A method for detecting ureteral stent encrustations in medical CT images based on Mask-RCNN and 3D morphological analysis.

Objective: To develop and validate a method for detecting ureteral stent encrustations in medical CT images based on Mask-RCNN and 3D morphological analysis. Method: All 222 cases of ureteral stent data were obtained from the Fifth Affiliated Hospital of Sun Yat-sen University. Firstly, a neural network was used to detect the region of the ureteral stent, and the results of the coarse detection were completed and connected domain filtered based on the continuity of the ureteral stent in 3D space to obtain a 3D segmentation result. Secondly, the segmentation results were analyzed and detected based on the 3D morphology, and the centerline was obtained through thinning the 3D image, fitting and deriving the ureteral stent, and obtaining radial sections. Finally, the abnormal areas of the radial section were detected through polar coordinate transformation to detect the encrustation area of the ureteral stent. Results: For the detection of ureteral stent encrustations in the ureter, the algorithm's confusion matrix achieved an accuracy of 79.6% in the validation of residual stones/ureteral stent encrustations at 186 locations. Ultimately, the algorithm was validated in 222 cases, achieving a ureteral stent segmentation accuracy of 94.4% and a positive and negative judgment accuracy of 87.3%. The average detection time per case was 12 s. Conclusion: The proposed medical CT image ureteral stent wall stone detection method based on Mask-RCNN and 3D morphological analysis can effectively assist clinical doctors in diagnosing ureteral stent encrustations.

Managing a challenging case of bilaterally fractured DJ stents following extracorporeal shock waves lithotripsy for chronic encrustations: A case report.

Double-j stents are commonly used in many urological procedures to facilitate the drainage of renal systems postoperatively. Their usage has revolutionized the world of urological interventions but if left forgotten present serious complications. We report a case of an old man who was diagnosed with bilaterally fragmented DJ stents in situ in our urology department following his sessions of extracorporeal shock wave lithotripsy for chronic encrustations. These stents were placed after complete breakdown of bilateral ureteral stones through ureterorenoscopy and laser lithotripsy.

An in-vitro model for bacteria-related catheter encrustations.

PURPOSE: About 50% of individuals with long-term indwelling catheters are affected by catheter encrustations and bladder stone formation. Therefore, prophylaxis of catheter encrustations is important. Currently, however, neither an established prophylaxis nor a standardized in-vitro model to test different measures exist. We have therefore developed and qualitatively evaluated an in-vitro model of catheter encrustation. METHODS: Size 14 French suprapubic catheters were incubated under sterile conditions at 37 degrees Celsius in five different media: (1) sterile artificial urine (n = 16), (2) artificial urine with E. coli (n = 8), (3) with Pseudomonas aeruginosa (n = 8), (4) with Proteus mirabilis (n = 8), and (5) with a mix of these three strains (n = 8). Catheter balloons were inflated either a glycerine or a bactericidal solution. After 6 weeks, the catheters were removed from the solution, dried, and weighed, and a photometric determination of the retrieved encrustations was performed. RESULTS: Most frequently and pronounced encrustations were detected in the Pseudomonas group. The median weight of these encrustations (50% struvite and brushite) was 84.4 mg (47.7 mg / 127.3 mg). Even on catheters stored in sterile urine, encrustations (69.2% struvite) were found. Bacterial growth was not affected by the medium used for catheter blockage. CONCLUSION: Although in-vitro models appear to be limited because they lack "the human factor", they are valuable for systematically assessing physico-chemical factors affecting encrustations. Therefore, our model, being reliable and cost-effective, may foster further research despite its limitations.

Development and validation of a predictive model for double-J stent encrustation after upper urinary tract calculi surgery.

