Fetal Chest and Lungs

Question 1

What does fetal lie refer to?

Answer 1

The relationship between the LONG axis of the fetus with respect to the LONG axis of the mother.

Question 2

What are the three types of fetal lie?

Answer 2

• Longitudinal lie
• Transverse lie
• Oblique lie

Question 3

What is the embryonic period of fetal chest and lung development?

Answer 3

From 5-7 menstrual weeks, when normal anatomic structures in the chest are established.

Question 4

What is the alveolar period of fetal chest and lung development?

Answer 4

Beginning at 32 menstrual weeks until birth, determining the maturity and proper functionality of the lungs.

Question 5

What can abnormalities during the embryonic period lead to?

Answer 5

Absence or malformation of fundamental anatomic structures such as the trachea, bronchial tree, and alveolar bed.

Question 6

What marks the beginning of pulmonary development?

Answer 6

• End of the 5th menstrual
• A single lung bud appears at the distal end of each primordial bronchus.

Question 7

What are the four conditions necessary for lung development?

Answer 7

• Adequate thoracic space
• Normal fetal breathing movements
• Fluid production in the lungs
• Adequate amniotic fluid volume

Question 8

What is the function of amniotic fluid?

Answer 8

• Cushions the fetus
• Allows for free fetal movement
• Essential for fetal lung development
• Provides a source of fetal nutrition
• Aids in maintaining fetal temperature

Question 9

What is Polyhydramnios?

Answer 9

Abnormally increased amount of amniotic fluid, frequently a primary sign of an underlying fetal disorder. AF
DVP > 8 cm.

Associated abnormalities:

• Fetal neural tube defects
• Fetal upper GI obstructions
• Fetal hydrops
• Trisomy 18
• Cystic hygroma
• Placental abnormalities
• Twin-to-twin transfusion

Question 10

What is Oligohydramnios?

Answer 10

Abnormally decreased amount of amniotic fluid, associated with conditions that allow a DRIPP of fluid to remain. AF DVP <2 cm

Question 11

What is Oligohydramnios associated with that allow a DRIPP of fluid to remain?

Answer 11

Demise
Renal abnormalities
IUGR
PROM
Post dates

Question 12

What is the 4 Quadrant Amniotic Fluid Index (AFI) of Polyhydramnios and Oligohydramnios?

Answer 12

Polyhydramnios: AFI greater than 24 cm
Oligohydramnios: AFI less then 5 cm

Question 13

What is the Maximum Vertical Pocket estimate (MVP)?

Answer 13

• A pocket measuring 2-8 cm is considered normal

Polyhydramnios: greater than 8 cm and
Oligohydramnios: less than 2 cm.

Question 14

What is the sonographic appearance of the fetal lungs?

Answer 14

• Surrounds the heart
• Homogeneous echotexture
• Echogenicity increases with gestational age
• Initially equal to liver, later slightly more echogenic

Question 15

How do fetal lungs appear on ultrasound throughout pregnancy?

Answer 15

• 1st Trimester: Hard to distinguish from liver; similar echogenicity, diaphragm not visible
• 2nd Trimester: Visible; homogeneous mid-range echoes
• 3rd Trimester: More echogenic than liver; diaphragm wall clearly seen

Question 16

Second trimester of the lungs

Answer 16

Question 17

Third trimester of the lungs

Answer 17

Question 18

What is the thoracic circumference measurement used for?

Answer 18

• To rule out pulmonary hypoplasia or cardiomegaly.
• Heart should take up1/3 of the chest!

Question 19

What is pulmonary hypoplasia?

Answer 19

Underdevelopment or incomplete development of the lungs.

Question 20

What can cause pulmonary hypoplasia?

Answer 20

• Not enough thoracic space
• Abnormal fetal breathing movements
• Lack of fluid production in the lungs
• Not enough amniotic fluid

Question 21

What are the associated abnormalities with pulmonary hypoplasia?

