Chpt. 60 Fetal Thorax Flashcards
What is the single most important determinant for fetal viability?
Adequacy of pulmonary development
What is the major reason why fetuses younger than 24 weeks of gestation are generally considered nonviable?
Pulmonary immaturity
Breathing movements that occur before birth results in ?
The aspiration of fluid into the lungs
Name the three routes that fluid in the lungs (at birth) are cleared by?
1) through the mouth and nose
2) into the pulmonary copillaries
3) into the lymphatic’s and pulmonary vessels
The fetal thorax is examined in what planes?
transverse and coronal or parasagittal plane
what is the normal shape of the thoracic cavity?
symmetrically bell shaped, with the ribs forming the lateral margins, the clavicles forming the upper margins, and the diaphragm forming the lower margin
The lungs serve as lateral border for ? and lie superior to ?
heart and diaphragm
How much fluid is in the lungs at birth?
They are half full
describe the diaphragm sonographically
echogenic smooth hypoechoic muscular margin between the fetal liver or spleen and the lungs
Which is normally slightly smaller? thorax or abdominal cavity
thorax
where are the chest circumference measurements made from?
transverse plane at the level of the four chamber view of the heart
A fetus with a significant narrow diameter of the chest may have?
asphyxiating thoracic dystrophy
What syndrom is associated with asphyxiating thoracic dystrophy?
Thanatophoric dwarfism
The central portion of the thorax is occupied by the _________.
mediastinum
Majority of the heart is positioned in the ?
midline and left chest
How should the apex of the heart be directed?
toward the left chest wall at an axis that is 45 degrees from midline
The heart occupies _______ of the chest?
1/3
What direction does the base of the heart lie to the diaphragm?
Horizontal
why is the location of the heart important to document?
as detection of abnormal heart position may indicate the presence of a chest mass, pleural effusion, or cardiac malformation
How do the fetal lungs appear sonographically?
homogenous with moderate echogenicity
In early gestation, the lungs are similar to or slightly _____ echogenic than the liver?
less
As gestation progresses, there is a trend toward increased pulmonary echogencicty relative to ?
liver
When is fetal breathing movements considered absent?
if no such fetal activity is noted during a 20 minute observation period
what is used to detect fetal breathing through the nostrils?
Color flow doppler
when does fetal breathing become more prominent?
2nd and 3rd trimesters
The mature fetus spends how much time breathing?
almost 1/3
when are fetal breathing movements documented?
when seesaw movements of the fetal chest or abdomen are sustained for 20 seconds
What should you evaluate when looking at a fetus for a lung mass?
1) postion of the heart
2) orientation of the cardiac axis
3) Measurement of the thoracic circumference
What should you look for when the heart position and axis vary from the normal position?
any abnormality that may be the cause of such displacement
What is fetal echo beneficial for excluding?
cardiac involvement, and evaluation of an intact diaphragm is necessary to exclude diaphragmatic hernia
The lungs will not grow or develop properly when?
1) small uterine cavity resulting from severe oligohydraminos
2) chest cavity os abnormally small
3) When the balance between tracheal and airway pressure and fluid volume is inadequate
4) fetus is unable to practice breathing movement
Pulmonary Hypoplasia is caused by?
a decrease in the number of lung cells, airways and alveoli, with a resulting decrease in organ size and weight
Pulmonary hypoplaia results in?
small inadequate development of lungs
pulmonary hypoplasia most commonly occurs from _________ _________ or is secondary to a small thoracic cabity as a result of a structural or ________ _________.
prolonged oligohydraminos; chromosomal abnormality
Pulmonary hypoplasia may also occur in fetuses with?
severe intrauterine grown restriction and early rupture of the membranes
Pulmonary hypoplasia may be caused by ?
masses within the thoracic cavity
Name the masses withing the thoracic cavity? (5)
1) pleural effusion
2) diaphragmatic hernia
3) cystic adenomatoid malformatin of the lung
4) bronchopulmonary sequestation
5) other lg. cyst and tumors of the lungs and thorax, may lead to pulmonary hypoplasia
what may manifest with pulmonary hypoplasia?
