Fetal lower urinary tract obstruction (LUTO) and pleural effusion are conditions that can disrupt fetal growth and lead to fetal death. LUTO inhibits the formation of amniotic fluid, which is vital for lung development, while pleural effusions can compress the fetal heart, potentially causing fatal cardiac failure. To manage these conditions, a fetal shunt (vesico-amniotic shunt) is placed inside the fetal bladder. This paper presents a study on a new design incorporating a Tesla valve in the shunt. Six groups of Tesla valves with loop angles of 50 degrees and 60 degrees, and different end dimensions, are examined and evaluated in terms of the urine flow rate from the fetal bladder into the amniotic cavity, the pressure buildup between the two sides, and their potential in developing fetal bladder muscles. A mathematical method is used to compare diode characteristics, analyze flow rates, identify the Tesla valve angle, determine the Reynolds number, and assess diodicity. The Computational Fluid Dynamics (CFD) method is also employed to verify calculation results and simulate fluid behavior inside the Tesla valve. Combining the calculations and simulations, a 50-degree Tesla valve with specific dimensions showed the best performance and will be the optimal design for the fetal shunt.

Fetal lower urinary tract obstruction (LUTO) is a severe malformation that is associated with significant neonatal and pediatric morbidity and mortality risk. Existing fetal shunts aimed at bypassing the obstruction and improving neonatal survival have significant limitations, primarily shunt dislodgement. Repeat in-utero invasive shunt replacement procedures are associated with maternal, fetal, and obstetric risks, highlighting a clinical need for a novel fetal shunt with improved performance. We used a biodesign approach to develop and validate a novel fetal shunt, the Vortex shunt, which can potentially reduce dislodgement and improve both neonatal and maternal outcomes. In this review, we will discuss our approach to assessing the clinical need, the initial prototyping and benchtop testing, and animal feasibility studies of the Vortex shunt. We will also discuss existing challenges and opportunities for innovation in the fetal medicine and surgery space, and how biodesign methodology can inform novel instrument development in high-impact small market areas.

Congenital fetal lower urinary tract obstruction is a heterogeneous group of diseases. The paper describes an analysis of outcomes of intrauterine treatment of fetal lower urinary tract obstruction with various shunts that are currently used in fetal surgery published over the last 10 years. The literature search was conducted in the PubMed/Medline, Scopus, Web of Science, Google Scholar, Wiley and Cochrane Library databases. Intrauterine vesicoamniotic shunting is the most common method to manage fetal lower urinary tract obstruction. Different shunt types have their own features, advantages and disadvantages that should be considered when choosing an appropriate treatment method. It is estimated that early management of fetal lower urinary tract obstruction (up to 18 weeks of pregnancy) significantly reduces fetal and newborn mortality, as well as postnatal morbidity. However, only limited series of studies are available. Randomized multicenter studies are not available, and novel shunt modifications are proposed due to high incidence of complications. Further researches should be conducted in the cohort. KEYWORDS: vesicoamniotic shunting, fetal surgery, posterior urethral valve, chronic renal failure. FOR CITATION: Kosovtsova N.V., Fyodorova N.A., Mamaev A.O. Different shunt types for intrauterine management of infravesical obstruction of fetal urinary system. Russian Journal of Woman and Child Health. 2025;8(3):223–229 (in Russ.). DOI: 10.32364/2618- 8430-2025-8-3-7

The Rapid Evolution of Fetal Lower Urinary Tract Obstruction in the Late Second Trimester—A Management Challenge: A Case Report

