Anatomía normal y patológica del abdomen fetal

1. 7/19/2011
Ultrasound Evaluation
Of the Fetal Abdomen
Mani Montazemi, RDMS
Director of Ultrasound Research & Education
Geisinger Medical Center
Danville, Pennsylvania
Fetal Abdomen
Current Official Practice Guideline
• Abdomen
– Anterior abdominal wall
– Cord insertion
– Stomach
• Presence, size, situs
– Kidneys
– Bladder
– Number of umbilical cord vessels
Fetal Abdomen
Scanning Tips
Fetal Abdomen
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2. 7/19/2011
Fetal Stomach
• Wide range of shapes
– Round to oval to kidney-shaped
• Wide range of sizes
– 4mm to 4cm
• Variable filling and emptying
– Based on fetal swallowing and peristalsis
Fetal Abdomen
Non-visualization of the Stomach
• < 19 wks, 50% ABNL
• > 19 wks, 100% ABNL
Fetal Abdomen
Esophageal Atresia
Fetal Abdomen
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3. 7/19/2011
Esophageal Atresia
• Incidence – 1 in 2500 to 4000 live births
• Overall detection rate – only 50%
– Most of the polyhydramnios occur after 24 weeks
– S ll stomach bubble could be dismissed as being
Small h b bbl ld b di i d b i
normal
Fetal Abdomen
Esophageal Atresia
• Small stomach depend on the type of
esophageal atresia
• 5 types - most common with
yp
tracheoesophageal fistula
– Fluid may cross the fistula
– Gastric secretions may accumulate
Fetal Abdomen
Esophageal Atresia
• High incidence of additional
anomalies > 50%
– Cardiac, other GI, GU track,
CNS, Facial, skeletal, T18/21
• 40 % have IUGR
• Incidence three times higher
in twins
• Classic findings
– Polyhydramnios
– Absent or small stomach
bubble
Fetal Abdomen
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4. 7/19/2011
Non-visualization or
Always Small Stomach (< 1cm)
Causes:
• High Gastrointestinal obstruction
– Mouth to esophagus
• Narrow/compressed chest
• Thoracic or neck mass
• Swallowing disorders
• Defect or mass in the fetal mouth (clefts)
• Severe neurologic or muscular abnormalities
Fetal Abdomen
What do you see?
Fetal Abdomen
Duodenal Obstruction
Large, obstructed stomach and a distended proximal duodenum
Fetal Abdomen
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5. 7/19/2011
Duodenal Obstruction
• Two cystic structures in the abdomen that
communicate with each other
– Classic “double bubble”
Fetal Abdomen
Duodenal Obstruction
• Can be seen as early as 22 weeks, usually it’s
not apparent up until 29-32 weeks
• Polyhydramnios after 24 weeks
– Detection rate = only 50%
• Associated with a 30% incidence of trisomy 21
• Associated with VACTERL complex
Fetal Abdomen
VACTERL Complex
Vertebral defects
Anal atresia
Cardiac defects
Tracheoesophageal fistula
Esophageal atresia
Renal anomalies
Limb defects
Fetal Abdomen
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6. 7/19/2011
Duodenal Obstruction
Majority of cases are due to mechanical problems
• Intrinsic causes – structural abnormalities
– Atresia (42%)
• half of all duodenal atresias occur with Down syndrome, although
conversely, few cases of Down syndrome have duodenal atresia
– Diaphragmatic web (10%)
– Stenosis (38%)
• Extrinsic causes – external cause
– Annular pancreas
– Malrotation
– Ladd’s bands
Fetal Abdomen
Duodenal Obstruction
• Prognosis is dependent
upon whether other
anomalies are present
and their severity
Fetal Abdomen
Polyhydramnios is a constant
feature in all intestinal atresia
Fetal Abdomen
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7. 7/19/2011
Ventral Wall Defects
Omphalocele Gastroschisis
– Central defect – Periumbilical defect
– Associated anomalies are common – Associated anomalies are uncommon
– High risk of aneuploidy – Little to no risk of aneuploidy
– High rate of bowel related
complications
– Associated with substance abuse &
medications
Fetal Abdomen
Omphalocele
• Herniation of intraabdominal contents
into the base of the cord
• ALWAYS covered by a membrane
Fetal Abdomen
Omphalocele
• Umbilical cord inserts onto membrane
– In large defects may be displaced eccentrically
• The herniated bowel is NOT directly exposed to
amniotic fluid
• Bowel usually does not thicken or dilate
Fetal Abdomen
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8. 7/19/2011
Is This an Omphalocele?
