Pleural Diseases



Pleural Diseases


Alexander C. Chen

Daniel J. Brown



General Principles



  • The pleural lining is a serous membrane covering the lung parenchyma, chest wall, diaphragm, and mediastinum.


  • The pleural membrane covering the surface of the lung is known as the visceral pleura, the parietal pleura covers the remaining structures.


  • In between the visceral and parietal pleurae of each lung is the pleural space, a potential space that contains a thin layer of fluid of ∼10 mL in volume.


  • The parietal pleura secretes2.5 L of fluid daily, which is reabsorbed by the visceral pleura.


Definition



  • A pleural effusion is >10 mL accumulation of fluid in the pleural space.



    • A hemothorax refers to a pleural effusion that is comprised mainly of blood.


    • Chylothorax is a collection of chyle within the pleural space.


    • A parapneumonic effusion is any effusion caused by bacterial pneumonia and occurs in about 40% of cases of bacterial pneumonia.1



      • Uncomplicated parapneumonic effusions do not require chest tube drainage for complete resolution and are presumed to be sterile.


      • Complicated parapneumonic effusions are accompanied by bacterial invasion of the pleural space and typically do require thoracostomy drainage, although occasionally may improve with antibiotic therapy alone.


      • Empyema simply refers to a complicated parapneumonic effusion with grossly purulent pleural fluid and is presumed to be infected even though cultures may not always be positive. On occasion, empyema may not be associated with a pneumonic process.


      • Other more complicated classifications of parapneumonic effusions have also been developed.2,3


  • A pneumothorax is a collection of gas in the pleural space.4,5



    • Primary spontaneous pneumothorax occurs when there is no obvious underlying lung disease.


    • Secondary spontaneous pneumothorax is a complication of underlying lung disease.


Epidemiology



  • More than 1 million cases of pleural effusion occur annually in the United States.


  • Incidence of pneumothorax varies widely by gender, country, and race.4


Etiology



  • Pleural effusions have a variety of causes (Table 23-1).



    • Empyema is generally caused by extension of an infection of the lung or surrounding tissue.



      • Common microbial pathogens are Staphylococcus aureus, Streptococcus species, and Haemophilus influenza.


      • Empyemas are frequently polymicrobial in cases where aspiration is suspected.









        TABLE 23-1 CAUSES OF PLEURAL EFFUSION






        Exudates
          Infection (viral, bacterial, mycobacterial, fungal, protozoal)
          Neoplastic
            Metastatic carcinoma
            Lymphoma
            Leukemia
            Mesothelioma
            Bronchogenic carcinoma
            Chest wall tumors
          Intra-abdominal disease
            Abdominal surgery
            Pancreatitis
            Meigs syndrome
            Intrahepatic abscess
            Incarcerated diaphragmatic hernia
            Subdiaphragmatic abscess
            Esophageal rupture
            Endoscopic variceal sclerotherapy
            Hepatitis
          Collagen vascular diseases
            Systemic lupus erythematosus
            Drug-induced lupus
            Rheumatoid arthritis
            Sjögren syndrome
            Granulomatosis with polyangiitis
            Churg–Strauss syndrome
          Drug induced
            Nitrofurantoin
            Dantrolene
            Methysergide
            Bromocriptine
            Procarbazine
            Amiodarone
          Pulmonary infarction
          Lipid laden
            Chylous
            Pseudochylous (chyliform, i.e., cholesterol effusion)
            Trauma
          Miscellaneous
            Dressler syndrome (postcardiac injury)
            Sarcoidosis
            Yellow nail syndrome
            Trapped lung
            Radiation therapy
            Electrical burns
            Iatrogenic injury
            Ovarian hyperstimulation syndrome
            Chronic atelectasis
            Asbestos exposure
            Familial Mediterranean fever
            Urinoma
          Idiopathic
        Transudates
          Increased hydrostatic pressure
            Heart failure
            Constrictive pericarditis
            Superior vena cava obstruction
          Decreased oncotic pressure
            Cirrhosis
            Nephrotic syndrome
            Hypoalbuminemia
            Peritoneal dialysis
          Miscellaneous
            Acute atelectasis
            Subclavian catheter misplacement
            Myxedema
            Idiopathic


    • The three major grouped causes of chylothorax are malignancy (50% of cases), trauma (25%), and idiopathic (15%). Other causes account for 10%.6



      • Seventy-five percent of chylous effusions related to malignancy are due to lymphomas related to obstruction of pleural lymphatics.


      • Trauma as a causative factor of chylothorax includes any cardiothoracic surgical procedure. It may take place 1–2 weeks postsurgery for the chylothorax to become apparent.


      • In a number of cases, chylothorax results from transdiaphragmatic leakage of chylous ascites. Causes of chylous ascites include nephrotic syndrome, hypothyroidism, and cirrhosis.









        TABLE 23-2 CRITERIA FOR DEFINING A PLEURAL EFFUSION9,10








        Light criteria
          Pleural fluid protein to serum protein ratio of >0.5
          Pleural fluid LDH to serum LDH ratio of >0.6
          Pleural fluid LDH >2/3 serum upper limit of normal
        Heffner criteria
          Pleural fluid protein >2.9 g/dL
          Pleural fluid cholesterol >45 mg/dL
          Pleural fluid LDH >45% of upper limits of normal serum value
        LDH, lactate dehydrogenase.


    • Hemothorax may result from trauma or iatrogenesis, and rarely can occur spontaneously.7


    • When the etiology for the effusion cannot be determined despite appropriate evaluation, a benign course is typical.8


  • Secondary pneumothorax is often seen in chronic obstructive pulmonary disease (COPD), AIDS, cystic fibrosis, TB, sarcoidosis, pulmonary fibrosis, asthma, Marfan disease, lymphangioleiomyomatosis, pulmonary Langerhans cell histiocytosis, trauma, or any disease with pulmonary cavity formation.4 Catamenial pneumothorax is a rare condition of spontaneous pneumothorax occurring in close proximity to menstruation and is often recurrent.4,5 It may also cause hemopneumothorax.


Pathophysiology

Nov 20, 2018 | Posted by in RESPIRATORY | Comments Off on Pleural Diseases
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