes reduced inflammation and improved antioxidant action in the kidneys, which suppressed renal crystal formation. This is the first report on the therapeutic role of brown and brown-like adipocytes for kidney stone formation.

Objectives To elucidate the difference in the lithogenesis of calcium oxalate and calcium phosphate stones. Methods Renal papillary tissues were obtained from 23 idiopathic calcium oxalate and seven calcium phosphate stone patients who had undergone endoscopic lithotripsy. Samples were individually collected from two different regions in each patient: the papillary mucosa containing Randall's plaque and mucosa not containing Randall's plaque. A microarray analysis was carried out on those tissues to compare their gene expression patterns. Furthermore, a causal pathway analysis comparing their differences was carried out. Results Cluster analysis showed that gene expression profiles of calcium phosphate stone patients markedly differed from those of calcium oxalate stone patients. Disease and function analysis showed that Randall's plaque-containing tissues of calcium phosphate stone-forming patients had significantly higher movement and migration of mononuclear leukocytes, and lower tendency toward infection and lymph node formation than Randall's plaque-containing tissues of calcium oxalate stone formers. Additional pathway analysis showed increased immune cell signaling in calcium phosphate formers, such as the helper T cell 1 and 2 pathways, which was confirmed by their messenger ribonucleic acid expression. Conclusions The present results show the upregulation of helper T-cell signaling pathways in Randall's plaque-containing papillae in calcium phosphate, but not in calcium oxalate stone formers. Thus, helper T-cell immune responses and the related inflammatory processes seem to lead to the formation of calcium phosphate stones on Randall's plaques.

Risk assessment for urinary stones has been mainly based on urinary biochemistry. We attempted to identify the risk factors for urinary stones by statistically analyzing urinary biochemical and inflammation-related factors. Male participants (age, 20–79 years) who visited Nagoya City University Hospital were divided into three groups: a control group (n = 48) with no history of stones and two stone groups with calcium oxalate stone experience (first-time group, n = 22; recurring group, n = 40). Using 25-µL spot urine samples, we determined the concentrations of 18 candidate urinary proteins, using multiplex analysis on a MagPix® system. In univariate logistic regression models classifying the control and first-time groups, interleukin (IL)-1a and IL-4 were independent factors, with significantly high areas under the receiver operating characteristic curve (1.00 and 0.87, respectively, P

Background: We previously discovered that renal macrophages (Mφs) phagocytose renal calcium oxalate monohydrate (COM) crystals. This study investigated the processing of engulfed crystals using in vitro models. Methods: J774.1 mouse Mφs were exposed to COM crystals and observed for 24 h using polarized light microscopy with/without cytochalasin B (CB), an inhibitor of phagocytosis, to confirm active crystal phagocytosis. LysoTracker and immunohistochemical staining using transmission electron microscopy for lysosomal-associated membrane protein 1 were used to confirm engulfed COM crystal uptake into lysosomes. Diachronic tracking of specific Mφs was performed to capture the entire course of engulfed COM crystal processing using polarized light microscopy. Follow-up studies of fluorescent COM (f-COM) crystals using imaging cytometry were performed in the presence and absence of nigericin to dissipate the pH gradient in acidic organelles. Results: Phagocytosis rates increased with COM density and were significantly lower in cells treated with CB (p < 0.01). We observed that engulfed crystals colocalized within lysosomes of the Mφs; moreover, diachronic observation indicated that the engulfed COM crystals were subdivided during Mφ division and eliminated by the 7th day of culture. Additionally, imaging cytometry showed that the fluorescence level of f-COM crystals in the nigericin (–) group after 48 h was significantly lower than that in the nigericin (+) group. Conclusions: This study confirmed active phagocytosis and lysosomal processing of engulfed COM crystals by Mφs. This discovery is expected to contribute to the development of future drugs that enhance the COM crystal phagocytic ability of Mφs.

BACKGROUND: Antegrade percutaneous ureterolithotripsy (URSL) could be a treatment option for large and/or impacted proximal ureteral stones, which are difficult to treat. To review the current approach and treatment outcomes and to compare the efficacy of retrograde and antegrade URSL for large proximal ureteral stones, we evaluated the unique perspectives of both surgical modalities. METHODS: This systematic literature review and meta-analysis was performed in July 2020. Articles on human studies and treatment of ureteral stones with URSL were extracted from the PubMed, MEDLINE, Embase, Cochrane Library, Scopus, and the Japan Medical Abstracts Society databases without any language restrictions. The risks of bias for randomized controlled trials (RCTs) and non-randomized controlled trials (non-RCTs) were assessed using the Cochrane risk of tool and the Risk of Bias in Non-randomized Studies- of Interventions tool, respectively. RESULTS: A total of 10 studies, including seven RCTs and three non-RCTs, were selected for the analysis; 433 and 420 cases underwent retrograde and antegrade URSL, respectively. The stone-free rate (SFR) was significantly higher in antegrade URSL than in retrograde URSL (SFR ratio: 1.17, 95% CI: 1.12–1.22; P

