A 62-year-old man comes to the emergency department due to fever, productive cough, and dyspnea for the past several days. His symptoms are becoming progressively worse. The patient has underlying mild chronic obstructive pulmonary disease and has smoked a pack of cigarettes daily for the last 40 years. On examination, temperature is 38.3 C (100.9 F), pulse is 110/min, and respirations are 24/min. Auscultation of the right lung reveals bronchial breath sounds and crackles. Laboratory evaluation shows leukocytosis. Chest x-ray is shown below. The mediastinal contour obscured by the lung consolidation on this patient's chest x-ray is primarily formed by which of the following structures?

Question

A 62-year-old man comes to the emergency department due to fever, productive cough, and dyspnea for the past several days.  His symptoms are becoming progressively worse.  The patient has underlying mild chronic obstructive pulmonary disease and has smoked a pack of cigarettes daily for the last 40 years.  On examination, temperature is 38.3 C (100.9 F), pulse is 110/min, and respirations are 24/min.  Auscultation of the right lung reveals bronchial breath sounds and crackles.  Laboratory evaluation shows leukocytosis.  Chest x-ray is shown below.  The mediastinal contour obscured by the lung consolidation on this patient's chest x-ray is primarily formed by which of the following structures?

Quizplus · Accepted Answer

11ec160b_3559_ee13_9249_ab2faa111cc6_MD0001_00 This patient has acute lobar pneumonia with consolidation involving the right middle lobe. The right middle lobe of the lung lies immediately adjacent to the right border of the heart, and any condition that increases radiographic density in the right middle lobe will obscure the adjacent cardiac silhouette. On posteroanterior (PA) chest x-ray projections, the right atrium composes most of the right side of the cardiac silhouette. (Choice A) The coronary sinus receives most of the venous drainage from the cardiac circulation. It courses posteriorly around the heart in the coronary sulcus to empty directly into the right atrium. It is difficult to visualize on standard chest x-ray. (Choice B) The inferior vena cava empties into the right atrium in the thorax. It composes only the most inferior edge of the right border of the cardiac silhouette. (Choice C) The pulmonary artery can be seen on PA chest x-ray on the left side of the cardiomediastinal silhouette just below the aortic arch. (Choice E) The right ventricle forms the anterior wall of the heart and is best seen on lateral chest x-ray. (Choice F) The superior vena cava is formed behind the first costal cartilage by the confluence of the right and left brachiocephalic veins. On PA chest x-ray, it is the flattened opacity parallel to the vertebral column that terminates inferiorly at the right atrium. Educational objective: On posteroanterior chest x-ray, the right middle lobe is seen adjacent to the right border of the heart, which is primarily formed by the right atrium. Consolidation in the right middle lobe can obscure the x-ray silhouette of the right heart border.

A 62-Year-Old Man Comes to the Emergency Department Due to Fever