The study is aimed to establish a predictive model of double-J stent encrustation after upper urinary tract calculi surgery. We collected the clinical data of 561 patients with indwelling double-J tubes admitted to a hospital in Shandong Province from January 2019 to December 2020 as the modeling group and 241 cases of indwelling double-J tubes from January 2021 to January 2022 as the verification group. Univariate and binary logistic regression analyses were used to explore risk factors, the risk prediction equation was established, and the receiver operating characteristic (ROC) curve analysis model was used for prediction. In this study, 104 of the 561 patients developed double-J stent encrustation, with an incidence rate of 18.5%. We finally screened out BMI (body mass index) > 23.9 (OR = 1.648), preoperative urine routine white blood cell quantification (OR = 1.149), double-J tube insertion time (OR = 1.566), postoperative water consumption did not reach 2000 ml/d (OR = 8.514), a total of four factors build a risk prediction model. From the ROC curve analysis, the area under the curve (AUC) was 0.844, and the maximum Oden index was 0.579. At this time, the sensitivity was 0.735 and the specificity was 0.844. The research established in this study has a high predictive value for the occurrence of double-J stent encrustation in the double-J tube after upper urinary tract stone surgery, which provides a basis for the prevention and treatment of double-J stent encrustation.

Single-center, double-blind, randomized, placebo-controlled pilot study of Canoxidin® for prevention of catheter encrustation in patients with indwelling catheters.

INTRODUCTION AND OBJECTIVES: Long-term use of an indwelling catheter is associated with complications such as catheter encrustation and infection. Canoxidin® is a novel oral treatment that can potentially prevent catheter encrustation, as it contains a urine acidifier and a combination of two crystallization inhibitors. This study aimed to evaluate the effects of Canoxidin® on catheter encrustation in patients with indwelling Foley catheters. PATIENTS AND METHODS: This was a single-center, double-blind, randomized, placebo-controlled study. Neuro-urology patients aged ≥18 years with an indwelling catheter (urethral or suprapubic) were randomized to treatment consisting of either Canoxidin® or placebo for one month. Foley catheters (two per patient, one before treatment and one after treatment) were removed for analysis of the presence and degree of encrustation. RESULTS: A total of 40 patients were enrolled and randomized, 28 of whom had analyzable catheters (13 assigned to Canoxidin® and 15 assigned to placebo). The patients had a mean age of 51.8 years, and eight (28.6%) were female. Two patients (13.3%) in the placebo group and eight patients (61.5%) in the Canoxidin® group experienced an improvement (less encrustation). There was a significant association between Canoxidin® and improvement (odds ratio: 10.4, 95% confidence interval: 1.6 to 66.9, P = 0.016). No adverse effects attributable to the treatment were reported. CONCLUSIONS: The overall rate of catheter encrustation was high among those with indwelling Foley catheters. One-month treatment with Canoxidin® reduced the formation of these encrustations, with an excellent short-term safety profile.

Seasonal variation of vessel pits in sapwood: microscopical analyses of the morphology and chemical components of pit membrane encrustations in Fraxinus mandshurica.

BACKGROUND AND AIMS: Pit pairs and their filter-like partition, i.e. pit membranes, play important roles as water pathways, barriers and regulators in the water-conducting system of angiosperms. In Fraxinus species, the intervessel and vessel-parenchyma pit membranes in sapwood are normally encrusted during winter. Although these encrustations inevitably influence the performance of pits, their properties and functions remain unclear. This study aimed to reveal the morphological and chemical characteristics of encrustations in F. mandshurica in order to deepen understanding of the seasonal encrustation of pit membranes. METHODS: Seasonal and positional variations in the presence and morphology of encrustations were examined by field-emission scanning electron microscopy (FE-SEM). Cryo-FE-SEM for freeze-fixed greenwood samples was conducted to clarify whether encrustations were present in living trees. Chemical components were examined by histochemical staining using light and electron microscopies, immunofluorescence labelling and ultraviolet microspectroscopy. KEY RESULTS: Encrustations began to deposit in fall before leaf senescence and disappeared in spring before bud flushing. They infiltrated within the pit membranes, which suggested that they severely limit the permeation of pits. The encrustations differed in morphology among positions: they entirely filled the pit chambers in latewood, while they covered the pit membranes in earlywood. The encrustations were similarly observed in the samples that were freeze-fixed immediately after collection, indicating that they are present in living trees. The encrustations contained polysaccharides, including xyloglucan and homogalacturonan, and phenolic compounds, possibly including flavonoids and coumarins. These chemical components were also detected in droplets found in the latewood vessels with the encrustations, suggesting that the materials constituting encrustations were supplied through the vessel lumens. CONCLUSIONS: Encrustations undoubtedly cover the pit membranes in living F. mandshurica trees in winter and their morphology and chemical composition indicate that they are impermeable, have positional differences in function and are characterised by elaborate deposition/removal processes.