Answer 21

• Diaphragmatic hernia
• Sequestration of the lung
• Agenesis of the diaphragm
• Intrathoracic masses
• Thanatophoric lung (associated - with lethal skeletal dysplasia: Thanatophoric dysplasia, type I).

Question 22

What is Thanatophoric Dysplasia (TD)?

Answer 22

• Severe, lethal short-limb dwarfism
• Perinatal lethal (usually results in death around birth)
  Sonographic features:
• Shortened limbs
• Severely small, bell-shaped thorax
• Large head with prominent forehead(“cloverleaf skull”)
• Curved femurs
• Flattened vertebral bodies

Question 23

What is the significance of the fetal diaphragm on ultrasound?

Answer 23

• Muscular structure forming the inferior border of the thoracic cavity
• Best seen in second trimester in the coronal plane as a curved, hypoechoic line
• Essential for evaluating diaphragmatic hernia

Question 24

What are the great vessels seen in the 3-vessel view (3VV) of the fetal thorax?

Answer 24

• Superior vena cava (SVC)
• Ascending and descending thoracic aorta
• Pulmonary artery
• Ductus arteriosus (connects pulmonary artery to descending aorta)

Pulmonary abnormalities that we can see by ultrasound are incompatible with life

Question 25

What is pleural effusion (hydrothorax) and how does it appear on ultrasound?

Answer 25

* **Pleural effusion** = fluid in the pleural cavity * May be caused by: * **Chylothorax** (lymphatic leakage) * **Hydrops fetalis** **Sonographic findings**: * **Anechoic fluid** around the lung * Conforms to pleural cavity shape * Can be **unilateral or bilateral**

Question 26

What is hydrops fetalis?

Answer 26

A serious condition where **abnormal amounts of fluid **build up in** two or more** body areas of a fetus or newborn.

Question 27

What are the two types of hydrops fetalis?

Answer 27

* Immune hydrops fetalis * Nonimmune hydrops fetalis

Question 28

What is **immune hydrops fetalis** and what causes it?

Answer 28

* A complication of **Rh incompatibility** between an **Rh-negative mother** and **Rh-positive fetus** * The mother produces **antibodies** that cross the placenta and destroy fetal red blood cells * Leads to **severe fetal anemia** and **total body swelling** * **Swelling** can impair organ function * **Preventable** with proper Rh immunoglobulin treatment

Question 29

What is RhoGAM and how does it help prevent immune hydrops fetalis?

Answer 29

* **RhoGAM** is a medication given to **Rh-negative pregnant women** * It **prevents the mother from producing antibodies** against **Rh-positive fetal red blood cells** * This significantly **reduces the risk** of developing **immune hydrops fetalis**

Question 30

What is **nonimmune hydrops** fetalis and what are its common causes?

Answer 30

* **More common** than immune hydrops; accounts for **up to 90%** of hydrops cases * Occurs when the body **cannot properly regulate fluid** due to an underlying condition **Main causes**: * **Heart or lung problems** * **Severe anemia** (e.g., thalassemia, infections) * **Genetic/developmental disorders** (e.g., Turner syndrome)

Question 31

What is congenital diaphragmatic hernia (CDH)?

Answer 31

A result of **incomplete fusion** of the diaphragmatic structures at **6-10 menstrual weeks.** * Allows abdominal organs to **herniate into the chest cavity** * **Left-sided hernias** are most common (**95% of cases**) - involve herniation of the **stomach, intestines, and spleen** * **Right-sided hernias** are rare ## Footnote Associated abnormalities with CDH: ▶ Pulmonary hypoplasia ▶ Pulmonary sequestration ▶ Trisomies 13, 18 and 21 ▶ Turner Syndrome ▶ Neural tube defects ▶ Congenital cardiac anomalies

Question 32

What is pulmonary sequestration?

Answer 32

* A **separated, accessory lung tissue** with **no connection** to the tracheobronchial tree * Has its own **independent arterial blood supply** *Two types:* * **Intralobar sequestration** * **Extralobar sequestration**

Question 33

What is intralobar sequestration and how does it appear on ultrasound?