We estimated the potential outcomes, costs, and cost-effectiveness of the Vortex shunt, a novel fetal vesicoamniotic shunt (VAS), compared to standard shunts for treating fetal lower urinary tract obstruction (LUTO). We designed a decision-analytic model comparing the Vortex shunt to current shunts using a theoretical cohort of 1000 pregnancies equivalent to the annual U.S. LUTO cases. Current literature indicates a 50% dislodgement risk and a 36% end-stage renal disease (ESRD) probability for current shunts versus the Vortex shunt's expected 10% dislodgement risk and 18% ESRD rate from pre-clinical studies. Outcomes included preterm delivery, preterm premature rupture of membrane (PPROM), ESRD, neurodevelopmental delay (NDD), neonatal death, costs, and quality-adjusted life years (QALYs). We derived model inputs from the literature and conducted sensitivity analyses. Of 1000 theoretical LUTO pregnancies, the Vortex shunt resulted in 70 fewer cases of ESRD, 110 fewer preterm deliveries, 50 fewer episodes of PPROM, and 10 fewer children with NDD. The Vortex shunt was the dominant strategy with higher QALYs and estimated lifetime savings of $168,520 for each fetus undergoing VAS. The Vortex shunt was cost-effective 98% of the time. Our theoretical model suggests that the Vortex shunt is cost-effective compared to current shunts.

Lower urinary tract obstruction (LUTO) is a chronic condition with a spectrum of outcomes. It is usually suspected prenatally based on ultrasound features (USFs). Given the unknown postnatal trajectory and the potential for significant morbidity and mortality, many families choose termination of pregnancy (TOP), often based on USFs alone. Herein, we sought to develop a tool that can be used to predict postnatal outcome based on combinations of USFs, which can aid prenatal counseling and parental decision-making. This was a retrospective study of cases with suspected fetal LUTO that were seen at a high-risk fetal center and a tertiary pediatric center in Canada. Data were collected on USFs, prenatal/postnatal death and postnatal need for transplantation and/or dialysis. USFs from pregnancies with a gestational age of 13-26 weeks on initial ultrasound at the high-risk fetal center that underwent TOP were collected and matched to fetuses with comparable prenatal USFs that were not terminated, which had a known postnatal outcome, to build a random forest model. The random forest model was fitted for each outcome (death, dialysis or transplantation) and tested for accuracy using leave-one-out cross-validation. Each predictor was assessed independently with combined importance when accounting for other predictors. The model was used to predict the most likely postnatal outcomes for cases of TOP had the pregnancy been continued. USF data from 85 cases of TOP and 125 cases of expectantly managed pregnancy with prenatally suspected LUTO were retrieved. For expectantly managed cases, there was a median follow-up duration of 5.7 (interquartile range, 0.2-14.5) years among the liveborn infants. There were 14 prenatal and 22 postnatal deaths in the expectantly managed cohort. The random forest model demonstrated the highest predictive accuracy for transplantation (77% accuracy, 50% sensitivity, 80% specificity), followed by death (72% accuracy, 83% sensitivity, 67% specificity) and dialysis (71% accuracy, 70% sensitivity, 71% specificity). For the TOP cohort, had the pregnancies been continued, the model predicted transplantation and dialysis in 21/85 (25%) and 37/85 (44%) cases, respectively; pre- or postnatal death was predicted in 69/85 (81%) cases. Our data suggest that it is possible to predict death and postnatal transplantation and/or dialysis from USFs in fetuses with suspected LUTO with acceptable accuracy. Predictive accuracy will improve with continued follow-up of more patients, enabling more personalized prenatal counseling and more informed decision-making for families. © 2024 The Author(s). Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

