Backflow Of Urine Research Articles

The Intrarenal Reflux Diagnosed by Contrast-Enhanced Voiding Urosonography (ceVUS): A Reason for the Reclassification of Vesicoureteral Reflux and New Therapeutic Approach?

Vesicoureteral reflux (VUR) is defined as the urine backflow from the urinary bladder to the pyelo-caliceal system. In contrast, intrarenal reflux (IRR) is the backflow of urine from the renal calyces into the tubulointerstitial space. VURs, particularly those associated with IRR can result in reflux nephropathy when accompanied by urinary tract infection (UTI). The prevalence of IRR in patients with diagnosed VUR is 1-11% when using voiding cystourethrography (VCUG), while 11.9-61% when applying the contrast-enhanced voiding urosonography (ceVUS). The presence of IRR diagnosed by VCUG often correlates with parenchymal scars, when diagnosed by a 99mTc dimercaptosuccinic acid scan (DMSA scan), mostly in kidneys with high-grade VURs, and when diagnosed by ceVUS, it correlates with the wide spectrum of parenchymal changes on DMSA scan. The study performed by both ceVUS and DMSA scans showed IRRs associated with non-dilated VURs in 21% of all detected VURs. A significant difference regarding the existence of parenchymal damage was disclosed between the IRR-associated and IRR-non-associated VURs. A higher portion of parenchymal changes existed in the IRR-associated VURs, regardless of the VUR grade. That means that kidneys with IRR-associated VURs represent the high-risk group of VURs, which must be considered in the future classification of VURs. When using ceVUS, 62% of places where IRR was found were still unaffected by parenchymal changes. That was the basis for our recommendation of preventive use of long-term antibiotic prophylaxis until the IRR disappearance, regardless of the VUR grade. We propose a new classification of VURs using the ceVUS method, in which each VUR grade is subdivided based on the presence of an IRR.

55: REDUCING CAUTI EVENTS WITH ACTIVE DRAIN LINE CLEARANCE: A RETROSPECTIVE OBSERVATIONAL STUDY

Introduction: Catheter-associated urinary tract infections (CAUTIs), represent approximately 9% of all hospital-associated infections and are associated with increased morbidity, mortality, and cost in intensive care units (ICUs). We performed a quality improvement study to assess if the use of a bladder catheter with integrated active drain line clearance reduced the rate of catheter-associated urinary tract infections (CAUTIs) in a burn ICU. Methods: We performed an eight-year (2015–2022) retrospective cohort study in a single-center burn ICU with seven beds. CAUTI events were compared from a 48-month period in which gravity bladder catheters had been the standard of care to a 28-month period after the implementation of a novel urinary catheter system. This urinary monitoring system features an active drain line clearance, two one-way valves preventing urinary backflow, and automation of intra-abdominal pressure measurements. Charts were reviewed to characterize the patients. Results: A total of 42 CAUTIs in 2243 patients were identified using the National Health and Safety Network (NHSN) definition during the analyzed period. The incidence of CAUTI events pre-implementation was 0.030 (mean 10 CAUTI events per year) compared to 0.002 (mean 1 CAUTI event per year) post-implementation of an automatic drain line clearing UO monitoring system showing a significant reduction in CAUTI events (P < 0.01, risk ratio Accuryn vs. no gravity bladder catheter 0.071, 95% confidence interval: 0.017-0.294). Median [IQR] urinary catheter dwell time to CAUTI events was 4.5 [2.0, 6.2] pre- and 6.0 [5.5, 6.5] post-novel catheter implementation. Conclusions: A novel urinary catheter system with integrated active drain line clearance reduced the rate of CAUTI after implementation. Active drain line clearance preventing standing urine in the bladder and tubing system and two one-way valves eliminating urine backflow might be favorable features potentially leading to a reduction in CAUTI events compared to gravity urinary catheters.