Answer 33

* **Most common type** of pulmonary sequestration (**85% of cases**) * Sequestered lung segment is **connected to normal lung** without its own pleura **Sonographic findings:** * **Well-defined, solid echogenic mass** near normal lung * **Feeding vessel** from the **aorta** seen on **color Doppler** * **Signs of hydrops** may be present (but not always)

Question 34

What is congenital cystic adenomatoid malformation of the lung (CCAM)? ## Footnote **Aka:** Congenital Pulmonary Airway Malformation **(CPAM)** and Cystic Adenomatoid Malformation of the Lung **(CAML)**

Answer 34

* A **lung development abnormality** where normal lung is replaced by **nonfunctioning cystic tissue** * Typically **unilateral**, involving an **entire lobe** * **Prognosis** depends on how much normal lung is replaced by abnormal tissue * **Mediastinal shift** caused by the mass increases the risk of **fetal demise**

Question 35

What is a common complication associated with CCAM?

Answer 35

Mediastinal shift by a cystic adenomatoid malformation mass.

Question 36

What are the three categories of CCAM?

Answer 36

1. **Type I (Macrocystic)**: Large cysts (2–10 cm); most common (70%) 2. **Type II**: Multiple small cysts (<2 cm); less common 3. **Type III (Microcystic/Noncystic)**: Very small cysts (<0.5 cm); often causes **mediastinal shift** Associated abnormalities: * **Renal anomalies** * **Cardiac defects** * **Gastrointestinal abnormalities** Possible complications: * **Fetal hydrops** * **Polyhydramnios** * **Pericardial effusion** * **Pleural effusion**

Question 37

What defines **Type I CCAM** and how does it appear on ultrasound?

Answer 37

* **Large (macrocystic) cysts**, 2–10 cm * Most common type (\~70%) * Appears as **nonvascular cystic masses** in the fetal lung

Question 38

What characterizes **Type II CCAM** and what is its ultrasound appearance?

Answer 38

* Multiple **small cysts (< 2cm)** * Appears as **homogeneously echogenic lobes** on ultrasound

Question 39

What defines **Type III CCAM** and how does it present on ultrasound?

Answer 39

* **Microcystic (< 0.5cm)** or noncystic lesions * Appears **solid** and causes **mediastinal shift** with lateral heart displacement * May show **pericardial and pleural effusions**

Question 40

True or False: The left-sided diaphragmatic hernias are more commonly observed than right-sided.

Answer 40

True

Question 41

What is Tracheal Atresia?

Answer 41

**Rare and lethal pulmonary anomaly** where the trachea fails to form or is obliterated, usually at the larynx. A **lethal condition** **Associated abnormalities:** * Renal anomalies * CNS malformations * Tracheoesophageal atresia ## Footnote Tracheal Atresia is often lethal and usually involves obstruction at the larynx.

Question 42

What are the sonographic signs of Tracheal Atresia?

Answer 42

* **Bilateral echogenic** lungs * **Fluid** filled trachea * **Enlarged** lungs adjacent to a **small compressed** heart * **Reduced** cardiothoracic circumference ratio * Polyhydramnios ## Footnote These signs are critical for diagnosing Tracheal Atresia during prenatal imaging.

Question 43

What is a characteristic chart of chest masses?

Answer 43

* **Cystic Masses: **CCAM **type I**, bronchogenic cyst, congenital diaphragmatic hernia, enteric cyst, mediastinal meningocele, and esophageal duplication cyst * **Cystic and Solid:** CCAM **type II**, enteric cyst, teratoma, congenital diaphragmatic hernia, mixed CAML type II sequestration, thoracic neuroblastoma * **Solid:** CCAM **type III**, pulmonary sequestration, congenital diaphragmatic hernia, esophageal duplication cyst ## Footnote This classification helps in identifying and differentiating between various congenital chest masses.

Question 44

True or False: Tracheal Atresia is characterized by a fluid-filled trachea.

Answer 44

True ## Footnote The presence of a fluid-filled trachea is a significant indicator in the ultrasound findings for Tracheal Atresia.