ABSTRACTObjectivesTo reach an international expert consensus on the diagnosis, prognosis and management of fetal lower urinary tract obstruction (LUTO) by means of a Delphi procedure, and to use this to define a core outcome set (COS).MethodsA three‐round Delphi procedure was conducted among an international panel of experts in fetal LUTO. The panel was provided with a list of literature‐based parameters to consider for the diagnosis, prognosis, management and outcomes of LUTO. A parallel procedure was conducted with patient groups during the development of the COS.ResultsA total of 168 experts were approached, of whom 99 completed the first round and 80/99 (80.8%) completed all three rounds of the study questionnaires. Consensus was reached that, in the first trimester, an objective measurement of longitudinal bladder diameter of ≥ 7 mm should be used to suspect LUTO. In the second trimester, imaging parameters suggestive of LUTO could include enlarged bladder, keyhole sign, bladder wall thickening, bilateral hydronephrosis, bilateral hydroureteronephrosis and male sex. There was 79% agreement that the current prognostic scoring systems in the literature should not be used clinically. However, experts agreed on the value of amniotic fluid volume (at < 24 weeks) to predict survival and that the value of fetal intervention is to improve the chance of neonatal survival. Experts endorsed sonographic parameters suggestive of renal dysplasia, at least one vesicocentesis, and renal biochemistry for prognosis and counseling, but these items did not reach a consensus for determining candidacy for fetal intervention. On the other hand, imaging parameters suggestive of LUTO, absence of life‐limiting structural or genetic anomalies, gestational age of ≥ 16 weeks and oligohydramnios (defined as deepest vertical pocket < 2 cm) should be used as candidacy criteria for fetal intervention based on expert consensus. If bladder refill was evaluated, it should be assessed subjectively. Vesicoamniotic shunt should be the first line of fetal intervention. In the presence of suspected fetal renal failure, serial amnioinfusion should be offered only as an experimental procedure under research protocols. A COS for future LUTO studies was agreed upon.ConclusionInternational consensus on the diagnosis, prognosis and management of fetal LUTO, as well as the COS, should inform clinical care and research to optimize perinatal outcomes. © 2024 The Author(s). Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Fetal lower urinary tract obstruction is a rare condition commonly associated with significant perinatal morbidity and mortality, particularly when detected in the second trimester. The concurrent presentation of a recto-urethral fistula with membranous urethral atresia and sacrococcygeal teratoma has not been reported. We describe a case of extrinsic fetal lower urinary tract obstruction related to a recto-urethral fistula, diagnosed at 33 weeks gestation and managed by serial vesicocentesis until 38 weeks. This case, notable for its absence of hypoplasia despite late diagnosis, resulted in a term delivery of a male infant. After delivery, pediatric surgeons performed an abdominal perineal resection of the tumor. Fetal vesicocentesis remains a viable management option for patients without access to intrauterine surgical interventions.

Background: Fetal lower urinary tract obstruction (LUTO) is a rare occurrence that is usually associatedwith major morbidity and mortality after birth. It has an incidence of 2.2 in 10000 pregnancies. In males,the most common cause is persistent posterior urethral valves (50-60%). Other causes include urethralatresia with a poor prognosis. Most fetuses that survive to term with LUTO need dialysis or renaltransplant.Case presentation: A 35-year-old gravida 3 presented for routine antenatal follow-up. Her antenatalfollow-up remained normal until she underwent a growth scan at 33 weeks. Ultrasound revealed a fetuswithin normal growth centiles, but the renal system had features of obstruction. Renal calyces weredilated with hyperechoic renal parenchyma. The bladder was also markedly distended and had athickened wall, and a keyhole sign was present. There was a multicystic lesion in the sacral regionwithout blood flow on Doppler imaging. There was oligohydramnios. She had fetal vesicocentesis, whichrevealed normal kidney function. She had serial fetal vesicocentesis, and renal ultrasound showedimprovement in the corticomedullary differentiation of the kidney. At 38 weeks, the patient underwent acesarean delivery. Imaging studies showed a sacrococcygeal teratoma that was causing pressure on therenal system. This was excised, and the patient was allowed to return home on physiotherapy. Renalfunction test after delivery remained normal.Conclusion: Fetal lower urinary tract obstruction in males is mostly managed using the placement ofvesicoamniotic shunts or stents. In male fetuses with posterior urethral valves, ablation is performed inutero using cystoscopy. In this case report, LUTO was managed by serial vesicocentesis, whichpreserved renal function. In low-resource settings where surgery is not available, serial vesicocentesiscan be performed to relieve obstruction.

Implementation of Novel Fetal Intervention for Fetal Lower Urinary Tract Obstruction and the Importance of Candidate Selection: A Case Report

1093 Management and Core Outcomes Set of Fetal Lower Urinary Tract Obstruction: Delphi Consensus

Outcomes in Fetal Lower Urinary Tract Obstruction: Analysis of Fetal Urinary Biochemistry and Ultrasound Features in Fetuses with and without Additional Upper Renal Tract Involvement

