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134 DISEASES OF THE PLEURA, MEDIASTINUM, AND DIAPHRAGM

134 DISEASES OF THE PLEURA, MEDIASTINUM, AND DIAPHRAGM
Harrison’s Manual of Medicine

134

DISEASES OF THE PLEURA, MEDIASTINUM, AND DIAPHRAGM

Pleural Disease
Mediastinal Disease
Disorders of Diaphragm
Bibliography

Pleural Disease
PLEURITIS   Inflammation of pleura may occur with pneumonia, tuberculosis, pulmonary infarction, and neoplasm. Pleuritic pain without physical and x-ray findings suggests epidemic pleurodynia (viral inflammation of intercostal muscles); hemoptysis and parenchymal involvement on CXR suggest infection or infarction. Pleural effusion without parenchymal disease suggests postprimary tuberculosis, subdiaphragmatic abscess, mesothelioma, connective tissue disease, or primary bacterial infection of pleural space.
PLEURAL EFFUSION   May or may not be associated with pleuritis. In general, effusions due to pleural disease resemble plasma (exudates); effusions with normal pleura are ultrafiltrates of plasma (transudates). Exudates have at least one of the following criteria: high total fluid/serum protein ratio (>0.5), pleural fluid LDH greater than two-thirds of the normal upper limit, or pleural/ serum LDH activity ratio >0.6. Leading causes of transudative pleural effusions in the U.S. are left ventricular failure, pulmonary embolism, and cirrhosis. Leading causes of exudative effusions are bacterial pneumonia, malignancy, viral infection, and pulmonary embolism. With empyema, pH < 7.2, WBCs
(>1000/mL), and glucose ¯. If neoplasm or tuberculosis is considered, closed pleural biopsy or thoracoscopic biopsy should be performed (Table 134-1 and Table 134-2; and Fig. 134-1). Despite full evaluation, no cause for effusion will be found in 25% of pts.

FIGURE 134-1. Approach to the diagnosis of pleural effusions. The special tests are summarized in Table 134-1. PF, pleural fluid; PE, pulmonary embolism. (From RW Light: HPIM-15.)

Table 134-1 Differential Diagnoses of Pleural Effusions

Table 134-2 Special Tests for Pleural Effusions

POSTPRIMARY TUBERCULOSIS EFFUSIONS   Fluid is exudative with predominant lymphocytosis; bacilli are rarely seen on smear, and fluid culture is positive in <20%; tuberculin test may be nonreactive early in illness; closed biopsy required for diagnosis.
NEOPLASTIC EFFUSIONS   Most often lung cancer, breast cancer, or lymphoma. Fluid is exudative; fluid cytology and pleural biopsy will confirm diagnosis in 60%; pleural sclerosis with bleomycin or minocycline may be required for management (Table 134-2).
RHEUMATOID ARTHRITIS (RA)   Exudative effusions may precede articular symptoms; very low glucose and pH; usually males.
PANCREATITIS   Typically left-sided; up to 15% of pts with pancreatitis; high pleural fluid amylase is suggestive but also may occur with effusions due to neoplasms, infection, and esophageal rupture.
EOSINOPHILIC EFFUSION   Defined as >10% eosinophils; nonspecific finding may occur with viral, bacterial, traumatic, and pancreatic effusions and may follow prior thoracentesis.
HEMOTHORAX   Most commonly follows blunt or penetrating trauma. Pts with bleeding disorders may develop hemothorax following trauma or invasive procedures on pleura. Adequate drainage mandatory to avoid fibrothorax and “trapped” lung.
PARAPNEUMONIC EFFUSION/EMPYEMA   An effusion associated with contiguous infection. The term complicated parapneumonic effusion refers to effusions that require tube thoracostomy for their resolution. Empyema is pus in the pleural space with positive Gram’s stain. Tube thoracostomy of parapneumonic effusions is likely indicated if any of the following applies (descending order of importance): (1) gross pus is present, (2) organisms are visible on Gram’s stain of pleural fluid, (3) pleural fluid glucose is <60 mg/dL, (4) pleural fluid pH is <7.20 and 0.15 units less than arterial pH, or (5) there is loculated pleural fluid. If closed drainage does not result in complete removal of fluid, streptokinase, 250,000 units, can be instilled through the tube. If fluid persists, open drainage is indicated, usually accomplished through a videoscope.
PNEUMOTHORAX (PNTX)   Spontaneous PNTX most commonly occurs between 20 and 40 years of age; causes sudden, sharp chest pain and dyspnea. Treatment depends on size—if small, observation is sufficient; if large, closed drainage with chest tube is necessary. 50% suffer recurrence, and pleural abrasion by thoracotomy or thoracostomy may be required so that surfaces become adherent (pleurodesis). Complications include hemothorax, cardiovascular compromise secondary to tension PNTX, and bronchopleural fistula. Many interstitial and obstructive lung diseases may predispose to PNTX.
Mediastinal Disease
MEDIASTINITIS   Usually infectious. Routes of infection include esophageal perforation or tracheal disruption (trauma, instrumentation, eroding carcinoma). Radiographic hallmarks include mediastinal widening, air in mediastinum, pneumo- or hydropneumothorax. Therapy usually involves surgical drainage and antibiotics.
TUMORS AND CYSTS   Most common mediastinal masses in adults are metastatic carcinomas and lymphomas. Sarcoidosis, infectious mononucleosis, and AIDS may produce mediastinal lymphadenopathy. Neurogenic tumors, teratodermoids, thymomas, and bronchogenic cysts account for two-thirds of remaining mediastinal masses. Specific locations for specific etiologies (Table 134-3). Evaluation includes CXR, CT, and when diagnosis remains in doubt, mediastinoscopy and biopsy.

Table 134-3 Nature of Masses in Various Locations in Mediastinum

Neurogenic Tumors   Most common primary mediastinal neoplasms; majority are benign; vague chest pain and cough.
Teratodermoids   Anterior mediastinum; 10–20% undergo malignant transformation.
Thymomas   10% primary mediastinal neoplasms; one-quarter are malignant; myasthenia gravis occurs in half.
SUPERIOR VENA CAVA SYNDROME   Dilation of veins of upper thorax and neck, plethora, facial and conjunctival edema, headache, visual disturbances, and reduced state of consciousness; most often due to malignant disease—75% bronchogenic carcinoma, most others lymphoma.
Disorders of Diaphragm
DIAPHRAGMATIC PARALYSIS   Unilateral Paralysis   Usually caused by phrenic nerve injury due to trauma or mediastinal tumor, but nearly half are unexplained; usually asymptomatic; suggested by CXR, confirmed by fluoroscopy.
Bilateral Paralysis   May be due to high cervical cord injury, motor neuron disease, poliomyelitis, polyneuropathies, bilateral phrenic involvement by mediastinal lesions, after cardiac surgery, dyspnea; paradoxical abdominal motion should be sought in supine pts.
Bibliography

For a more detailed discussion, see Light, RW: Disorders of the Pleura, Mediastinum, and Diaphragm, Chap. 262, p. 1513, in HPIM-15.

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