Findings: PA radiograph shows convexity of the aortopulmonary window (A, white arrow) and increased opacity of the left hilum (A, red arrow). The lateral view shows a faint opacity projected over the middle third of the thoracic spine (B, circle) that was overlooked in the initial reading.
The convexity of the APW suggested mediastinal lymphadenopathy, and CT was performed.

Coronal enhanced CT shows an enlarged lymph node in the APW (A, arrow). Axial CT depicts enlarged lymph nodes in the left hilum (B, circle). Lung window demonstrates air-space disease in the apical segment of the LLL (C, arrow), which explains the posterior faint opacity in the lateral view.

Summary of CT findings:

– Unilateral enlarged hilar lymph nodes
– Lymph node in APW
– Air-space disease in the apical segment of LLL

The most significant finding is the presence of unilateral hilar lymph nodes which have a limited differential diagnosis: in the great majority of patients they are due either to lung carcinoma or active tuberculosis. As this particular patient is 27 y.o., carcinoma is unlikely. Therefore, our tentative diagnosis should be active TB, which is also supported by disease in the apical segment of the LLL, a common location for TB.

The patient was placed in isolation, bronchoscopy was performed, and Mycobacterium tuberculosis was found in the aspirate.

Final diagnosis: active tuberculosis

YOUNG PERSON + UNILATERAL ENLARGED HILAR LYMPH NODES + PULMONARY INFILTRATE IN APICAL SEGMENT OF LLL = ACTIVE TUBERCULOSIS

Active pulmonary tuberculosis is not uncommon, and the chest radiograph plays an important role in its detection. Findings that help to suspect TB in the plain film are:

Location of the parenchymal disease. Involvement of the apices or the apical segment of either lower lobe should raise the possibility of a tuberculous infiltrate, although TB can affect any area of the lung.

Cavitation. The presence of cavities within a pulmonary infiltrate suggest tuberculosis or necrotic pneumonia.

Visible lymphadenopathies. Tuberculous lymph nodes are usually unilateral and located in the hilum and homolateral mediastinum. In about one third of patients they are bilateral. In such cases, lymphoma and sarcoidosis, among others, should also be considered.

CT refines these parameters by discovering cavitation or lymphadenopathy that is not evident in the plain film. The presence of low-attenuation lymph nodes due to caseous necrosis is highly suggestive of TB, although it is not pathognomonic. Other conditions can also show these features. However, normal-density lymph nodes do not exclude TB, as was seen in the present case.

Below, I show a few nice images of active TB in which low-attenuation lymph nodes
suggested the correct diagnosis.

CASE 1

23-year-old woman with cough and low-grade fever. Chest radiographs shows air-space disease in the RLL (A and B, white arrows). There is obvious widening of the right paratracheal line (A, red arrow), indicating mediastinal lymphadenopathy.

Enhanced axial CT confirms the RLL disease which is non-specific (C, arrow). No cavitations are visible. The mediastinal window shows numerous enlarged lymph nodes, some with a hypodense center (D and E, arrows) and others with peripheral enhancement (ring sign) (F, arrows).

Abdominal CT also shows enlarged mesenteric lymph nodes with the ring sign (G and H, circles).

It is interesting to note that lower lobe TB occurs in only 5% of patients. In this particular case the diagnosis of TB was suggested by the CT appearance of the affected lymph nodes. Mycobacterium tuberculosis was recovered from sputum.

Final diagnosis: active TB

Dr. Pepe’s teaching points:

1. Think of TB in unilateral hilar adenopathy in a young person.

2. Low-density lymph nodes on CT are highly suggestive of active TB, although normal-density nodes do not exclude it.

Findings: PA and lateral radiographs show a left superior middle mediastinal mass adjacent to the aortic knob (A and B, white arrows). Healed fractures of the right clavicle and second left rib are visible (A, red arrows). Pacemaker in the left hemithorax.

Analysis of relevant findings:

1. Left middle mediastinal mass adjacent to the aortic knob
2. Old fracture right clavicle
3. Old fracture second left rib

Summing up the findings: Although the appearance of the mediastinal mass is non-specific, the proximity to the aortic arch raises the possibility of an aortic aneurysm.
The bone fractures indicate previous trauma. Especially relevant is the fractured second rib. The first and second ribs are well protected by the thoracic cage and breaking either of them needs a strong impact, significant enough to shear the thoracic aorta and lead to pseudoaneurysm formation.

Therefore, our tentative diagnosis should be traumatic pseudoaneurysm of aorta, followed by a request for enhanced CT to confirm the diagnosis.

MEDIASTINAL MASS ADJACENT TO THE AORTIC KNOB + FRACTURED SECOND RIB = TRAUMATIC AORTIC PSEUDOANEURYSM.

Enhanced CT confirms a partially thrombosed aneurysm with a connection to the inferior aspect of the aortic arch (A-C, red arrows). On questioning, the patient mentioned an automobile accident fifteen years earlier. Because of his age, it was decided to control the aneurysm in six months’ time.

Final diagnosis: traumatic aortic pseudoaneurysm

Rupture of the thoracic aorta is not uncommon in severe blunt trauma, usually after high impact accidents or falls from a height of more than three meters (see case 1, below). About 85% of affected patients die immediately. The remaining 15% may survive if they arrive to the hospital in time to be treated.

A small percentage of cases are overlooked and patients survive without treatment. Over time a pseudoaneurysm develops at the point of rupture, most commonly the aortic arch.
About half these cases are discovered in routine chest examinations because of the typical location of the pseudoaneurysm around the aortic arch. Another diagnostic tip is that the patients are usually younger than patients with atherosclerotic aneurysms (see Case 2).

Discovering signs of previous trauma facilitates the diagnosis, especially when the first or second ribs are affected. After a history of severe trauma is elicited, the diagnosis is confirmed with enhanced CT. The pseudoaneurysm is usually located in the inferior aspect of the aortic arch, distal to the origin of the left subclavian artery.

Traumatic aortic pseudoaneurysms are infrequent, but I have seen several cases during my professional life. I am showing two representative cases to familiarize you with their radiographic appearance.

CASE 1

Chest radiographs of a 75-year-old male tourist with chest pain . A peripherally calcified mediastinal mass is projected over the aortic knob in the PA radiograph (A, arrow). The lateral view shows that the mass arises from the inferior aspect of the aortic arch (B, arrow).

Coronal and sagittal enhanced CT images demonstrate a calcified aneurysm arising from the inferior aspect of the aortic arch (C and D, arrows), distal to the origin of the left subclavian artery (E, circle). On questioning, the patient mentioned surviving a helicopter crash six years earlier. A diagnosis of traumatic pseudoaneurysm was made. The patient returned to his country of origin and was lost to follow-up.

CASE 2

42-year-old man with vague chest symptoms. A chest radiograph from another center (unavailable) showed a mediastinal mass with peripheral calcification. CT scout view yields the same finding (A, arrow).

Enhanced CT shows a large calcified aneurysm distal to the origin of the left subclavian artery (B and C, arrows). The rest of the aorta is normal. The patient had experienced an automobile accident ten years earlier. Traumatic pseudoaneurysm was proven at surgery.

Dr. Pepe’s teaching points:

Tips to suspect a traumatic aortic pseudoaneurysm in the chest radiograph:

1. Mediastinal mass around the aortic arch

2. Signs of previous trauma, especially fractures of the first or second ribs.