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CH. 60 The Fetal Thorax > Ch. 60-The Fetal Thorax > Flashcards

Ch. 60-The Fetal Thorax Flashcards

1
Q

What is probably the single most important determinant for fetal viability?

A

Adequacy of pulmonary development

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2
Q

What is the major reason why fetuses younger than 24 weeks of gestation are generally considered nonviable?

A

Pulmonary immaturity

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3
Q

Breathing movements before birth result in:

A

*the aspiration of fluid into the lungs

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4
Q

How much of the lungs are filled with fluid at birth?

A

About half

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5
Q

What are the 3 routes that the fluid in the lungs at birth clears by?

A

1) Through the mouth and nose 2)Into the pulmonary capillaries 3) Into the lymphatic’s and the pulmonary vessels

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6
Q

What planes is the fetal thorax examined?

A

Transverse and coronal or parasagittal planes

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7
Q

The normal shape of the thoracic cavity is:

A

*symmetrically bell shaped, with the ribs forming the lateral margins, the clavicles forming the upper margins, and the diaphragm forming the lower margin.

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8
Q

What serve as the lateral borders for the heart and lie superior to the diaphragm?

A

The lungs

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9
Q

What does the diaphragm look like on real-time sonography?

A

An echogenic smooth hypoechoic muscular margin between the fetal liver and the lungs.

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10
Q

The thorax is normally slightly _______ than the abdominal cavity, and this ratio has been reported to remain _______ throughout pregnancy.

A

smaller; constant

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11
Q

What measurements are made in the transverse plane at the level of the four-chamber view of the heart?

A

Chest circumference measurements

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12
Q

A fetus with a significant narrow diameter of the chest may have:

A

asphyxiating thoracic dystrophy

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13
Q

What type of dwarfism may be associated with asphyxiating thoracic dystrophy?

A

Thanatophoric dwarfism

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14
Q

The central portion of the thorax is occupied by the mediastinum, with the majority of the heart positioned in the:

A

midline and left chest.

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15
Q

The apex of the heart should be directed toward the _______ chest wall at an axis that is _______ degrees from the midline.

A

left; 45

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16
Q

Where does the base of the heart lie in regards to the diaphragm?

A

Horizontal to the diaphragm.

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17
Q

The location of the heart is important to document as detection of abnormal heart position may indicate the presence of: (3 things)

A
  • chest mass
  • pleural effusion
  • cardiac malformation
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18
Q

The fetal lungs appear _______ on sonography with moderate _______.

A

homogenous; echogenicity

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19
Q

Early in gestation, the lungs are similar to or slightly _______ echogenic than the liver.

A

less

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20
Q

As gestation progresses, there is a trend toward increased:

A

pulmonary echogenicity relative to the liver.

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21
Q

The lungs will not grow properly or develop properly when: (4 things)

A
  • there is a small uterine cavity resulting from severe oligohydramnios
  • when the chest cavity is abnormally small
  • when the balance b/n tracheal and airway pressure and fluid volume is inadequate
  • when the fetus is unable to practice breathing movements
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22
Q

What is pulmonary hypoplasia caused by?

A

A decrease in the # of lung cells, airways, and alveoli, with a resulting decrease in organ size and weight.

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23
Q

What does the reduction in lung volume due to pulmonary hypoplasia result in?

A

Small, inadequately developed lungs.

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24
Q

Pulmonary hypoplasia is a condition that most commonly occurs from:

A

*prolonged oligohydramnios or is secondary to a small thoracic cavity as a result of a structural or chromosomal abnormality

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25
Q

Pulmonary hypoplasia may also occur in fetuses with severe:

A

IUGR and early rupture of the membranes.

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26
Q

Pulmonary hypoplasia may be caused by masses within the thoracic cavity including: (5)

A
  • pleural effusion
  • diaphragmatic hernia
  • cystic adenomatoid malformation of the lung
  • bronchopulmonary sequestration
  • other large cysts and tumors of the lung and thorax
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27
Q

Other abnormalities resulting from pulmonary hypoplasia: (4)

A
  • cardiac defects
  • skeletal dysplasias
  • CNS disorder
  • chromosomal trisomies (13, 18 & 21)
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28
Q

Sonographic findings used to determine the presence of pulmonary hypoplasia: (5)

A
  • thoracic measurements
  • various lung measurements
  • estimation of lung volume
  • Doppler studies of the pulmonary arteries
  • Assessment of fetal breathing activity
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29
Q

What are echo-free masses that replace normal lunch parenchyma?

