Current State of Fetal Intervention for Lower Urinary Tract Obstruction

Pop-off mechanisms as renoprotective mediators in children with posterior urethral valves: A systematic review and meta-analysis

BACKGROUND

Pop-off mechanisms are potential pressure-relieving mediators in patients diagnosed with posterior urethral valves (PUV). This systematic review aimed to synthesize the existing evidence regarding the protective effect of pop-off mechanisms on renal function in children with PUV.

METHODS

We conducted a systematic review of the literature that involved an extensive search in the main databases of the medical bibliography. Three independent reviewers selected the relevant articles. Methodological quality was rated using the Newcastle Ottawa Scale index. We used random meta-analyses to compare different outcomes (serum creatine, Nadir serum creatinine, and Chronic Kidney Disease) between children with PUV and pop-off mechanisms and those with PUV without pop-off mechanisms.

RESULTS

10 studies with data from 896 participants were included in this review. Seven articles reported serum creatinine values for each group and 3 of them found significant differences between groups. The random-effects meta-analysis for serum creatinine showed significant lower mean (diff = -52.88 μmol/L [95 % CI -73.65 to -32.11]) in the group of children with pop-off mechanisms, and the random-effects meta-analysis for Nadir serum creatinine showed a marginally significantly lower mean in the group of children with pop-off mechanisms (diff = -12.00 μmol/L [95 % CI -24.04 to 0.04]). The random-effect meta-analysis for Chronic Kidney Disease resulted in a significant risk reduction for the group of children with pop-off mechanisms (odds ratio = 0.48 [95 % CI 0.23 to 0.98]).

CONCLUSIONS

Children with PUV and pop-off mechanisms show better renal function and lower risk of Chronic Kidney Disease than those with PUV without pop-off mechanisms suggesting these mechanisms may act as renoprotective mediators. The high heterogeneity between studies in the assessment of renal function and long-term outcomes calls for a cautious interpretation of these findings. Future studies that stratify by different types of pop-off mechanisms and use standardized metrics, such as Nadir creatinine, are needed.

Technical details and long-term outcomes of P.A.D.U.A. for congenital urethral narrowing; a case series and review of the literature

INTRODUCTION

The P.A.D.U.A. technique is a method of addressing congenital urethral narrowing. It involves passive dilation with a series of progressively larger indwelling catheters. Utilization is limited by scant literature, particularly regarding technical details and long-term durability. Tools for achieving safe and reliable urinary drainage are critical in these patients, who require careful stewardship of their kidney and bladder function.

OBJECTIVE

To describe long-term urethral patency and urinary function following P.A.D.U.A., and to provide sufficient technical detail to reproduce the technique.

STUDY DESIGN

Patients with congenital urethral narrowing managed with P.A.D.U.A. were identified and chart review was performed. Details of catheter exchange sequences were compiled and described. The primary outcome was the attainment of adequate urethral caliber by successful completion of P.A.D.U.A., and the secondary outcome was voiding per urethra at most recent follow-up.

RESULTS

P.A.D.U.A. achieved adequate urethral caliber in 9/11 (82%) of patients. This included seven patients with Prune Belly Syndrome, one with isolated urethral atresia, and one with a cloacal anomaly. P.A.D.U.A. failed to achieve urethral patency in one patient with urethral duplication, who was unable to progress through the catheter sequence, and one patient with Prune Belly Syndrome, who completed P.A.D.U.A. but developed recurrent narrowing one week later. There were no delayed failures of urethral patency. Patients who achieved patency underwent a median of seven catheter placements over 92 days. Median (range) initial and final catheter sizes were 3.5F (1.9-8F) and 14F (8-16F). While 82% achieved patency, only 3/11 (27%) were voiding spontaneously per native urethra at most recent follow-up.

DISCUSSION

This series of patients undergoing P.A.D.U.A. for primary treatment of congenital urethral narrowing is the largest to date and provides granular technical details. It aligns with prior reports suggesting that P.A.D.U.A. achieves urethral patency in most patients with Prune Belly Syndrome or isolated urethral atresia, but has limited application in the hypoplastic duplicated urethra. Despite high rates of urethral patency in this select population, many patients will not achieve and maintain spontaneous voiding without catheterization. This is likely due to ongoing deterioration of bladder function caused by the prenatal developmental insult, paralleling the phenomenon seen in posterior urethral valves.

