Fetal Megacystis: Etiologies, Management, and Outcome According to the Trimester

Obstructive or non-obstructive megacystis: a prenatal dilemma

Introduction

Diagnosis of prenatal megacystis has a significant impact on the pregnancy, as it can have severe adverse effects on fetal and neonatal survival and renal and pulmonary function. The study aims to investigate the natural history of fetal megacystis, to try to differentiate in utero congenital lower urinary tract obstruction (LUTO) from non-obstructive megacystis, and, possibly, to predict postnatal outcome.

Materials and methods

A retrospective single-center observational study was conducted from July 2015 to November 2023. The inclusion criteria were a longitudinal bladder diameter (LBD) >7 mm in the first trimester or an overdistended/thickened-walled bladder failing to empty in the second and third trimesters. Close ultrasound follow-up, multidisciplinary prenatal counseling, and invasive and non-invasive genetic tests were offered. Informed consent for fetal autopsy was obtained in cases of termination of pregnancy or intrauterine fetal demise (IUFD). Following birth, neonates were followed up at the same center. Patients were stratified based on diagnosis: LUTO (G1), urogenital anomalies other than LUTO ("non-LUTO") (G2), and normal urinary tract (G3).

Results

This study included 27 fetuses, of whom 26 were males. Megacystis was diagnosed during the second and third trimesters in 92% of the fetuses. Of the 27 fetuses, 3 (11.1%) underwent an abortion, and 1 had IUFD. Twenty-three newborns were live births (85%) at a mean gestational age (GA) of 34 ± 2 weeks. Two patients (neonates) died postnatally due to severe associated malformations. Several prenatal parameters were evaluated to differentiate patients with LUTO from those with non-LUTO, including the severity of upper tract dilatation, keyhole sign, oligohydramnios, LBD, and GA at diagnosis. However, none proved predictive of the postnatal diagnosis. Similarly, none of the prenatal parameters evaluated were predictive of postnatal renal function.

Discussion

The diagnosis of megacystis in the second and third trimesters was associated with live births in up to 85% of cases, with LUTO identified as the main cause of fetal megacystis. This potentially more favorable outcome, compared to the majority reported in literature, should be taken into account in prenatal counseling. Megacystis is an often misinterpreted antennal sign that may hide a wide range of diagnoses with different prognoses, beyond an increased risk of adverse renal and respiratory outcomes.

Long-Term Outcomes, Including Fetal and Neonatal Prognosis, of Renal Oligohydramnios: A Retrospective Study over 22 Years

OBJECTIVE

To assess the long-term outcome of renal oligohydramnios and risk factors for fetal, neonatal, and postneonatal death.

STUDY DESIGN

This retrospective cohort study included fetuses with prenatally detected renal oligohydramnios between 2002 and 2023. Patients who were lost to follow-up were excluded. Fetal, neonatal, and long-term outcomes were evaluated, and their risk factors were analyzed.

RESULTS

Of 131 fetuses with renal oligohydramnios, 46 (35%) underwent a termination of pregnancy, 11 (8%) had an intrauterine fetal death, 26 (20%) had a neonatal death, nine (7%) had a postneonatal death, and 39 (30%) survived. Logistic regression analyses showed that an earlier gestational age at onset (OR 1.16, 95% CI 1.01-1.37) was significantly associated with intrauterine fetal death; anhydramnios (OR 12.7, 95% CI 1.52-106.7) was significantly associated with neonatal death as a prenatal factor. Although neonatal survival rates for bilateral renal agenesis, bilateral multicystic dysplastic kidney (MCDK), and unilateral MCDK with contralateral renal agenesis were lower than for other kidney diseases, 1 case of bilateral renal agenesis and two of bilateral MCDK survived with fetal intervention. Kaplan-Meier overall survival rates were 57%, 55%, and 51% for 1, 3, and 5 years, respectively. In the Cox proportional hazards model, birth weight <2000 g (hazard ratio 7.33, 95% CI 1.48-36.1) and gastrointestinal comorbidity (hazard ratio 4.37, 95% CI 1.03-18.5) were significant risk factors for postneonatal death.

CONCLUSION

Long-term survival following renal oligohydramnios is a feasible goal and its appropriate risk assessment is important.

Single-center outcome analysis of 46 fetuses with megacystis after intrauterine vesico-amniotic shunting with the Somatex®intrauterine shunt

OBJECTIVES

To assess the spectrum of underlying pathologies, the intrauterine course and postnatal outcome of 46 fetuses with megacystis that underwent intrauterine vesico-amniotic shunting (VAS) with the Somatex® shunt in a single center.

