A 64-year-old man comes to the office due to a month of dyspnea on exertion, nonproductive cough, and right-sided pleuritic chest pain. The patient's medical history is significant for hypertension, type 2 diabetes, chronic kidney disease (baseline creatinine of 2 mg/dL), and chronic obstructive pulmonary disease. He smoked cigarettes for 40 years and quit 4 years ago. Temperature is 38.2 C (100.8 F), blood pressure is 128/72 mm Hg, pulse is 92/min, and respirations are 18/min. Chest x-ray shows a moderate right-sided pleural effusion. Pleural fluid results are as follows: Serum total protein is 6.0 g/dL, and serum lactate dehydrogenase is 120 U/L. Which of the following is the most likely mechanism underlying the development of this pleural effusion?

Question

A 64-year-old man comes to the office due to a month of dyspnea on exertion, nonproductive cough, and right-sided pleuritic chest pain.  The patient's medical history is significant for hypertension, type 2 diabetes, chronic kidney disease (baseline creatinine of 2 mg/dL), and chronic obstructive pulmonary disease.  He smoked cigarettes for 40 years and quit 4 years ago.  Temperature is 38.2 C (100.8 F), blood pressure is 128/72 mm Hg, pulse is 92/min, and respirations are 18/min.  Chest x-ray shows a moderate right-sided pleural effusion.  Pleural fluid results are as follows:  Serum total protein is 6.0 g/dL, and serum lactate dehydrogenase is 120 U/L.  Which of the following is the most likely mechanism underlying the development of this pleural effusion?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d4c2_1a19_bc81_6facc709879a_MD0003_00 Pleural effusions are categorized by Light's criteria as transudative or exudative. This patient's pleural fluid is exudative by all 3 parameters: Fluid/serum protein ratio = 5.2/6 ~0.87 >0.5 Fluid/serum lactate dehydrogenase (LDH) ratio = 340/120 ~2.83 >0.6 Fluid LDH level = 340 >2/3 of the upper limit of normal (90×2/3 = 60) Determining the cause of an exudative effusion is not always possible by symptoms and laboratory examination alone. However, this patient has pleuritic pain and fever, suggesting an infectious or inflammatory etiology. Cytokines released during inflammation or infection increase capillary permeability, resulting in the translocation of cells and fluid from the vasculature into the pericapillary space. This aids in the immune response but can also result in an exudative pleural effusion. With pleural fluid analysis showing a moderate lymphocytosis, very elevated protein (>4 g/dL), and elevated LDH, it is quite likely that this patient has a tuberculous effusion. These effusions tend to occur on the right side, and pleural pH and glucose are often low. Although the patient does not have traditional social risk factors for tuberculosis (eg, incarceration, travel to an endemic region, group living), chronic kidney disease, diabetes mellitus, and cigarette smoking all increase the risk of tuberculosis reactivation. A malignant effusion may also have similar features, although pleural fluid lymphocytosis of >70% is uncommon. (Choices A, B, and D) Transudative effusions are marked by the movement of fluid from the microvasculature into the pleural space across an intact vascular wall, resulting in a low protein effusion. Causes include: Decreased intrapleural pressure (eg, atelectasis) - reduced perivascular pressure pulls fluid across the vascular membrane into the pleural space Decreased plasma oncotic pressure (eg, hypoalbuminemia) - fluid moves into tissue and space (eg, abdominal, pleural) until pressures equalize Elevated hydrostatic pressure (eg, congestive heart failure) - increased microvascular pressure pushes fluid through the vascular membrane into the pleural space (Choice C) Disruption of the thoracic duct results in chylothorax. Malignancy and trauma are 2 common causes of chylothorax. Chylothorax causes an exudative effusion, high in triglyceride content and milky white in appearance. Fever and chest pain are uncommon because chyle does not provoke inflammation. Educational objective: Transudative effusions are commonly caused by decreased intrapleural or plasma oncotic pressures or elevated hydrostatic pressure. Exudative effusions are often the result of increased capillary or pleural membrane permeability or disruptions to lymphatic outflow.

A 64-Year-Old Man Comes to the Office Due to a Month