CONCLUSION

P.A.D.U.A. is an effective and durable technique for achieving urethral patency. However, due to complicating factors such as the underlying bladder pathology present in many patients, urethral patency achieved with P.A.D.U.A. does not guarantee long-term safe and reliable spontaneous emptying per urethra.

Vesico-amniotic shunt insertion prior to the completion of 16 weeks results in improved preservation of renal function in surviving fetuses with isolated severe lower urinary tract obstruction (LUTO)

PURPOSE

The purpose of this retrospective cohort study was to compare the outcome of human fetuses with isolated severe lower urinary tract obstructions (LUTO) that were first treated before the completion of 16 weeks of gestation to fetuses first treated later in gestation.

PATIENTS AND METHODS

Vesicoamniotic shunt insertion (VAS) was performed in 63 subsequent fetuses with LUTO between 12 + 5 and 30 + 3 weeks. The fetuses were analyzed in three groups: Group-I-fetuses underwent their first intervention until the completion of 16 weeks, Group-II-fetuses were first treated between 16 + 1 and 24 + 0 weeks and Group-III-fetuses beyond 24 + 1 weeks. Renal and pulmonary outcome parameters and complicating factors were assessed.

RESULTS

- All mothers tolerated the procedures well. Overall fetal survival was 47 of 63 (75%). The mean age at delivery of survivors was 35 weeks. 68% of Group-I-fetuses, 77% of group-II-fetuses, and 100% of group-III-fetuses survived beyond postnatal hospital discharge. Amongst the survivors the chance for normal renal function was higher for group I with 79% (15/19) compared to first fetal intervention after the completion of 16 weeks with 32% (9/28, p = 0.003, OR = 7.9 [2.0, 30.8] 95% CI). Clinically relevant pulmonary hypoplasia was observed in 11% of Group-I-, 27% of Group-II-, and 20% of Group-III-fetuses.

CONCLUSIONS

Early intervention in fetal LUTO before the completion of 16 weeks may achieve a higher rate of normal renal and pulmonary function in survivors than treatment beyond that point in time. This observation is important for the future management of this challenging patient population.

Predictors of advanced chronic kidney disease in infancy after definitive vesicoamniotic shunting for congenital lower urinary tract obstruction

BACKGROUND

Severe congenital lower urinary tract obstruction (cLUTO) is associated with poor postnatal outcomes, including chronic and end stage kidney disease, and high mortality. Studies of the impact of fetal intervention through vesicoamniotic shunting are marred by a device malfunction rate of up to 60%. In this study, we delineate the postnatal course and infant kidney function following definitive urinary diversion in utero.

MATERIALS AND METHODS

This is a retrospective, single-center cohort study of 16 male infants who survived the fetal intervention to birth, from 2010 to 2014 at a single center. All had patent shunts in place at birth. Perinatal and biochemical characteristics were collected with patients followed for one year, or until demise, with serial measures of serum creatinine (SCr) and serum cystatin C (CysC).

RESULTS

Of the 16 males, 81% were non-white (38% black, 43% Hispanic). Shunts were placed at a median of 20 weeks (IQR 19,23) gestation, with median fetal bladder volume of 39 cm³ (IQR 9.9,65). All neonates were born preterm [median 34 weeks (IQR 31,35)] and the majority with low birth weight [median 2340 grams (1,895, 2,600)]. 63% required positive pressure ventilation. Advanced chronic kidney disease stage 4-5 at 1 year of age was predicted by neonatal characteristics: peak SCr ≥2 mg/dl, time to peak SCr > 6 days, discharge SCr ≥1.0 mg/dl, CysC ≥2.5 mg/l, urine protein:creatinine ≥4.8 mg/mg, urine microalbumin:creatinine ≥2.2 mg/mg. In infancy, a nadir SCr ≥0.5 mg/dl occurring before 160 days (5.3 months) of age was also predictive of advanced chronic kidney disease stage 4-5 at 1 year. Three patients died in the neonatal period, with 1 receiving kidney replacement therapy (KRT). Three additional patients required KRT before 12 months of age.

