Morgagni Hernia

Etiology

Morgagni hernias discovered during infancy or early childhood are often associated with other congenital anomalies, with the incidence ranging from 34% to 50%.[7][8] The most common anomalies include cardiac defects (25-60%) and trisomy 21 (15%-71%). Malrotation, anorectal malformations, omphalocele, skeletal anomalies, and pentalogy of Cantrell have also been associated with a Morgagni hernia. Defective dorsoventral migration of rhabdomyoblasts, linked to increased cellular adhesiveness in patients with trisomy 21, may explain the higher recurrence rate of hernia repair in individuals with Down syndrome.[9]

In contrast to patients with a Bochdalek hernia, who usually become symptomatic soon after birth due to pulmonary hypoplasia, up to 50% of patients with Morgagni hernias are asymptomatic upon diagnosis.[10] Patients younger than age 2 are more likely to be symptomatic at the time of diagnosis.[11][12] However, the diagnosis may not be made until adulthood, when chest imaging is performed for unrelated reasons. Due to pericardial attachments supporting the left side of the diaphragm, up to 91% of Morgagni hernias are found on the right side, 5% are on the left side, and 4% are bilateral.[13]

Epidemiology

The estimated incidence of Morgagni hernias is between 1 in 2000 and 1 in 5000 live births. However, the true incidence of this condition is unknown. Morgagni hernias comprise 2% to 5% of all CDH cases.

Pathophysiology

The central tendinous portion of the diaphragm, formed by the septum transversum (a mesodermal sheet), plays a key role in separating the thoracic from the abdominal cavity. The diaphragm is anchored anteriorly by small muscle bundles attached to the sternal part of the xiphoid process and is further supported by attachments along its costal and lumbar regions. A Morgagni hernia arises from a defect at the junction where the diaphragm's septum transversum and costal elements meet, allowing abdominal contents to herniate into the thoracic cavity. A Morgagni hernia is located posterolaterally to the sternum and is caused by a failure of the pars tendinalis part of the costochondral arches to fuse with the pars sternalis.[14] Failure of fusion on the right side gives rise to a Morgagni hernia, while a failure on the left is often called a Larrey hernia.

Although left-sided and bilateral hernias occur, 90% of Morgagni hernias occur on the right side due to the pericardial attachments to the diaphragm that provide protection and support to the left side. The defects are initially small, and over 90% of defects have a hernia sac. The defects can grow over time due to increased intraabdominal pressure, causing diaphragm weakness.[15] The hernia most often contains a portion of the large intestine (54% to 72%) or omentum (65%) but may also have parts of the small intestine, stomach, and liver.[16][17] 

History and Physical

A Morgagni hernia usually presents later in life than a Bochdalek hernia, with patients reporting respiratory and upper gastrointestinal symptoms as their main complaint. However, up to 50% of patients may be asymptomatic on presentation, with diagnosis occurring during the workup for an unrelated problem.[18] Respiratory manifestations, such as respiratory distress or tachypnea (20%-73%) and recurrent pulmonary infections (29%-55%), are most common in children. However, poor feeding, failure to thrive, and coughing and choking with feeds may also be seen.[19][20][21]

Likewise, adults may experience gastrointestinal and respiratory symptoms, including retrosternal or chest pain often relieved by standing, dyspnea, flatulence, indigestion, or cramping. Trauma, obesity, pregnancy, chronic constipation, or chronic cough may precipitate the onset of symptoms by increasing intraabdominal pressure, causing herniation of the omentum and intestine into the defect. The physical exam may reveal bowel sounds on chest auscultation if the intestine is present in the hernia.[22] One must also be aware of acute strangulation or volvulus, as evidenced by rebound tenderness, tachycardia, persistent vomiting, and blood on the rectal exam.[23] These patients require prompt resuscitation, diagnosis, evaluation of the bowel with possible bowel resection, and repair of the hernia defect.[24]

Evaluation

The definitive diagnosis is made radiologically, particularly with anteroposterior and lateral chest radiographs. With bowel herniation, a radiolucent paracardiac shadow is seen on the anteroposterior view that is retrosternal on lateral radiographs. Chest radiographs alone can make the diagnosis approximately 71% of the time, usually when the bowel is seen in the chest. A rounded opacity is usually found at the right cardiophrenic angle when the omentum or solid organs herniate through the defect.

Further imaging, such as a chest computed tomography (CT) scan, swallow study, or barium enema, may be used to confirm the diagnosis. A CT scan is often the next step in the evaluation, as it is easy to obtain and has up to a 100% rate of correctly identifying the defect. The CT scan typically shows a retrosternal fat density mass when omentum is included or an air-containing viscus if the bowel has herniated through the defect. A swallow study may be performed if a hiatal hernia is part of the differential diagnosis. A barium enema has also been employed, where an upward angulation of the midtransverse colon can identify a herniated colon into the defect (see Image. Morgagni Hernia on Radiography).

