Unraveling the Mystery: Expert Insights into Morgagni Hernia – The Rare Adult Congenital Diaphragmatic Defect (Morgagni Hernia, Diaphragmatic Hernia, Chest CT)

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Introduction

Morgagni Hernia (MH) is an elusive form of diaphragmatic hernia, a rare congenital defect that often remains clinically silent until adulthood. 

Representing a small fraction of all congenital diaphragmatic hernias, its diagnosis requires keen radiological expertise and a high index of suspicion, especially in the adult population where it is most frequently identified. 

This expert column, drawing upon the latest global literature, provides a comprehensive review of the pathophysiology, clinical presentation, imaging characteristics, and contemporary management of this condition.

Case Study Introduction: A 63-Year-Old Male with a Coincidental Finding

A 63-year-old male presenting with a chief complaint of headache. 

The patient, with an underlying condition of Waldenström macroglobulinemia , was preparing for plasma exchange due to suspected hyperviscosity.

During the workup, a routine portable chest X-ray (post central venous catheter insertion) revealed an abnormal opacity in the right lower lobe area. 

Subsequent imaging was pivotal for the final diagnosis.

Imaging Findings


Figure 1. Portable Chest X-ray (Supine); The initial portable chest X-ray showed a right internal jugular central venous catheter positioned in the superior vena cava (SVC). Crucially, a triangular opacity was observed in the lower aspect of the right lower hemithorax. The surrounding lung parenchyma appeared normal. Although the opacity superficially resembled atelectasis (lung collapse), this was considered unlikely because the pulmonary vascular structures were visible through the opacification.


Figure 2. Chest Computed Tomography (CT); A follow-up Chest CT provided the pathognomonic findings. The CT scans (Axial, Coronal, Sagittal reconstructions) clearly demonstrated a diaphragmatic defect in the anterosternal/retrosternal region. Through this defect, the abdominal omentum was seen herniating into the thoracic cavity.

The specific location of the defect was the right anterior diaphragm—the Foramen of Morgagni. The herniated contents were confirmed to be fat density.

➡️ Final Diagnosis: Morgagni Hernia 

Pathophysiology of Morgagni Hernia

Morgagni Hernia is a rare congenital diaphragmatic hernia resulting from a failure of the diaphragm to fully fuse during embryogenesis. 

The diaphragm normally forms from the fusion of four distinct structures: the Septum transversum, the Pleuroperitoneal membranes, the Dorsal mesentery of the esophagus, and the Body wall musculature.

The key mechanism in MH is the failure of fusion in the anterior portion. 

This leads to a persistent gap known as the sternocostal hiatus, which constitutes the Morgagni foramen. 

This space allows abdominal contents—most commonly the omentum (abdominal fat), but sometimes the colon, liver, or stomach—to protrude into the thoracic cavity.

While the underlying defect is congenital, the actual herniation in adults is often an acquired event triggered by conditions that increase intra-abdominal pressure, such as obesity, pregnancy, chronic cough, or chronic constipation.

Epidemiology and Clinical Presentation

Epidemiology

Morgagni hernia is significantly rarer than its posterior counterpart, the Bochdalek hernia.

  • Prevalence: It accounts for less than 2-3% of all congenital diaphragmatic hernias.

  • Diagnosis Age: Over 90% of cases are diagnosed in adulthood.

  • Location: Approximately 90% occur on the right side. Left-sided Morgagni hernias are uncommon due to the protective presence of the heart and pericardial structures.

  • Associated Conditions: It has been linked to other congenital conditions, including Down syndrome, congenital heart disease, and Williams syndrome.

Clinical Presentation

Morgagni hernia is often an incidental finding. Over half of adult cases are asymptomatic and discovered during unrelated imaging studies.

When symptoms do occur, they can be categorized as follows:

Symptom TypeKey Examples
RespiratoryDyspnea (shortness of breath), cough, chest pain
GastrointestinalAbdominal pain, nausea, vomiting, constipation, intermittent bowel obstruction
OtherChest compression/fullness, symptoms of gastroesophageal reflux disease (GERD)

Symptoms are known to worsen during periods of increased intra-abdominal pressure.

Imaging Features and Differential Diagnosis

Accurate diagnosis relies on recognizing the characteristic features in both chest radiography and CT.

Imaging Features

Chest X-ray (CXR)

  • Appears as a round or triangular opacity in the right lower hemithorax.

  • The mass is typically located adjacent to the right heart border.

  • A distinguishing feature is the preservation of normal lung parenchyma with the pulmonary vascular markings visible through the opacity.

  • A Lateral CXR can be helpful, showing the mass is situated in the anterior chest, which differentiates it from the posterior Bochdalek hernia.

Computed Tomography (CT)

CT is essential for definitive diagnosis, as it directly visualizes the diaphragmatic defect and its contents.

  • Diaphragmatic Defect: Clearly shows an anterior diaphragmatic defect in the retrosternal region.

  • Contents: Herniated material is typically abdominal fatty tissue (omentum) or bowel (most commonly colon).

  • Density: The herniated contents appear as fat density or a mix of air and soft tissue density.

