Hyperechogenic fetal bowel: Current evidence-based prenatal diagnosis and management

Echogenic fetal bowel (EB) is a prenatal ultrasound finding (0.2%-1.4% of all pregnancies) defined as bowel of similar or greater echogenicity than surrounding bone. In fact, the ultrasound assessment is strongly subjective with inter-observer variability. The pathophysiology depends on the underlying condition, apparently related with meconium stasis and hypercellularity. It is often an isolated finding, with possible association with other structural anomalies. About the origin, it was observed in fetuses with cystic fibrosis, congenital infections, thalassemia, intraamniotic bleeding, fetal growth restriction. Fetuses with EB are at increased risk of adverse perinatal outcome, such as intrauterine growth restriction, placental dysfunction and perinatal death, highlighting the need for a thorough antenatal management and post-natal follow-up. It seems to be associated with a plenty of conditions, such as a poor fetal outcome, fetal growth restriction and placental dysfunction. Therefore management requires a multidisciplinary approach with different specialties' involvement and the prognosis is influenced by the underlying pathophysiology. In this complex scenario, the present review aims to define the clinical pathway which should be offered to pregnant women in case of finding of fetal EB ultrasound marker, to rule out any suspected pathological cause.

Echogenic Bowel as an Indicator of Necrotizing Enterocolitis in a Term Newborn

A 3.5-kilogram infant was born at 40 weeks gestation with an uncomplicated delivery. Prenatal ultrasounds showed echogenic bowel and a ventricular septal defect (VSD), of no clinical significance. Abdominal radiographs showed pneumatosis at 21, 36, and 48 hours of life (HOL). She was treated for necrotizing enterocolitis (NEC) with intravenous antibiotics and parenteral nutrition for 7 days, before working up on feeds and discharging home with breast milk. The only prenatal finding in this case was hyperechogenic bowel, which is a soft marker and often disregarded in the absence of other signs. Chronic intrauterine gut ischemia can cause hyperechogenicity of the bowel. That same intrauterine gut ischemia may have been responsible for NEC in our patient. If a patient has persistent echogenic bowel on prenatal imaging, a critical need exists to make sure NEC is not present.

Prenatal chromosomal microarray analysis in 2466 fetuses with ultrasonographic soft markers: a prospective cohort study

BACKGROUND

Soft markers are nonspecific findings detected by ultrasonography during the second trimester that are often transient and nonpathologic but may imply an increased risk of underlying fetal aneuploidy. However, large-scale prospectively stratified studies focusing on the prevalence of chromosomal aberrations, including copy number variants, in fetuses with different types of isolated soft markers have rarely been published in the literature.

OBJECTIVE

This study aimed to investigate clinical outcomes in fetuses with isolated soft markers by single nucleotide polymorphism array with long-term follow-up and to propose a diagnostic algorithm based on specific types of soft markers.

STUDY DESIGN

The prevalence of fetal isolated soft markers was 13.2% (7869 of 59,503). A total of 2466 fetuses with ultrasonographic soft markers during the second trimester, which were subjected to single nucleotide polymorphism array with long-term follow-up, were selected in this prospective study over a 5-year period. Soft markers were categorized into 12 groups. The demographic profile and chromosomal microarray analysis detection results were analyzed and compared among different groups.

RESULTS

The overall prevalence of chromosomal aberrations in fetuses with soft markers was 4.3% (107 of 2466), which comprised 40.2% with numeric chromosomal abnormalities, 48.6% with pathogenic copy number variants, and 11.2% with likely pathogenic copy number variants. The incidence of numeric chromosomal abnormalities was significantly higher in multiple soft markers (5.5% vs 1.5%; P=.001) and the thickened nuchal fold group (8.3% vs 1.7%; P=.024). Meanwhile, the incidence of pathogenic copy number variants was significantly higher in multiple soft markers (5.5% vs 2.4%; P=.046) and the short femur length group (6.6% vs 2.2%; P<.0001). The incidences of pathogenic copy number variants in fetuses with isolated echogenic intracardiac focus, enlarged cisterna magna, choroid plexus cysts, echogenic bowel, or single umbilical artery were lower than 1.5%. The normal infant rate in fetuses without chromosomal aberrations was 91.7%; however, it was significantly lower in the mild ventriculomegaly (86.2% vs 93.0%; P<.0001) and short femur length groups (71.4% vs 93.6%; P<.0001).

CONCLUSION

The potential chromosomal aberrations and clinical prognoses varied widely among different types of isolated soft markers. Pathogenic copy number variants are more often present in specific soft markers, especially when multiple soft markers are found. Thus, a specific soft marker type-based prenatal genetic testing algorithm was proposed.

Prenatal Ultrasound Suspicion of Cystic Fibrosis in a Multiethnic Population: Is Extensive CFTR Genotyping Needed?