Unusual presentation of duplex kidney with poor functioning upper moiety in an adult patient a case report

Renal duplexing (also known as a duplicate collection system) occurs in about 1% of children and does not usually require medical attention. The condition results in two tubes rather than the normal single ureter tube for each kidney. Medical problems that warrant attention are obstruction of urine flow or the backflow of urine into the kidney (reflux). These double ureter tubes can join in a "y" shape before reaching the bladder (partial duplex) and combining their urine delivery. In other cases, each duplicate ureter empties into the bladder on its own (complete duplex). There is cause for concern when a duplex kidney is associated with urological conditions requiring treatment. Renal duplexing can cause urine to reflux into the kidney (vesicoureteral reflux) rather than going into the bladder and can cause subsequent Urinary Tract Infection (UTI). This can result in serious consequences like the loss of renal parenchyma (reflux nephropathy) and sometimes death in acute infections if not attended to in a timely manner. Weigert-Meyer postulated that rule i-e in a complete duplex system is mostly associated with reflux in lower moiety and obstruction in upper moiety with ectopic insertion and ureterocele. Ureteroceles may require simple management of symptoms or surgery, depending on the size of the ballooning, the functioning of the kidney and bladder and the degree of urine obstruction. An ectopic ureter is when the ureter opens and drains urine outside the bladder rather than inside.

Relationship Between Vesicoureteric Reflux and Nephrocalcinosis in Children: A Case-Control Study at a Tertiary Medical Center in Saudi Arabia.

Vesicoureteral reflux (VUR), one of the most common pediatric congenital urogenital abnormalities, refers to the abnormal backflow of urine from the urinary bladder back into the ureter or to the kidney. This causes urinary tract infections. Nephrocalcinosis (NC) refers to abnormal deposits of calcium within the renal parenchyma and/or in the renal cortex.Patients with NC are mostly asymptomatic and severe disease may progress to renal failure. Early diagnosis through examinationssuchas radiography, computed tomography, and ultrasonography, is crucial for therapeutic treatment. Ultrasonography is the preferred method for scanning and grading nephrocalcinosis in children, primarily because it emits no radiation. This study aimed to increase the body of knowledge regarding VUR and nephrocalcinosis by determining its prevalence and assessingthe relationship between VUR and nephrocalcinosis in children presenting at our institution. ​​​​Methods:A case-control study was conducted using data from the medical records of 632 children younger than 14 years in a tertiary medical center in Riyadh, Saudi Arabia. Eligible participants were assigned to two groups: Group 1 consisted of 316 patients with VUR, while Group 2 consisted of 316 sex- and age-matched patients without VUR. The difference in the prevalence of nephrocalcinosis between the two groups was assessed. Frequency and percentage were used to present the categorical variables; Pearson product-moment correlation was utilized to establish the association between VUR and nephrocalcinosis. Statistical significance was established at p<0.05. ​​​​​Result:Only two cases in Group 1 were positive for nephrocalcinosis (0.63%, one male and one female), while four cases in Group 2 were positive for the condition (1.26%, two males and two females). There was no significant difference in the incidence of nephrocalcinosis between the two groups (p=0.873), indicating no relationship between VUR and nephrocalcinosis in children. There is no relationship between VUR and nephrocalcinosis in children under the age of 14 years.

A Randomized, Single-Blind Clinical Trial Comparing Robotic-Assisted Fluoroscopic-Guided with Ultrasound-Guided Renal Access for Percutaneous Nephrolithotomy.

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.

Study the Possibility of Creating Mucosal Valve Mechanism at Ureteric Orifice without Obstructing the Urine Outflow but Preventing the Urine Backflow into the Ureters.

Objective:To study the possibility of creating mucosal valve mechanism at ureteric orifice without obstructing the urine outflow but preventing the urine backflow into the ureters.Materials and Methods:Ethical waiver was obtained from the institutional ethical committee. Prospective experimental study was conducted on the post-mortem specimen of intact bladder with urethra and bilateral ureters retrieved from the already slaughtered lamb available in the meat market. Feeding tube inserted via urethral opening into the bladder lumen and bladder inflated with saline demonstrated no reflux of urine via transverse cut opening of ureters. Bladder lumen opened, ureteric orifices incised backwards to eliminate the obliquity. After closing the bladder opening, saline inflation test demonstrated bilateral reflux of saline via cut openings of bilateral ureters. Bladder was re-opened. The upper limb of horizontal U started 10 mm lateral and 8 mm above the refluxing ureteric orifice. Distal most curvature of horizontal U was kept 5 mm medial to ureteric orifice continuing along the lower limb of horizontal U terminating 10 mm lateral and 8 mm below the refluxing ureteric orifice, mucosal flaps from superior and inferior incision mobilized and edges joined to cover the ureteric orifice creating a flap valve mechanism. Influx of saline via cut end of ureters demonstrated no obstruction. Bladder was closed. Saline inflation test and contrast study demonstrated abolition of reflux on flap side and persistence of reflux on another side.Results:Five such experiments were conducted. On the side where the valve was created, Vesicoureteral reflux was abolished in four but in one minimal reflux still persisted.Conclusion:Creating a mucosal flap valve around the ureteric orifice can prevent reflux in 80% of cases without obstruction and without the necessity of ureteric mobilization or creating submucosal tunnel.

