Antenatal diagnosis of congenital anterior abdominal wall defects

60 Pages·2015·7.44 MB·English

Antenatal diagnosis of congenital anterior abdominal wall
defects: A holistic approach
Poster No.: C-2612
Congress: ECR 2015
Type: Educational Exhibit
Authors: 1 2 2 3
M. D. Mahajan , R. N. Chaubal , N. G. CHAUBAL , S. Garg , R.
4 4 1 2 3
M. Kakkar , S. S. Soneji ; Bangalore/IN, THANE/IN, Mumbi/IN,
4
Mumbai/IN
Keywords: Abdomen, Obstetrics (Pregnancy / birth / postnatal period), Foetal
imaging, Ultrasound, Ultrasound-Colour Doppler, Ultrasound-
Spectral Doppler, Surgery, Diagnostic procedure, Intrauterine
diagnosis, Congenital, Hernia, Education and training
DOI: 10.1594/ecr2015/C-2612
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Page 1 of 60
Learning objectives
1.1 INTRODUCTION:
Fetal anterior abdominal wall defect (AAWD) is an important finding of antenatal
ultrasonography; the etiology of which ranges from 'physiological' or 'an isolated anomaly'
to 'polymalformative syndromes' and 'lethal complex malformations'. One must be aware
of several crucial predictors of viability and prognosis. A detailed ultrasound examination
is required to exclude co-existent structural anomalies (especially cardiac) and for
consideration of karyotyping.
1.2 THE LEARNING OBJECTIVES OF THIS POSTER ARE:
• A systematic approach to AAWD in a clinical setting with prenatal
ultrasonography
• An overview of spectrum of etiologies and their key diagnostic features, viz.
Omphalocele, Gastroschisis, Pentology of Cantrel (POC), Limb body wall
complex (LBWC), Amniotic band syndrome, Bladder exstrophy, Cloacal
exstrophy, OEIS complex, and Prune belly syndrome.
• Important prognostic and management implications
1.3 OVERVIEW OF HEADINGS:
1.0 Learning objectives
1.1 Introduction
1.2 Learning objectives
1.3 Overview of headings
2.0 Background
2.1 Embryology
2.2 Incidence of anterior abdominal wall defects
2.3 Obstetric ultrasound protocol & other screening tests
2.3.1 In first trimester
2.3.2 In second trimester
2.3.3 In third trimester
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3.0 Findings and procedure details
3.1 Omphalocele
3.2 Gastroschisis
3.3 Pentology of Cantrel (POC)
3.4 Limb body wall complex (LBWC)
3.5 Amniotic band syndrome
3.6 Bladder exstrophy
3.7 Cloacal exstrophy
3.8 OEIS complex
3.9 Prune belly syndrome
4.0 Conclusion
Background
2.1 EMBRYOLOGY:
Normal development of anterior abdominal wall depends on the fusion of four ecto-
th
mesodermic folds- cephalic, caudal and two lateral. This process begins by the 6 week
th
and is completed by the 8 week of gestation.
• Failure of these folds to migrate centrally results in different types of anterior
abdominal wall defects. [1] (Table 1)
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Table 1: Failure of central migration of four ecto-mesodermic folds results in different
types of anterior abdominal wall defects.
References: "Diagnostic and Interventional Radiology, Manipal University, Manipal
Hospital - Bangalore/IN 2015"
• Abnormal involution of right umbilical vein (normally occurring in 6th-7th
week) or vascular accident involving omphalo-mesenteric artery (considered
less likely) are the two mechanisms proposed for Gastroschisis.
• Complete failure of body folding along all three axes results in body stalk
deformity, also known as Limb body wall complex.
• Failure of fusion of lateral folds in thorax, with failure of development of
transverse septum of diaphragm is considered as the possible etiology for
Pentalogy of Cantrell. Other components of pentalogy are a consequence
of this initial failure. Midline developmental field defect is believed to account
for facial clefts and encephalocele, which are sometimes present.