CONCLUSIONS

Even with definitive vesicoamniotic shunting for cLUTO, postnatal morbidity and mortality remain high, emphasizing the role of renal dysplasia, in spite of urinary diversion, in postnatal kidney dysfunction. Neonatal and infant biochemical parameters exhibit distinct trends that offer families and physicians a better understanding of the prognosis of childhood kidney function.

Fetal body MRI for fetal and perinatal management

Fetal magnetic resonance imaging (MRI) has become a valuable adjunct to ultrasound (US) in diagnosing fetal abnormalities. This review is intended to highlight the contribution of MRI in parental counselling and perinatal treatment. A state-of-the-art fetal MRI protocol with experts of maternal-fetal medicine present in the MRI suite allows emphasis on patient-centred care and maximises therapeutic options.

New Trends in Fetal Anesthesia

Fetal anesthesia teams must understand the pathophysiology and rationale for the treatment of each disease process. Treatment can range from minimally invasive procedures to maternal laparotomy, hysterotomy, and major fetal surgery. Timing may be in early, mid-, or late gestation. Techniques continue to be refined, and the anesthetic plans must evolve to meet the needs of the procedures. Anesthetic plans range from moderate sedation to general anesthesia that includes monitoring of 2 patients simultaneously, fluid restriction, invasive blood pressure monitoring, vasopressor administration, and advanced medication choices to optimize fetal cardiac function.

Clinical predictors of chronic kidney disease in congenital lower urinary tract obstruction

Congenital lower urinary tract obstruction is associated with oligohydramnios and significant perinatal mortality and long-term chronic kidney disease. The counseling of families facing this diagnosis, especially when prenatal intervention is proposed, is fraught with ambiguity. This review aims to equip the provider with the current evidence behind the conventional and novel biomarkers predictive of chronic kidney disease. The relevant clinical predictors are categorized by when they are identified, antenatally or postnatally, and as either anatomic or chemical. They are considered for their prognostic value and the challenges in obtaining them, specifically the risk to the fetus in the case of prenatal biomarkers. Serum creatinine in infancy is the traditional chemical biomarker of kidney function and continues to be a consistent predictor of future serum creatinine. β-2 microglobulin may provide earlier information regarding fetal glomerular and tubular function and is also predictive of long-term serum creatinine. Renal parenchymal area is an anatomic surrogate of nephron mass that is used in both prenatal and postnatal settings. Understanding the anatomic and chemical biomarkers is essential for future refinement of the staging algorithm used to distinguish which patients may benefit from early in utero intervention.

Fetal anesthesia: intrauterine therapies and immediate postnatal anesthesia for noncardiac surgical interventions

PURPOSE OF REVIEW

This review describes maternal and fetal anesthetic management for noncardiac fetal surgical procedures, including the management of lower urinary tract obstruction, congenital diaphragmatic hernia (CDH), myelomeningocele, sacrococcygeal teratoma, prenatally anticipated difficult airway and congenital lung lesions.

RECENT FINDINGS

Fetal interventions range from minimally invasive fetoscopic procedures to mid-gestation open surgery, to ex-utero intrapartum treatment procedure. Anesthetic management depends on the fetal intervention and patient characteristics. Anesthesia for most minimally invasive procedures can consist of intravenous sedation and local anesthetic infiltration in clinically appropriate maternal patients. Open fetal and ex-utero intrapartum treatment procedures require maternal general anesthesia with volatile anesthetic and other medications to maintain uterine relaxation. Tracheal balloons are a promising therapy for CDH and can be inserted via minimally invasive techniques. Management of the prenatally anticipated difficult airway during delivery and removal of tracheal balloons from patients with CDH during delivery can be clinically dynamic and require flexibility, seamless communication and a high-functioning, multidisciplinary care team.

SUMMARY

Maternal and fetal anesthetic management is tailored to the fetal intervention and the underlying health of the fetus and mother.

