Pericardial recess through the eyes of endobronchial ultrasound.

Dear Editor,

Superior aortic pericardial recess (SAPR) manifests as a fluid collection adjacent to the posterior wall of the aorta at the level of the left pulmonary artery on computed tomographic (CT) imaging. Occasionally it can be misinterpreted as enlarged lymph nodes (4L nodal station) that could lead to radiographic upstaging of existing pulmonary tumors. The use of endobronchial ultrasound (EBUS) gives the advantage of identifying the cystic structure of the pericardial recess, and avoids the misinterpretation with lymphadenopathy. We are presenting a case of SAPR identified by EBUS that has not been previously reported.

A 69-year-old active male smoker was admitted with worsening dyspnea. He was incidentally found to have mediastinal adenopathy and was suspected to have myocardial sarcoidosis. A CT scan of the chest revealed enlarged subcarinal lymph node and a left paratracheal homogenous fluid density structure [Figure 1]. The patient underwent flexible bronchoscopy, and an EBUS guided transbronchial needle aspiration was performed, which demonstrated lymphoid tissue from the nodal stations sampled. Interestingly the EBUS imaging revealed a triangular, homogenous echo-free structure at the lower left paratracheal region (4L nodal station). Doppler ultrasound confirmed the absence of blood flow at that area between the aorta and the left pulmonary artery [Figure 2]. Based on the correlation between the CT and EBUS findings, this structure was confirmed as the SAPR.

Figure 1

Computed tomographic scan of the chest revealing superior aortic recess (arrow) posterior to the ascending aorta (a) at level of left pulmonary artery. This recess can be misinterpreted as enlarged lymph node at station 4L

Figure 2

Endobronchial ultrasound depiction of superior aortic recess (arrow) between ascending aorta (a) and the left pulmonary artery. Same location of 4L nodal station

Pericardial recess generates the pericardium, which surrounds the heart. Pericardium consists of two layers; an outer fibrous layer and an inner double-layered visceral sac (epicardium). The epicardium surrounds the heart and great vessels and normally contains 15-20 mL of pericardial fluid.[1] Fluid in the pericardial space can produce a well-circumscribed contour with a beaklike extension as it drapes behind the aorta.[12] Accumulation of fluid in one or multiple locations through the pericardial sac forms pericardial recess which can be misinterpreted as enlarged lymph nodes in different nodal stations [Figure 3].

Figure 3

Illustration of the hilar and mediastinal lymph node stations. Blue areas

The most common pericardial recesses locations are: Superior aortic recess,[2] like our case, which mimics adenopathy at the 4R or 4L nodal stations. Right and left pulmonic recesses can be misinterpreted as 10R or 10L nodal stations. Oblique sinus recess occupies the same anatomic location of 7 nodal stations [Table 1]. The difficulty in differentiating pericardial recesses from adenopathy with CT-imaging can lead to upstaging of tumors in oncologic imaging. Superior aortic recess can also be misinterpreted as bronchogenic cyst on CT. The use of EBUS gives the advantage of identifying the cystic structure of the pericardial recess, and avoids the misinterpretation with lymphadenopathy or the bronchogenic cyst. It is also possible that this location could also be used for draining the pericardial fluid if required

Table 1

Pericardial recess location and correlating hilar and mediastinal lymph node stations