2. Anatomy of Diaphragm
In human anatomy, the thoracic diaphragm, or simply the
diaphragm is a sheet of internal skeletal muscle that extends
across the bottom of the thoracic cavity. The diaphragm
separates the thoracic cavity, containing the heart and lungs,
from the abdominal cavity and performs an important function in
respiration: as the diaphragm contracts, the volume of the
thoracic cavity increases and air is drawn into the lungs.
It is a musculotendinous dome-shaped structure that demarcates
pleural and peritoneal cavities.
7. Diaphragmatic Hernia
Diaphragmatic hernia is a defect or hole in the diaphragm that
allows the abdominal contents to move into the chest cavity.
Treatment is usually surgical.
Types
Congenital diaphragmatic hernia
a. Morgagni’s hernia
b. Bochdalek hernia
8.
9. Congenital Diaphragmatic Hernia
Congenital diaphragmatic hernia (CDH) is a birth defect of the diaphragm. The
most common type of CDH is a Bochdalek hernia; other types include
Morgagni hernia, diaphragm eventration and central tendon defects of the
diaphragm. Malformation of the diaphragm allows the abdominal organs to
push into the chest cavity, hindering proper lung formation.
Most CDH defects occur on the left side (80%); bilateral defects are
extremely rare.
Accurate determination of true survival rate is distorted by the fact
that many infants with CDH are stillborn, and many reports
tend to exclude infants with complex associated anomalies
from survival calculations.
10. Types
Bochdalek hernia
The Bochdalek hernia, also known as a postero-lateral diaphragmatic hernia, is the most common
manifestation of CDH.
In this instance the diaphragm abnormality is characterized by a hole in the postero-lateral corner of the
diaphragm which allows passage of the abdominal viscera into the chest cavity. The majority of Bochdalek
hernias (80–85%) occur on the left side of the diaphragm, a large proportion of the remaining cases occur on
the right side. To date, it carries a high mortality and an active area of clinical research
Morgagni hernia
This rare anterior defect of the diaphragm is variably referred to as Morgagni, retrosternal, or parasternal
hernia. Accounting for approximately 2% of all CDH cases, it is characterized by herniation through the
foramina of Morgagni which are located immediately adjacent and posterior to the xiphoid process of the
sternum.
11. Diaphragm eventration
The diagnosis of congenital diaphragmatic eventration is used when there is abnormal displacement (i.e.
elevation) of part or all of an otherwise intact diaphragm into the chest cavity. This rare type of CDH occurs
because in the region of eventration the diaphragm is thinner, allowing the abdominal viscera to protrude
upwards.
12. Pathogenesis
CDH is thought to result from failure of closure of the pleuro- peritoneal canal in the
developing fetus.
Normally, the pleuroperi- toneal cavities become separated by the developing
membrane during weeks 8 to 10 of gestation.
When this process fails, the pleuroperitoneal canal does not close, and a
posterolateral dia- phragmatic defect results. The posterolateral location of this
hernia is known as Bochdalek hernia; it is distinguished from a CDH of the
anteromedial location known as Morgagni hernia.
As a result of the defect, abdominal contents herniate into the thoracic cavity,
compressing the ipsilateral developing lung. These lungs have smaller bronchi, with
less bronchial branching and less alveolar surface area than lungs in normal
infants. The ipsilateral lung is affected more severely; however, both lungs are affected
by pulmonary hypoplasia. In addition to the abnormal airway development, the
pulmonary vasculature is also significantly affected by increased thickness of
arteriolar smooth muscle. Also, arteriolar vasculature is extremely sensitive to the
multiple local and systemic vasoactive factors. Hence, the severity of pulmonary
hypoplasia and pulmonary hypertension significantly affect the overall morbidity and
mortality in CDH infants.
13. Clinical Presentation and
Diagnosis
Most infants with CDH experience respiratory distress at birth.
The initial symptoms and signs may include
grunting respiration
chest retractions
dyspnea
cyanosis with scaphoid abdomen.
Decreased breath sounds along with bowel sounds may be auscultated over the chest
with CDH
The shifting of heart sounds to the right (for left-sided CDH) is common.
A significant differential of preductal and postductal pulse oximetry indicates the right-
to-left shunting due to PPHN.
14. The diagnosis of CDH is frequently made prenatally as early as 15 weeks of
gestation during a routine ultrasound evaluation.
Infants who have a late onset of CDH (beyond 25 weeks of gestation) have
been reported to have better overall survival.
The herniation of the stomach and liver, polyhydramnios, and associated
anomalies have been associated with poor outcome.
The chest radiograph demonstrates multiple bowel loops in the
thoracic cavity along with mediastinal shift.