Difficulty in Removing a Ureteral Stent post Childbirth due to Encrustation: A Case Report.

BACKGROUND: We present a case involving a pregnant woman who needed transurethral lithotripsy for ureteral stent removal because of the stent encrustation. CLINICAL CASE: A 34-year-old woman was diagnosed with calculous pyelonephritis, and a double-loop ureteral stent was placed in her right ureter, after which the pyelonephritis resolved. One week after her delivery, we attempted to remove the ureteral stent; however, the encrustation of the proximal and distal coils made it impossible. We then crushed the encrustation by transurethral lithotripsy and removed the ureteral stent successfully. The encrustation component was calcium phosphate, and the urinary pH during pregnancy and after delivery was 7.5. CONCLUSION: Even in pregnant patients, patients placed ureteral stents for obstructive pyelonephritis with high urine pH might need to be replaced in the short term due to concerns regarding phosphate encrustation.

A case report on the management of neglected and forgotten DJ stent for 18 years with severe encrustation and giant bladder stone.

Ureteral stents play a vital role in urologic surgeries, aiding in urinary flow maintenance, obstruction alleviation and facilitating healing. However, when stents are forgotten, they can lead to encrustation, resulting in significant patient morbidity and posing challenges for urologists Stent-related complications have been shown to increase with the duration of time the stent is left in place. This report details the clinical presentation, diagnostic process, and treatment of a 68-year-old male patient had a neglected stent placed 18 years ago after extracorporeal shockwave lithotripsy. He presented with severe stent encrustation, a solitary giant bladder stone, and renal stones. The patient underwent a cystolithotomy to remove the bladder stone followed by an ultrasound-guided percutaneous nephrolithotomy with pneumatic lithotripsy in a separate procedure. Preventive strategies such as implementing a stent registry, enhancing patient education, and encouraging follow-up appointments are crucial to avoid such complications.

Ureteral stents: What your eyes can't see! An in vitro study.

OBJECTIVES: To characterize and compare in vitro the surfaces of ureteral stents (STENTS) before utilization. METHODS: Our in vitro experiment included six unused STENTS models: three double-pigtail with side orifices (ImaJin and Stenostent [Coloplast©,France], TriaSoft [BostonScientific©,USA]), two double-pigtail without side orifice (Vortek-TumorStent [Coloplast©,France], Urosoft-TumorStent [Bard-Angiomed©,Germany]) and one single-pigtail (J-Fil [Rocamed©,Monaco]). STENTS were made of polyurethane except for ImaJin (silicone). For all STENTS, four parts of the stent were specifically analyzed under high-resolution scanning electron microscopy (HR-SEM,FEI-XL40 [Philips©,France]): surface core, lateral orifice, ureteral loop, and black marking surface. Each experiment was repeated with three different samples from three different stents. STENTS analysis included multiple imperfection searches, defined as irregularities>10µm. RESULTS: All STENTS presented imperfections with no discernible differences. Imperfections were mainly located on the stent loop and on the lateral orifice. For STENTS without side orifice (J-Fil, Urosoft) imperfections were also reported, on the beveled cut as well as the distal loop orifice. Marking surfaces examinations found defects in the Urosoft and imperfections in the ImaJin and Stenostent. The Triasoft presented a better smoothness on marking surfaces compared to other STENTS. Additional matter was reported on the loop distal orifice for J-Fil and ImaJin but all STENTS presented irregular cross-sectional aeras. CONCLUSION: All ureteral stents are not perfectly smooth even before utilization. Imperfections were noticed regardless to stent composition or shape, and could play a role in the incrustation phenomenon, is association with inner irregularities, infection, and urine composition. Both manufacturing and material could have an impact on the stent external surface's smoothness.