Fetal Abdomen
Pseudo-Omphalocele
Caused by scanning oblique or
by excessive transducer pressure
Fetal Abdomen
Omphalocele
Can be a small or large wall defect
Fetal Abdomen
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9. 7/19/2011
Omphalocele
• Small
– Failure of normal midgut rotation
– Cord midpositioned
– Usually
Us all contains onl bowel
only bo el
– Associated with chromosomal
anomalies
Fetal Abdomen
Omphalocele
• Large
– Failure of anterior abdominal
wall closure
– Cord eccentric
– May contain organs
– Scoliosis
– Associated with structural
anomalies
Fetal Abdomen
Omphalocele
Measurements of AC
inaccurate and should
be excluded from
biometric calculations
Fetal Abdomen
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10. 7/19/2011
Omphalocele
• IUGR has been reported in 20% of patients
• 50% have associated anomalies (20% cardiac)
• 30% are associated with trisomy 13 & 18
• Elevated maternal serum alpha-fetoprotein (70%)
Fetal Abdomen
Omphalocele
• Omphalocele and cord cyst may co-exist
– Whartons jelly cyst – mucoid degeneration of Wharton Jelly
– Allantoic cyst – always near insertion site
– Omphalomesenteric duct cyst – associated with intraabdominal
mesenteric cysts
Jane J.K. Burns, RDMS
Fetal Abdomen
Diagnostic Challenge
Separate from but contiguous with the bladder
Fetal Abdomen
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11. 7/19/2011
Patent Urachus With Allantoic Cyst
Urachus is an embryological remnant of the
allantois which runs from the apex of the bladder
through the umbilical ring to terminate in the
proximal umbilical cord
Yolk Stalk
Allantoic Stalk
Umbilical Cord
Cloaca
Fetal Abdomen
A Ruptured Omphalocele
Can Resemble Gastroschisis
Fetal Abdomen
Omphalocele @11 Weeks ?
Potential Pitfall
Fetal Abdomen
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12. 7/19/2011
Normal Midgut Herniation
• Fetal bowel normally herniates into the base
of the umbilical cord at approx. the 7-8 weeks
MA
• Detected sonographically from 9-11 wks
9 11
• Should not be visible by 12 week
“Possible Anomaly”
CRL > 44mm with persistent herniation
Maximum dimension of abdominal mass > 7mm
Fetal Abdomen
Normal Midgut Herniation
• This appearance should not be mistaken for a
ventral wall defect
Fetal Abdomen
Midgut (umbilical) herniation
beyond the 12th week of gestation
has to be considered pathological
Fetal Abdomen
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13. 7/19/2011
Gastroschisis
Small defect to right of cord insertion
No membrane over bowel
Fetal Abdomen
Gastroschisis
• Incidence is 1 in 3000 births
– Varies considerably with
maternal age
– Strong association reported
among younger patients
• Less likely for organ
herniation
• Variable amounts of bowel
herniated
• Bowel floats within
amniotic fluid
Fetal Abdomen
Gastroschisis
• Hepatic herniation is less frequent with
gastroschisis than with omphaloceles
Fetal Abdomen
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14. 7/19/2011
Gastroschisis
• Small defect (2-4cm)
Fetal Abdomen
Gastroschisis
• Associated anomalies in about < 10% of fetuses
• IUGR in up to 50%
• No chromosomal abnormalities
• Elevated maternal serum alpha-fetoprotein (70%)
alpha fetoprotein
Fetal Abdomen
Gastroschisis
• Oligohydramnios
– More common than polyhydramnios
– Suggest fetal distress
• Polyhydramnios
– Suggest bowel obstruction or atresia
Fetal Abdomen
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15. 7/19/2011
Gastroschisis
• Marked bowel dilatation, which may be either
external or internal to the abdominal cavity, suggests
bowel obstruction and/or ischemia
Fetal Abdomen
Gastroschisis
• Bowel can twist and cut off blood supply
Fetal Abdomen
Gastroschisis
Fetal Abdomen
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16. 7/19/2011
Gastroschisis
Fetal Abdomen
Gastroschisis
Fetal Abdomen
Ectopic Cordis
“Large omphalocele coming all the way to heart”
• Rare malformation
• Protrusion of heart through chest wall
• Association - Pentalogy of Cantrell
Fetal Abdomen
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17. 7/19/2011
Pentalogy of Cantrell
A term used to describe the association of 5 anomalies:
1. Midline supraumbilical abdominal defect
2. Defect of the lower sternum
3.