A prostate biopsy is essential for prostate cancer diagnosis. However, infections are one of the biopsy-associated complications, and post-biopsy fever is estimated to occur in approximately 1% of all cases. It may thus be beneficial to perform a rectal swab culture before a transrectal prostate biopsy to confirm the presence of resistant bacteria and select preventive antibacterial agents according to the drug susceptibility results. This study aimed to determine whether there is a difference between the drug susceptibility of bacteria detected in the stool of patients who were scheduled to undergo prostate biopsy and the hospital-wide urine antibiogram. Patients suspected of having prostate cancer who underwent transrectal prostate biopsy via transrectal ultrasonography between August 1, 2016, and June 30, 2020, were included in this study. Stool samples were collected and cultured before biopsy. Overall, 99 patients underwent prostate biopsy, and of these, culture results were available for 81 patients (81.8%). Escherichia coli was detected in 74.0% (60 samples) of the stool culture samples, of which 4 samples were extended-spectrum β-lactamase-producing types. We found greater susceptibility of Escherichia coli to ampicillin, fluoroquinolones, sulfamethoxazole/trimethoprim, and cefixime in the stool culture antibiogram than in the hospital-wide urine antibiogram. We also found a significantly low incidence of ESBL-positive Escherichia coli in the stool culture antibiogram with p-values of 0.009, 0.007, and 0.03 compared to the hospital-wide urine antibiograms for 2017, 2018, and 2019, respectively. Stool culture of prostate cancer patients undergoing biopsy may provide useful information for selecting prophylactic antimicrobial agents.

Background Ureteroscopic lithotripsy is a common treatment for middle and lower ureteral stones. Although effective and minimally invasive, this technique might cause significant complications, including postoperative ureteral strictures, which occur in 1–4% of patients after ordinary ureteroscopic lithotripsy and in 7.8–24% when lithotripsy is performed for impacted stones. The main purpose of the management of ureteral strictures is to improve hydronephrosis and protect renal function. However, factors that influence the success rate of the endoscopic management of US (e.g., the cause and length of stricture, the duration of hydronephrosis, surgical management technique, and the number of placed ureteral stents) are controversial. The aim of this study was to investigate factors determining the outcomes of endoscopic management for stone-related ureteral stricture. Methods This multi-center case series study was performed at one of the highest-volume centers and the affiliated institutions in Japan. Data of patients who underwent endoscopic surgery for ureteral stricture from January 2016 to March 2019 were retrospectively analyzed. Laser incision and/or balloon dilation were performed for management; single or double stents were placed at the end of the surgery. Treatment success was defined as improvement in hydronephrosis status. Results Nineteen patients were treated for stone-related ureteral stricture. Hydronephrosis successfully improved in 12 patients (63.2%). All seven patients with failed endoscopic management had ureteroscopic lithotripsy-related stricture, whereas 3/12 (25.0%) and 7/12 (58.3%) patients with ureteroscopic lithotripsy-related stricture and impacted stone-related stricture, respectively, underwent successful endoscopic treatment (P = 0.004). Stricture length > 15 mm was observed in five patients (71.4%) with failed management, two patients (16.6%) with successful management (P = 0.046), 7/10 patients (70.0%) with ureteroscopic lithotripsy-related stricture, and 1/7 patients (14.3%) with impacted stone-related stricture (P = 0.049). Among patients with ureteroscopic lithotripsy-related stricture and impacted stone-related stricture, both laser incision and balloon dilation were performed in 5/10 (50.0%) and 2/7 (28.6%) patients (P = 0.874) while double stents were placed in 5/10 (50.0%) and 5/7 (57.1%) patients (P = 0.874), respectively. Conclusions Ureteroscopic lithotripsy as a cause and stricture length > 15 mm could strongly affect the success rate of endoscopic management of ureteral stricture. In such cases, reconstructive management should be considered in the early stages.

INTRODUCTION AND OBJECTIVE:The pathogenesis of urinary stone formation is a multistep process involving complex interactions between the mineral elements and protein matrix. Topographic relations b...