Management of neglected and fragmented DJ stent with severe encrustation and stone: A case report.

INTRODUCTION AND IMPORTANCE: DJ stents are widely used in urological procedures and interventions. One of the main problems associated with DJ stent is encrustation and stone formation. The main risk factor for Forgotten, encrusted and calcified (FECal) stent is duration of the stent placement. In addition to high index of suspicion, Imaging like U/S and CT scan are important diagnostic modality. Multiple endourologic and open procedure may be needed for management of fecal stent. CASE PRESENTATION: This case report is to discuss a 23 years old female patient with a neglected stent after right pyelolithotomy was done 6 years back. The presence of the stent was identified incidentally after she visited local health facility for recurrent LUTS. The CT scan shows fragmented and encrusted stent with in the bladder and pelvis, stones in stent coils and isolated lower pole stone. She was managed by a procedure of cystolithotomy and right PCNL in separate sessions. CLINICAL DISCUSSION: Common complication of DJ stent placement especially if left for long duration is encrustation, stent migration, fragmentation and stone formation. Patient or relatives unawareness about the stent placement is the most important cause for neglecting stent. Multiple Endourologic procedures may be needed for the management of FECal stent. However some resource limited settings do combination of endourologic and open surgery. CONCLUSION: Minimizing the duration of the stent especially for patient with risk factors is advised to decrease encrustation. Since management of FECal stent is challenging both for patient and urologists, prevention is the way to tackle it. Multiple procedures may be required to manage FECal stent.

Surface Modification of Zn-Cu Alloy with Heparin Nanoparticles for Urinary Implant Applications.

In this work, an investigation on the Zn-Cu alloy coated with heparin was conducted in order to explore the potentiality of its application as a feasible alternative for biodegradable implants, with the specific goal of addressing the issue of encrustation in the urinary system. The stability of the nanoparticles were characterized by dynamic light scattering. Typical surface characterization such as X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy were used to demonstrate a successful immobilization of the NPs. The in vitro corrosion behavior was studied by potentiodynamic polarization and immersion tests in artificial urine (AU) at 37 °C. The 8 weeks in vivo degradation, encrustation resistance, hemocompatibility, and histocompatibility were investigated by means of implantation into the bladders of rats. Both in vitro and in vivo degradation tests exhibited a higher degradation rate for Zn-Cu and NPs groups when compared to pure Zn. Histological evaluations and hemocompatibility revealed that there was no tissue damage or pathological alterations caused by the degradation process. Furthermore, antiencrustation performance and urinalysis results confirmed that the modified alloy demonstrated significant encrustation inhibitory properties and bactericidal activity compared to the pure Zn control. Our findings highlight the potential of this modified alloy as an antiencrustation biodegradable ureteral stent.

In vitro and in vivo study of antibacterial and anti-encrustation coating on ureteric stents.

OBJECTIVES: To investigate the ability of propolis-coated ureteric stents to solve complications, especially urinary tract infections (UTIs) and crusting, in patients with long-term indwelling ureteric stents through antimicrobial and anti-calculus activities. MATERIALS AND METHODS: Polyurethane (PU) ureteric stents were immersed in the ethanol extract of propolis (EEP), a well-known antimicrobial honeybee product, and subjected to chemical, hydrophilic, and seismic tests. The antimicrobial activity of the EEP coating was then examined by in vitro investigation. Proteus mirabilis infection was induced in rats within uncoated and EEP-coated groups, and the infection, stone formation, and inflammation were monitored at various time points. RESULTS: The characterisation results showed that the hydrophilicity and stability of the EEP surface improved. In vitro tests revealed that the EEP coating was biocompatible, could eliminate >90% of bacteria biofilms attached to the stent and could maintain bacteriostatic properties for up to 3 months. The in vivo experiment revealed that the EEP-coating significantly reduced the amount of bacteria, stones, and salt deposits on the surface of the ureteric stents and decreased inflammation in the host tissue. CONCLUSIONS: Compared with clinically used PU stents, EEP-coated ureteric stents could better mitigate infections and prevent encrustation. Thus, this study demonstrated that propolis is a promising natural dressing material for ureteric stents.