METHODS

Retrospective analysis of 46 fetuses with megacystis that underwent VAS either up to 14 + 0 weeks (early VAS), between 14 + 1 and 17 + 0 weeks (intermediate VAS) or after 17 + 0 weeks of gestation (late VAS) in a single tertiary referral center. Intrauterine course, underlying pathology and postnatal outcome were assessed and correlated with the underlying pathology and gestational age at first VAS.

RESULTS

46 fetuses underwent VAS, 41 (89%) were male and 5 (11%) were female. 28 (61%) fetuses had isolated and 18 (39%) had complex megacystis with either aneuploidy (n = 1), anorectal malformations (n = 6), cloacal malformations (n = 3), congenital anomalies overlapping with VACTER association (n = 6) or Megacystis-Microcolon Intestinal-Hypoperistalsis Syndrome (MMIHS) (n = 2). The sonographic 'keyhole sign' significantly predicted isolated megacystis (p < 0.001). 7 pregnancies were terminated, 4 babies died in the neonatal period, 1 baby died at the age of 2.5 months and 34 (74%) infants survived until last follow-up. After exclusion of the terminated pregnancies, intention-to-treat survival rate was 87%. Mean follow-up period was 24 months (range 1-72). The underlying pathology was highly variable and included posterior urethral valve (46%), hypoplastic or atretic urethra (35%), MMIHS or prune belly syndrome (10%) and primary vesico-ureteral reflux (2%). In 7% no pathology could be detected postnatally. No sonographic marker was identified to predict the underlying pathology prenatally. 14 fetuses underwent early, 24 intermediate and 8 late VAS. In the early VAS subgroup, amnion infusion prior to VAS was significantly less often necessary (7%), shunt complications were significantly less common (29%) and immediate kidney replacement therapy postnatally became less often necessary (0%). In contrast, preterm delivery ≤ 32 + 0 weeks was more common (30%) and survival rate was lower (70%) after early VAS compared to intermediate or late VAS. Overall, 90% of liveborn babies had sufficient kidney function without need for kidney replacement therapy until last follow-up, and 95% had sufficient pulmonary function without need for mechanical respiratory support. 18% of babies with complex megacystis suffered from additional health restrictions due to their major concomitant malformations.

CONCLUSIONS

Our data suggest that VAS is feasible from the first trimester onward. Early intervention has the potential to preserve neonatal kidney function in the majority of cases and enables neonatal survival in up to 87% of cases. Despite successful fetal intervention, parents should be aware of the potential of mid- or long-term kidney failure and of additional health impairments due to concomitant extra-renal anomalies that cannot be excluded at time of intervention.

Postnatal surgical treatment and complications following intrauterine vesicoamniotic shunting with the SOMATEX® intrauterine shunt. A single center experience

INTRODUCTION

Intrauterine vesicoamniotic shunting (VAS) using a Somatex® shunt was shown to significantly affect survival of male fetuses with megacystis in suspected lower urinary tract obstruction (LUTO) [Figure 1]. Data on postnatal surgical management and complications are largely lacking.

OBJECTIVE

To describe the postnatal management of patients with prenatal VAS for megacystitis in suspected severe LUTO.

STUDY DESIGN

All male newborns with previous intrauterine VAS using a Somatex® shunt treated in our institution were retrospectively analyzed. We evaluated the spectrum of urethral pathologies and postnatal surgical management, especially focusing on shunt removal.

RESULTS

Between 2016 and 2022, 17 patients (all male) were treated postnatally in our institution after VAS for suspected severe LUTO. Five fetuses with dislocated shunts underwent re-implantation in utero. Overall, premature birth before the 38th week of gestation was observed in eight patients (8/17). Seven shunts could be removed without further anesthesia as a bedside procedure. Ten patients required surgical shunt removal under general anesthesia due to migration (59%). Laparoscopic shunt extraction was performed in 8/10 cases. Most frequently, dislocated shunts were located incorporated in the detrusor in eight cases and the removal required a bladder suture in 2/8 patients. In one case, the shunt was removed from the abdominal wall and in one case from the intestine wall [Figure 2]. Posterior urethral valves were found in 8/17 patients, 6/17 patients showed a urethral atresia and one patient had urethral duplication. In two patients, we identified a high grade bilateral vesicoureteral reflux without LUTO.

CONCLUSION

In our observation, more than half of the newborns with megacystis in suspected LUTO require a shunt removal surgery after early VAS using a Somatex® shunt. Urethral atresia may be found more frequently in these patients. These data should be taken into consideration for prenatal counselling of parents and planning of postnatal management.