INTRODUCTION AND OBJECTIVE:Renal calculus is thought to be promoted by inflammation and oxidative stress that occur in renal tubular cells. In this study, we investigated the inhibitory effect of a...

INTRODUCTION AND OBJECTIVE:We reported earlier that hands-on training (HOT) significantly improved the SWL success rate from 66.3% to 87.2% at the AUA annual meeting 2012. In this study, we tracked...

INTRODUCTION AND OBJECTIVE:Laser incision (laser endoureterotomy: LE) and balloon dilatation (BD) are the treatments for ureteral strictures measuring ≤20 mm; however, these treatments are associat...

Kidney stone disease is a lifestyle-related disease prevalent in developed countries; however, effective medical treatment for the disease is not yet well established. As cellular damage in renal tubular cells (RTCs) is responsible for the disease, here, we focused on the role of macroautophagy/autophagy in RTCs. We found that autophagic activity was significantly decreased in mouse RTCs exposed to calcium oxalate (CaOx) monohydrate crystals and in the kidneys of GFP-conjugated MAP1LC3B (microtubule- associated protein 1 light chain 3 beta) transgenic mice with CaOx nephrocalcinosis induced by glyoxylate. This caused accumulation of damaged intracellular organelles, such as mitochondria and lysosomes, the normal functioning of which is mediated by functional autophagy. An impairment of autophagy was also observed in the mucosa with plaques of CaOx kidney stone formers. We determined that the decrease in autophagy was caused by an upregulation of MTOR (mechanistic target of rapamycin kinase), which consequently resulted in the suppression of the upstream autophagy regulator TFEB (transcription factor EB). Furthermore, we showed that an MTOR inhibitor could recover a decrease in autophagy and alleviate crystal-cell interactions and the formation of crystals associated with increased inflammatory responses. Taken together, we conclude that autophagy compromised by MTOR deregulation is a fundamental feature in the pathology of kidney stone formation, and propose that chemical inhibition of MTOR could be a prospective strategy for disease suppression. Abbreviations: ACTB: actin, beta; CaOx: calcium oxalate; CKD: chronic kidney disease; COM: calcium oxalate monohydrate; LGALS3/galectin-3: lectin, galactose binding, soluble 3; GFP: green fluorescent protein; GOX: glyoxylate; HE: hematoxylin and eosin; MAPLC3B: microtubule- associated protein 1 light chain 3 beta; MTOR: mechanistic target of rapamycin kinase; NAC: N-acetyl-L-cysteine; ROS: reactive oxygen species; RTC: renal tubular cell; SQSTM1/p62: sequestosome 1; TFEB: transcription factor EB; TEM: transmission electron microscopy; tfLC3: tandem fluorescent-tagged LC3; 3-MA: 3-methyladenine.

According to recent studies, kidney stones are associated with metabolic syndrome. We focused on brown adipocytes and β

INTRODUCTION AND OBJECTIVES:We found that cellular damage caused by calcium oxalate (CaOx) was repaired by the induction of autophagy using renal tubule cultured cells and CaOx crystal model mice, ...

INTRODUCTION AND OBJECTIVES:Kidney stone structure may provide clinical information in addition to the stone composition. The morphology and succession of different layers can reliably describe the...

Nephrolithiasis is a significant source of morbidity, and its incidence has increased significantly over the last decades. This rise has been attributed to concurrent increasing rates of obesity, associated with a 3-time risk of developing NL. To date, the mechanism by which obesity is linked to stone formation has not been elucidated. We aimed to utilize a transcriptomics approach to discover the missing link between these two epidemic diseases. We investigated gene expression profiling of nephrolithiasis patients by two RNA-sequencing approaches: comparison between renal papilla tissue with and without the presence of calcified Randall's plaques (RP), and comparison between the papilla, medulla, and cortex regions from within a single recurrent stone forming kidney. Results were overlaid between differently expressed genes found in the patient cohort and in the severely lithogenic kidney to identify common genes. Overlay of these two RNA-sequencing datasets demonstrated there is impairment of lipid metabolism in renal papilla tissue containing RP linked to downregulation of fatty acid binding protein (FABP) 4. Immunohistochemistry of human kidney specimens and microarray analysis of renal tissue from a nephrolithiasis mouse model confirmed that FABP4 downregulation is associated with renal stone formation. In a FABP4 knockout mouse model, FABP4 deficiency resulted in development of both renal and urinary crystals. Our study revealed that FABP4 plays an important, previously unrecognized role in kidney stone formation, providing a feasible mechanism to explain the link between nephrolithiasis and metabolic syndrome.