Comparison of Superhydrophilic, Liquid-Like, Liquid-Infused, and Superhydrophobic Surfaces in Preventing Catheter-Associated Urinary Tract Infection and Encrustation.

Over the past decade, superhydrophilic zwitterionic surfaces, slippery liquid-infused porous surfaces, covalently attached liquid-like surfaces, and superhydrophobic surfaces have emerged as the most promising strategies to prevent biofouling on biomedical devices. Despite working through different mechanisms, they have demonstrated superior efficacy in preventing the adhesion of biomolecules (e.g., proteins and bacteria) compared with conventional material surfaces. However, their potential in combating catheter-associated urinary tract infection (CAUTI) remains uncertain. In this research, we present the fabrication of these four coatings for urinary catheters and conduct a comparative assessment of their antifouling properties through a stepwise approach. Notably, the superhydrophilic zwitterionic coating demonstrated the highest antifouling activity, reducing 72.3% of fibrinogen deposition and over 75% of bacterial adhesion (Escherichia coli and Staphylococcus aureus) when compared with an uncoated polyvinyl chloride (PVC) surface. The zwitterionic coating also exhibited robust repellence against blood and improved surface lubricity, decreasing the dynamic coefficient of friction from 0.63 to 0.35 as compared with the PVC surface. Despite the fact that the superhydrophilic zwitterionic and hydrophobic liquid-like surfaces showed great promise in retarding crystalline biofilm formation in the presence of Proteus mirabilis, it is worth noting that their long-term antifouling efficacy may be compromised by the proliferation and migration of colonized bacteria as they are unable to kill them or inhibit their swarming. These findings underscore both the potential and limitations of these ultralow fouling materials as urinary catheter coatings for preventing CAUTI.

New insights into the prevention of ureteral stents encrustation.

Ureteral stents are commonly used medical devices for the treatment of urinary system diseases. However, while providing benefits to patients, they often give rise to various issues, with stent encrustation being a major concern for clinical physicians. This phenomenon involves the formation of attached stones on the stent's surface, leading to potential complications such as increased fragility and laxity of the ureter, difficulties in stent removal, and a higher risk of stent fracture. Therefore, this review starts from the pathological mechanisms of stone formation and discusses in detail the two major mechanisms of stent encrustation: the conditioning film and the biofilm pathway. It also examines multiple risk factors associated with ureteral stents and patients. Furthermore, the review updates the research progress on the structure, materials, and bio-coatings of ureteral stents in the prevention and treatment of stent encrustation. It presents new insights into the prevention and treatment of stent encrustation. This includes individualized and comprehensive clinical guidance, the use of novel materials, and early intervention based on physiological and pathological considerations. Ultimately, the study offers an encompassing overview of the advancements in research within this field and provides the latest insights into strategies for preventing and treating stent encrustation.

Fe(II) Oxidation Shaped Functional Genes and Bacteria Involved in Denitrification and Dissimilatory Nitrate Reduction to Ammonium from Different Paddy Soils.