Fetal uropathies: pre- and postnatal imaging, management and follow-up

Congenital uropathies are the most common fetal anomalies. They include a wide spectrum of anomalies ranging from mild pelvis dilation to complex urinary tract malformations. Prenatal imaging not only allows for their diagnosis but, in experienced hands, it can differentiate obstructive from refluxing or malformative uropathies. Such precise prenatal information allows for intervention before birth in select cases or for adapting the postnatal workup to provide a better long-term outcome. For the different types of congenital uropathies, we describe their prenatal presentations on US and the complementary role of fetal MRI where indicated. We correlate these findings with postnatal workup and summarize the updated neonatal diagnostic and clinical/surgical management.

Fetal Megacystis in the first trimester: Comparing management and outcomes between longitudinal bladder length groups

Fetal megacystis is a sonographic sign, defined in first trimester as a longitudinal bladder length (LBD)>7 mm. Different causes may be associated with megacystis and outcomes vary with many factors. There are no international guidelines on how to manage megacystis cases, and invasive testing is controversial when no other abnormalities are found. The main objective of this study is to compare etiologies, management and outcomes of fetuses with first trimester megacystis, specifically between groups of LBD≤15 mm and >15 mm. This is a retrospective cohort study of megacystis cases managed in a Prenatal Diagnosis Center, between January 2009 and September 2020. Descriptive and bivariate analysis were performed. We studied 43 fetuses: 67.4% with LBD≤15 mm and 32.6% with LBD>15 mm. We found an association between LBD and isolated Low Urinary Tract Obstruction (LUTO) (3.4% vs 64.3%; p<0.001) and with isolated megacystis (44.8% vs 0.0%; p = 0.001). No differences were seen regarding the presence of aneuploidies (31.0% vs 14.3%; p = 0.213). Invasive testing was performed in 93.0% of cases. Overall, we report 41.9% of live births, 39.5% of pregnancy termination and 18.6% of intrauterine fetal demise. We found a higher rate of live births in fetuses with LBD≤15 mm (55.2% vs 14.3%; p = 0.011). For a mean follow-up time of 20.6 months, we report one neonatal death and one case of renal insufficiency. In conclusion, isolated LUTO is more frequent if LBD>15 mm whereas isolated megacystis is more frequently found if LBD≤15 mm. If LBD≤15 mm, live birth rates and long-term outcomes seem to be enhanced.

Vesicoamniotic Shunting before 17 + 0 Weeks in Fetuses with Lower Urinary Tract Obstruction (LUTO): Comparison of Somatex vs. Harrison Shunt Systems

(1) Background: The aim of this study was to compare perinatal outcomes and complication rates of vesicoamniotic shunting (VAS) before 17 + 0 weeks in isolated LUTO (lower urinary tract obstruction) with the Somatex® intrauterine shunt vs. the Harrison fetal bladder shunt. (2) Methods: This is a retrospective cohort study in two tertiary fetal medicine centers. From 2004−2014, the Harrison fetal bladder shunt was used, and from late 2014−2017, the Somatex shunt. Obstetrics and pediatric charts were reviewed for complications, course of pregnancy, perinatal outcome, and postnatal renal function. (3) Results: Twenty-four fetuses underwent VAS with a Harrison (H) shunt and 33 fetuses with a Somatex (S) shunt. Live birth rates and survival to last follow-up were significantly higher in the Somatex group, at 84.8% and 81.8%, respectively, vs. 50% and 33.3% in the Harrison group (p = 0.007 and p < 0.001). The dislocation rate in the Somatex group (36.4%) was significantly lower than in the Harrison group (87.5%) (p < 0.001). The median time to dislocation was significantly different, at 20.6 days (H) vs. 73.9 days (S) (p = 0.002), as was gestational age at dislocation (17 (H) vs. 25 (S) weeks, p < 0.001). Renal function was normal in early childhood in 51% (S) vs. 29% (H) (p = 0.11). (4) Conclusions: VAS before 17 + 0 weeks gestational age with a Somatex shunt improves perinatal survival significantly and might even have a positive effect on renal function, probably due to the lower dislocation rates. A normal amount of amniotic fluid in the third trimester was the best predictor of normal renal function in early childhood.

Fetal therapy of LUTO (lower urinary tract obstruction) - a follow-up observational study

PURPOSE

Fetal megacystis (MC) can be severe and is mainly caused by fetal lower urinary tract obstruction (LUTO). Mortality of fetal LUTO can be high as a result of pulmonary hypoplasia and/or (chronic) renal insufficiency. Several technical procedures for vesicoamniotic shunting (VAS) were developed to improve fetal MC outcomes.