Computational flow analysis of a single peristaltic wave propagation in the ureter

Background and objectiveThe bladder receives the urine from the kidney and ureter. The series of peristaltic waves facilitate urine transport to the bladder. The peristaltic flow in the ureter is associated with fluid trapping and material reflux, which may cause an increase in bladder pressure. It is difficult to visualize the complex peristalsis phenomenon, in the ureter using image and radiography experiments. A numerical simulation will help in the understanding of urine bolus formation and its effect on the ureter wall. MethodsA three-dimensional computational fluid dynamic analysis is carried out to understand the flow physics associated with bolus formation and the effect of reflux on the ureter. ANSYS-CFX, a commercially available computational dynamics package is used to simulate the peristalsis. A single sinusoidal peristaltic wave traveling along a circular tube will yield the velocity, pressure, wall shear stress distributions inside the ureter. ResultsThe propagation of the peristaltic wave results in the backflow of urine near the inlet at the beginning of the flow. As the wave propagates towards the outlet, the flow rate decreases. It is observed that pressure distribution along the ureter axis will deteriorate towards the outlet. The contraction produces a very high-pressure gradient which causes the urine backflow. The trapping and the bolus formation cause a significant rise in bolus pressure, simultaneously developing negative pressure at the contraction neck. ConclusionsThe effect of peristalsis on the ureter biofluid dynamic behavior of the ureter is visualized in this study. It is established that the peristaltic contraction results in high-pressure formation at the bolus and negative pressure at the neck. It was found to be a maximum of 1.1 Pa at the bolus center and —1.13 Pa at the neck region. At the ureter pelvis junction, a higher wall shear of 0.095 Pa is observed as the wave starts to propagate. The velocity vectors show that the trapping of urine causes reflux and results in an adverse pressure gradient near the wall. A maximum pressure gradient of 485 Pa/meter was observed at the contraction of the ureter wall.

Increased rates of vesicoureteral reflux in mice from deletion of Dicer in the peri-Wolffian duct stroma.

BACKGROUND:Vesicoureteral reflux (VUR), backflow of urine into the kidney, is associated with urinary tract infections and chronic kidney disease. Integrity of the vesicoureteral junction (VUJ), where reflux occurs, is determined largely by proper induction of the ureteric bud from the Wolffian duct. Induction is modulated by signals from the surrounding peri-Wolffian duct stroma. We evaluated whether miRNAs in the peri-Wolffian duct stroma are necessary for proper ureteric induction, VUJ formation, and suppression of VUR.METHODS:We generated a mouse with loss of miRNAs in the peri-Wolffian duct stroma. We evaluated embryos for ureteric bud induction defects and expression of genes that regulate induction. We performed cystograms to assess for reflux and assessed VUJs in postnatal mice.RESULTS:Mutant embryos had cranially displaced ureteric bud induction sites versus controls. We observed no changes in expression of genes known to regulate induction. While mutants were early postnatal lethal, they had high rates of VUR versus controls. Mutant VUJs that refluxed had low inserting ureters and shortened intravesicular tunnels versus non-refluxing mice.CONCLUSIONS:We found that miRNAs in the peri-Wolffian duct stroma are required for normal ureteric bud induction, VUJ formation, and prevention of VUR.

Proper indwelling catheter use to prevent CAUTIs

Proper indwelling catheter use to prevent CAUTIs

Pathological changes associated with DEFLUX use in vesicoureteric reflux

Vesicouretral reflux (VUR) which is the backflow of urine from the bladder to the kidneys leading to renal dysfunction. It is a common problem that is being encountered. Most of children and infants with UTI turn to be having VUR and patients who left untreated turned to have renal scarring and in turn to have end stage renal disease. For preventing these consequences, an intervention is needed. Previously, surgical intervention was the mainstay treatment and the new practice have endoscopic injection of deflux that is a gel-like material that consist of Dextranomer/Hyaluronic acid copolymer, which had replaced other methods of invasive antireflux surgeries and becoming the preferred method used in practice for solving VUR by building an artificial valve system. In the following case, we will highlight the histologic manifestation of the deflux injection.