Biomaterials in fetal surgery

Fetal surgery and fetal therapy involve surgical interventions on the fetus in utero to correct or ameliorate congenital abnormalities and give a developing fetus the best chance at a healthy life. Historical use of biomaterials in fetal surgery has been limited, and most biomaterials used in fetal surgeries today were originally developed for adult or pediatric patients. However, as the field of fetal surgery moves from open surgeries to minimally invasive procedures, many opportunities exist for innovative biomaterials engineers to create materials designed specifically for the unique challenges and opportunities of maternal-fetal surgery. Here, we review biomaterials currently used in clinical fetal surgery as well as promising biomaterials in development for eventual clinical translation. We also highlight unmet challenges in fetal surgery that could particularly benefit from novel biomaterials, including fetal membrane sealing and minimally invasive myelomeningocele defect repair. Finally, we conclude with a discussion of the underdeveloped fetal immune system and opportunities for exploitation with novel immunomodulating biomaterials.

Effectiveness of Prenatal Intervention on the Outcome of Diseases That Have a Postnatal Urological Impact

We reviewed the literature addressing outcomes of fetal intervention of conditions that require post-natal urological management including lower urinary tract obstruction, hydrometrocolpos, congenital adrenal hyperplasia, and myelomeningocele. Despite several decades of fetal intervention for these conditions, benefits remain elusive in part because of the enormous difficulty of conducting prospective randomized studies. In this review, we reached the following conclusions: Prenatal intervention in lower urinary tract obstruction (LUTO) improves survival in the worst cases by improving pulmonary function and it may be advantageous for renal function, particularly in patients with adverse urine parameters.Prenatal treatment of female fetuses at risk of having congenital adrenal hyperplasia (CAH) reduces virilization. Non-invasive fetal DNA analysis allows earlier diagnosis, reducing the risk of treating with dexamethasone males and non-affected fetuses.Fetal treatment of myelomeningocele (MMC) is gaining momentum. Prospective studies including standardized urologic evaluation will determine if the encouraging results reported by some hold on the long term follow-up.

Branching morphogenesis of the urinary collecting system in the human embryonic metanephros

An elaborate system of ducts collects urine from all nephrons, and this structure is known as the urinary collecting system (UCS). This study focused on how the UCS is formed during human embryogenesis. Fifty human embryos between the Carnegie stage (CS) 14 and CS23 were selected from the Kyoto Collection at the Congenital Anomaly Research Center of Kyoto University, Japan. Metanephroses, including the UCS, were segmented on serial digital virtual histological sections. Three-dimensional images were computationally reconstructed for morphological and quantitative analyses. A CS timeline was plotted. It consisted of the 3-D structural morphogenesis of UCS and quantification of the total amount of end-branching, average and maximum numbers of generations, deviation in the metanephros, differentiation of the urothelial epithelium in the renal pelvis, and timing of the rapid expansion of the renal pelvis. The first UCS branching generation occurred by CS16. The average branching generation reached a maximum of 8.74 ± 1.60 and was already the twelfth in CS23. The total end-branching number squared between the start and the end of the embryonic period. UCS would reach the fifteenth branching generation soon after CS23. The number of nephrons per UCS end-branch was low (0.21 ± 0.14 at CS19, 1.34 ± 0.49 at CS23), indicating that the bifid branching occurred rapidly and that the formation of nephrons followed after. The renal pelvis expanded mainly in CS23, which was earlier than that reported in a previous study. The number of nephrons connected to the UCS in the expanded group (246.0 ± 13.2) was significantly larger than that of the pre-expanded group (130.8 ± 80.1) (P < 0.05). The urothelial epithelium differentiated from the zeroth to the third generations at CS23. Differentiation may have continued up until the tenth generation to allow for renal pelvis expansion. The branching speed was not uniform. There were significantly more branching generations in the polar- than in the interpolar regions (P < 0.05). Branching speed reflects the growth orientation required to form the metanephros. Further study will be necessary to understand the renal pelvis expansion mechanism in CS23. Our CS-based timeline enabled us to map UCS formation and predict functional renal capacity after differentiation and growth.