cardiac defect, skeletal dysplasias, central nervous system disorder, and chromosomal trisomies ( 13, 18 and 21)
Sonographic finding of pulmonary hypoplasia
1) Thoracic measurements
2) various lung measurements
3) estimation fo lung volume
4) doppler studies of the pulmonary arteries
5) assessment of fetal breathing activity
Accumulation of fluid within the pleural cavity that may appear as an isolated lesion or secondary to multiple fetal anomalies is called?
pleural effusion or hydrothorax
what is the sonographic appearance of pleural effusion?
echo free peripheral masses on one or both sides of the fetal heart
________ are ehco free masses that replace normal lung parenchyma
Lung Cyst
Lung cystic masses may cause notable shifts of the ?
intrathoracic structures
what is the most common lung cyst detected prenatally?
Bronchogenic cyst
where does bronchogenic cyst usually occur?
within the mediastinum or lung; infrequently they are inferior to the diaphragm
Sonographically the bronchogenic cyst appear?
as small circumscribed masses without evidence of a mediastinal shift or heart failure
amniotic fluid volume is within a norma range
Pleural effusions conform to the _______ cavity and often compress ________ tissue.
thoracic, lung
T/F; The lung appears to float in fluid
True
Pleural fluid is rarely encountered before the _____ week of gestation, except in association with _______ or_______ syndrom
15th, down or turner’s
compression of lung parenchyma may cause?
pulmonary hypoplasia (repersent life threating consequence for neonate)
The presence of a pleural effusion may cause a shift of ?
mediatinal structures, compression fo the heart, and inversion fo the diaphragm
In the presence of _____ the shpe of the lung appears normal
pleural effusion
Once a pleural effusion has been discovered a careful search for ______ (3)should be attempted?
cardiac, lung, and diaphragmatic lesions
when pleural effusion is large, lung develoopment is impaired, which may result in?
pulmonary hypoplasia
with pleural effusion signs of ________ should be performed?
hydrops (ascites, scalp edema, and tissue edema)
solid tumors of the fetal lungs appear as?
echo dense masses in the lung tissue
Name two solid lung masses?
pulmonary sequestration and certain types of cystic ademomatoid malformations
__________ is a supernumerary lobe of the lung, separated from the normal tracheobronchial tree
pulmonary sequestration
In pulmonary sequestration, extra pulmonary tissue is present within the ______ ______ ___ or is connected to the inferior border of the _______ within its own pleural sac.
pleural lung sac; lung
In solid lung masses the lung tissue is nonfuntional and recieves its blood supply for what?
systemic circulation
In solid lung masses the arterial supply is usually from?
thoracic aorta, with venous drainage into the vena cava
Sonographically solid lung mass appear?
echo-dense solid mass resembling lung tissue is observed, usually in the lower lobe of the lung
Majority of extralobar defects occur on the ?
left side, rarely below the diaphragm
describe intralobar lesions?
spherical, and extralobar sequestration appears as a cone shaped or triangular mass
______ is one of the bronchopulmonary foregut malformations?
CCAM
is a multicystic mass within the lung consisting of primitive lung tissue and abnormal bronchial and bronchiolar-like structures?
Congenital cystic adenomatioid malformation
How may forms of cystic adenomatoid malformation are there?
3
1) CCAM type I
2) TypeII
3) type III
one or more large systs replace normal lung tissue ) single or multiple cysts measuring more than 2 cm and up to 19 cm)
CCAM type I
Type II of cystic adenomatoid malformation constist of ?
multiple small cysts (less than 1 cm)
In cystic adenomatoid malformation type II lesions are assoicated with?
fetal and/or chromosomal abnormalities in 25% of cases
In type II lesions of cystic adenomatoid malformation name the three chromosomal abnormalities?
1) renal agenesis
2) pulmonary anomalies
2) diaphragmatic hernia
Type III malformation fo cystic adenomatoid are characterized as?
bulky, large, noncystic lesions appearing as echo-dense masses of the entire lung lobe
