Ch. 63 Flashcards
Fetal abdominal organs are well formed by
The 2nd trimester
In the fetal body, Umbilical arteries & vein are anatomic landmarks for
fetal abdominal anatomy & measurements
In the fetus, _ is present
Ductus venosus
Fetal liver is
Larger and occupies a larger volume of the fetal abdomen
Umbilical hernias form when
Intestines return normally to the abdominal cavity & herniate either prenatally or postnatally through an inadequately closed
umbilicus
How does hernia differ from omphalocele?
Hernia is covered by skin and subcutaneous tissue
Meckels diverticulum
Remnant of the proximal part of the yolk sac that fails to degenerate and disappear during the early fetal period
o Usually a small finger-like sac about 5 cm long projects from the border of the ileum
Most common malformation of the midgut
Meckels diverticulum
Most fetuses older than _ should have fluid in their stomach. If the fluid is not seen _
16 weeks
Stomach should be reevaluated in 20-30 minutes to rule out possible CNS problems, obstruction, oligohydramnios, and atresia
If fluid is not seen in the stomach after reevaluation
Fetus may be reexamined the following day or week to
see if there is a change in stomach size
Fluid within the stomach should be
Anechoic
If an echogenic mass is seen in the fetal stomach in a patient with clinical or sonographic evidence that suggests an abruption this could possibly be a
hematoma associated w/ intraamniotic hemorrhage
Normal esophagus can be visualized in the thorax during
The 2nd and 3rd trimesters
Esophagus appears as
2 or more parallel echogenic lines
Multilayered pattern
Occasionally fluid can be seen in the esophagus During fetal swallowing
Umbilical Cord Insertion visualization must be made to rule out
Omphalocele
Gastroschisis
Hernia
Mass formation
After birth, umbilical vein
Collapses and forms the ligamentum teres
Appearance of bowel varies changes depending on
Gestational age
In 1st trimester- Fetus is capable of _, this permits visualization of the stomach by approx.
swallowing sufficient amounts of amniotic
fluid
11 menstrual weeks
In the 2nd trimester, Movement & swallowing increase the _
This is where _
amniotic fluid volume in the small bowel & colon
Fluid and nutrients are absorbed
Meconium begins to accumulate in the _ after _ weeks
Distal part of the small intestines
15-16
Meconium is a combination of
- Desquamated cells
- Bile pigments
- Mucoproteins
Until mid-2nd trimester the small bowel lumen is
Difficult to demonstrate
Bowel appears as
ill-defined area of increased echogenicity in the mid to lower abdomen
Distinction of large bowel from small bowel is possible after
20 weeks
Small bowel is slightly _ compared to the liver
Hyperechoic
Small bowel may appear
“Mass like” in the central abdomen and oelvis
Small bowel appears _ throughout the rest of the pregnancy
Hyperechoic
Small bowel: as pregnancy progresses:
_ becomes less prominent.
Small bowel is located _.
After _ weeks, normal peristalsis is increasingly observed
Hyperechoic area
more central in the abdomen than colon
27 weeks
Colon can be identified at the end of
The second trimester
Colon appears as
A long tubular hypoechoic structures w/ well defined walls
What differentiates colon from small bowel
Haustral folds
Colon is more _ than small bowel
Peripheral
Colon doesn’t have
Peristalsis like small bowel
After _ weeks, lipids absorbed from fetal colon & the remaining contents collect as
14
Meconium
After 14 weeks, meconium appears
Hypoechoic compared to fetal liver
After 14 weeks, normal colon can be
Mistaken form abnormally dilated small bowel or other pathological processes
After 14 weeks, meconium _ in echogenicity closer to term
Increases slightly
Liver is involved in
several congenital anomalies but rarely affected by an isolated
hepatic lesion
Liver cysts & hemangiomas have
Been reported in the fetal liver
Liver enlarges in fetuses with _ due to _
Rh isoimmunization
Increased hematopoiesis
Uncommon but may be seen in the liver
Tumors
Hamartoma
Hepatoblastoma
Most liver tumors appear as _ masses
Solid hypoechoic
Cystic components and solid masses have also been reported
About _% of benign and malignant liver tumors are
5
Calcified
Liver calcifications may be seen and appear as
Isolated echogenic focus, ususally benign
If multiple liver calcifications are seen
Other organs may be affected
Situs inversus
Reversal of thoracic and abdominal organs
Total reversal
Complete reversal of thoracic & abdominal organs
Prognosis- normal outcome
Partial situs inversus
More severe than total
High mortality rate
Partial situs inversus can develop 2 combinations of organ reversal
Thoracic viscera usually reversed and abdominal viscera may or may not be reversed
Occasionally, abdominal organs are reversed without reversal of
heart position
Partial situs is divided into
Asplenia
Polysplenia
Asplenia partial situs
Absence of spleen
