A 32-year-old man comes to the hospital due to 1 week of progressive shortness of breath and cough. He also reports sharp right-sided chest pain that is worsened by deep inspiration. Examination reveals decreased tactile fremitus, dullness on percussion, and decreased breath sounds over the right lower lung. Chest x-ray shows consolidation of the right lower lobe and a right-sided effusion. A thoracentesis is performed, during which the needle is inserted along the upper border of the 10th rib at the right midaxillary line. Which of the following structures is most at risk of being injured as a result of the intervention?

Question

A 32-year-old man comes to the hospital due to 1 week of progressive shortness of breath and cough.  He also reports sharp right-sided chest pain that is worsened by deep inspiration.  Examination reveals decreased tactile fremitus, dullness on percussion, and decreased breath sounds over the right lower lung.  Chest x-ray shows consolidation of the right lower lobe and a right-sided effusion.  A thoracentesis is performed, during which the needle is inserted along the upper border of the 10th rib at the right midaxillary line.  Which of the following structures is most at risk of being injured as a result of the intervention?

Quizplus · Accepted Answer

11ec160b_35db_c845_9249_094d6e2f78a8_MD0001_00 The visceral pleura covers the surface of the lung, whereas the parietal pleura lines the inner surface of the chest wall and diaphragm. The parietal pleura generally extends approximately 2 ribs below the inferior margin of the lungs. The potential space at the reflection of the costal pleura onto diaphragmatic pleura is called the costodiaphragmatic recess, where pleural fluid accumulates when the body is erect. Thoracentesis is typically performed between the 6th and 8th ribs along the midclavicular line, the 8th and 10th ribs along the midaxillary line (above image), and the 10th and 12th ribs along the paravertebral line. This allows pleural fluid to be drained without risking lung injury (which can occur at higher insertion sites). However, insertion of a needle below the 9th rib still risks penetrating abdominal structures. In this case, thoracentesis is being performed along the upper border of the 10th rib at the right midaxillary line, putting the patient at risk of liver injury if the needle is inserted too deep. (Choice A) Hepatic veins are found deep in the liver parenchyma and are not likely to be injured during thoracentesis. (Choices B and C) The intercostal vein, artery, and nerve lie in the subcostal groove along the lower border of the rib. Thoracentesis should be performed just above the upper border of the rib to prevent injury to the intercostal vessels. (Choice E) The lower border of the right lung is located 2 intercostal spaces above the pleural border. Therefore, the lung is less likely to be injured by insertion of a needle into the 10th intercostal space at the midaxillary line. Educational objective: Thoracentesis should be performed below the 6th rib in the midclavicular line, the 8th rib along the midaxillary line, or the 10th rib along the paravertebral line in order to minimize the risk of lung injury. Insertion of a needle lower than 9th rib increases the risk of penetrating abdominal structures. The needle should also be inserted along the upper border of the rib to prevent injury to the intercostal vessels.

A 32-Year-Old Man Comes to the Hospital Due to 1