First, let’s quickly review some anatomy and physiology. Remember that the pleura is a serous membrane that consists of two layers: the visceral pleura, which sticks to the surface of the lungs; and the parietal pleura, which lines the inside of the chest wall. Between these two layers is the pleural space, which contains 20 to 25 milliliters of pleural fluid. This lubricating fluid reduces friction between the two pleural layers, which allows them to slide over each other during respiration, as the lungs expand with inhalation and then relax with exhalation. Finally, it’s worth mentioning that the parietal pleura also has pain receptors, called nociceptors, with innervation coming from the intercostal nerves and fibers from the phrenic nerve that also innervates the diaphragm.
Now, the most common cause of pleurisy is a viral infection caused by the influenza virus, which causes the flu. Less frequently, pleurisy can be caused by a parainfluenza virus, adenovirus, coxsackieviruses, cytomegalovirus, Epstein-Barr virus, or respiratory syncytial virus. Pleurisy can also be caused by bacterial infections, such as pneumonia from Streptococcus pneumoniae, or tuberculosis; as well as fungal infections such as coccidioidomycosis or histoplasmosis.
Other causes and risk factors include pulmonary conditions like pneumothorax or pulmonary embolism, as well as autoimmune diseases like systemic lupus erythematosus or rheumatoid arthritis; cardiovascular diseases like myocardial infarction and myocarditis; and cancers, including pleural lymphoma or metastatic pleural tumors. Other causes and risk factors of pleurisy include chest trauma, surgery, and medications like hydralazine.
Alright, so the pathology of pleurisy starts with inflammation of the visceral and parietal pleura, which causes them to become swollen, limiting their movement. As a result, the two membranes rub against each other instead of gliding past during respiration.
So, the typical clinical manifestations of pleurisy include pleuritic pain, which is a sudden, severe, sharp or stabbing chest pain which is most often felt in the lower portion of the chest and can also be referred to the shoulder or neck. This pain worsens with coughing, sneezing, or with deep inhalation. Thus, clients with pleurisy often present with shallow and rapid breathing in order to avoid worsening of their pleuritic pain. There is often limited chest wall expansion on the affected side. Upon chest auscultation, the rubbing of the two inflamed pleural membranes produces a sound called a pleural friction rub, which is a loud, rough, and grating sound, similar to a squeaking door.
Some clients with pleurisy can also develop complications, such as pleural effusion, when there is an excessive buildup of fluid in the pleural cavity; as well as empyema, when there is a buildup of pus in the pleural cavity. In addition, some clients can even develop atelectasis, when parts of the lungs collapse and become unable to expand while breathing as they should.
Pleurisy is a symptom of a variety of localized and systemic disease processes. So identifying the underlying cause starts with the client's history and physical assessment, followed by additional diagnostic tests. These include laboratory tests to determine if the client has an infection and to identify the causative pathogen; or to indicate potential autoimmune disorders by finding autoantibodies. Other tests like an electrocardiogram or ECG can be performed to rule out a myocardial infarction; as well as imaging studies like chest X-rays or CT scan to visualize the lungs. Finally, some clients may require further testing, such as a pleural biopsy or thoracocentesis, to confirm the diagnosis.