A 24-year-old primigravida has a fetal ultrasound p formed at 18 weeks’ gestation that shows a normal amniotic fluid index, but there is a large echogenic region in the right lung. A term infant is delivered with no apparent external anomalies, but soon after birth the infant has respiratory distress. CT imaging shows a normal left lung, but there is an area of opacification in the right lung supplied by a vessel from the aorta. Which of the following is the most likely diagnosis?
A Extralobar sequestration
B Foregut cyst
C Hyaline membrane disease
D Oligohydramnios sequence
E Tracheoesophageal fistula

审题

1. a large echogenic强回声代表着什么？
2. amniotic fluid index（羊水指数？）是什么，有什么临床意义？
3. 羊水指数与本题中的肺部疾病有什么关系？这种病容易与什么疾病混淆？

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做题

自选答案：c

归类：d类题

标准答案：a
解析：
An extralobar sequestration produces an external mass effect upon normal lung and limits gas exchange because it is not connected to airways and has an anomalous systemic arterial connection.
Intralobar sequestrations within lung parenchyma typically are diagnosed in childhood in association with recurrent infections.
Foregut cysts in the hilum or mediastinum are not connected to airways and can produce a mass effect if large, but most are not.
The term gestation likely excludes pulmonary immaturity with lack of surfactant.
The normal amount of amniotic fluid excludes the oligohydramnios sequence that often leads to pulmonary hypoplasia.
A tracheoesophageal fistula predisposes to pulmonary infection.

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知识辐射

1. Pulmonary sequestration：肺隔离症

叶内型与叶外型

UPToDate: Bronchopulmonary sequestration (BPS), sometimes referred to simply as pulmonary sequestration, is a rare congenital abnormality of the lower airway. It consists of a nonfunctioning mass of lung tissue that lacks normal communication with the tracheobronchial tree and that receives its arterial blood supply from the systemic circulation.
Extralobar BPS are often identified on prenatal ultrasound and become symptomatic early in life, whereas Intralobar BPS are more commonly identified later in life secondary to recurrent infection.
支气管肺隔离症

2. Foregut cyst前肠囊肿 百度

3. Hyaline membrane disease透明膜病

又称：Respiratory distress syndrome (RDS)呼吸衰竭综合征

a common problem in preterm infants. This disorder is caused primarily by deficiency of pulmonary surfactant in an immature lung. RDS is a major cause of morbidity and mortality in preterm infants.
RDS即呼吸窘迫综合征，最常见的病因是早产（NRDS），足月儿出现RDS是遗传性呼衰。

Normal fetal alveolar development occurs in the following stages :

• Embryonic period – At approximately 26 days gestation, the embryonic stage begins with the first appearance of the fetal lung, which appears as a protrusion of the foregut. The initial branching of the lung occurs at 33 days gestation forming the prospective main bronchi, which begin to extend into the mesenchyme. Further branching forms the segmental bronchi as the lung enters the next stage of development.

• Pseudoglandular stage – In the pseudoglandular stage (5th to 16th weeks of gestation), 15 to 20 generations of airway branching occur starting from the main segmental bronchi and ending as terminal bronchioles. At the end of the pseudoglandular stage, the airways are surrounded by a loosely packed mesenchyme, which includes a few blood vessels, and is lined by glycogen-rich and morphologically undifferentiated epithelial cells with a columnar to cuboidal shape. In general, epithelial differentiation is centrifugal, so the proximal airways are lined with the most differentiated cells, with progressively less differentiation in the more distal tubules.

• Canalicular stage – During the canalicular stage (16th to 25th weeks of gestation), the transition from previable to a potential viable lung occurs as the respiratory bronchioles and alveolar ducts of the gas exchange region of the lung are formed. The surrounding mesenchyme becomes more vascular and condenses around the airways. The closer vascular proximity ultimately results in fusion of the capillary and epithelial basement membranes. After 20 weeks gestation, cuboidal epithelial cells begin to differentiate into alveolar type II cells with formation of cytoplasmic lamellar bodies . The presence of lamellar bodies indicates the production of surfactant, which is produced from glycogen and stored in the lamellar bodies.

• Saccular stage – At the beginning of the saccular stage (approximately 24 weeks gestation), there is potential for viability because gas exchange is possible due to the presence of large and primitive forms of the future alveoli. In this stage, formation of alveoli (ie, alveolarization) occurs by the outgrowth of septae that subdivide terminal saccules into anatomic alveoli, where air exchange occurs. The number of alveoli in each lung increases from zero at 32 weeks gestation to between 50 and 150 million alveoli in term infants and 300 million in adults. Alveolar growth continues for at least two years after birth at term.

4. Oligohydramnios sequence：又称potter 综合征

Maternal oligohydramnios (decreased amniotic fluid); newborns have Potter facies, a deformation due to oligohydramnios—findings include low-set ears, parrot beak nose, and lung hypoplasia 、renal agenesis/polycystic kidney disease.

Tracheoesophageal fistula气管食管瘘：

气管食管瘘/最常见的为C

1. Epidemiology

a. Most common congenital anomaly of esophagus
b. Characteristics of the most common type：(1) Proximal esophagus ends blindly(2) Distal esophagus arises from the trachea.
c. Risk factors include:Advanced maternal age, smoking, and obesity

2. Pathogenesis is unknown

3. Clinical findings

a. Maternal polyhydramnios (excess amniotic fluid)
• Swallowed amniotic fluid cannot be reabsorbed in the small intestine.
b. Abdominal distention in newborn (NB)
• Air in the stomach from tracheal fistula
c. Frothing and bubbling around the mouth at birth
d. Difficulty with feeding：(1) Food is regurgitated out of the mouth.(2) NB develops chemical pneumonia from aspiration.
e. VATER syndrome
(1) Vertebral abnormalities
(2) Anorectal (usually anal atresia)
(3) TE fistula
(4) Renal disease and absent radius
f. VACTERL syndrome
• Same as VATER syndrome except C stands for cardiac and L stands for limb abnormalities