Microbial nitrate reduction can drive Fe(II) oxidation in anoxic environments, affecting the nitrous oxide emission and ammonium availability. The nitrate-reducing Fe(II) oxidation usually causes severe cell encrustation via chemodenitrification and potentially inhibits bacterial activity due to the blocking effect of secondary minerals. However, it remains unclear how Fe(II) oxidation and subsequent cell encrustation affect the functional genes and bacteria for denitrification and dissimilatory nitrate reduction to ammonium (DNRA). Here, bacteria were enriched from different paddy soils with and without Fe(II) under nitrate-reducing conditions. Fe(II) addition decelerated nitrate reduction and increased NO2- accumulation, due to the rapid Fe(II) oxidation and cell encrustation in the periplasm and on the cell surface. The N2O accumulation was lower in the treatment with Fe(II) and nitrate than that in the treatment with nitrate only, although the proportions of N2O and NH4+ to the reduced NO3- were low (3.25% ∼ 6.51%) at the end of incubation regardless of Fe(II) addition. The dominant bacteria varied from soils under nitrate-reducing conditions, while Fe(II) addition shaped a similar microbial community, including Dechloromonas, Azospira, and Pseudomonas. Fe(II) addition increased the relative abundance of napAB, nirS, norBC, nosZ, and nirBD genes but decreased that of narG and nrfA, suggesting that Fe(II) oxidation favored denitrification in the periplasm and NO2--to-NH4+ reduction in the cytoplasm. Dechloromonas dominated the NO2--to-N2O reduction, while Thauera mediated the periplasmic nitrate reduction and cytoplasmic NO2--to-NH4+ during Fe(II) oxidation. However, Thauera showed much lower abundance than the dominant genera, resulting in slow nitrate reduction and limited NH4+ production. These findings provide new insights into the response of denitrification and DNRA bacteria to Fe(II) oxidation and cell encrustation in anoxic environments.

Bladder stone formation due to neglected double J stent: a case report.

Introduction and importance: Double J (DJ) stents are commonly used in genitourinary procedures, but they can lead to complications including infection, hematuria, encrustation, and stone formation. The longer the duration of encrustation, the greater the risk of complications and renal dysfunction. Forgotten stents pose challenges for patients and can require endourological or open surgical procedures. Case presentation: A 40-year-old man with hypertension and coronary artery disease had a forgotten DJ stent for 3 years, causing suprapubic pain and dysuria. Kidney, ureter, and bladder (KUB) revealed a coiled DJ stent with a large bladder stone and encrustation, and an open cystolithotomy was successfully performed. Recovery was uneventful, and the patient was discharged without complication. Clinical discussion: Ureteral stents, including the DJ stent, are commonly used for urological conditions but can cause complications if retained beyond the intended timeframe. Optimal timing for stent removal is crucial, and patients' healthcare knowledge and adherence are critical to preventing retention. KUB X-ray can evaluate stent encrustation and bladder stones. Cystoscopy is the typical approach for stent removal, but supplementary interventions may be necessary. Open surgery was recommended for removing a large bladder stone and encrusted stent in this case. Conclusion: Timely removal of DJ stents is crucial to avoid complications. Extended retention can cause problems such as encrustation and stone formation. Patient education and adherence are essential to prevent retention and forgetfulness. This case report highlights the importance of careful management of patients with DJ stents for optimal outcomes and prevention of complications.

Retained Ureteral Stent Encrustation After Stent Removal: A Case Report.

Ureteral stents are used to relieve acute or chronic urinary tract obstructions and may be complicated by stent encrustation. The development of encrustation is related to indwelling time, stent composition, bacterial biofilm formation, malabsorptive disorders, metabolic disorders (hypercalcemia, hyperuricosuria, pH imbalance), and cancer. Without intervention, encrustation may lead to luminal obstruction, infection, stent fracture, or ureteral avulsion during removal. Rarely, forced removal of an encrusted stent may cause the encrustation to remain in the urinary tract which can lead to further complications. Diagnosis of a retained encrustation includes evaluation with X-ray, ultrasound, and CT. Management strategies of retained encrustations are not standardized but may include removal with flexible ureteroscopy. In the following case, we present a 58-year-old male with retained encrustation material following non-forced stent removal that was not readily observed on initial imaging. CT demonstrated a curved, tubular radiodensity representing calcified encrustation material, and the diagnosis of retained encrustation was confirmed after successful removal with flexible ureteroscopy. We concluded that ureteral stent encrustation can remain in the urinary collecting system following stent removal, although this complication is rare and not well studied.

An Evaluation of Parylene Thin Films to Prevent Encrustation for a Urinary Bladder Pressure MEMS Sensor System.

