The diaphragm is the major muscle of respiration and the second most important muscle after the heart. Because the body relies so much on the diaphragm for respiratory function, understanding how many different diseases processes ultimately result in dysfunction of the diaphragm is vitally important.

When a decrease in diaphragmatic function occurs, a concomitant respiratory dysfunction occurs. The body has many inherent mechanisms to compensation for decreased diaphragmatic function. However, none of these processes can prevent respiratory compromise successfully if excursion of the diaphragm is moderately diminished or simply absent.

Diaphragmatic hernias can be classified into 2 categories: congenital defects and acquired defects. Congenital diaphragmatic hernias (CDH) occur through embryologic defects in the diaphragm. The majority of patients with CDH present early in life rather than later. However, a subset of adults may present with a congenital hernia undetected during childhood.

Blunt and penetrating traumas cause most of the acquired diaphragmatic hernias. As many as 1.6% of patients admitted to the hospital for blunt trauma have a diaphragmatic hernia.

History of the Procedure: The discussion of CDH dates back to the first description in 1679 by Lazarus Riverius who incidentally noted a CDH during a postmortem examination of a 24-year-old person.

In 1701, Sir Charles Holt described the classical clinical and postmortem findings of an infant with CDH in Philosophical Transactions of Royal Society of London. Giovanni Battista Morgagni in 1761 reviewed earlier literature and other accounts of both CDH and traumatic diaphragmatic hernias. He published his discussion along with the description of various types of diaphragmatic hernias in De Sedibus, Et Causis Morborum Per Anatomen Indagatis Libri Quinique (On the Seats and Causes of Disease, Investigated by Anatomy). In this masterpiece, he described the classical anterior diaphragmatic hernia, which today bears his name—Morgagni hernia. In 1848, Victor Alexander Bochdalek, a professor of anatomy at Prague, described both right and left posterolateral CDH. To this day, CDH commonly is referred to as Bochdalek hernia in honor of Victor Bochdalek's contribution to the field.

René Laennec published a treatise entitled Traite de l'auscultation mediate, et de des maladies des poumons et du coeur (A Treatise in the Diseases of the Lungs and Heart and on Mediate Auscultation), which described the numerous causes of diaphragmatic hernias and also an auscultatory mechanism by which to diagnosis a diaphragmatic hernia. In this treatise, Laennec also discussed the potential for surgical repair of a diaphragmatic hernia.

In 1888, Nauman of Sweden proposed a 2-cavity approach to repair diaphragmatic hernias after unsuccessfully operating on a 19-year-old patient with infarcted bowel that had herniated through a defect in the diaphragm. In 1889, J. O'Dwyer of New York attempted the first reported repair of a CDH in an infant. At that time, O'Dwyer discovered the loss of "right of domain" commonly encountered during attempts to repair CDH. In 1929, as reported in the Journal of the American Medical Association, the first successful CDH repair was performed in an infant, a 3.5-month-old girl.

In 1977, extracorporeal membrane oxygenation (ECMO) was introduced as a treatment for neonates with respiratory failure refractory to conventional care, and its application in the field of CDH has increased the survival rate of infants born with CDH from around 20% to 55%-75%. ECMO provides a modality by which blood can be withdrawn (either by arteries [venoarterial] or veins [venovenous]), oxygenated, and finally returned back into the body for circulation. By utilizing ECMO, infants are medically stabilized prior to surgery; surgical intervention after stabilization produces better outcomes.

Since the time of the first successful repair, great strides have been made in the field of CDH. However, until 1982, when ECMO was first used in the treatment of CDH, the mortality rate remained extremely high for infants born with CDH and severe pulmonary hypoplasia. The field of CDH continues to grow as knowledge of the disease entity increases and progress is made with newer treatment modalities.

Frequency: The occurrence of CDH is 0.08-0.45 cases per 1000 births. The survival rate is 55-65%.

Etiology: CDH occurs when the muscular entities of the diaphragm fail to develop normally, resulting in displacement of abdominal components into the thorax.

Bochdalek hernias of the diaphragm

These hernias make up the majority of cases of CDH. The major problem in Bochdalek hernias is posterolateral defects of the diaphragm, which results in either failure in the development of the pleuroperitoneal folds or improper or absent migration of the diaphragmatic musculature. As many as 90% of patients with CDH present in the neonatal period or within the first year of life. These cases have a mortality rate of 45-50%. Most of the morbidity and mortality of CDH relates to hypoplasia of the lung on the affected side. Thus, timely diagnosis and proper management remains the key to survival.