MATERIAL AND METHODS

We present the outcome of nine fetuses with MC who received VAS in the prenatal period (14 + 6 to 27 + 6 weeks GA) using the Somatex^® intrauterine shunt system. MC was defined as an increased longitudinal measurement of the bladder >15 mm. The median follow-up time after birth was 18 months.

RESULTS

Eight Fetuses had uncomplicated VAS intervention. One case developed PPROM 24 h after VAS leading to abortion. Pregnancy was later terminated in further two cases. All six live-born infants received intensive care treatment. Invasive-mechanical ventilation was necessary in one case who died 24 h post-partum of severe cardiac depression. Five infants who survived the follow-up time developed chronic renal insufficiency (CRI), with one infant developing end-stage renal failure requiring peritoneal dialysis.

CONCLUSION

Overall, 5 of 9 LUTO fetuses (55%) undergoing VAS with the Somatex^® intrauterine shunt system showed long-term survival beyond the neonatal period of 28 d (5/9; 55%) with varying morbidity.

Megacystis in the first trimester of pregnancy: Prognostic factors and perinatal outcomes

OBJECTIVE

To determine whether bladder size is associated with an unfavorable neonatal outcome, in the case of first-trimester megacystis.

MATERIALS AND METHODS

This was a retrospective observational study between 2009 and 2019 in two prenatal diagnosis centers. The inclusion criterion was an enlarged bladder (> 7 mm) diagnosed at the first ultrasound exam between 11 and 13+6 weeks of gestation. The main study endpoint was neonatal outcome based on bladder size. An adverse outcome was defined by the completion of a medical termination of pregnancy, the occurrence of in utero fetal death, or a neonatal death. Neonatal survival was considered as a favorable outcome and was defined by a live birth, with or without normal renal function, and with a normal karyotype.

RESULTS

Among 75 cases of first-trimester megacystis referred to prenatal diagnosis centers and included, there were 63 (84%) adverse outcomes and 12 (16%) live births. Fetuses with a bladder diameter of less than 12.5 mm may have a favorable outcome, with or without urological problems, with a high sensitivity (83.3%) and specificity (87.3%), area under the ROC curve = 0.93, 95% CI (0.86-0.99), p< 0.001. Fetal autopsy was performed in 52 (82.5%) cases of adverse outcome. In the 12 cases of favorable outcome, pediatric follow-up was normal and non-pathological in 8 (66.7%).

CONCLUSION

Bladder diameter appears to be a predictive marker for neonatal outcome. Fetuses with smaller megacystis (7-10 mm) have a significantly higher chance of progressing to a favorable outcome. Urethral stenosis and atresia are the main diagnoses made when first-trimester megacystis is observed. Karyotyping is important regardless of bladder diameter.

Predictive accuracy of prenatal ultrasound findings for lower urinary tract obstruction: A systematic review and Bayesian meta-analysis

BACKGROUND

Lower urinary tract obstruction (LUTO) is a rare but critical fetal diagnosis. Different ultrasound markers have been reported with varying sensitivity and specificity.

AIMS

The objective of this systematic review and meta-analysis was to identify the diagnostic accuracy of ultrasound markers for LUTO.

MATERIALS AND METHODS

We performed a systematic literature review of studies reporting on fetuses with hydronephrosis or a prenatally suspected and/or postnatally confirmed diagnosis of LUTO. Bayesian bivariate random effects meta-analytic models were fitted, and we calculated posterior means and 95% credible intervals for the pooled diagnostic odds ratio (DOR).

RESULTS

A total of 36,189 studies were identified; 636 studies were available for full text review and a total of 42 studies were included in the Bayesian meta-analysis. Among the ultrasound signs assessed, megacystis (DOR 49.15, [15.28, 177.44]), bilateral hydroureteronephrosis (DOR 41.33, [13.36,164.83]), bladder thickening (DOR 13.73, [1.23, 115.20]), bilateral hydronephrosis (DOR 8.36 [3.17, 21.91]), male sex (DOR 8.08 [3.05, 22.82]), oligo- or anhydramnios (DOR 7.75 [4.23, 14.46]), and urinoma (DOR 7.47 [1.14, 33.18]) were found to be predictive of LUTO (Table 1). The predictive sensitivities and specificities however are low and wide study heterogeneity existed.