Vesicoureteral reflux and recurrent urinary tract infections

Vesicoureteral reflux (VUR) refers to backflow of urine from the bladder into the upper urinary tract. Children with high-grade VUR are at risk of recurrent urinary tract infections (UTIs). It is commonly associated with bladder–bowel dysfunction, necessitating treatment because it further increases the risk of recurrent UTI and results in delayed resolution of VUR. Almost one-third of patients with VUR diagnosed following UTI show renal scarring. It is debated whether scarring in VUR is entirely acquired following UTI or due to dysplasia. The efficacy of antibiotic prophylaxis has been variable for the prevention of UTI in children with VUR. A meta-analysis suggests that it might be of some benefit in preventing UTI, but not renal scarring and at cost of bacterial resistance. Due to questionable efficacy and potential risk, use of antibiotic prophylaxis should be based on risk stratification rather than mere presence of reflux. In view of lack of significant improvement in long-term outcomes with current available interventions, there is ongoing debate on the aggressiveness of algorithms for diagnosing VUR following UTI. Long-term complications of VUR include proteinuria, hypertension, and end-stage renal disease. As opposed to previous assumption, the risk of end-stage renal failure and hypertension is fairly small with scarring following UTI.

Detection of Vesicoureteral Reflux Using Electrical Impedance Tomography.

The purpose of this study is to detect vesicoureteral reflux (VUR) noninvasively using an electrical impedance tomography (EIT). VUR is characterized by the backflow of urine from the bladder to the kidneys. Using porcine models, small quantities of a solution mimicking the electrical properties of urine were infused into each ureter. EIT measurements were taken before, during and after the infusion using electrodes positioned around the abdomen. The collected data from 116 experiments were then processed and time-difference images reconstructed. Objective VUR detection was determined through statistical analysis of the mean change in the voltage signals and EIT image pixel intensities. Unilateral VUR was successfully detected in 94.83% of all mean voltage signals and in over 98.28% of the reconstructed images. The images showed strong visual contrast between the region of interest and the background. In animal models, EIT has the capability to detect reflux in the kidneys with high accuracy. The results show promise for EIT to be used for screening of VUR in children. VUR is the most common congenital urinary tract abnormality in children. The condition predisposes children to urinary tract infections and kidney damage. The current gold standard diagnostic test, a voiding cystourethrogram, is invasive and uses ionizing radiation; therefore, there is a need for new tools for identifying VUR in children. This study presents a noninvasive method to detect VUR in animal models, illustrating the potential for EIT as a screening tool in clinical scenarios.

A fluid-structure interaction (FSI)-based numerical investigation of peristalsis in an obstructed human ureter.

Urine moves from the kidney to the bladder through the ureter. A series of compression waves facilitates this transport. Due to the highly concentrated mineral deposits in urine, stones are formed in the kidney and travel down through the urinary tract. While passing, a larger stone can get stuck and cause severe damage to ureter wall. Also, stones in the ureter obstructing the urine flow can cause pain and backflow of urine which in turn might require surgical intervention. The current study develops a 2D axisymmetric numerical model to gain an understanding of the ureter obstruction and its effects on the flow, which are critical in assessing the different treatment options. Transient computational analysis involving a two-way fully coupled fluid-structure interaction with the arbitrary Lagrangian-Eulerian method between the ureteral wall and urine flow is conducted with an obstruction in the ureter. The ureter wall is modeled as an anisotropic hyperelastic material, data of which, is based on biaxial tests on human ureter from previous literature, while the incompressible Navier-Stokes equations are solved to calculate urine flow. A finite element-based monolithic solver is used for the simulations here. The obstruction is placed in the fluid domain as a circular stone at the proximal part of the ureter. One of the objectives of this study is to quantify the effect of the ureteral obstruction. A sharp jump in pressure gradient and wall shear stress, as well as retrograde urine flow, is observed as a result of the obstruction.

