Pleural Disease Readings PDF

14 Pleural Disease The pleura is a thin tissue covered by a layer of cells (mesothelial cells) that surrounds the lungs and lines the inside of the chest wall. The pleural space is the area between the lungs and the chest wall. It is normally a...

14 Pleural Disease The pleura is a thin tissue covered by a layer of cells (mesothelial cells) that surrounds the lungs and lines the inside of the chest wall. The pleural space is the area between the lungs and the chest wall. It is normally at subatmospheric pressure, which keeps the lungs inflated. The normal pleural space has only a few milliliters of liquid, which helps lubricate the normal to and fro motion of the lungs during breathing. Fluid, air, and particles can move into the pleural space from different parts of the body because of its low pressure and its ability to hold large amounts of liquid or air. Pleural effusion (large amounts of liquid in the pleural space) or pneumothorax (air in the pleural space) can lead to a partial or complete compression of the lung. If a tear or hole develops in the lung, air escapes into the pleural space, causing a pneumothorax. Sometimes, air goes into the pleural space and is trapped there under high pressure, causing a “tension pneumothorax” that can stop blood from returning to the heart and lead to death if not recognized and treated promptly. In addition, inhaled toxic particles such as asbestos can move into the pleural space where, decades later, mesothelioma can develop. 145 Whitebook_breathing_Ch14.indd 145 6/25/10 12:50:25 PM  Pleural Disease Chapter 14 Whom does it affect? Epidemiology, prevalence, economic burden, vulnerable populations Many diseases affect the pleural space in both adults and children, including common diseases such as pneumonia, breast cancer, and heart failure. Pleural disease is, therefore, often a secondary effect of another disease process. Pleu- ral effusion is the most common manifestation of pleural disease and a common presentation of other conditions such as heart failure or kidney failure. It is esti- mated that a million Americans develop a pleural effusion each year (1). “­Pleurisy” is any inflammatory condition of the pleura. Because the pleura is richly supplied with nerves, pleurisy can be quite painful. Usually, when the pleural space is involved in pneumonia or lung cancer, the patient is sicker and has a worse prognosis than in the absence of pleural involvement. A common cause of pleural disease is cancer. It is estimated that malignant pleural effusion affects 150,000 people per year in the United States (2). Most patients with pleural effusion come to the doctor complaining of shortness of breath, which is caused by fluid accumulating in the chest and compressing the lung (2). Once a malignant pleural effusion is diagnosed, the prognosis is very poor, with patients living only another four months on average. Approximate annual incidence of various types of pleural effusions in adults in the United States Type Incidence Congestive heart failure 500,000 Parapneumonic effusion 300,000 Malignant pleural effusion 200,000 Pulmonary embolism 150,000 Viral disease 100,000 Post–coronary artery bypass 50,000 Gastrointestinal disease 25,000 Tuberculosis    2,500 Mesothelioma    2,704 Asbestos exposure    2,000 Adapted from (5). 146 Whitebook_breathing_Ch14.indd 146 6/25/10 12:50:25 PM  Chapter 14 Pleural Disease Case Study In 1979, film icon Steve McQueen was diagnosed with mesothelioma at age 49, John Kobal Foundation/Hulton Archive/Getty Images after complaining to his doctor of chronic cough and shortness of breath with exertion. He was told the cause of the disease was his exposure to asbestos as a young man working in construction and as a merchant marine. Asbestos insulation was used extensively in ships at that time, and he recalled occasions when the air was clouded with asbestos dust as he cleaned a ship’s engine room after pipe installation. After being told that his condition was terminal and that he had less than a year to live, McQueen sought help from a clinic in Mexico that claimed miraculous cures. He underwent a regimen involving animal cell injections, coffee enemas, Laetrile, and huge daily doses of vitamin pills. But his health only worsened, and the tumors in his chest and abdomen continued to grow, causing him pain and shortness of breath. In a final attempt to extend his life and reduce his discomfort, he underwent an operation in Mexico to remove a tumor from his abdomen, but died shortly afterward. Comment At the time of his diagnosis, there was no treatment for mesothelioma, a cancer that progressively reduces a person’s ability to breathe and can cause considerable pain. Although the public accounts of McQueen’s illness do not mention chest pain, this symptom is a nearly universal complaint among those with mesothelioma. Unfortunately, more than 30 years later, the prognosis for malignant mesothelioma is not much different than it was in McQueen’s time. The McQueen story of a ­desperate attempt to find a cure continues to challenge science and ­medicine today. 