3 Defect of the diaphragmatic pericardium
4. Anterior diaphragmatic hernia
5. Intracardiac abnormalities
Fetal Abdomen
Pentalogy of Cantrell – US Findings
• Midline anterior wall defect
usually upper abdomen
• Ectopic heart
• Pericardial or pleural effusion
• Craniofacial anomalies
• Ascites
• Two vessel cord
Fetal Abdomen
Limb-Body Wall Complex
• Also known as “body stalk” anomaly
• Failure of ventral abdominal wall to close
– Often left sided
Jane J.K. Burns, RDMS
Fetal Abdomen
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18. 7/19/2011
Limb-Body Wall Complex
• Abdominal organs lie in a sac outside the abdominal cavity
• Short or absent umbilical cord
• Fetus lies directly on placenta*
• Universally fatal
Fetal Abdomen
Limb-Body Wall Complex
• Amniotic bands attached broadly to the fetus &
placenta
• Large thoraco-abdominal wall defect
– no covering membrane
• Distorted body axis
Jane J.K. Burns, RDMS
Fetal Abdomen
Limb-Body Wall Complex
• Severe scoliosis – prominent feature
• Limb defects common
• Complex array of multiple malformations
– Craniofacial & Internal organ anomalies
Fetal Abdomen
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19. 7/19/2011
Bladder & Cloacal Exstrophy
• Failure of closure of lower
abdominal wall resulting in
exposed bladder
• Omphalocele
• Absent bladder
• Imperforate anus
• Spinal abnormalities
• Malformation of the
genitalia
• Single umbilical artery
Fetal Abdomen
Bladder Exstrophy
• 2o to abnormal development of
the cloacal membrane
• Incidence is 1:30,000 births
• Eversion & exteriorization of
the pelvic viscera on the
abdominal surface
– Inferiorly displaced umbilicus
– Widely separared pubic bones
Reports of T21 & 13
Fetal Abdomen
Bladder Exstrophy – US Findings
• Non-visible bladder
• Normal kidneys
• Normal amniotic fluid
volume
• Low CI
• Bulging mass
protruding from the
lower abdominal wall
• Small penis
• Splayed iliac bones
Fetal Abdomen
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20. 7/19/2011
Cloacal Exstrophy
Omphalocele & bladder extrophy with prolapsed ileum between the two bladder halves
Fetal Abdomen
Ventral Wall Defects
Relation to Umbilicus
• Above umbilicus
– Consider pentalogy of cantrell
• At umbilicus
– C id gastroschisis or omphalocele
Consider hi i h l l
• Below umbilicus
– Consider exstrophy of bladder or cloaca
• Difficult to tell because of size
– Consider body stalk anomaly
Fetal Abdomen
Normal Appearance of Bowel
• Amniotic fluid is swallowed & as it gets to the small
bowel it mixes with bowel mucopolysaccharide
• Moves to the large bowel – water is resorbed, leaving
meconium
• Meconium is expelled at birth
• If there is obstruction or if meconium is abnormally
thick that wouldn’t pass it causes obstruction in the
bowel – meconium ileus
Fetal Abdomen
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21. 7/19/2011
Normal Appearance of Bowel
• Meconium
– Variable in echogenicity (hypo to hyperechoic), can be
seen throughout the later part of pregnancy, particularly in
late 3rd trimester
Fetal Abdomen
Hyperechoic Bowel
What Does
That Mean?
Fetal Abdomen
Hyperechoic Bowel
• Increased echogenicity of the mesentery and small
bowel walls
The bowel itself is not echogenic
Fetal Abdomen
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22. 7/19/2011
Hyperechoic Bowel
• Often normal variant
– Related to higher
frequency transducers
and to images with
greater contrast
Fetal Abdomen
Fetal Abdomen
Echogenic Fetal Bowel
• Abnormal if
– > 4 cm in size
– May have mass effect
– Homogeneous heterogeneo s
Homogeneo s or heterogeneous
– Brightness > bone (femur, spine, iliacs)
Fetal Abdomen
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23. 7/19/2011
Echogenic Fetal Bowel
• Seen in association with:
– Cystic fibrosis, trisomy 21, cytomegalovirus
(CMV), parvo virus (5th disease), GI obstruction
and IUGR
Fetal Abdomen
Echogenic Bowel
• Swallowed blood (intra-amniotic hemorrhage)
4 days post-amniocentesis
Fetal Abdomen
Meconium Peritonitis
• Leaking of bowel contents leading to an
intense peritoneal reaction
Fetal Abdomen
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24. 7/19/2011
Meconium Peritonitis
• 50% have underlying bowel pathology
Fetal Abdomen
Meconium Peritonitis
• Calcifications 85%
– Usually punctate, linear or clumped foci
Fetal Abdomen
Meconium Peritonitis
• Calcifications 85%
– Usually punctate, linear or clumped foci
• Ascities 54%
– U ll complex
Usually l
Fetal Abdomen
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25. 7/19/2011
Meconium Peritonitis
• Calcifications 85%
– Usually punctate, linear or clumped foci
• Ascities 54%
– U ll complex
Usually l
• Bowel dilatations 27%
Fetal Abdomen
Meconium Peritonitis
• Calcifications 85%
– Usually punctate, linear or clumped foci
• Ascities 54%
– U ll complex
Usually l
• Bowel dilatations 27%
• Pseudocysts 14%
• Polyhydramnios 65%
Fetal Abdomen
Meconium Peritonitis
• Calcifications can extend to thorax
Fetal Abdomen
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26. 7/19/2011
Meconium Peritonitis
• Calcifications can extend to scrotal sac
Fetal Abdomen
Abdominal Calcifications
• Infections: herpes, toxoplasmosis, cytomegalovirus
• Tumors: teratoma, hepatoblastoma, neuroblastoma
• Peritonitis: meconium leak
• Infarcted bowel
• Gallstones
• Idiopathic
Fetal Abdomen
Small & Large
Bowel Obstruction
Obstructions below the duodenum are even harder to diagnose
Fetal Abdomen
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27. 7/19/2011
Small Bowel Obstruction
• Jejunal & ileal obstruction is more common
than duodenal obstruction!