Fetal Lower Urinary Tract Obstruction (LUTO) is associated with oligohydramnios and significant fetal morbidity, resulting in poor lung development and perinatal death. However, oligohydramnios may develop at different gestational periods, and the impact of timing on fetal outcomes remains unknown. Our objective was to characterize the impact onset of oligohydramnios had on prenatal outcomes. This study is a retrospective cohort study of all patients with a prenatal diagnosis of LUTO at our tertiary referral center from 2014 to 2023. All patients underwent detailed ultrasonography and interdisciplinary counseling and were subsequently delivered at our institution. Data were obtained from electronic medical records and complete extraction was required for final inclusion. During the study time period, 93 patients met inclusion criteria of which 68 (73.1%) developed oligohydramnios during their pregnancy. 63 (93%) of these pregnancies resulted in livebirths with 28 (41.1%) perinatal deaths. Onset of oligohydramnios was earlier in pregnancies with perinatal death (23 vs. 28weeks, p=0.004) and associated with pulmonary hypoplasia. Our data show the impact of oligohydramnios timing in pregnancy on pulmonary hypoplasia and ultimately perinatal death. This allows for detailed patient counseling on the impact oligohydramnios may have on pregnancies by the gestational age of onset.

Fetal lower urinary tract obstruction (LUTO) is a severe malformation associated with an up to 80% mortality risk as well as significant renal and pulmonary morbidity in survivors. Fetal vesico-amniotic shunts (VAS) bypass the bladder obstruction, improve amniotic fluid volume and enhance in-utero pulmonary development. VAS has been shown to reduce respiratory morbidity and mortality in the neonatal period without proven benefit on long-term renal and bladder function. Clinically available shunts are associated with an up to 80% dislodgement rate, leading to repeat invasive procedures which increase fetal and maternal risks. We developed a novel "Vortex" shunt, which incorporates enhanced fixation to reduce dislodgement, a one-way valve to optimize in-utero bladder function, and enhanced sonographic echogenicity that optimizes the accurate deployment. Following the validation of these characteristics in initial benchtop experiments we have moved to feasibility studies in the fetal lamb model. We hope that the Vortex shunt may ultimately facilitate shunt deployment, reduce dislodgement risk, improve neonatal morbidity and mortality, and decrease the significant healthcare expenditures associated with long-term morbidity in LUTO survivors. In this manuscript, we review the natural history of LUTO, the risks and benefits of clinically available fetal shunts, and our development and early validation experiments.

Fetal megacystis generally presents as suspected lower urinary tract obstruction (LUTO), which is associated with severe perinatal morbidity. Genetic etiologies underlying LUTO or a LUTO-like initial presentation are poorly understood. Our objectives are to describe single gene etiologies in fetuses initially ascertained to have suspected LUTO and to elucidate genotype-phenotype correlations. A retrospective case series of suspected fetal LUTO positive for a molecular diagnosis was collected from five centers in the Fetal Sequencing Consortium. Demographics, sonograms, genetic testing including variant classification, and delivery outcomes were abstracted. Seven cases of initially prenatally suspected LUTO-positive for a molecular diagnosis were identified. In no case was the final diagnosis established as urethral obstruction that is, LUTO. All variants were classified as likely pathogenic or pathogenic. Smooth muscle deficiencies involving the bladder wall and interfering with bladder emptying were identified in five cases: MYOCD (2), ACTG2 (2), and MYH11 (1). Other genitourinary and/or non-genitourinary malformations were seen in two cases involving KMT2D (1) and BBS10 (1). Our series illustrates the value of molecular diagnostics in the workup of fetuses who present with prenatally suspected LUTO but who may have a non-LUTO explanation for their prenatal ultrasound findings.

