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A term newborn has severe respiratory distress and cyanosis at birth. On
examination, he has a scaphoid abdomen, and no breath sounds on the left with
shift of the precordial pulse and heart sounds to the right. The baby undergoes
intubation and is placed on assisted ventilation. Chest radiograph confirms a
diagnosis of left congenital diaphragmatic hernia (Figure).
Figure: Congenital diaphragmatic hernia
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Despite intensive care support, including inhaled nitric oxide and extracorporeal
membrane oxygenation, the baby dies. Autopsy reveals marked bilateral lung
hypoplasia.
Of the following, the MOST likely stage at which congenital diaphragmatic hernia
affects lung development is:
embryonic (3-7 weeks after conception)
pseudoglandular (5-17 weeks after conception)
canalicular (16-26 weeks after conception)
saccular (24-38 weeks after conception)
alveolar (36 weeks after conception to 2 years)
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Lung development can be divided into five stages of
organogenesis. These stages display all of the histologic
changes that the lung undergoes during morphogenesis and
maturation of its structural elements. These are the
embryonic, pseudoglandular, canalicular, saccular, and
alveolar phases of lung development, which extend
throughout gestation and into the postnatal period. These
stages of lung development and the consequences of altered
lung development during these stages are summarized in the
Table.
Table. Stages in Lung Development*
Stage/Postconceptional Major Developmental Events
Age
Embryonic/3-7 wks
Development of proximal
airways
Separation of trachea
and esophagus
Development of
pulmonary arteries and
veins
Pseudoglandular/5-17 wks
Abnormalities/Syndromes
Laryngeal, esophageal,
tracheal atresia
Tracheal and bronchial
stenosis
Tracheo-esophageal
fistula
Pulmonary
agenesis/aplasia
Bronchogenic cysts
Extralobar pulmonary
sequestration
Development of lower
conducting airways
Pulmonary arterial
development parallels
airway branching
Pulmonary lymphatics
appear
Pleuroperitoneal cavity
closes
Renal agenesis-pulmonary
hypoplasia
Intralobar pulmonary
sequestration
Pulmonary cysts
Cystic adenomatoid
malformation
Pulmonary
lymphangiectasia
Tracheomalacia and
bronchomalacia
Congenital diaphragmatic
hernia
Canalicular/16-26 wks
Formation of gasexchanging acini
Air-blood barrier and
capillary network forms
Alveoalar type I and
type II cells differentiate
Lamellar bodies form in
type II cells
Renal dysplasiapulmonary hypoplasia
Alveolar capillary
dysplasia
Respiratory insufficiency
Surfactant deficiency
Saccular/ 24-38 wks
Distal air spaces continue
Oligohydramnios and
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Alveolar/36 wks to 2 y
to branch and grow
Surfactant synthesized
and secreted by typ2 II
cells
Fetal lung fluid and fetal
breathing
pulmonary hypoplasia
Alveolar capillary
dysplasia
Surfactant deficiency
Respiratory distress
syndrome
Apnea of prematurity
Secondary sept form,
subdividing saccules into
alveoli
Surfactant production
increases in type II cells
Lobar emphysema
Pleural effusions and fetal
hydrops
Persistent fetal circulation
Pulmonary hypertension
Pneumonia
Meconium aspiration
syndrome
Respiratory distress
syndrome/hyaline
membrane
disease/surfactant
deficiency
* Adapted from Wert SE. Normal and abnormal structural development of the lung.
In: Polin RA, Fox WW, Abman SH, eds. Fetal and Neonatal Physiology. 3 rd ed.
Philadelphia, Pa: WB Saunders; 2004
Congenital diaphragmatic hernias result from failure of fusion of the multiple
developing components of the diaphragm. The diaphragm is derived from the
septum transversum (separating the peritoneal and pericardial spaces), the
mesentery of the esophagus, the pleuroperitoneal membranes, and the muscle of
the chest wall. Congenital diaphragmatic hernias occur where fusion of these
components fails.