147 Whitebook_breathing_Ch14.indd 147 6/25/10 12:50:32 PM  Pleural Disease Chapter 14 Persons involved in automobile accidents or any trauma are also at increased risk for pneumothorax. Pleural fibrosis and lung compression can fol- low pleural infection or injury. The primary pleural cancer, mesothelioma, is a risk for anyone exposed to asbestos. Asbestos continues to be used in certain U.S. industries and is found in many buildings. Disruption of these buildings can expose persons to asbestos (2). The World Trade Center collapse introduced tons of asbestos into the environment, and it is believed that there will be an increased risk of mesothelioma among those who worked at the site (3). ­However, because mesothelioma develops an average of 35 to 40 years after the time of exposure, these cases are not expected to be identified until approx- imately 2036. Unfortunately, there is no effective screening tool for early detec- tion of this disease. An uncommon disease that affects the pleural space is lymphangioleiomyo- matosis (LAM). This disorder almost exclusively affects women of reproductive age and is characterized by abnormal growth of smooth-muscle cells around the small airways and small blood and lymph vessels of the lung. The pleural space involve- ment is a major issue for these patients. As of June 2009, there were 1,247 living patients in the database of the LAM Foundation. Of these, 483 persons had suffered a pneumothorax, 187 had a pleural effusion, and 24 developed a very unusual pleural effusion caused by a rupture of a lymphatic channel that spills essential dietary fats into the pleural space (chylous pleural effusion). Patients with LAM have the highest rate of pneumothorax of all chronic lung diseases (60 to 70 percent); the recurrence rate is 66 percent without treatment (4). The economic burden of pleural disease is difficult to estimate, but it is undoubtedly enormous, given the number of diseases with which the pleura is involved and the frequent need for hospitalization and surgery to treat pleural involvement. What are we learning about this disease? Pathophysiology, causes: genetic, environment, microbes A great deal has been learned about the diseases that involve the pleural space. These diseases often reflect diseases elsewhere in the body that spread to the pleural space, whether the process is infection, inflammation, cancer, or edema. The fluid movement into and out of the pleural space is governed by pressure 148 Whitebook_breathing_Ch14.indd 148 6/25/10 12:50:32 PM  Chapter 14 Pleural Disease In this CT scan, mesothelioma is shown growing extensively in the pleural space (arrows) and is completely surrounding the lung on one side of the chest. The thickened pleura can be appreciated in comparison to the same area on the opposite side, which is normal. Note how the chest on the side of the mesothelioma is smaller than the opposite side; mesothelioma characteristically shrinks the chest and constricts the lung, making it difficult to take a breath. One can also appreciate how difficult it would be to treat a tumor that spreads in this way (2). differences that arise from breathing and blood flow, but there are many active cellular processes that keep excessive fluid out of the normal pleural space. There are genetic, environmental, and infectious causes of diseases that spread to the pleura, and certain ones affect the pleura more than the rest of the lung. Mesothelioma, the cancer of mesothelial cells suffered by Steve McQueen, is caused by inhalation of asbestos fibers, which commonly cause other disor- ders of the pleura as well, including chronic pleural effusions and benign tumors. Tuberculosis and certain other infections also commonly affect the pleura. Some disease processes do not generally affect the pleura, and this feature is useful in diagnosis. For example, collagen vascular diseases (see Chapter 6) often involve the pleura, while most interstitial lung diseases do not. Other genetic and environmental factors have lesser effects on pleural disease. 149 Whitebook_breathing_Ch14.indd 149 6/25/10 12:50:36 PM  Pleural Disease Chapter 14 Deaths due to mesothelioma in the United States Deaths per million >20.0 15.1–20.0 10.1–15.0