Discussion

Morgagni hernia

Morgagni hernias, or retrosternal diaphragmatic defects with herniation of abdominal contents, are the least common type of congenital hernia. They are also more likely to be discovered as an incidental finding during adulthood due to relatively less severe symptoms early in life. Most adult patients present in the fourth decade of life or later. Though the diaphragmatic defect is congenital, herniation of abdominal contents through the defect in adulthood is felt to be related to increases in abdominal pressure, for example in the setting of pregnancy or obesity.

Clinical presentation and management

Less than half of Morgagni hernias in adults are asymptomatic at presentation and are diagnosed incidentally on chest imaging performed for unrelated reasons, as in this case. For those who are symptomatic, they may present with shortness of breath, abdominal pain, nausea, or intermittent bowel obstruction. Morgagni hernias occur on the right side more than 90% of the time. Morgagni hernia is associated with Down syndrome and other congenital anomalies.

In cases of symptomatic Morgagni hernia, surgical repair is performed, most commonly via a laparoscopic transabdominal approach. Though surgical and nonsurgical outcomes for asymptomatic Morgagni hernia have not been compared, surgical repair is usually recommended given the theoretical risk of bowel incarceration.

Imaging features

On chest x-ray, Morgagni hernias appear as lower lung zone opacities adjacent to the diaphragm and, most often, the right heart border. On a lateral view, they are anterior (versus Bochdalek hernias, which are posterior). They may also contain bowel, most frequently colon.

On CT, a retrosternal diaphragmatic defect can be seen, through which omental fat and possibly bowel herniates.

Differential considerations on imaging

The differential for a Morgagni hernia on chest x-ray includes pericardial cysts and lipomas, a large pericardial fat pad, anterior mediastinal masses, lung or pleural masses, diaphragmatic eventration, or other diaphragmatic hernias, like Bochdalek hernias.

On CT, Morgagni hernias should be straightforward to identify once the diaphragmatic defect is identified. Sagittal and coronal reformatted images can help to identify the defect.

References

1. Eren S, Ciriş F. Diaphragmatic hernia: Diagnostic approaches with review of the literature. Eur J Radiol. 2005; 54(3):448-59. 
2. Minneci PC, Deans KJ, Kim P, Mathisen DJ. Foramen of Morgagni hernia: Changes in diagnosis and treatment. Ann Thorac Surg. 2004; 77(6):1956-1959.
3. Nasr A, Fecteau A. Foramen of Morgagni hernia: Presentation and treatment. Thorac Surg Clin. 2009; 19(4):463-8. 
4. Simson JN, Eckstein HB. Congenital diaphragmatic hernia: A 20-year experience. Br J Surg. 1985; 72(9):733-6. 
5. Thomas TV. Subcostosternal diaphragmatic hernia. J Thorac Cardiovasc Surg. 1972; 63(2): 279-283.
6. Young MC, Saddoughi SA, Aho JM, Harmsen WS, Allen MS, Blackmon SH, Cassivi SD, Nichols FC, Shen KR, Wigle DA. Comparison of laparoscopic versus open surgical management of Morgagni Hernia. Ann Thorac Surg. 2019;107(1):257-261. 

Our appreciation is extended to Dr. Sarah Santucci, University of Pennsylvania Department of Radiology, for contributing this case.