DISCUSSION

Classically, LUTO is suspected in the presence of prenatally detected megacystis with a dilated posterior urethra (i.e., the keyhole sign), and bilateral hydroureteronephrosis. However, keyhole sign has been found to have modest diagnostic performance in predicting the presence of LUTO in the literature which we confirmed in our analysis. The surprisingly low specificity may be influenced by several factors, including the degree of obstruction, and the diligence of the sonographer at searching for and documenting it during the scan. As a result, providers should consider this when establishing the differential for a fetus with hydronephrosis as the presence or absence of keyhole sign does not reliably rule in or rule out LUTO.

CONCLUSIONS

Megacystis, bilateral hydroureteronephrosis and bladder wall thickening are the most accurate predictors of LUTO. Given the significant consequences of a missed LUTO diagnosis, clinicians providing counselling for prenatal hydronephrosis should maintain a low threshold for considering LUTO as part of the differential diagnosis.

Perinatal outcome and prognostic factors of fetal megacystis diagnosed at 11-14 week's gestation

OBJECTIVES

To evaluate aneuploidy rate, prognostic factors, and perinatal outcomes following a diagnosis of fetal megacystis at 11-14 week's gestation.

METHODS

A retrospective study of first trimester fetal megacystis from 2010 to 2020 was performed, including ultrasound finding, perinatal outcomes, pathology reports, genetic tests, and neonatal investigations.

RESULTS

A total of 98 cases of first trimester fetal megacystis was identified with an overall aneuploidy rate of 12%. There were 54% live births and 46% fetal losses including spontaneous fetal demise and elective termination. Among the 45 fetal losses, 64% had additional structural abnormalities at index ultrasound and final diagnoses were achievable in 64% cases. Among the 53 livebirths, additional ultrasound abnormalities were detected in only 1 fetus and spontaneous resolution of megacystis was detected in 96% of cases. The two cases where fetal megacystis persisted had major postnatal diagnoses: cloacal malformation and megacystis-microcolon-intestinal hypoperistalsis syndrome, respectively. Our data showed LBD ≥ 12 mm was the best individual predictor of adverse perinatal outcome and all 11 cases of lower urinary tract obstruction (LUTO) were diagnosed in fetuses with LBD ≥ 12 mm.

CONCLUSIONS

First trimester ultrasound provides important prognostic factors and isolated megacystis <12 mm is associated with a positive outcome.

Vesicoamniotic shunting for fetal megacystis in the first trimester with a Somatex® intrauterine shunt

Purpose

The objective was to evaluate the feasibility of vesicoamniotic shunting (VAS) in the first trimester with the Somatex^® intrauterine shunt and report on complications and neonatal outcome.

Methods

Retrospective cohort study of all VAS before 14 weeks at two tertiary fetal medicine centres from 2015 to 2018 using a Somatex^® intrauterine shunt. All patients with a first trimester diagnosis of megacystis in male fetuses with a longitudinal bladder diameter of at least 15 mm were offered VAS. All patients that opted for VAS after counselling by prenatal medicine specialists, neonatologists and pediatric nephrologists were included in the study. Charts were reviewed for complications, obstetric and neonatal outcomes.

Results

Ten VAS were performed during the study period in male fetuses at a median GA of 13.3 (12.6–13.9) weeks. There were two terminations of pregnancy (TOP) due to additional malformations and one IUFD. Overall there were four shunt dislocations (40%); three of those between 25–30 weeks GA.

Seven neonates were born alive at a median GA of 35.1 weeks (31.0–38.9). There was one neonatal death due to pulmonary hypoplasia. Neonatal kidney function was normal in the six neonates surviving the neonatal period. After exclusion of TOP, perinatal survival was 75%, and 85.7% if only live-born children were considered.

Conclusion

VAS in the first trimester is feasible with the Somatex^® Intrauterine shunt with low fetal and maternal complication rates. Neonatal survival rates are high due to a reduction in pulmonary hypoplasia and the rate of renal failure at birth is very low. VAS can be safely offered from the late first trimester using the Somatex^® intrauterine shunt.

The perineal midsagittal view in male fetuses - pivotal for assessing genitourinary disorders

A wide range of genitourinary pathologies can be diagnosed in utero, from a simple vesicoureteral reflux to a more complex disorder of sexual differentiation. The prognosis and neonatal management of these conditions differ significantly. Evaluation of the fetal perineal anatomy is paramount to making the right diagnosis. The aim of this pictorial essay is to show sonographers how to acquire a perineal midsagittal view in a male fetus, and to demonstrate how this specific view allows assessment of the urethra and penis, to differentiate various genitourinary pathologies.