Morgagni hernias

This is a less common CDH, occurring in only 5-10% of CDH cases. The foramen of Morgagni hernia occurs in the anterior midline through the sternocostal hiatus of the diaphragm, with 90% of cases occurring on the right side.

Pathophysiology: See Relevant Anatomy for a detailed discussion. CDH involves associated anomalies, pulmonary hypoplasia, and pulmonary hypertension.

Clinical:

• Early diagnosis - Right-sided heart; decreased breath sounds on affected side; scaphoid abdomen; and bowel sounds in the thorax, respiratory distress, and/or cyanosis on auscultation

   

• Late diagnosis - Chest mass on chest radiograph, gastric volvulus, splenic volvulus, and/or large bowel obstruction

   

• Congenital hernias (neonatal onset): Respiratory distress and/or cyanosis occurs within the first 24 hours of life. CDH may not be diagnosed for several years if the defect is small enough.

   

• Congenital hernias (childhood or adult onset): Obstructive symptoms from protrusion of the colon, chest pain, tightness or fullness the in chest, sepsis following strangulation or perforation, and many respiratory symptoms occur.

   

• Traumatic rupture

   

  • Acute phase: Abdominal pain, concurrent injuries, respiratory distress, and cardiac dysfunction occur. Diagnosis often is missed during this phase because 95-100% of patients have associated injuries such as shock, respiratory depression, and visceral injury.

     

  • Latent phase: Upper GI symptoms, pain in the left upper quadrant or chest, pain in the left shoulder, dyspnea, and orthopnea occur.

     

  • GI obstructive phase: Nausea and vomiting occur with unrelenting abdominal pain, prostration, and respiratory distress.

INDICATIONS

The diaphragm is the major muscle of respiration and the second most important muscle after the heart. When a decrease in diaphragmatic function occurs, a concomitant respiratory dysfunction occurs. Although the body has many compensatory mechanisms in situations of decreased diaphragmatic function, none of these processes can prevent respiratory compromise successfully if excursion of the diaphragm is moderately diminished or simply absent. Appropriate treatment is essential in cases of CDH.

RELEVANT ANATOMY AND CONTRAINDICATIONS

Relevant Anatomy: The diaphragm is a modified half-dome of musculofibrous tissue that separates the thorax from the abdomen. Four embryologic components make up the formation of the diaphragm: the septum transversum, 2 pleuroperitoneal folds, cervical myotomes, and the dorsal mesentery.

Development begins during the third week of gestation and is completed by the eighth week. Failure of the development of the pleuroperitoneal folds and subsequent muscle migration results in congenital defects.

The muscular origin of the diaphragm is from the lower 6 ribs bilaterally, the posterior xiphoid process, and from the external and internal arcuate ligaments. A number of different structures traverse the diaphragm, including 3 distinct apertures that allow the passage of the aorta, the esophagus, and the vena cava.

The aortic aperture is the lowest and most posterior of the openings, lying at the level of the 12th thoracic vertebra. The aortic opening also transmits the thoracic duct and sometimes the azygous and hemiazygous veins. The esophageal aperture is surrounded by diaphragmatic muscle and lies at the level of the 10th thoracic vertebra. The vena caval aperture is the highest of the 3 openings and lies level with the disc space between the 8th and 9th thoracic vertebra.

Arterial supply to the diaphragm comes from the right and left phrenic arteries, the intercostal arteries, and the musculophrenic branches of the internal thoracic arteries. Some arterial blood is provided from small branches of the pericardiophrenic arteries that run with the phrenic nerve mainly where the nerves penetrate the diaphragm. Venous drainage is via the inferior vena cava and azygous vein on the right and the adrenal/renal and hemizygous veins on the left.

The diaphragm receives its sole muscular neurologic impulse from the phrenic nerve, which originates primarily from the fourth cervical ramus but also has contributions from the third and fifth rami. Originating around the level of the scalenus anterior muscle, the phrenic nerve courses inferiorly through the neck and thorax before reaching its terminal point, the diaphragm. Because the phrenic nerve has such a long course before reaching its final destination, any processes that disrupt the transmission of neurologic impulse through the nerve directly affect the diaphragm.

Contraindications: Some reports exist of increased mortality rates with early surgical intervention for CDH in infants. Many authors suggest that the patient be stabilized (often with the use of ECMO) and that repair be delayed until the infant is better prepared to survive the operation.