Treatment / Management

Current recommendations for the initial ventilator settings in managing CDH include the following:

• Peak inspiratory pressure less than 25 cm H2O
• Positive end-expiratory pressure 3 to 5 cm H2O
• 40 to 60 breaths/min rate to maintain the partial pressure of CO2 between 50 and 70 mm Hg [25]

Repair is recommended for all Morgagni hernias due to the risk of incarceration. However, the repair approach and type are still under debate.[26] The hernia defect may be approached either through an abdominal or thoracic incision. A posterolateral right thoracotomy is made through the 6 intercostal spaces when utilizing the thoracic approach. The advantages of this technique are a more accurate vision of the right-sided defect, easier dissection of the hernia sac off the pericardium, mediastinal, and pleural structures, and a potentially safer reduction of abdominal viscerae such as the liver. The hernia sac may or may not be excised. Afterward, 0-silk or 0-polypropylene sutures are used to close the defect. The thoracic approach has several disadvantages, including the risk of missing a bilateral defect due to limited visibility, a higher chance of requiring postoperative ventilation based on preoperative respiratory status, and the risk of chest wall deformity in children if performed before significant growth.

Meanwhile, the abdominal approach may be performed either through an open laparotomy incision or with minimally invasive laparoscopic techniques. The advantages of the abdominal technique include the ability to identify and repair bilateral defects and evaluate and repair other intraabdominal pathology, such as malrotation, during the same operation. Open laparotomy is typically reserved for patients who require an emergency repair, cannot tolerate laparoscopy, have severe scoliosis or extensive adhesions, or warrant extensive bowel resection or retrieval from an incarcerated hernia.

An upper abdominal incision is performed, and the hernia contents are reduced. Some debate exists about whether the hernia sac should be excised or incorporated into the sutures. However, primary repairs should be under minimal tension. Nasr recommends placing a mesh for hernias larger than 20 to 30 cm. The defect is repaired with nonabsorbable sutures in a mattress fashion, incorporating the costal margins. Open laparotomy has been shown to have shorter operating times than laparoscopy. Still, the minimally invasive approach confers a shorter recovery time and faster return to normal activities and eating, with no difference in complication rates while providing more space for dissection and better visualization.[27](B2)

Georgacopulo was the first to report a successful laparoscopic Morgagni hernia in a child in 1997.[28] With the laparoscopic approach, the patient is placed in reverse Trendelenburg with the surgeon located at the foot of the bed.[29] The camera port is placed through the umbilicus, and 2 working ports are positioned in the right and left upper abdomen in the midclavicular line.[30] Depending on the defect's size, the falciform ligament may need to be divided for adequate exposure. The hernia contents are reduced, with the sac excised at this time if required. The defect often has a greater transverse than anteroposterior diameter, so closure with sutures brought through the abdominal wall may be used.[31](B2)

Patch placement in large defects occurs first by suturing the patch to the posterior rim of the hernia defect. The patch is then incorporated with nonabsorbable sutures that travel full-thickness through the anterior abdominal wall and are tied in the subcutaneous tissue. For defects that do not require a patch, closure is performed using U-type stitches that pass through the abdominal wall (including the hernia sac if present), incorporate the posterior rim of the diaphragmatic defect, and exit through the abdominal wall, secured in the subcutaneous tissue. This type of repair is beneficial in the absence of an anterior diaphragmatic rim and is easier to perform than intracorporeal sutures. Recovery is usually uneventful, with most patients discharged within 3 days of surgery. The robotic technique has also been described, with improved ergonomics, articulation, and tremor filtration cited as benefits of this minimally invasive version.[32](B3)

Differential Diagnosis

The differential diagnosis may include a pericardial cyst, loculated pneumothorax, or hiatal hernia if a bowel loop is seen herniating through a diaphragmatic defect on chest radiography. A herniated part of the omentum or liver may be visualized as a solid structure on chest x-rays. However, this radiologic finding may also be present in atelectasis, pneumonia, pericardial fat pad, intrathoracic lipoma, bronchial carcinoma, pleural mesothelioma, or an atypical mediastinal tumor. Further imaging with a lateral chest radiograph or CT scan can confirm the Morgagni defect.[33]

Prognosis

For defects found in infancy, the risk factors for mortality from a Morgagni hernia are often prematurity-associated, such as low birth weight, early gestational age, and low APGAR (appearance, pulse, grimace, activity, and respiration) scores. The presence of other congenital anomalies also increases this risk. Although pulmonary hypoplasia is not commonly seen in Morgagni hernias, factors that can impact outcomes include prenatal identification and the defect's size, especially if a sac is included. However, the condition's lifelong implications for children are unknown. After repair, most patients recover well with a resolution of preoperative symptoms and a low recurrence rate.

Complications

Nonhiatal transdiaphragmatic hernias in adults, whether congenital or posttraumatic, are rare conditions that need to be differentiated from paraesophageal hernias. According to specialized literature, these hernias often present as unexpected diagnoses. A combination of digestive symptoms with respiratory or cardiac issues may suggest the presence of a congenital or posttraumatic hernia.[34] Even asymptomatic should be referred for surgical correction due to concerns for bowel obstruction, strangulation, volvulus, and necrosis, which can occur in up to 10% of cases. Potential postsurgical complications include wound infections, incisional or port site hernias, stitch abscesses, and bowel obstruction.

Recurrence rates range from 2% to 42%, though many studies report no recurrences even after 10 years of follow-up. Risk factors for recurrence include closing the defect under tension without using a patch, leaving the sac in place without resection, use of absorbable sutures for repair, and a patient history of Down syndrome. Repair techniques vary, each with unique pitfalls. The transthoracic approach risks missing bilateral defects, is suboptimal for sac removal, may require postoperative ventilation, and can potentially cause chest wall deformity in children. Open laparotomy, ideal for complicated or emergent cases, has longer recovery, higher wound complication rates, and worse cosmesis than minimally invasive methods. All approaches yield good outcomes if their benefits and risks are well understood.