A

lung cysts

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30
Q

Lung cysts may vary in size, ranging from:

A

small isolated lesions to large cystic masses that may cause notable shifts of intrathoracic structures.

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31
Q

What is the most common lung cyst detected prenataly?

A

bronchogenic cyst

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32
Q

Where do bronchogenic cysts typically occur?

A

within the mediastinum or lung, infrequently they are inferior to the diaphragm.

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33
Q

How do bronchogenic cysts appear sonographically?

A

as small circumscribed masses w/o evidence of a mediastinal shift or heart failure
–amniotic fluid volume is w/in a normal range

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34
Q

What is pleural effusion or hydrothorax?

A

Accumulation of fluid w/in the pleural cavity that may appear as an isolated lesion or 2ndary to multiple fetal anomalies.

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35
Q

How does pleural effusion appear sonographically?

A

As echo-free peripheral masses on one or both sides of the fetal heart.

36
Q

Effusions conform to the thoracic cavity and often compress what?

A

lung tissue

37
Q

The lung appears to ________ in the fluid.

A

float

38
Q

Pleural fluid is rarely encountered before the ________ week of gestation, except in association with ________ or _________ syndrome.

A

15th week; Down or Turner syndrome

39
Q

What may cause pulmonary hypoplasia, which often represents a life-threatening consequence for the neonate?

A

Compression of lung parenchyma

40
Q

The presence of a pleural effusion may cause: (3 things)

A
  • a shift of mediastinal structures
  • compression of the heart
  • inversion of the diaphragm
41
Q

How does the shape of the lung appear in the presence of pleural effusion?

A

normal

42
Q

What should be searched for once a pleural effusion has been discoverd? (4 things)

A
  • lung
  • cardiac
  • diaphragmatic lesions
  • hydrops–ascites, scalp edema, tissue edema)
43
Q

When the pleural effusion is large, what is impared and what may this result in?

A

lung development, which may result in pulmonary hypoplasia

44
Q

Solid tumors of the fetal lungs have been reported by US, appearing as:

A

echo-dense masses in the lung tissue

  • -pulmonary sequestration
  • -certain types of CAMS
45
Q

What does CAMS stand for?

A

cystic adenomatoid malformations

46
Q

What is pulmonary sequestration?

A

A supernumerary lobe of the lung, separated from teh normal tracheobronchial tree.

47
Q

In pulmonary sequestration, where is extra pulmonary tissue present?

A

Within the pleural lung sac or is connected to the inferior border of the lung w/in it’s own pleural sac.

48
Q

True or false: The extra lung tissue caused by pulmonary sequestration is functional.

A

False, it is nonfunctional and receives its blood supply from systemic circulation

49
Q

The arterial supply to the extra lung tissue is usually from:

A

the thoracic aorta, with venous drainage into the vena cava

50
Q

Sonographic features of pulmonary sequestration:

A
  • echo-dense solid mass resembling lung tissue, usually in the lower lobe of the lung
  • the majority of estralobar defects occur on the lt. side and rarely below the diagram
51
Q

Intralobar lesions appear:

A

spherical

52
Q

Extralobar sequestration appears:

A

cone-shaped or triangular mass

53
Q

What is congenital cystic adenomatoid malformation (CCAM)?

A

A multicystic mass w/in the lung consisting of primitive lung tissue and abnormal bronchial and bronchiolar-like structures

54
Q

CCAM is one of the __________ ________ malformations.

A

bronchopulmonary foregut

55
Q

How may forms of cystic adenomatoid malformation are there?

A

3–CCAM type I-III

56
Q

What happens in CCAM type I?

A

One or more large cysts replace normal lung tissue–single or multiple cysts measuring more than 2 cm and up to 19 cm.

57
Q

CCAM type II lesions consist of:

A

multiple small cysts–less than 1 cm.

58
Q

CCAM type II lesions are associated with fetal and/or chromosomal abnormalities in _____% of cases including: (3 things)

A
  • 25%

* renal agenesis, pulmonary anomalies and diaphragmatic hernia

59
Q

How are CCAM type III malformations characterized?

A

As bulky, large, noncystic lesions appearing as echo-dense masses of the entire lung lobe.

60
Q

What is differentiation of the CCAM types imperative?

A

B/c prognosis varies depending on the type of lesion.

61
Q

When there is a shift of the mediastinal structures, what may happen? (3 things)

A
  • lung compression may occur
  • hydrops may develop
  • Hydramnios may be seen due to esophageal compression, preventing normal swallowing
62
Q

US findings when a cystic or solid lung mass has been identified, attempt to do the following: (6 things)

A
  • Determine the # and size(s) of the cystic structure(s)
  • check for presence or absence of a mediastinal shift
  • identify and assess the size of the lungs
  • look for fetal hydrops
  • exclude cardiac masses
  • search for other fetal anomalies
63
Q

What is congenital bronchial atresia?