Recent developments in urological implants have focused on preventive strategies to mitigate encrustation and biofilm formation. Parylene, a conformal, pinhole-free polymer coating, has gained attention due to its high biocompatibility and chemical resistance, excellent barrier properties, and low friction coefficient. This study aims to evaluate the effectiveness of parylene C in comparison to a parylene VT4 grade coating in preventing encrustation on a urinary bladder pressure MEMS sensor system. Additionally, silicon oxide (SiOx) applied as a finish coating was investigated for further improvements. An in vitro encrustation system mimicking natural urine flow was used to quantify the formation of urinary stones. These stones were subsequently analyzed using Fourier transform infrared spectrometry (FTIR). Encrustation results were then discussed in relation to coating surface chemical properties. Parylene C and VT4 grades demonstrated a very low encrustation mass, making them attractive options for encrustation prevention. The best performance was achieved after the addition of a hydrophilic SiOx finish coating on parylene VT4 grade. Parylene-based encapsulation proved to be an outstanding solution to prevent encrustation for urological implants.

Effects of size and shape of the side holes of a double J stent on the ureter fluid flow after stenosis.

The effect of side holes morphology changes in double J stent (DJS) on encrustation was analyzed using computational fluid dynamics (CFD). We analyzed DJS side holes with inner diameter of 1 mm and outer diameters of 1 (type A), 1.2 (type B) and 1.4 (type C) mm, respectively. Concentric stenosis with three intraureteral degree (0%, 12%, and 88%) was analyzed. The flow rate, shear stress and wall shear stress (WSS) distribution were investigated. Urine flow through SH1 before the ureteropelvic junction (UPJ) differed based on the ureteral stenosis degree. The sum of flow rates through the SHs increased with diameter. In the stented ureter with 12% stenosis, the flow rate through SH1 approximately doubled than that without ureteral stenosis, and the flow rate through SH1 was maximal for the type 'C' stent in both 12% and 88% ureteral stenosis. The mean shear stress in the SHs increased with the degree of stenosis. The WSS around the SHs was higher for type 'C' than types A and B. From the flow rates and shear stresses in and around the SHs, the larger SH diameter of the DJS from the UPJ to mid-ureter is expected to induce encrustation reduction, especially in patients with urinary lithiasis.

Relationship between Urinary Parameters and Double-J Stent Encrustation.

(1) Background: This study aimed to determine the relationship between metabolic urine conditions and the formation, severity, and composition of encrustations in ureteral stents. (2) Methods: Ninety stone-former patients requiring a double-J stent were prospectively enrolled. We collected 24 h metabolic urine samples and demographic data, including indwelling time and previous stone composition. The total deposit weight was obtained, and a macroscopic classification according to the degree of encrustation (null, low, moderate, and high) was created, allowing for intergroup comparisons. Stereoscopic and scanning electron microscopy were performed to identify the type of embedded deposits (calcium oxalate, uric acid, and infectious and non-infectious phosphates). (3) Results: In total, 70% of stents were encrusted; thereof, 42% had a moderate degree of encrustation. The most common encrustation type was calcium oxalate, but infectious phosphates were predominant in the high-encrustation group (p < 0.05). A direct correlation was observed between the purpose-built macroscopic classification and the encrustation weights (p < 0.001). Greater calciuria, uricosuria, indwelling time, and decreased diuresis were observed in stents with a higher degree of encrustation (p < 0.05). The urinary pH values were lower in patients with uric acid encrustations and higher in those with infectious phosphate encrustations (p < 0.05). When compared to non-encrusted stents, patients with calcium-oxalate-encrusted stent showed greater calciuria, phosphaturia, indwelling time, and reduced diuresis; patients with uric-acid-encrusted stent showed greater uricosuria; and patients with infectious and non-infectious phosphate encrustation showed greater urinary pH (p < 0.05). (4) Conclusions: Metabolic urine conditions play a critical role in the formation, composition, and severity of double-J stent encrustation.