Chapter 62 The Fetal Abdomen Flashcards
what serves as a conduit between the portal and systemic veins?
ductus venosus
in what 3 ways do the proportions of the fetal abdomen differ from the adult abdomen
- fetal abdomen is larger relative to body length
- fetal liver occupies more space in abdomen
- fetal pelvic cavity is smaller so bladder, ovaries and uterus lie in abdomen
pharynx, lower respiratory system, esophagus, stomach, part of duodenum, liver and biliary apparatus, and the pancreas are all derivatives of what?
the foregut
what are the derivatives of the midgut?
small intestines, cecum and cloaca, ascending colon, transverse colon
how does umbilical hernia differ from omphalocele?
omentum or loop of bowel is covered by subcutaneous tissue and skin
what is the most common malformation of the midgut?
Meckel’s diverticulum
what is Meckel’s diverticulum?
remnant of the proximal part of the yolk sac that fails to degenerate
the left part of the transverse colon, descending colon, sigmoid colon, rectum, superior portion of the anal canal, epithelium of the bladder, and most of the urethra are all derivatives of what?
the hindgut
most fetuses older than _______ should have fluid in their stomachs
14-16 weeks
when can the normal esophagus be visualized?
second and third trimesters
appears as two or more parallel echogenic lines
where is the abdominal circumference taken
at the level of the portal sinus and the umbilical portion of the left portal vein
umbilical vein coarses
cephalically
umbilical vein joins _____ in the liver
left portal vein
after birth the umbilical vein becomes
ligamentum teres
fetus is capable of swallowing to permit visualization of the stomach by
11 weeks
when does meconium begin to accumulate
15-16 weeks
small bowel is _____ in echogenicity compared to the liver
hyperechoic
when can peristalsis be observed
after 27 weeks
meconium within the colon appears _____ in echogenicity compared to the liver
hypoechoic
hepatic veins and fissures are formed by
the end of the first trimester
which lobe of the fetal liver is larger
left
when may the gallbladder be seen
20 weeks
the spleen is imaged in what plane
transverse
how does asplenia appear
abnormally positioned liver, gallbladder, IVC and aorta
what is common with polysplenia
heart block
how does polysplenia appear
transposition of the liver and stomach, absence of the gallbladder, and disruption of the IVC
what is the mortality rate for partial situs inversus
90-95% with asplenia and 80% with polysplenia
what is the sonolucent band near the fetal anterior abdominal wall that is identified after 18 weeks
normal musculature surrounding the abdominal wall
pseudoascites is always confined to _____ and never outlines the _____ like true ascites
anterior or anterolateral aspect of the fetal abdomen
falciform ligament
what may appear with a choledocal cyst
a cystic mass adjacent to the fetal stomach and gallbladder
what 2 organs may enlarge with Rh-immune disease
spleen and liver
what is esophageal atresia
blockage of the esophagus resulting from faulty separation of the foregut
what are the 2 primary sonographic findings with esophageal atresia
polyhydramnios and absence of stomach bubble
what is the most common coexisting anomaly of esophageal atresia
anorectal atresia
sonographic findings of duodenal atresia
2 echo free structures (stomach and duodenum) appear in upper abdomen
this is termed double bubble sign
about 30% of fetuses with duodenal atresia have what
trisomy 21
how will blockage of the jejunum and ileal bowel segments appear
as multiple cystic structures proximal to the site of atresia
what are the 5 causes of fetal small bowel obstruction
malrotation atresias volvulus peritoneal bands cystic fibrosis
what is a small bowel disorder marked by the presence of thick meconium in the distal ileum
meconium ileus
meconium ileus is the earliest manifestation of what
cystic fibrosis
it is important that the small bowel appear _____ during the second trimester
echogenic
what does VACTERL stand for
Vertebral abnormalities Anal atresia Cardiac abnormalities TracheoEsophagela fistula Renal and Limb abnormalities
what is caudal regression syndrome
lack of development of the lower limbs
in whom may caudal regression syndrome occur
fetus of diabetic mother
how does anorectal atresia appear sonographically
dilated colon and calcified meconium
what is Hirchsprung’s disease or mega colon
abnormal innervation of the large intestine
what is meconium peritonitis
fetus has a sterile chemical peritonitis secondary to an in utero bowel perforation
how does meconium peritonitis appear sonographically
calcifications are seen on the peritoneal surface or in the scrotum
what may cause hyperechoic bowel
decreased water content, alterations of meconium or both
decreased water content may be secondary to what
hypoperistalsis
in the fetus ascites collects where
between the two leaves of unfused omentum
ascites usually outlines
the falciform ligament and umbilical vein