Stomach and GB are more midline in position
More centrally located liver
Abnormal positioning of the aorta & IVC on the same side
Mortality rate =95%
Polysplenia
More than one spleen [at least 2 are present] o Located along the greater curvature of the stomach [Right side] • Transposition of: o Liver o Spleen o Stomach • Absence of GB • There is an interruption of the IVC • Heart block is common • Normal size spleen is NOT seen between stomach and left kidney on trans abdomen image. • Mortality rate = 80%
Cause of situs inversus
Unclear
Are cardiac malformations common in situs inversus
Yes
Cardiac malformation in situs w/ asplenia _%, polysplenia _%
99
90
Cardiac malformations with situs
Endocardinal cushion defect
Hypoplastic left heart
Transportation of the great vessels
Sonographically
▪ Total situs inversus
Right sided heart axis & aorta • Transposition of the liver • Stomach • Spleen • Left-sided gallbladder
Sono
▪ Partial situs inversus
• Right-sided stomach
• Left-sided liver
• Dextrocardia with
o Normal stomach position
With situs, other anomalies to check for include
- Gastrointestinal
- Genitourinary
- Neural tube
• Ascites
o Many causes in the fetus:
Gastrointestinal obstruction with bowel perforation
•present as meconium peritonitis & ascites
Nongastrointestinal causes include: • Immune & nonimmune hydrops • Urinary tract obstruction • Congenital infection • Some abdominal tumors
True ascites is seen within the
peritoneal recesses and in the spaces between small bowel loops (outlines the falciform ligament)
Pseudoascites
Sonolucent band near the fetal anterior abdominal wall is commonly seen in routine OB exams over 18 weeks
Pseudoascites: band results from
normal musculature surrounding the abdominal wall
Pseudoascites is always confined to _. Never outline _
The anterior fetal abdomen
Falciform ligament
Cholelithiasis: _ are seen in the GB
Calcifications
Gallstones will _ in utero or in childhood
Resolve spontaneously
Coledochal cyst
Dilation of the CBD
▪ Cystic mass adjacent to the fetal stomach & gallbladder
▪ May be confused with malformations of the stomach, bowel or duodenal
atresia
Sono
Choledochal cyst
- Close proximity of cyst to neck of gallbladder
- Ovoid right upper quadrant cyst with entering bile duct
- Cyst & gallbladder enlarge as pregnancy progresses
- Absence of peristaltic activity in cyst
Agenesis of the gallbladder
occurs in approximate
20% of pts with biliary atresia
Agenesis of the gallbladder May be associated with
Partial situs inversus w/ polysplenia
Rare multiple anomaly syndromes
Ability to visualize the GB _ w/ gestational age
Increases
When asplenia is associated w/ congenital heart disease _ should be considered
Polysplenia-asplenia syndrome should be considered
Majority of GI malformations can be corrected after birth but it’s important to detect
prenatally to prevent complications of dehydration, bowel necrosis and respiratory difficulties that can happen if these lesions are not suspected before delivery.
GI atresia develops when
Portion of bowel grows and infarcts ( doesn’t develop all the way)
GI atresia occurs
Anywhere in the GI tract
With GI atresia _ can occur
Obstruction to normal swallowing
GI atresia: The membrane covering the lumen & intestinal loops _
Bowel loops below the atresia _
The blockage results in _
enlarge above the
obstruction
are narrowed [stenotic]
Polyhydramnios (and backup of amniotic fluid)
Esophageal atresia
Congenital blockage of the esophagus
Esophageal atresia results from
faulty separation of the foregut into its respiratory & digestive
components
Esophageal atresia in conjunction with a fistula (most commonly)
▪ Communication between trachea & esophagus [tracheoesophageal fistula]
▪ Allows passage of amniotic fluid into the stomach
Esophageal atresia: sometime there is no fistula so
Fluid will not reach the stomach
Although gastric secretions can contribute to stomach fluid
Stomach will not be visualized
Combination of polyhydramnios & absent stomach over repeated exams suggest
Esophageal atresia
Esophageal atresia is not diagnosed in a majority of cases because
Tracheoesophageal fistula is usually present
Esophageal atresia:
Coexisting anomalies are _
Common
Esophageal atresia:
Most common anomaly seen
Anorectal atresia
Esophageal atresia is associated with
VACTERL
(Vertebral defect, heart defects, renal, and limb abnormalities)
Growth restriction
Trisomies 18 & 21
Duodenal Atresia
Blockage of the duodenal lumen by a membrane
Prevents passage of swallowed amniotic fluid
Narrowing of the bowel below the obstruction occurs
Amniotic fluid fails to move past the obstruction
• Amniotic fluid backs up in the duodenum & stomach
Sono duodenal atresia
Two anechoic communicating structures [stomach & duodenum] seen in the upper fetal abdomen
• double bubble
▪ Polyhydramnios [later in pregnancy]
▪ Often coexist with annular pancreaS
What trisomy is associated with duodenal atresia?