Congenital urinary tract obstruction

Congenital bladder neck obstruction (or lower urinary tract obstruction [LUTO]) describes a heterogeneous group of congenital anomalies presenting with similar prenatal ultrasonographic findings of dilated posterior urethra, megacystis, hydronephrosis, oligohydramnios and often with associated renal dysplasia. Untreated LUTO has high rate of perinatal morbidity and mortality from associated pulmonary hypoplasia and early-onset renal failure in infancy. Ultrasonographic features and prospective fetal urinalysis may help in predicting the overall prognosis of congenital LUTO. Currently, fetal vesicoamniotic shunt (of various designs), and fetal cystoscopy and fulguration of the obstruction are potential prenatal interventions. Retrospective and prospective cohort studies and a relatively small randomized controlled trial have demonstrated these treatments may possibly improve perinatal survival. Despite this, concerns remain as to the high rates of renal impairment observed in paediatric survivors. A clinical prospective scoring/staging system may improve prenatal diagnostic criteria and case selection for fetal therapy.

Outcomes in fetuses diagnosed with megacystis: Systematic review and meta-analysis

OBJECTIVE

To explore the outcomes and prognostic factors associated with fetal megacystis (enlarged bladder).

STUDY DESIGN

The MEDLINE and EMBASE databases were searched for studies reporting on outcomes of fetal megacystis. The outcomes observed were chromosomal abnormalities, associated structural anomalies, spontaneous resolution, and survival rates. We also evaluated the potential role of fetal gender, oligohydramnios, gestational age at diagnosis, and intrauterine intervention as prenatal prognostic factors.

RESULTS

The search identified 558 articles in total, and 13 studies (1675 fetuses) were included in this systematic review. The overall incidences of chromosomal abnormalities and associated structural anomalies in fetal megacystis were 10% and 24%, respectively. Spontaneous resolution of megacystis occurred in 32% of fetuses, and 44% of fetuses were born alive and survived until the follow-up. The odds ratio of survival with oligohydramnios was 0.14, and the mean difference in gestational age at diagnosis between survival and non-survival was 3.43 weeks. No significant difference in survival rate was observed between the genders, and an intrauterine intervention did not significantly improve the prognosis.

CONCLUSIONS

A considerable proportion of fetuses with megacystis are born with a good prognosis. Oligohydramnios and lower gestational age at diagnosis are associated with worse outcomes.

Fetal megacystis: prediction of spontaneous resolution and outcome

OBJECTIVES

To investigate the natural history of fetal megacystis from diagnosis in utero to postnatal outcome, and to identify prognostic indicators of spontaneous resolution and postnatal outcome after resolution.

METHODS

This was a national retrospective cohort study. Fetal megacystis was defined in the first trimester as a longitudinal bladder diameter (LBD) ≥ 7 mm, and in the second and third trimesters as an enlarged bladder failing to empty during the entire extended ultrasound examination. LBD and gestational age (GA) at resolution were investigated with respect to likelihood of resolution and postnatal outcome, respectively. Sensitivity, specificity and area under the receiver-operating characteristics curve (AUC) were calculated.

RESULTS

In total, 284 cases of fetal megacystis (93 early megacystis, identified before the 18^th week, and 191 late megacystis, identified at or after the 18^th week) were available for analysis. Spontaneous resolution occurred before birth in 58 (20%) cases. In cases with early megacystis, LBD was predictive of the likelihood of spontaneous resolution (sensitivity, 80%; specificity, 79%; AUC, 0.84), and, in the whole population, GA at regression was predictive of postnatal outcome, with an optimal cut-off at 23 weeks (sensitivity, 100%; specificity, 82%; AUC, 0.91). In the group with early megacystis, the outcome was invariably good when resolution occurred before the 23^rd week of gestation, whereas urological sequelae requiring postnatal surgery were diagnosed in 3/8 (38%) cases with resolution after 23 weeks. In the group with late megacystis, spontaneous resolution was associated with urological complications after birth, ranging from mild postnatal hydronephrosis in infants with resolution before 23 weeks, to more severe urological anomalies requiring postnatal surgery in those with resolution later in pregnancy. This supports the hypothesis that an early resolution of megacystis is often related to a paraphysiological bladder enlargement that resolves early in pregnancy without consequences, while antenatal resolution occurring later in pregnancy (after the 23^rd week of gestation) should suggest a pathological condition with urological sequelae.