We evaluate survival of fetuses with severe Lower Urinary Tract Obstruction (LUTO) based on bladder morphology. We hypothesize that fetuses with a "floppy" appearing bladder on initial prenatal ultrasound will have worse infant outcomes than fetuses with full/rounded bladders. We retrospectively reviewed all cases of LUTO evaluated in our fetal center between January 2013 and December 2021. Ultrasonographic assessment, renal biochemistry, and bladder refilling contributed to a "favorable" or "unfavorable" evaluation. Bladder morphology on initial ultrasound was classified as "floppy" or "full/rounded." Vesicoamniotic shunting was offered for favorably evaluated fetuses. Baseline demographics, ultrasound parameters, prenatal evaluations of fetal renal function, and infant outcomes were collected. Fetuses diagnosed with severe LUTO were included in analysis using descriptive statistics. The primary outcome measured was survival at 6months of life. 104 LUTO patients were evaluated; 24 were included in analysis. Infant survival rate at 6months was 60% for rounded bladders and 0% for floppy bladders (p=0.003). Bladder refill adequacy was lower in fetuses with floppy bladders compared with rounded bladders (p value<0.00001). We propose that bladder morphology in fetuses with severe LUTO may be a prognostication factor for predicting infant outcomes and provides a valuable, noninvasive assessment tool.

Fetal bladder morphology may predict neonatal outcomes in fetal lower urinary tract obstruction (LUTO)

Introduction Fetal lower urinary tract obstruction (LUTO) can be mild or severe with oligohydramnios, renal dysplasia and pulmonary hypoplasia. Fetal urine biochemical markers correlate with fetal prognosis and, if favorable, surgical intervention is feasible. Methods We report a patient in her 18th gestational week whose fetus was diagnosed with LUTO and underwent fetal urine sampling for calcium, sodium, chloride, beta2-microglobulin and total protein of the routine LUTO panel, with the addition of creatinine, glucose, phosphate, urea, ammonia, albumin, and NGAL. Results Although the routine fetal urine biochemistry seemed to be favorably trending favorably, sodium, beta2-microglobulin, glucose, and urea did not decrease to the reference ranges, and ammonia and creatinine were lower than the reference ranges. Ultrasound demonstrated no improvement of the obstruction. Conclusions This case highlights the need to acquire further experience with biochemical fetal urine markers in order to better manage LUTO.

Fetal lower urinary tract obstruction (LUTO) is associated with high mortality and postnatal morbidity caused by lung hypoplasia and impaired kidney function. Specific diagnostic features that can guide clinical approach and decisions are lacking; thus, the European Reference Network for Rare Kidney Diseases established a work group to develop recommendations regarding the clinical definition, diagnosis and management of prenatally detected LUTO. The work group recommends the use of antero-posterior diameter of renal pelvis as the most reliable parameter for suspecting obstructive uropathies and for suspecting prenatal LUTO in the presence of fetal megacystis. Regarding prenatal and postnatal prognosis of fetuses with LUTO, the risk of fetal and neonatal death depends on the presence of oligohydramnios or anhydramnios before 20 weeks' gestation, whereas the risk of kidney replacement therapy cannot be reliably foreseen before birth. Parents of fetuses with LUTO must be referred to a tertiary obstetric centre with multidisciplinary expertise in prenatal and postnatal management of obstructive uropathies, and vesico-amniotic shunt placement should be offered in selected instances, as it increases perinatal survival of fetuses with LUTO.

To develop and test a novel vesicoamniotic shunt (VAS) to treat fetal lower urinary tract obstruction (LUTO), decrease dislodgement and optimize shunt deployment in-vitro. Vesicoamniotic shunt design objectives included: (1) robust and atraumatic fixation elements, (2) kink resistant conduit to adjust to fetal movement and growth, (3) one-way pressure valve to facilitate bladder cycling, and (4) echogenic deployment visualization aids. The force to dislodge the novel Vortex shunt was compared with existing commercially available shunts in a bench-top porcine bladder model. Sonographic echogenicity was evaluated with ultrasound-guided deployment, and the shunt valve pressure measured. A prototype novel Vortex shunt was developed using braided nitinol "umbrella-type" ends with a kink-resistant stem incorporating an internal one-way valve. The peak force required to dislodge the Vortex shunt was significantly higher than commercially available shunts (p<0.01). Shunt deployment in the bench-top model was easily confirmed with ultrasound guidance and the brisk decompression of the inflated porcine bladder thereafter. In-vitro valve gauge pressure testing mirrored bladder pressures in human LUTO cases. In-vitro testing shows that the Vortex shunt may improve deployment, sonographic visualization, kink resistance, and dynamic size adjustment. Validation in preclinical animal models are warranted and currently underway.