A

A rare pulmonary anomaly that results from the focal obliteration of a segment of the bronchial lumen

64
Q

Where is congenital bronchial atresia most commonly found?

A

In the left upper lobe and appears on US as an echogenic pulmonary mass lesion

65
Q

What is an important muscle separating the thoracic cavity from the abdomen?

A

the diaphragm

66
Q

How should the diaphragm appear in a normal fetus?

A

As a curvilinear hypoechoic structure coursing anteriorly to posteriorly

67
Q

The ________ ________ and ________ should be identified _________ to the diaphragm, with the lungs and heart positioned __________.

A

fetal stomach and liver; caudal; cephalad.

**Failure to recognize these normal relationships should prompt you to search for diaphragmatic defects

68
Q

When does the muscular diaphragm form?

A

Between the 6th and 14th week of gestation

69
Q

The diaphragm forms as a result of a chain of events involving the fusion of four structures:

A
  • the septum transversum
  • pleuroperitoneal membranes
  • dorsal mesentery of the esophagus
  • body wall
70
Q

What is the part of the diaphragm that forms last and is the most commonly defective?

A

The most posterior aspect

71
Q

What is a congenital diaphragmatic hernia?

A

A herniation of the abdominal viscera into the chest that results from a congenital defect in the fetal diaphragm.

72
Q

Where does the diaphragmatic hernia permit the abdominal organs to enter?

A

The fetal chest

73
Q

Where does the most common type of diaphragmatic defect occur? What percentage?

A

90% of defects occur posteriorly and laterally in the diaphragm–herniation through the **foramen of Bochdalek

74
Q

Where does the diaphragmatic hernia usually found?

A

On the left side of the diaphragm, and the left-sided organs enter the chest through the opening.

75
Q

The abnormally positioned abdominal organs shift the heart and mediastinal structures to the _______ side of the chest. Usually the stomach is in the chest near the heart, instead of below the ________.

A

right; diaphragm

76
Q

In left-sided hernias, what should you look for to be in the thoracic cavity? (4 things)

A
  • stomach
  • portions of the small and large intestines
  • left lobe of the liver
  • spleen
77
Q

Diaphragmatic hernias may occur ________ and ________ in the diaphragm, through the ____________, and may communicate with the pericardial sac.

A

anteriorly and medially; foramen of Morgagn

78
Q

What happens with the heart and stomach in anteromedial defects?

A

The heart may be normally positioned but surrounded by pleural fluid, while the fetal stomach may be located in its normal position in the abdomen.

79
Q

Defects on the right side of the diaphragm allow:

A

the right side abdominal organs (liver, gb, intestines) to enter the chest. As a result, the lungs are compressed and may become hypoplastic

80
Q

Sonographic findings of a left congenital diaphragmatic hernia:

A
  • cardiac silhouette is displaced to the right and an ectopic stomach is in the chest.
  • apex of the heart will be abnormally shifted, depending on the size of the defect
  • small bowel and colon are commonly intrathoracic, but are often collapsed and difficult to specifically identify if peristalsis isn’t present
81
Q

What is very important to note in order to make the diagnosis of a hernia?

A

The cardiomediastinal shift

82
Q

In a right-sided diaphragmatic hernia, you will see: (4 things)

A
  • the liver in the chest
  • possibly a collapsed bowel
  • the heart deviated far to the left
  • stomach alignment will be abnormal, but inferior to the diaphragm and moved to the right.
83
Q

The prognosis for congenital diaphragmatic hernias is poor for the fetus if: (4 things)

A
  • if the hernia is detected before birth
  • the presence of the stomach is found in the chest, especially if it’s dialted
  • if the left heart is underdeveloped
  • if congenital heart disease is present
  • -The primary cause of death is pulmonary hyplasia
84
Q

Frequently associated abnormalities include: (7 things)

A
  • cardiac malformations (20%)
  • CNS malformations (30%)
  • renal anomalies
  • vertebral defects
  • pulmonary hypoplasia
  • facial clefts
  • chromosomal abnormalities
85
Q

At birth, the majority of infants with congenital diaphragmatic hernia have 2 things:

A
  • pulmonary hypoplasia

* 2ndary respiratory insufficiency

86
Q

What is the mortality rate b/c of the increased frequency of coexisting fetal congenital anomalies?

A

75%

CH. 60 The Fetal Thorax (1 decks)

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