High-riding superior pericardial recess: temporal change can help distinguish from mediastinal pathology.

Abstract: A high-riding superior pericardial recess is an infrequently encountered normal variant which may mimic mediastinal pathology. We present a patient in whom a high-riding superior pericardial recess could confidently be diagnosed on a neck CT due to its change in size and shape demonstrated on a chest CT which was done 4 minutes later.

Key Words: superior pericardial recess, mediastinal lesion, computed tomography

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The pericardial cavity may normally contain, under physiologic conditions, up to 25 mL of serous fluid. The pericardial cavity forms the pericardial sinuses, which represent extension of the pericardial cavity. (1) The superior pericardial recess, called the high-riding superior pericardial recess, is the posterior portion of the superior aortic recess and may sometimes extend more superiorly than normal, which may mimic a paratracheal lymph node. (2) We describe a patient with a high-riding superior pericardial recess which was diagnosed due to its change in size and shape between performance of a neck CT and chest CT scan, which were done 4 minutes apart.

Case Report

A 50-year-old male patient had a CT of the neck followed by CT of the chest for Behcet disease and left vocal cord paralysis. CT of the neck and chest did not demonstrate a cause for the vocal cord paralysis, but a fluid density lesion was noted in the right paratracheal region on the neck CT (Fig. 1). The chest CT scan, however, obtained 4 minutes later, showed significant decreased size and changed shape of this apparent lesion, confirming it to be a high-riding superior pericardial recess (Fig. 2). The fluid appeared to be redistributed to the inferior aortic recess and the transverse sinus. Although the high-riding superior pericardial recess could be confused for a cystic mediastinal lesion or a cystic/necrotic lymph node in the neck CT, definitive demonstration of the change in size and shape on the chest CT conclusively proved the finding to be fluid in the superior pericardial recess.

Discussion

With increased use of thin section multislice CT scans, pericardial recesses are now commonly identified. The superior aortic recess is the upward extension of the transverse sinus of the pericardial cavity and can be identified in up to 47% of normal patients. (1) It is seen surrounding the ascending aorta and has anterior, posterior and right lateral portions. The right lateral portion insinuates between the ascending aorta and the superior vena cava. (1) The anterior portion lies between the aorta and the main pulmonary artery, whereas the posterior portion lies directly posterior to the ascending aorta, where it is sometimes referred to as the superior pericardial recess or the superior sinus.

The superior pericardial recess is usually caudad to the aortic arch, but sometimes extends cephalad and rightward into the right paratracheal region between the brachiocephalic vessels and the trachea, even in patients without pericardial effusion. This is called the "high riding" superior pericardial recess and may mimic paratracheal lymphadenopathy or a cystic mediastinal lesion. (2)

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

The inferior portion of the superior aortic recess communicates with the inferior aortic recess and the transverse sinus, although most often the connection itself is not demonstrable on cross sectional imaging. The redistribution of the pericardial fluid between the superior aortic recess and the inferior aortic recess of the transverse sinus is to be expected, but this is the first time that it was demonstrated in a patient on cross-sectional imaging.

When the pericardial recess fluid is significant, it may mimic a cystic mediastinal mass or an enlarged mediastinal lymph node, especially in the setting of known primary malignancy. (3) However, pericardial recesses tend to have a linear, crescent, or triangular shape, unlike enlarged lymph nodes which tend to be round or oval. Lymph nodes and mediastinal masses have soft tissue density while pericardial recesses have fluid density. The fat plane between the superior aortic recess and the aorta is usually absent. Sometimes superior pericardial recess fluid may even mimic aortic dissection or thrombus. Thin section images using fast multislice CT as well as sagittal and coronal reconstructed images are helpful in correctly diagnosing this anatomic variant. (4) Change in configuration between two scans, as demonstrated in this patient, could also be helpful in making the correct diagnosis.

In conclusion, a high-riding superior pericardial recess is not an uncommon variant that may mimic mediastinal lesion. Change in the configuration of its appearance on CT scans obtained within a short interval may be helpful in identifying its true nature and avoiding a misdiagnosis of a pathologic lesion.

References

1. Groell R, Schaffler GJ, Rienmueller R. Pericardial sinuses and recesses: findings at electrocardiographically triggered electron-beam CT. Radiology 1999;212:69-73.

2. Choi YW, McAdams HP, Jeon SC, et al. The 'high-riding' superior pericardial recess: CT findings. AJR Am J Roentgenol 2000;175:1025-1028.

3. Truong MT, Erasmus JJ, Gladish GW, et al. Anatomy of pericardial recesses on multidetector CT: implications for oncologic imaging. AJR Am J Roentgenol 2003;181:1109-1113.

4. Kodama F, Fultz PJ, Wandtke JC. Comparing thin-section and thick-section CT of pericardial sinuses and recesses. AJR Am J Roentgenol 2003;181:1101-1108.

Manohar Aribandi, MD

From the Department of Radiology, Geisinger Medical Center, Danville, PA.

Reprint requests to Dr. Manohar Aribandi, Department of Radiology, 100 North Academy Avenue, Geisinger Medical Center, Danville, PA 17822. Email: [e-mail]

Accepted July 6, 2006.

RELATED ARTICLE: Key Points

* The superior pericardial recess, called the high-riding superior pericardial recess, is the posterior portion of the superior aortic recess and may sometimes extend more superiorly than normal.

* The high-riding superior pericardial recess may mimic a cystic mediastinal mass or an enlarged mediastinal lymph node.

* Change in configuration of this structure between two scans, as demonstrated in this patient, could be helpful in making the correct diagnosis and avoiding a false interpretation.