• Bladder extrophy: Persistance of cloacal membrane and its failure to
retract normally prevents ingrowth of mesenchymal cells. These cells are
responsible for normal development of lower anterior abdominal wall.
Eventually the cloacal membrane ruptures and exposes the bladder mucosa
directly to amniotic cavity.
• Descent of urogenital septum separates urogenital sinus and hindgut. This
is the important embryological event that differentiates bladder exstrophy
from cloacal exstrophy. Cloacal exstrophy develops before the descent
of urogenital septum, resulting in anomalies of both, genitourinary and
gastrointestinal tracts.
• OEIS syndrome is believed to result from a single defect in the
development of infra-umbilical mesoderm. Hence it is associated with
abdominal wall, cloacal and spinal defects.
Although etiologies of AAWD are likely to be widely discrepant, the pathophysiology of
each defect leads to key characteristics that make it possible to differentiate one entity
from another. [1][2]
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2.2 INCIDENCE OF ANTERIOR ABDOMINAL WALL DEFECTS:
Table 2: Incidence of different etiologies of anterior abdominal wall defects [1,9]
References: "Diagnostic and Interventional Radiology, Manipal University, Manipal
Hospital - Bangalore/IN 2015"
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2.3 OBSTETRIC ULTRASOUND PROTOCOL & OTHER SCREENING TESTS:
As a standard of care, following protocol maximizes the possibility of detecting as many
fetal abnormalities as possible while acknowledging that more detailed or specialized
examinations may be necessary. [3][4]
• First trimester ultrasound (11-14 weeks)
• Second trimester ultrasound (18-22 weeks)
• Third trimester ultrasound (31-33 weeks)
Physiological variations/ anomalies at different stages of fetal development prompt
following actions:
• No change in the routine screening protocol
• Comprehensive/ targeted scan with attention to specific detail
• Further evaluation with MRI, amniocentesis and karyotyping
• Prognostication of fetal anomaly
• Prenatal consultation and counseling regarding continuation or termination
of pregnancy
• Genetic counseling, implications on future pregnancies.
Anterior abdominal wall defects present as abnormalities in various screening tests
depending on the gestational age. Role of antenatal ultrasonography, maternal serum
Alpha-fetoprotein and Amniocentesis have been summarized in this section.
2.3.1 ANTERIOR ABDOMINAL WALL ANOMALIES IN FIRST TRIMESTER (11-14
WEEKS)
First trimester ultrasound examination traditionally has been used to assess fetal viability,
to accurately date the pregnancy and for screening of fetal nuchal translucency thickness.
Early anatomical survey is possible (however, not mandatory) in first trimester with high
resolution trans-abdominal and especially with trans-vaginal ultrasound.
Following limitations must be acknowledged while screening for structural anomalies in
first trimester:
• Varying normal structural appearances of fetal development
• Structural defects may subsequently resolve
• Early detection of anomalies in fetuses that might spontaneously miscarry
• No evidence to support that first trimester scan can replace the 20 week
scan in a low-risk population.
Advantages, however of early anatomical survey are:
• Reassurance of normally developing fetus.
• Particularly important in high risk pregnancies with a previous fetal anomaly
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• Option of earlier termination of pregnancy with lower mortality and morbidity
of a surgical procedure in first trimester.
Key learning points:
Checklist for anatomical survey pertaining to AAWD in first trimester-
• Measure abdominal girth
• Check for cord insertion
• th
Disappearance of physiological hernia by 12 week.
• Stomach and its location- Visible by 11wks. Intrathoracic/ intraabdominal/
exteralised
• Location of liver and heart
• Check for bladder (<7mm) and
• Check for two supravesicle arteries (=3VC)
2.3.1.1 PHYSIOLOGICAL HERNIA- THE GREAT MIMICK OF OMPHALOCELE
At 8-10 weeks of gestation, all fetuses demonstrate physiologic umbilical herniation of
the midgut that is visualized as a hyperechogenic mass in the base of umbilical cord.
