A pleural effusion occurs when excess fluid accumulates within the pleural space. As the fluid accumulates within the pleural space the underlying lung is compromised and may collapse as the volume of fluid increases. Once a pleural effusion has been diagnosed, fluid often will be aspirated to determine the cause, which can include infection, malignancy, cardiac failure, hepatic disease, and pulmonary embolism. A large pleural effusion needs to be drained to allow the collapsed part of the lung to reexpand and improve breathing (Fig. 3.41).
In the clinic
A pneumothorax is a collection of gas or air within the pleural cavity (Fig. 3.42). When air enters the pleural cavity the tissue elasticity of the parenchyma causes the lung to collapse within the chest, impairing the lung function. Occasionally, the gas within the pleural cavity may accumulate to such an extent that the mediastinum is “pushed” to the opposite side, compromising the other lung. This is termed a tension pneumothorax and requires urgent treatment.
Most pneumothoraces are spontaneous (i.e., they occur in the absence of no known pathology and no known lung disease). In addition, pneumothoraces may occur as a result of trauma, inflammation, smoking, and other underlying pulmonary diseases. Certain pulmonary metastases, such as in patients with osteosarcoma, may cause spontaneous pneumothorax especially after chemotherapy. The occurrence of pneumothorax interferes with cancer treatment and increases mortality.
The symptoms of pneumothorax are often determined by the degree of air leak and the rate at which the accumulation of gas occurs and the ensuing lung collapses. They include pain, shortness of breath, and cardiorespiratory collapse, if severe.
In the clinic
Imaging the lungs
Medical imaging of the lungs is important because they are one of the commonest sites for disease in the body. While the body is at rest, the lungs exchange up to 5 L of air per minute, and this may contain pathogens and other potentially harmful elements (e.g., allergens). Techniques to visualize the lung range from plain chest radiographs to high-resolution computed tomography (CT), which enables precise localization of a lesion within the lung.
In the clinic
High-resolution computed tomography (HRCT) is a diagnostic method for assessing the lungs but more specifically the interstitium of the lungs. The technique involves obtaining narrow cross-sectional slices of 1 to 2 mm. These scans enable the physician and radiologist to view the patterns of disease and their distribution. Diseases that may be easily demonstrated using this procedure include emphysema (Fig. 3.52), pneumoconiosis (coal worker’s pneumoconiosis), and asbestosis. HRCT is also useful in regular follow-ups of patients with interstitial disease to monitor disease progression.
In the clinic
Patients who have an endobronchial lesion (i.e., a lesion within a bronchus) may undergo bronchoscopic evaluation of the trachea and its main branches (Fig. 3.53). The bronchoscope is passed through the nose into the oropharynx and is then directed by a control system past the vocal cords into the trachea. The bronchi are inspected and, if necessary, small biopsies are obtained. Bronchoscopy can also be used in combination with ultrasound (a technique known as EBUS, endobronchial ultrasound). An ultrasound probe is inserted through a working channel of the bronchoscope to visualize the airway walls and adjacent structures. EBUS allows an accurate localization of the lesion and therefore provides a higher diagnostic yield. It can be used for sampling of mediastinal and hilar lymph nodes or to assist in transbronchial biopsy of pulmonary nodules.
In the clinic
It is important to stage lung cancer because the treatment depends on its stage.