1337326 - An Unusual Case of Granulomatous Inflammation Mimicking Hematoma around Replaced Ascending Aorta in MRI.

Ten years postoperatively, a 75-year-old female presented to the emergency department with a history of seven days of chest pain without fever. She had a background of hemi-arch replacement with a Hemashield platinum woven double velour vascular graft for ascending aortic dissection 10 years earlier. The initial chest computed tomography (CT) was suggestive of hematoma or abscess (Fig. 1, A). The size of the mediastinal mass was about 4.5 × 3.3 cm. In patients with previous aortic surgery, the existence of a radiological perigraft hematoma means clinically that there can be an ascending aortic pseudoaneurysm, which is an uncommon complication of cardiac surgery but could be catastrophic in 0.5% of the patients [1]. The chest magnetic resonance imaging (MRI) scan with enhancement revealed a hematoma on the ascending aortic graft consistent with the CT findings (Fig. 1, B and C). An infection could not be excluded because there was rim enhancement suspicious of an abscess on the contrast image (Fig. 1, D).

A well-prepared surgery was planned in case repeat aortic surgery was needed. After endotracheal general anesthesia, a redo median sternotomy was performed, revealing severe adhesion in the retrosternal space. Inspection of the pericardial space showed a sac containing yellowish and pus-like material (Fig. 2, A). We confirmed that there was no hematoma around the ascending aortic graft.

The pathologic findings showed chronic granulomatous inflammation with necrosis (Fig. 2, B). The microbiologic tests of the tissue specimen including cultures and polymerase chain reaction analysis for Mycobacteria tuberculosis complex and non-tuberculosis Mycobacteria were negative.

Diagnostic Techniques and Their Most Important Findings:

In our case, the granulomatous inflammatory subtype pattern was necrotizing granuloma. On MRI, chronic granulomatous inflammation can be found as ring-enhancing lesions [2], as in our case (Fig. 1, D). T2-weighted or contrast-enhanced T1-weighted high signal intensity can be found in granulomatous inflammation [2].

Learning Points from this Case:

As a specific form of chronic inflammation, granulomatous inflammation can be caused by infections, allergic reactions, and neoplastic conditions. It presents with mononuclear leukocytes, specifically macrophages, responding to cell injury. This histologic response especially affects the lungs, skin, kidneys, liver, and lymph nodes, although it can occur in all tissues [3]. Foreign body-like synthetic fibers can also cause granulomatous inflammation [3]. We encountered a case where the preoperative differential diagnosis was very important for surgical planning. In the imaging findings of patients who underwent previous cardiovascular surgery, a radiological hematoma on the anastomosis sites may mean a pseudoaneurysm clinically. Our experience showed that an MRI finding of a hematoma at the site long after cardiovascular surgery suggests that there may be granulomatous inflammation. It is hoped that this case will help surgical planning in similar cases.