Chapter 106

The spectrum of benign conditions that affect the pleural spaces includes infectious, inflammatory, spontaneous, and traumatic etiologies. The pleural space represents one of the body's potential spaces and thus can be occupied pathologically by liquid, gas, or solid components, all of which can alter respiratory function. This chapter provides a brief overview of the clinical presentation, diagnosis, etiology, and treatment of benign pleural conditions. Since malignant diseases that affect the pleura are covered in Part 13 (see Overview), for the purposes of our discussion, these pathologies are described only in the context of understanding how to confirm a benign diagnosis.

The pleural space is defined anatomically by a double-layered sac that covers the lung and lines the chest wall, diaphragm, and mediastinum. The sac is lined by mesothelial cells. The pleural layer itself is composed of a monolayer of mesothelial cells supported by a thin membrane of collagen and elastin connective tissue.1 The pleural surfaces are categorized as the visceral and parietal pleurae. The interior surface, termed the visceral pleura, covers the lung. The exterior surface, denoted the parietal pleura, is adjacent to the chest wall, mediastinum, and diaphragm (Fig. 106-1). An analogous representation of this configuration can be created by invaginating an inflated balloon with one's fist (Fig. 106-2). The portion of the balloon that covers the hand is analogous to the visceral pleural surface, and the exterior surface of the balloon represents the parietal pleural surface. The transition from visceral to parietal pleura occurs at the hilum of the lung. Inferior to the hilum, the anterior and posterior leaves of the visceral pleura fuse together at the inferior pulmonary ligament and anchor the medial aspect of the lower lobe to the mediastinum. The sulci, or sinuses, of the pleural space are defined by various structures: the upward bowing of the diaphragm into the hemithorax, the costophrenic sinus, the costomediastinal sinuses anteriorly and posteriorly, and the mediastinophrenic sinus medially. As the diaphragm descends with inspiration, these sinuses are occupied with inflated lung.

###### Figure 106-1.

A. The double-layered pleural sac mimics the topography of the lungs, including the fissures. The exterior surface exposed to the chest wall, diaphragm, and mediastinum is termed the parietal pleura. The interior surface adjacent to lung is called visceral pleura. B. The transition between parietal and visceral pleura occurs at the hilum. C. The anterior and posterior leaves of the visceral pleura fuse together at the inferior pulmonary ligament.

###### Figure 106-2.

There are two pleural sacs, one covering each lobe of the lung. The anatomy of this double-layered structure can be best appreciated by imagining one's fist invaginating a balloon. The hilum is at the wrist.

The pleural space develops between the fourth and seventh weeks of gestation. ...

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