CONCLUSIONS

In fetal megacystis, LBD and GA at regression can be used as predictors of resolution and outcome, respectively. These parameters could help in fine-tuning the prognosis and optimizing the frequency of follow-up scans. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Prenatal detection of megacystis: not always an adverse prognostic factor. Experience in 25 consecutive cases in a tertiary referral center, with complete neonatal outcome and follow-up

INTRODUCTION

Megacystis is a condition of abnormal enlarged fetal bladder for gestational age, which is usually associated with urological malformations that may constitute a life-threatening condition for the baby.

OBJECTIVE

The purpose of this study was to assess the prognostic and etiological criteria of fetal megacystis and to describe the neonatal outcome in a large series collected in a single tertiary center.

STUDY DESIGN

A retrospective observational study was conducted between 2008 and 2012. We reviewed all consecutive cases of fetal megacystis diagnosed during routine ultrasound (US) screening. The following data were collected and analyzed: maternal age, gestational age at diagnosis, prenatal ultrasonographic details of the urinary system, extra-urinary ultrasonographic anomalies, fetal karyotype, pregnancy outcome, postnatal diagnosis, and medical/surgical follow-up.

RESULTS

Of the 25 fetuses included in this study, 76% were males. The mean gestational age (GA) at diagnosis was 23.1 ± 7.5 weeks (range 12-34), among them only four (16%) were diagnosed during the first trimester. Associated urological malformations were detected in 92% (n = 23) of the cases, while other malformations were detected in 36% (n = 9). Oligohydramnios or anyhydramnios were observed in 52% (n = 13) of the cases. Twelve (48%) fetuses were considered as having poor prognosis for renal function. Vesicocentesis with or without vesico-amniotic infusion were performed in 28% (n = 7) of the cases. Pregnancy outcome was surprisingly good, with only one case of prenatal death and survival rate of 96% (n = 24) of liveborn babies. Posterior urethral valve (PUV) (n = 9, 36%) was the most common etiology of the fetal megacystis, followed by persistent urogenital sinus (n = 2, 8%), Prune belly syndrome (n = 2, 8%) and bilateral vescico-ureteral reflux (VUR) (n = 2, 8%). Surgical or endoscopic procedures were performed in 75% (n = 18) of the cases. Six (24%) newborns presented with moderate/severe respiratory distress that requested invasive assisted ventilation. Three cases (n = 3, 12%) of perinatal death were observed due to severe impaired renal function. After a median follow-up of 29 months renal function was good in 79% (n = 19) of the cases.

CONCLUSIONS

Fetal megacystis may underline a wide range of associated pathologies with the highest prevalence of urinary malformation. Optimal counseling of the involved parents requires a multidisciplinary approach to allow the best management during the pregnancy and the perinatal period. Despite the high risk of renal failure, lung hypoplasia, and severe associated anomalies, the outcome of fetuses with megacystis could be improved thanks to an appropriate perinatal diagnosis and neonatal management.

[Ultrasound of the fetal urinary system during the first trimester of pregnancy]

The detection of abnormalities of the fetal urinary system in the first trimester of pregnancy is constantly improving, namely owing to the improved resolution of the image, the use of the endovaginal approach and thanks to sonographers' constant training. The pathological aspects, usually detected in the second trimester of pregnancy, can be suspected early in the first trimester and range from kidneys' cavity dilation to bilateral renal agenesis, polycystic kidney disease, multi-cystic dysplasia and bladder megavessia or bladder exstrophy. A poly-malformative syndrome is to be found out. The detection of an abnormality of the urinary tract requires a close ultrasound check. Very often, the pathological aspects tend to disappear spontaneously. In particular, the non-visualization of the bladder requires repeated examinations during the same session or even a little later in the pregnancy. We will carry out a review of the literature by pointing out the usual and unusual aspects of the fetal urinary system visible in the first trimester and we will as well propose an algorithm describing how to deal with abnormalities of the urinary tract that can be found out at first trimester ultrasound.