Lymphocryptovirus-dependent occurrence of lymphoma in SIV-infected rhesus macaques with particular consideration to two uncommon cases of non-Hodgkin's lymphoma

Abstract. Despite combination antiretroviral therapy, high-grade malignant non-Hodgkin's lymphoma (NHL) is still one of the most frequently acquired immunodeficiency syndrome (AIDS)-defining disorders in the end stage of infection with human immunodeficiency virus (HIV). NHL can also be observed in rhesus macaques infected with the simian immunodeficiency virus (SIV). Thus, they represent a useful model to study morphological characteristics and oncogenetic mechanisms of NHL in humans.When reviewing the occurrence of lymphoma at the German Primate Center over the past 25 years within the context of pathogenic SIV infection we noticed a strikingly high incidence (four out of seven animals) of these tumors in rhesus macaques infected with ex vivo derived SIVmac251/32H/spleen in AIDS-defining end-stage disease. Polymerase chain reaction analysis of this virus stock revealed the co-presence of rhesus lymphocryptovirus (rhLCV), which represents the monkey homologue to human Epstein–Barr virus (EBV), suggesting an association between co-application of SIV and rhLCV and increased tumorigenesis.In addition, we present two cases of NHL in rhesus macaques infected with a SIVmac239 nef-mutant variant because one exhibited an unusual immunophenotype and the other an uncommon organ manifestation. Histological and immunohistochemical examinations of tumors of the first animal revealed metastatic diffuse large B-cell lymphomas (DLBCL) affecting the stomach and the pancreaticoduodenal lymph nodes, of which the one in the stomach presented the rare dual expression of CD20 and CD3. Necropsy of the second animal revealed an obstructive DLBCL around the urinary bladder neck that led to urine backflow and eventually death due to acute uremia without any further AIDS-like manifestations. In the tumors of both animals, abundant Epstein–Barr nuclear antigen-2 expression was demonstrated, thus verifying concurrent rhLCV infection. Flow cytometric analyses revealed a high percentage of activation as well as proliferation in B cells from peripheral lymph nodes in both animals. Moreover, CD4+ T cells were depleted in blood, colon and lymphoid tissue. Concomitantly, CD8+ T cells showed an exhausted phenotype. The two case reports and the increased incidence of NHL following co-application of SIV and rhLCV underline the role of rhLCV in lymphomagenesis.

Identifying potential problems with intermittent self-catheterisation in patients with neurological conditions

Lower urinary tract dysfunction (LUTD) is common in patients with neurological conditions and can result in loss of voluntary control and a bladder that cannot empty fully or at all. LUTD causes urinary frequency, urgency and incontinence and can have a significant impact on an individual's quality of life as well as presenting a significant risk of damage to the upper renal tract due to urine backflow. Intermittent catheterisation (IC) is the insertion and removal of a catheter several times a day to ensure that the bladder is emptied. Intermittent self-catheterisation (ISC) is the preferred option for the management of residual urine resulting from lower urinary tract dysfunction. ISC is not without risk of potential complications, although these can be reduced by effective and timely patient education.

Fundamental Study On Proposed Cad Based Paediatric Hydronephrosis Classification Model Framework By Enhanced Seed Pixel Region Growing Segmentation And Logistic Regression Classifier Algorithm

Hydronephrosis is the disease which will accumulate the urine in the kidney’s drainage system (—the calyces and renal pelvis) and makes the kidney to swell [1] [2].The reason of occurrence is due to obstacle in the normal urine flow (Urinary tract) or backflow of urine from the urinary bladder. Swelling normally affects one kidney; sometimes it can affect both kidneys. As per the statistics in US, hydronephrosis disease affects one out of every 100 babies. The hyderonephrosis disease is not a primary; it is a secondary disease which results due to other principal diseases. Below figure 1 illustrates images are the normal urinary tract and infected urinary tract.

Vesico-ureteral reflux: Diagnosis and treatment recommendations

Vesico-ureteral reflux (VUR) is one of the most common urologic diseases in childhood. About every third child that presents with a urinary tract infection (UTI) has urinary reflux to the ureter or kidney. Demonstration of a backflow of urine into the ureters or kidneys proves vesicoureteral reflux. In unclear cases, a positioned instillation of contrast agent (PIC) cystogram might be performed and is able to prove vesico-ureteral reflux. Since low-grade VUR has a high probability of maturation and self-limitation, infants with VUR should be given prophylactic antibiotics during their first year of life, reevaluating the status of VUR after 12 months. The aim of any treatment is to prevent renal damage. The individual risk of renal scarring is decisive for the choice of adequate therapy. This risk is mainly dependent on reflux grade, age, and gender of the child as well as parental therapy adherence. In principle, therapeutic options include conservative as well as endoscopic or open surgical antireflux therapies. Decisions on treatment should be made individually with parents taking into account all the findings available.

