Ch. 61 Flashcards
__ is the single most important determine for fetal viability
Adequacy of pulmonary development
__ is the major reason fetuses younger than 24 weeks are generally considered nonviable
Pulmonary immaturity
Breathing movements that occur before birth results in _
Aspiration of fluid into the lungs
The lungs at birth are about half filled with
Fluid from the amniotic cavity
The fluid in the lungs at birth clears via 3 routes:
Nose and mouth
Into pulmonary capillaries
Into lymphatic and pulmonary vessels
Normally the thoracic cavity is
Symmetric and bell shaped
The lungs serve as __ for the heart, and lie __ to the diaphragm
Lateral borders
Superior
The diaphragm can be seen as __ between the fetal liver and lungs
A smooth hypoechoic muscular curvilinear margin
Normally the fetal thorax is slightly __ than the abdominal cavity
Smaller
The ratio [TC:AC] __ throughout pregnancy
Remains constant
Extreme variations in thoracic size should signal
Further investigation for other anomalies
___ can result in pulmonary hypoplasia, which may cause __
Oligohydramnios
Overall reduction in the thoracic size
Thoracic circumference measurements are made in the __ plane at the level of __
Transverse
4 chamber heart
A fetus that has significantly narrower chest diameter may have
Asphyxiating thoracic dystrophy
Sever syndromes are associated with asphyxiating thoracic dystrophy including
Dwarfism
The majority of the heart is positioned in the
Midline and left chest
The apex of the heart should be directed
Toward the spleen (left)
It is important to document sonographically the position of the
the heart
Detection for abnormal position of the heart may indicate the presence of
Chest mass
Pleural effusion
Cardiac malformation
Fetal lungs appear
Homogeneous with moderate echogenicity
Echogenicity of the fetal lungs __ as pregnancy progresses
Increases
Fetal breathing becomes ___ in the 2nd & 3rd trimesters
More prominent
A mature fetus spends almost __ of its time “breathing”
1/3
Color doppler may be used to detect __, however it is not a well-recognized practice
fetal breathing through the nostrils
When evaluating the fetus for a lung mass the following should be assessed
Position of the fetal heart
Orientation of the cardiac axis (normal is 45 degree angle pointing left)
Measurement of the thoracic circmference
Deviation from the normal cardiac axis may suggest the presence of
an intrathoracic mass
Thoracic circumference measurements estimate ___& may predict ___
the size of the thoracic cavity
secondary pulmonary hypoplasia
When the heart position & axis vary from the normal position:
look closely for any abnormalities that may be causing the displacement such as pleural effusion or diaphragmatic hernia
Lungs may not grow or develop properly with
oligohydramnios
A mass within the throacic cavity may have ___ on lung development. The heart may be displaced & the lungs may be __. These effects may lead to __
detrimental effects
compressed and destroyed
pulmonary hypoplasia
Pulmonary hypoplasia is caused by __ and results in __
a decrese in the number of lung cells, airways, and alveoli
decrease in organ size and weight
Reduction in lung volume results in __
small inadequately developed lungs
Pulmonary hypoplasia most commonly ocurs from __ or secondary to __
prolonged oligohydramnios
small thoracic cavity as a result of structural or chromosomal abnormality
Kidney abnormalities may result in __
lethal pulmonary hypoplasia
Kindey abnormalities that may result in lethal pulmonary hypoplasia
▪Bilateral renal agenesis ▪Bilateral multicystic kidney disease ▪Severe renal obstruction ▪Unilateral renal agenesis with contralateral multicystic kidney development ▪Severe obstruction ▪Infantile polycystic kidney disease
Pulmonary hypoplasia may occur in fetuses with
severe IUGR & early rupture of membranes
Masses within the thoracic cavity may lead to
Pulmonary hypoplasia
Abnormalities that can cause pulmonary hypoplasia are
▪Cardiac defects
▪Some skeletal dysplasias
▪CNS disorders
▪Chromosomal Trisomies
A small percentage of infants have pulmonary hypoplasia without
any fetal or uterine problems
_ pulmonary agenesis or hypoplasia is rare, often associated with __
Unilateral
other fetal abnormalities
An absent lung should be considered a differential diagnosis of every fetus with
mediastinal shift and apparent chest mass
Prognosis of pulmonary hypoplasia
grave
80% die after birth
Severity of pulmonary hypoplasia depends on
▪when pulmonary hypoplasia occured during pregnancy ▪severity ▪duration Other contributing factors: ▪Pulmonary fluid dynamics ▪Fetal breathing movements ▪Hormonal influences
Various methods are used to determine the presence of pulmonary hypoplasia
▪thoracic measurements ▪Various lung measurements ▪Estimation of lung volume ▪Doppler studies of pulmonary arteries ▪Assessment of fetal breathing activity
A thoracic circumference below the _____percentile suggests the possibility of pulmonary hypoplasia
5th
Cystic Lung Masses
Echo free masses that replace normal lung parenchyma
Cystic lung masses vary in __
size, ranging from small isolated lesions to large cystic masses
Cystic lung masses may cause
notable shifts of intrathoracic structures