Subcarinal lymph node enlargement: radiographic findings and CT correlation

Area of Science:

• Radiology
• Oncology
• Pulmonology

Background:

• Subcarinal lymph node enlargement is a significant indicator of various thoracic pathologies, including malignancy and infection.
• Accurate detection of subcarinal adenopathy on standard chest radiographs (posteroanterior view) is often limited.
• Computed tomography (CT) provides detailed anatomical information but involves higher radiation exposure and cost.

Purpose of the Study:

• To evaluate the effectiveness of specific radiographic signs in detecting subcarinal lymph node enlargement.
• To compare the diagnostic accuracy of plain radiography with computed tomography (CT) for subcarinal lymphadenopathy.
• To identify reliable radiological markers on chest X-rays indicative of enlarged subcarinal lymph nodes.

Main Methods:

• Retrospective analysis of 90 patients with available posteroanterior chest radiographs and computed tomography (CT) scans.
• CT was used as the gold standard to categorize patients into normal (≤15 mm diameter) and enlarged (>15 mm diameter) subcarinal lymph node groups.
• Radiographic findings, including azygoesophageal recess contour abnormalities and subcarinal opacity, were assessed.
• Visibility of the medial wall of the right main-stem bronchus and bronchus intermedius was specifically evaluated on plain radiographs.

Main Results:

• Out of 90 patients, 60 had normal and 30 had enlarged subcarinal lymph nodes on CT.
• Abnormalities in the azygoesophageal recess contour were present in only 23% of patients with lymphadenopathy.
• Increased subcarinal opacity was observed in 40% of patients with enlarged nodes.
• The medial wall of the right main-stem bronchus and intermediate bronchi was visible in 87% of patients with normal nodes but only 27% of those with lymphadenopathy.
• Nonvisualization of this bronchial wall correlated significantly with enlarged subcarinal lymph nodes or tumor infiltration.

Conclusions:

• Standard chest radiography has limitations in directly visualizing subcarinal lymphadenopathy.
• The loss of visualization of the medial wall of the right main-stem bronchus and bronchus intermedius on plain radiographs is a potentially useful sign of enlarged subcarinal lymph nodes.
• This radiographic finding may aid in identifying patients who require further investigation with CT for suspected subcarinal adenopathy.