  • Reconstruction: Sagittal and Coronal reconstructions are invaluable for precisely localizing the defect.

Differential Diagnosis

The mass-like opacity on imaging can be confused with other thoracic pathologies. The confirmation of a diaphragmatic defect on CT is the crucial differentiator.

Differential DiagnosisKey Distinguishing Points
Bochdalek herniaPosterior location, predominantly left-sided 


Pericardial cystFluid density, well-defined border, no diaphragmatic defect 


Pericardial fat pad

Localized fat density anterior to the pericardium, no diaphragmatic defect

Diaphragmatic eventration

Abnormal bulging/elevation of the diaphragm, absence of a defect 

Mediastinal massSoft tissue density, suspicion of a mediastinal tumor


Treatment and Prognosis

Treatment

The fundamental principle for Morgagni hernia management is surgical repair of the diaphragmatic defect. 

Surgery is strongly recommended for symptomatic patients or those with bowel involvement due to the significant risk of incarceration (entrapment) and strangulation.

Current surgical trends favor minimally invasive techniques:

  • Laparoscopic Approach: This is the most widely utilized method. It offers easy localization of the abdominal organs, faster recovery, and fewer complications.

  • Thoracoscopic Approach: Used selectively.

  • Open Repair: Reserved for complicated or recurrent hernias.

The defect is typically closed via primary suture or reinforced with a synthetic mesh. 

Notably, even asymptomatic patients are increasingly advised to undergo prophylactic surgery due to the latent risk of organ incarceration.

Prognosis

The prognosis following surgical repair is excellent. 

The recurrence rate is low, typically less than 2-5%. 

With early diagnosis and appropriate surgical intervention, the survival rate is near 100%. 

Untreated cases, though rare, carry the risk of serious complications like bowel obstruction or respiratory failure.

Quiz 

Question 1. A 63-year-old male's chest X-ray shows a triangular opacity near the right heart border. CT confirms a mass of fat density herniating into the thorax via an anterior retrosternal diaphragmatic defect. What is the most likely diagnosis?

A. Bochdalek hernia

B. Pericardial cyst

C. Morgagni hernia

D. Eventration of diaphragm

Question 2. The pathogenesis of Morgagni hernia is most accurately attributed to which of the following?

A. Failure of the pleuroperitoneal canal to close.

B. Failure of fusion between the septum transversum and sternocostal muscle.

C. A defect in the posterior diaphragm.

D. Esophageal hiatus widening.

Question 3. What is the most common anatomical location for Morgagni hernia?

A. Left posterior

B. Right anterior

C. Left anterior

D. Central posterior

Answer & Explanation

1. Answer C, Explanation: Morgagni hernia. The presence of a fatty mass (omentum) herniating through an anterior retrosternal diaphragmatic defect is the classic, definitive presentation of Morgagni hernia.

2. Answer B. Explanation: Failure of fusion between the septum transversum and sternocostal muscle. Morgagni hernia results from the failure of anterior fusion (specifically involving the septum transversum and sternocostal muscle). Option A refers to the mechanism for Bochdalek hernia, which is a posterior diaphragmatic defect (Option C).

3. Answer B.  Explanation: Right anterior. Morgagni hernias occur in the anterior diaphragm and are overwhelmingly (over 90%) found on the right side. The heart and pericardial structures typically inhibit left-sided herniation.

Conclusion

Morgagni hernia is a rare, yet clinically significant, congenital diaphragmatic defect often discovered incidentally in adults. 

While the initial diagnosis can be suggested by a characteristic triangular opacity on chest X-ray, CT visualization of the anterior diaphragmatic defect and its contents is mandatory for confirmation. 

The standard of care is surgical repair, most commonly via a laparoscopic approach, to prevent the life-threatening complications of organ incarceration. 

A thorough understanding of its imaging features and pathophysiology is crucial for early diagnosis and optimal patient outcomes.

References

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[2] P. C. Minneci, K. J. Deans, P. Kim, and D. J. Mathisen, "Foramen of Morgagni hernia: Changes in diagnosis and treatment," Ann. Thorac. Surg., vol. 77, no. 6, pp. 1956–1959, 200477.

[3] A. Nasr and A. Fecteau, "Foramen of Morgagni hernia: Presentation and treatment," Thorac. Surg. Clin., vol. 19, no. 4, pp. 463–468, 200978.

[4] J. N. Simson and H. B. Eckstein, "Congenital diaphragmatic hernia: A 20-year experience," Br. J. Surg., vol. 72, no. 9, pp. 733–736, 198579.

[5] T. V. Thomas, "Subcostosternal diaphragmatic hernia," J. Thorac. Cardiovasc. Surg., vol. 63, no. 2, pp. 279–283, 197280.

[6] M. C. Young et al., "Comparison of laparoscopic versus open surgical management of Morgagni hernia," Ann. Thorac. Surg., vol. 107, no. 1, pp. 257–261, 201981.

[7] J. A. Kocaoglu, M. Yildirim, et al., "Adult Morgagni hernia: Radiological findings and surgical outcomes," Clin. Imaging, vol. 83, pp. 100–107, 202282.

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