– Vascular injury
• Small bowel loops can be seen specially in 3rd
trimester
Fetal Abdomen
Small Bowel Obstruction
• They peristalsis and change
in configuration
• Do not persist, and should
not be >15 mm in length and
7 mm in diameter
• Can rarely present as cyst
like mass
• Polyhydramnios
– Timing & severity dependent Small bowels are
on site of atresia centrally located
Fetal Abdomen
Small Bowel Obstruction
Causes:
• Intestinal atresia
– Related to an in utero vascular accident
• Stenosis
• Volvulus
• Meconium ileus
– In fetuses with cystic fibrosis
Fetal Abdomen
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28. 7/19/2011
Pitfalls
• Different processes can be mistaken for dilated
small bowel
– Cysts in an enlarged multicystic displastic kidney
– Dilated tortuous ureter
Fetal Abdomen
Large Bowel Obstruction
• Normal large bowel < 20 mm
diameter
• Rare - It occurs at the anal-rectal
region
• Additional structural &
chromosomal anomalies are very
common (75%)
– VACTERL & caudal regression
syndrome
Causes:
• Atresia
• Stenosis
Fetal Abdomen
Solid Abdominal Masses
Mesoblastic nephroma Neuroblastoma Hepatoblastoma
Subdiaphragmatic extralobar
Fetal Abdomen
pulmonary sequestration
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29. 7/19/2011
Fetal Abdomen
Abdominal Cysts
Differential Diagnosis
• RUQ
– Hepatic/choledochal cyst
• LUQ
– Splenic cyst
• Posterior
– Renal cyst, hydronephrosis
cyst
• Anterior/mid-abdomen
– Mesenteric cyst, umbilical vein varix
• Lower abdomen
– Ovarian cyst (but may migrate to mid-abdomen)
– Ureterocele
– Urachal cyst
– Hydrometrocolpos
Fetal Abdomen
Diagnostic Challenge
Fetal Abdomen
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30. 7/19/2011
Diagnostic Challenge
Fetal Abdomen
There is Flow! Is it venous or arterial?
Fetal Abdomen
Umbilical Vein Varix
• Focal dilatation of umbilical vein
• Usually intraabdominal but extrahepatic may
occur in association with persistent right
umbilical vein
• It may also occur in free floating loops of cord
• Umbilical vein varix of intra-amniotic segment
is rarer than intra-abdominal
Fetal Abdomen
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31. 7/19/2011
Umbilical Vein Varix
• Focal dilatation of intra-abdominal portion
– Usually near cord insertion
– Abnormal if internal diameter > 9 mm or twice size of
intrahepatic portion of vein
– Normal size at week 20 is 3-4 mm with linear increase up
34
to 8 mm at term
Fetal Abdomen
Umbilical Vein Varix
Fetal Abdomen
Umbilical Vein Varix
• Can be associated with:
– Chromosome abnl (T-21, 18, 9)
– Congenital malformations
– Decreased growth
– Hydrops
H d
– Thrombosis
• May be first manifestation of elevated venous
pressure therefore may signify increased risk of
cardiac decompensation
• As isolated finding: normal outcome
Fetal Abdomen
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32. 7/19/2011
Choledochal Cyst
• Cystic dilatation of the CBD
• Separate from gallbladder
• No communication with stomach
Fetal Abdomen
Abdominal Cysts
Fetal Abdomen
Abdominal Cysts
• Lower abdomen
– Female: think ovarian: may migrate/auto-amputate
• Torsion in ~ 40 % if > 5 cm
Fetal Abdomen
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33. 7/19/2011
Thank You
Fetal Abdomen
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