Fetal megacystis: A systematic review

Fetal megacystis is variably defined and understood. The literature on fetal megacystis was systematically reviewed, focusing on prenatal diagnosis, associations and outcomes. This yielded a total of 18 primary references and eight secondary references. Fetal megacystis has an estimated first-trimester prevalence of between 1:330 and 1:1670, with a male to female ratio of 8:1. In the first trimester, megacystis is most commonly defined as a longitudinal bladder dimension of ≥7 mm. Later in pregnancy, a sagittal dimension (in mm) greater than gestational age (in weeks) + 12 is often accepted. Megacystis can be associated with a thickened bladder wall, which has been objectively defined as >3 mm. Oligohydramnios is present in approximately half of all cases. The most common underlying diagnosis is posterior urethral valves (57%), followed by urethral atresia/stenosis (7%), prune belly syndrome (4%), megacystis-microcolon-intestinal-hypoperistalsis syndrome (MMIHS) (1%), and cloacal anomalies (0.7%). Karyotype anomalies are found in 15%, and include trisomy 18, trisomy 13 and trisomy 21. Ultrasound imaging alone is often insufficient to enable a definitive diagnosis, although it may indicate that a specific diagnosis is more likely. Overall, about 50% of reported fetuses with megacystis are terminated, but this proportion varies considerably between countries and over time. Prognostic stratification is evolving, with the most important factors being oligohydramnios, gestational age at diagnosis, degree of bladder enlargement, renal hyperechogenicity, karyotype, and sex.

CONCLUSIONS

This review demonstrated some consensus on the ultrasound criteria for defining fetal megacystis, and illustrated the spectrum of pathologies and their relative frequencies that can cause this condition. It also underlined important associated karyotype anomalies. To progress understanding of the natural history of enlarged fetal bladders, more accurate diagnostics are required, and risk stratification needs to be refined to facilitate prenatal counseling.

Fetal bladder outlet obstruction: Embryopathology, in utero intervention and outcome

Fetal bladder outlet obstruction (BOO), most commonly caused by posterior urethral valves (PUV), remains a challenging and multi-faceted condition. Evolving techniques, and refinement in ultrasound, optics and instrumentation, have increased our rate of prenatal diagnosis, and enabled valve ablation not only in smaller newborns, but also in fetuses. Long-term outcome studies have raised our awareness of the silent damage caused by bladder dysfunction and polyuria and encouraged their proactive management. In spite of our best efforts, the proportion of boys with PUV who progress to chronic and end-stage renal disease (ESRD) has not changed in the last 25 years. Evidence suggests a reduction in perinatal mortality following prenatal intervention, probably resulting from amelioration of oligohydramnios at the crucial time of lung development between 16 and 28 weeks' gestation, but no improvement in postnatal renal outcome. There are no bladder functional outcome studies in patients who have undergone prenatal intervention and hence the long-term effect of in utero defunctionalisation of the bladder is not known. This aim of this review is to revisit the embryopathology of fetal BOO, in particular the renal and bladder structural and functional changes that occur with in utero obstruction. The effect of earlier prenatal diagnosis, and therapy, on postnatal outcome is also explored and compared with outcomes published for traditional postnatal treatment.

Megacystis Microcolon Intestinal Hypoperistalsis Syndrome: Case Reports and Discussion of the Literature

Megacystis microcolon intestinal hypoperistalsis syndrome (MMIHS) is a rare intestinal dysmotility condition that also involves a dilated urinary bladder. It was believed to be an autosomal recessive condition, but genetic studies have suggested possibly an autosomal dominant inheritance pattern. Prenatal diagnosis can be challenging, but MRI and amniotic fluid/digestive fluid studies may be complementary investigations to improve diagnostic accuracy. Prognosis of MMIHS is generally poor and treatment is mostly supportive. To date, bowel transplantation remains the only viable treatment to restore bowel motility. Here we present two additional cases to contribute towards the scant literature on this condition.

Prenatal Diagnosis and Perinatal Outcomes of Congenital Megalourethra: A Multicenter Cohort Study and Systematic Review of the Literature

OBJECTIVES

The purpose of this study was to evaluate the prenatal findings and postnatal outcomes in fetuses with congenital megalourethra.

METHODS

This retrospective study reviewed our experience and the literature between 1989 and 2014. Prenatal findings were evaluated and compared with postnatal findings, including neonatal mortality and abnormal renal function (need for dialysis or renal transplantation).

RESULTS

Fifty fetuses with congenital megalourethra were analyzed, including 6 cases diagnosed in our centers. Most cases (n = 43 [86.0%]) were diagnosed in the second trimester. Only 1 case was diagnosed in the first trimester, whereas 6 cases (12.0%) were diagnosed in the third trimester. Thirty-five fetuses (70.0%) survived. Bilateral hydroureters were associated with perinatal death (P= .024). Among the survivors, 41.9% of the neonates had renal impairment. The following factors were associated with postnatal renal impairment: presence of severe oligohydramnios/anhydramnios (P = .033), bilateral hydronephrosis (P = .008), and earlier gestational age at delivery (P = .022).

CONCLUSIONS

In fetal megalourethra, bilateral hydroureters, bilateral hydronephrosis, and severe oligohydramnios/anhydramnios are associated with neonatal mortality and renal impairment.