In Morgagni hernia, the diagnosis is often delayed until childhood
because most infants are asymptomatic. Typically, the infant does well for
several hours after delivery during the so-called honeymoon period and
then begins to demonstrate worsening respiratory function.
In approximately 10% to 20% of cases, CDH is diagnosed beyond the
first 24 hours of life, at which time infants present with various symptoms of
feeding difficulties, respiratory distress, and pneumonia.
15.
16. Imaging Studies:
Level III ultrasonography and echocardiography should accompany a
diagnosis of CDH. Prenatal echocardiography may identify cardiac
anomalies (more commonly, ventricular hypoplasia, atrial septal defects, and
ventricular septal defects)
Chest radiography
An early chest radiograph is obtained to confirm the diagnosis of CDH.
Findings include loops of bowel in the chest, mediastinal shift, paucity of
bowel gas in the abdomen, and presence of the tip of a nasogastric tube in
the thoracic stomach. Repeated chest radiographs may reveal a change in
the intrathoracic gas pattern.
Right-sided lesions are difficult to differentiate from diaphragmatic
eventration and lobar consolidation.
Echocardiography
Further investigations should include early echocardiography, which may
reveal cardiac defects, decreased left ventricular mass, poor ventricular
contractility, pulmonary and tricuspid valve regurgitation, and right-to-left
shunting.
Repeated echocardiography is recommended to measure changes in the
pulmonary artery pressure, left-to-right shunt, and flow across the ductus
arteriosus.
17. TREATMENT
Laparoscopic occlusion of the fetal trachea, resulting in accumulation of lung fluid
to stimulate lung growth, has gained increasing interest.
External tracheal clips or endotracheal balloons can be placed laparoscopically
(often referred to as fetoscopy) to occlude the fetal trachea. The Tracheal
Occlusion To Accelerate Lung growth (TOTAL) trial is led by several European
centres.
The post- natal management of CDH is directed toward stabilization of the
cardiorespiratory status while minimizing iatrogenic injury from therapeutic interventions.
Immediate securing of the airway with endotracheal intubation is critical. Excessive mean
airway pressure ventilation can result in pneumothorax and compromised venous blood
return to the heart.
The first step in management is orogastric tube placement and securing the airway
(intubation).
Inhaled nitric oxide is used widely for its pulmonary vasodilatory effect.
Sildenafil, a phosphodiesterase type 5 inhibitor, works by inducing pulmonary vascular smooth
muscle relaxation and has been used in many centers with various results.
18.
19.
20. Surgical Repair
For infants with relatively stable pulmonary status, CDH repair can be safely performed on the
second to fourth day of life after the potential honeymoon period.
CDH repair after ECMO is associated with improved survival compared with repair while on
ECMO.
At operation, the preferred approach for a posterolateral CDH is through a subcostal
abdominal incision. The viscera are reduced into the abdominal cavity, and the
pos- terolateral defect in the diaphragm is approximated with interrupted
nonabsorbable sutures.
When present (10% to 15% of cases), a hernia sac should be excised.
Typically, the hernia defect is large, with only a small leaflet of diaphragmatic
tissue present anteromedially. Although primary repair of the defect is ideal,
closure with excessive tension must be avoided to prevent hernia
recurrence.
21. A number of reconstructive techniques and materials are available for the repair
of large hernia defects.
The surgical technique of abdominal or thoracic muscle flaps can be considered, but
the use of prosthetic material, most commonly Gore-Tex patch, has become
widespread
The advantages of a prosthetic patch are shorter operative time and a tension-free
repair. However, the major potential problems with prosthetic patches are the risks of
infection and recurrence of the hernia.
When CDH is repaired on ECMO, particular attention must be paid to achieve
hemostasis.
However, despite the use of careful surgical techniques with diligent hemostasis,
postoperative bleeding is a common major complication.
Beyond the immediate postoperative period, many infants with CDH experience
significant morbidity because of PPHN and respiratory dysfunction.
For example, infants who survive aggressive management of severe respiratory failure may
manifest neurologic problems, such as motor and cognitive deficits, developmental delay,
seizures, and hearing loss. Other problems include gastroesophageal reflux (GER) disease
and foregut dysmotility.
22.
23. Complications
Complications observed in the early post operative
period include recurrent pulmonary hypertension and a
deterioration in respiratory mechanics and gaseous
exchange
Less commonly observed complications are the
disruption of suture line, recurrence of diaphragmatic
hernia, leakage of peritoneal fluid and blood into the
thorax and development of an ipsilateral hydrothorax
Small bowel obstruction may occur secondary to
adhesions or volvulus