Retraction into the abdominal cavity occurs at 10-12 weeks and is completed by 11 weeks
and 5 days. [5][6]
Key learning points:
• Maximum dimension of normal bowel herniation is 7 to 10mm.
• Another criteria for predicting possible anomaly at 12 weeks is 'Crown-
rump length > 44 mm with persistent herniation'.
• Generally, the accepted recommendation is that the diagnosis of
abdominal wall defect be delayed until 14 weeks' gestation to account for
any potential errors in gestational dating. [7]
• Herniated liver is never normal.
• Hypoechoic band beneath echogenic fetal skin may potentially be
confused with ascites.
2.3.1.2 NUCHAL TRANSLUCENCY SCREENING:
Fetal nuchal translucency is one of the non-invasive screening methods for chromosomal
abnormalities and is often performed in first trimester (11-14weeks). It is important to note
that several extensive abdominal wall defects with other structural anomalies present
with increased NT measurement. (Table 3)
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Table 3: Anterior abdominal wall defects that may present with increased thickness of
nuchal translucency.
References: "Diagnostic and Interventional Radiology, Manipal University, Manipal
Hospital - Bangalore/IN 2015"
2.3.2 ANTERIOR ABDOMINAL WALL ANOMALIES IN SECOND TRIMESTER (18-22
WEEKS)
Current standard of care in screening for fetal structural abnormalities is a detailed
scan in the second trimester, most commonly at 20 weeks' gestation.
For pregnancies in which isolated omphalocele is detected at early ultrasound, follow-up
scan is adviced specially at 20-24 weeks gestation for the detection of late-manifesting
fetal anomalies. Follow-up ultrasound also helps in detection of complete disappearance
of a small defect, which may occur later in the pregnancy. [8]
2.3.2.1 ABDOMINAL GIRTH FOR CALCULATION OF GESTATIONAL AGE
Measurement of abdominal circumference can be inaccurate and should be excluded
from biometric calculations in a fetus with anterior abdominal wall defect. (Table 6)
Table 4: Miscalculation of gestational age by measurement of abdominal
circumference in presence of wall defects.
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References: "Diagnostic and Interventional Radiology, Manipal University, Manipal
Hospital - Bangalore/IN 2015"
2.3.2.2 MATERNAL SERUM BIOCHEMISTRY:
As a part of the serological screen for chromosomal abnormalities, maternal serum alpha
feto protein (MSAFP) test is performed in second trimester (between 15-18 weeks). One
of the several causes of raised MSAFP is anterior abdominal wall defect. Hence, thorough
assessment of the abdominal wall is a prerequisite of any second trimester anomaly scan,
especially in pregnancies complicated with raised MSAFP. (Table 4)
Table 5: Anterior abdominal wall defects that may present with elevated maternal
serum alpha-fetoprotein (MSAFP).
References: "Diagnostic and Interventional Radiology, Manipal University, Manipal
Hospital - Bangalore/IN 2015"
2.3.2.3 INVASIVE TESTS FOR KARYOTYPING:
Chorionic villous sampling (11-14 weeks) and Amniocentesis (15-18 weeks) are the
invasive screening tests performed for appropriate clinical indications. (Table 5)
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Table 6: Role of karyotyping in anterior abdominal wall defects.
References: "Diagnostic and Interventional Radiology, Manipal University, Manipal
Hospital - Bangalore/IN 2015"
2.3.3 ANTERIOR ABDOMINAL WALL ANOMALIES IN THIRD TRIMESTER (31-33
WEEKS)
Isolated omphalocele, bladder exstrophy, gastroschisis are some of the etiologies with
high survival rate and low long-term morbidity.
In such pregnancies, the third trimester ultrasonography is helpful to
• Assess evolution of anomalies diagnosed in second trimester
• Watch for associated complications
• Monitor fetal growth and fetal distress
Images for this section:
Table 1: Failure of central migration of four ecto-mesodermic folds results in different
types of anterior abdominal wall defects.
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