In families without a Cystic Fibrosis (CF) history, fetal ultrasound bowel abnormalities can unexpectedly reveal the disease. Isolated or in association, the signs can be fetal bowel hyperechogenicity, intestinal loop dilatation and non-visualization of fetal gallbladder. In these cases, search for CF transmembrane conductance regulator (CFTR) gene mutations is part of the recommended diagnostic practices, with a search for frequent mutations according to ethnicity, and, in case of the triad of signs, with an exhaustive study of the gene. However, the molecular diagnosis remains a challenge in populations without well-known frequent pathogenic variants. We present a multiethnic cohort of 108 pregnancies with fetal bowel abnormalities in which the parents benefited from an exhaustive study of the CFTR gene. We describe the new homozygous p.Cys1410* mutation in a fetus of African origin. We did not observe the most frequent p.Phe508del mutation in our cohort but evidenced variants undetected by our frequent mutations kit. Thanks to the progress of sequencing techniques and despite the difficulties of interpretation occasionally encountered, we discuss the need to carry out a comprehensive CFTR study in all patients in case of fetal bowel abnormalities.

First trimester expression of anorectal malformation: Case report and review of the literature

A 26-years-old woman, underwent an ultrasound examination at 13.4 weeks. A cystic structure was identified in the right lower abdomen. Gradually, the cystic mass was replaced by echogenic content and eventually attained the appearance of hyperechoic bowel. At 21.2 weeks, the anal sphincter could not be demonstrated which was consistent with the diagnosis of isolated anal agenesis. Amniocentesis revealed 46XY karyotype with normal comparative genomic hybridization. After termination of pregnancy at 23 weeks, an autopsy revealed an isolated high type anorectal malformation (ARM) without fistula. We reviewed all 14 cases reported in the literature of first trimester sonographic expression of ARM.

Incidence and Carrier Frequency of CFTR Gene Mutations in Pregnancies With Echogenic Bowel in Nova Scotia and Prince Edward Island

OBJECTIVE

Fetal echogenic bowel (echogenic bowel) is associated with cystic fibrosis (CF), with a reported incidence ranging from 1% to 13%. Prenatal testing for CF in the setting of echogenic bowel can be done by screening parental or fetal samples for pathogenic CFTR variants. If only one pathogenic variant is identified, sequencing of the CFTR gene can be undertaken, to identify a second pathogenic variant not covered in the standard screening panel. Full gene sequencing, however, also introduces the potential to identify variants of uncertain significance (VUSs) that can create counselling challenges and cause parental anxiety. To provide accurate counselling for families in the study population, the incidence of CF associated with echogenic bowel and the carrier frequency of CFTR variants were investigated.

METHODS

All pregnancies for which CF testing was undertaken for the indication of echogenic bowel (from Nova Scotia and Prince Edward Island) were identified (January 2007-July 2017). The CFTR screening and sequencing results were reviewed, and fetal outcomes related to CF were assessed.

RESULTS

A total of 463 pregnancies with echogenic bowel were tested. Four were confirmed to be affected with CF, giving an incidence of 0.9% in this cohort. The carrier frequency of CF among all parents in the cohort was 5.0% (1 in 20); however, when excluding parents of affected fetuses, the carrier frequency for the population was estimated at 4.1% (1 in 25). CFTR gene sequencing identified an additional VUS in two samples.

CONCLUSION

The incidence of CF in pregnancies with echogenic bowel in Nova Scotia and Prince Edward Island is 0.9%, with an estimated population carrier frequency of 4.1%. These results provide the basis for improved counselling to assess the risk of CF in the pregnancy, after parental carrier screening, using Bayesian probability. Counselling regarding VUSs should be undertaken before gene sequencing.

The Welsh study of mothers and babies: protocol for a population-based cohort study to investigate the clinical significance of defined ultrasound findings of uncertain significance

BACKGROUND

Improvement in ultrasound imaging has led to the identification of subtle non-structural markers during the 18 - 20 week fetal anomaly scan, such as echogenic bowel, mild cerebral ventriculomegaly, renal pelvicalyceal dilatation, and nuchal thickening. These markers are estimated to occur in between 0.6% and 4.3% of pregnancies. Their clinical significance, for pregnancy outcomes or childhood morbidity, is largely unknown. The aim of this study is to estimate the prevalence of seven markers in the general obstetric population and establish a cohort of children for longer terms follow-up to assess the clinical significance of these markers.

METHODS/DESIGN

All women receiving antenatal care within six of seven Welsh Health Boards who had an 18 to 20 week ultrasound scan in Welsh NHS Trusts between July 2008 and March 2011 were eligible for inclusion. Data were collected on seven markers (echogenic bowel, cerebral ventriculomegaly, renal pelvicalyceal dilatation, nuchal thickening, cardiac echogenic foci, choroid plexus cysts, and short femur) at the time of 18 - 20 week fetal anomaly scan. Ultrasound records were linked to routinely collected data on pregnancy outcomes (work completed during 2012 and 2013). Images were stored and reviewed by an expert panel.The prevalence of each marker (reported and validated) will be estimated. A projected sample size of 23,000 will allow the prevalence of each marker to be estimated with the following precision: a marker with 0.50% prevalence to within 0.10%; a marker with 1.00% prevalence to within 0.13%; and a marker with 4.50% prevalence to within 0.27%. The relative risk of major congenital abnormalities, stillbirths, pre-term birth and small for gestational age, given the presence of a validated marker, will be reported.

DISCUSSION

This is a large, prospective study designed to estimate the prevalence of markers in a population-based cohort of pregnant women and to investigate associations with adverse pregnancy outcomes. The study will also establish a cohort of children that can be followed-up to explore associations between specific markers and longer-term health and social outcomes.