Role of Central and Peripheral Chemoreceptors in Vasopressin Secretion Control

In this review, we analyzed the role played by central and peripheral chemoreceptors (CHRs) in vasopressin (AVP) secretion control. Central neural pathways subserving osmotic and non-osmotic control of AVP secretion are strictly correlated to brain areas participating in chemoreception mechanisms. Among the different brain areas involved in central chemoreception, the most important site has been localized in the retrotrapezoid nucleus of the rostral ventrolateral medulla. These central CHRs are able to detect very small pH/CO2 fluctuations, participating in brain blood flow regulation, acid-base balance and blood pressure control. Decreases in arterial pH and increases in arterial pCO2 stimulate AVP release by the Supraoptic and Paraventricular Nuclei. Carotid CHRs transduce low arterial O2 tension into increased action potential activity, leading to bradycardia and coronary vasodilatation via vagal stimulation, and systemic vasoconstriction via catecholaminergic stimulation. Stimulation of carotid CHRs by hypoxia increases neurohypophyseal blood flow and AVP release, an effect inhibited by CHRs denervation. Two renal CHRs have been identified: Type R1 CHRs do not have a resting discharge but are activated by renal ischemia and hypotension; Type R2 CHRs have a resting discharge and respond to backflow of urine into the renal pelvis. Signals arising from renal CHRs modulate the activity of hypothalamic AVPergic neurons: activation of R1 and R2 CHRs, following increased intrapelvic pressure with solutions of mannitol, NaCl and KCl, produces a significant increase of AVP secretion and the same effect has been obtained by the intrarenal infusion of bradykinin, which excites afferent renal nerves, as well as by the electrical stimulation of these nerves.

Hygiene for invasive procedures

This article highlights the importance of best practice in insertion of invasive devices, such as urinary catheters, in a way that minimises the risk of infection. One of the main risks is the length of time the catheter remains in place. All wards should have clear documentation of when the catheter was inserted and evidence of daily reviews about its continued use. Other important factors are: ■ Hand hygiene when inserting and managing catheters. ■ Ensuring meatal (urethral opening) hygiene is performed daily. ■ Preventing backflow of urine into the bladder by keeping the drainage bag lower than the bladder. ■ Avoiding unnecessary emptying of the drainage bag and, when emptying is clinically indicated, using a clean disposable container for each patient.

A Mathematical Simulation of the Ureter: Effects of the Model Parameters on Ureteral Pressure/Flow Relations

Ureteral peristaltic mechanism facilitates urine transport from the kidney to the bladder. Numerical analysis of the peristaltic flow in the ureter aims to further our understanding of the reflux phenomenon and other ureteral abnormalities. Fluid-structure interaction (FSI) plays an important role in accuracy of this approach and the arbitrary Lagrangian-Eulerian (ALE) formulation is a strong method to analyze the coupled fluid-structure interaction between the compliant wall and the surrounding fluid. This formulation, however, was not used in previous studies of peristalsis in living organisms. In the present investigation, a numerical simulation is introduced and solved through ALE formulation to perform the ureteral flow and stress analysis. The incompressible Navier-Stokes equations are used as the governing equations for the fluid, and a linear elastic model is utilized for the compliant wall. The wall stimulation is modeled by nonlinear contact analysis using a rigid contact surface since an appropriate model for simulation of ureteral peristalsis needs to contain cell-to-cell wall stimulation. In contrast to previous studies, the wall displacements are not predetermined in the presented model of this finite-length compliant tube, neither the peristalsis needs to be periodic. Moreover, the temporal changes of ureteral wall intraluminal shear stress during peristalsis are included in our study. Iterative computing of two-way coupling is used to solve the governing equations. Two phases of nonperistaltic and peristaltic transport of urine in the ureter are discussed. Results are obtained following an analysis of the effects of the ureteral wall compliance, the pressure difference between the ureteral inlet and outlet, the maximum height of the contraction wave, the contraction wave velocity, and the number of contraction waves on the ureteral outlet flow. The results indicate that the proximal part of the ureter is prone to a higher shear stress during peristalsis compared with its middle and distal parts. It is also shown that the peristalsis is more efficient as the maximum height of the contraction wave increases. Finally, it is concluded that improper function of ureteropelvic junction results in the passage of part of urine back flow even in the case of slow start-up of the peristaltic contraction wave.