Following folding of the fetal head at four to five weeks' gestation, the septum
transversum comes to lie as a semicircular shelf separating the heart from the
liver. The septum transversum does not completely separate the thoracic cavity
from the peritoneal cavity but allows pericardioperitoneal canals to exist on either
side of the esophagus. During the fifth week of gestation, the pleuroperitoneal
membranes develop along a line connecting the root of the 12th rib with the tips
of the 7th to 12th ribs. The pleuroperitoneal membranes grow ventrally to fuse
with the posterior margins of the septum transversum and the dorsal mesentery
of the esophagus. Hence, at six to seven weeks' gestation, the pleuroperitoneal
canals are closed; the left closes after the right. The mesentery of the esophagus
condenses to form the left and right crura of the diaphragm, and the mesoderm of
the body wall forms the outer rim of diaphragmatic muscle.
The posterolateral diaphragmatic defect or Bochdalek hernia is postulated to
result from failure of closure of the pleuroperitoneal canals. The canal remains
open when the intestines return to the abdomen at 10 weeks' gestation. Some
portion of the intestine and other viscera enter the thorax and lead to compression
of the developing lung at the crucial pseudoglandular stage and shifting of the
mediastinum to the contralateral side. This shift causes compression of the heart
and the contralateral lung as well. Morgagni hernias form at the sternocostal
junctions of the diaphragm anteriorly.
Congenital hernias occur in about 0.1 to 0.5 per 1,000 births. Those presenting in
neonates are most often Bochdalek hernias; of these, 80% occur on the left.
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Morgagni hernias make up about 2% to 3% of surgically treated diaphragmatic
hernias. Although congenital, they usually present in adults and occur on the right
side in 80% to 90% of cases.
The presentation of congenital diaphragmatic hernias varies greatly, from death in
the neonatal period to an asymptomatic serendipitous finding in adults. Newborns
with Bochdalek hernia have respiratory distress, diminished breath sounds on one
side of the chest, and a scaphoid abdomen. Serious chromosomal anomalies are
found in 30% to 40% of cases. The most common of these are trisomies 13, 18,
and 21. Pulmonary hypoplasia occurs on the side of the hernia, but some degree of
hypoplasia may also occur in the contralateral lung. Pulmonary hypertension is
common. The major causes of mortality in infants with Bochdalek hernias are
associated anomalies and respiratory failure. Prenatal diagnosis may be made
with an ultrasonographic examination by visualizing stomach or loops of bowel in
the chest.
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References:
Behrman RE, Kliegman RM, Jenson HB. Diaphragmatic hernia. In: Nelson Textbook
of Pediatrics. 17th ed. Philadelphia, Pa: WB Saunders Co; 2004
Feldman M, Friedman LS, Sleisenger MH. Sleisenger & Fordtran's Gastrointestinal
and Liver Disease. 7th ed. Philadelphia, Pa: WB Saunders Co; 2002
Harford W, Jeyarajah R. Abdominal hernias and their complications, including
gastric volvulus. Sleisenger & Fordtran's Gastrointestinal and Liver Disease. 7th
ed. Philadelphia, Pa: WB Saunders Co; 2002;chap 20:369-385
Lewis N, Glick PL. Diaphragmatic hernias. Accessed May 15, 2006,
at: http://www.emedicine.com/ped/topic2937.htm
Townsend CM, Beauchamp RD, Evers BM, Mattox KL, eds. Sabiston Textbook of
Surgery: The Biological Basis of Modern Surgical Practice. 17th ed. Philadelphia,
Pa: WB Saunders Co; 2004
Wert SE. Normal and abnormal structural development of the lung. In: Polin RA,
Fox WW, Abman SH, eds. Fetal and Neonatal Physiology. 3 rd ed. Philadelphia, Pa:
WB Saunders; 2004
American Board of Pediatrics Content Specification(s):
Know the indications for assisted ventilation in the delivery room
Understand the pathogenesis, pathophysiology, and risk factors of persistent
pulmonary hypertension
Recognize the clinical features of persistent pulmonary hypertension
Recognize the clinical features of congenital malformations of the lung, including
congenital pulmonary lymphangiectasia and the cystic lung diseases, such as
congenital lobar emphysema, cystic adenomatoid malformation, and mediastinal
tumors
Recognize the radiographic features of congenital malformations of the lung,
including congenital pulmonary lymphangiectasia and the cystic lung diseases,
such as congenital lobar emphysema, cystic adenomatoid malformation, and
mediastinal tumors
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