Trisomy 21
About 30% of fetuses are affected
Associated anomalies occur in about % of fetuses with duodenal atresia. Associated anomalies include
50 ▪ Cardiovascular anomalies are common ▪ Genitourinary anomalies may coexist ▪ Can find esophageal atresia along with duodenal atresia ▪ Growth restriction
Duodenal atresia AFP
is elevated due to faulty swallowing
Duodenal atresia: _ is required after birth to _
Immediate surgery
connect the stomach to the jejunum bypass the obstruction
Causes of double bubble
▪ Duodenal atresia (most common) ▪ Duodenal stenosis ▪ Annular pancreas ▪ Ladd’s bands [peritoneal tissue attach to the cecum to the abdominal wall & create an obstruction of the duodenum] ▪ Proximal jejunal atresia ▪ Malrotation ▪ Diaphragmatic hernia
Atresia of the _ slightly more common than duodenal
atresia
Jejunum, ileum, or both
Bowel atresia is caused by
▪ vascular accident ▪ sporadic ▪ maternal drug usage ▪ secondary to: • volvulus •gastroschesis
_ length of bowel is subject to obstruction
Entire
Blockage of jejunum and ileum bowel segments appear as
Multiple cystic structures
Proximal to the site of atresia
Bowel atresia:
_ may be present because structures are high in the abdomen
Polyhydramnios
The more distal the obstruction
The less severe the hydramnios
The later it will develop
Causes of small bowel obstruction include:
▪ Malrotation ▪ Atresia ▪ Volvulus ▪ Peritoneal bands ▪ Cystic fibrosis
Dilated bowel loops can be _
Isolated or associated with other anomalies
Anomalies associated with dilated bowel loops
Ascites
Meconium peritonitis
Sono
Bowel obstruction/ atresia
▪ Intestinal obstructions appear as cystic bowel loops not connected to the stomach
▪ Obstruction should be suspected when clear cystic structures are found in the pelvis
Meconium Ileus
Presence of thick overproduced meconium in the distal ileum
Meconium ileum is the earliest manifestation of
Cystic fibrosis
Cystic fibrosis
Genetic disorder that mostly effects the lungs & digestive system
Overproduction of meconium is caused by:
Increased production of mucus by GI organs & electrolyte imbalance
oCharacteristic of cystic fibrosis
3rd most common form of neonatal bowel obstruction (after atresia and malrotation)
Meconium ileus
Meconium begins to accumulate in the _ because _
Fetal bowel in the 2nd trimester.
the colon does not exhibit peristalsis in utero, Meconium
remains suspended at the rectum
The anal sphincter prevents the
assage of meconium [meconium plug]
into the amniotic fluid unless the fetus is stressed or traumatized
Sono meconium ileus
▪ Appears as tiny echogenic reflections within the peristaltic small bowel
▪ Impacted meconium causes the ilium to dilate
• Appears echogenic
▪ Normal small bowel appears echogenic during 2nd trimester ▪ Other conditions associated with echogenic bowel:
• Cytomegalovirus • Trisomy 21
Anorectal atresia
Complex disorder of the bowel & genitourinary tract
_ is found in anorectal atresia
Imperforate anus
Imperforate anus occurs when _
A membrane covers the anus prohibiting expulsion of meconium
Anorectal atresia may present as part of
VACTERL association or in caudal regression
Prognosis of anorectal atresia
Poor due to associated anomalies
Sono
Anorectal atresia
▪ Dilated colon & calcified meconium may be seen ▪ Typically, normal amniotic fluid
• May be decreased if there are associated renal problems
Hirschsprung’s Disease aka
Megacolon
Hirschsprungs disease
Congenital disorder
Abnormal innervation of large intestines
Sono Hischsprung disease
▪ Difficult to diagnose prenatally
▪ Dilated bowel loops observed
Meconium Peritonitis
Arises when fetus has sterile chemical peritonitis secondary to in utero bowel perforation
Meconium peritonitis: polyhydramnios is _
Common
Meconium peritonitis mat result in formation of
Meconium pseudocyst
Sono meconium peritonitis
▪Calcifications seen on peritoneal surfaces or in scrotum
▪ Ascites fluid may be echogenic
• Unusual to see calcification in meconium in fetus with cystic fibrosis
▪ Chronic meconium peritonitis may cause a pseudocyst to develop
Hyperechoic Bowel
Impression [subjective] of unusually echogenic bowel
o Typically seen in 2nd trimester
o Bowel is compared to the brightness of bone
Grade 1 hyperechoic bowel
Mildly echogenic typically diffuse
Grade 2 hyperechoic bowel
Moderate echogenic and typically focal
Grade 3 hyperechoic bowel
Very echogenic- similar to bone
True ascites is always
Abnormal
Ascites fluid collects between
2 leaves of unfused omentum
Prognosis of ascites in non- immune hydrops
Poor
Other conditions that may cause ascites to develop include
▪ Bowel perforation
▪ Urinary ascites
• Secondary to bladder rupture
Cystic Masses of the Abdomen: important to determine
o Precise location of the mass o Size of the mass o Resultant compression of other organ systems ▪Hydronephrosis ▪ Hydroureter ▪ Fetal hydrops Attempt to determine origin of mass Determine fetal gender (beneficial when an ovarian mass is suspected
Cystic Masses of the Abdomen: important to Describe
oEchogenicity
o Presence or absence of septations oCoexisting anomalies
