Clinical Signs and Diagnostic Tests for Pleural and Mediastinal Disease

Lecture 38

What pleural abnormality is defined as an accumulation of fluid?

pleural effusion

What pleural abnormaltiies are defined as an accumulation of air?

pneumothorax, pneumomediastinum

Respiratory function as a result of pleural abnormalities is associated with what?

interference with normal lung expansion

True or false: The pleura is not normally visible on radiographs.

True

What produces pleural fissure lines seen on radiographs?

pleural thickening

What amount of pleural effusion needs to be present to become visible on radiographs?

50-100mL

What abnormality can be seen in this radiograph?

pleural effusion

What type of pleural fluid is composed of a low protein concentration, low nucleated cell count, and primarily contains macrophages, lympocytes, and mesothelial cells?

transudates

What can cause transudative pleural fluid accumulation?

increased hydrostatic pressure —> right sided CHF, pericardial disease

decreased plasma oncotic pressure —> hypoalbuminemia

lymphatic obstruction —> neoplasia, diaphragmatic hernias

What type of pleural fluid is composed of higher protein content up to 3.5g/dL, nucleated cell counts up to 5000/microliter, and primarily contains neutrophils and mononuclear cells?

modified transudates

What can cause accumulation of modified transudative pleural fluid?

chronic diaphragmatic hernias

What type of pleural fluid is composed of high protein >3g/dL, high nucleated cell counts >5000/microlter, and primarily contains nondegenerate neutrophils, macrophages, eosinophils, lymphocytes, and no organisms?

nonseptic exudate

What can cause accumulation of non septic exudative pleural fluid?

FIP, neoplasia, chronic diaphragmatic hernia, lung lobe torsion, resolving septic exudates

What type of pleural fluid is composed of very high nucleated cell types, degenerate neutrophils and contains organisms?

septic exudates

What can cause accumulation of septic exudative pleural fluid?

spontaneous, penetrating wound, foreign bodies, extension of bacterial pneumonia

What type of pleural effusion is usually milky white and tubid but may be blood tinged, has a moderate concentration of protein >2.5g/dL, and a low to moderate nucleated cell count; predominant cell type is small lymphocytes?

chylous effusion

How can we diagnose chylous effusion?

by measuring triglycerides in pleural fluid and serum; level is higher in pleural fluid

What can cause chylous pleural effusion?

leaking from thoracic duct due to idiopathic, congenital, secondary due to trauma, neoplasia, cardiac disease, pericardial disease, lung lobe torsion, heartworm disease, or diaphragmatic hernia

What type of pleural effusion is grossly red due to RBCs, has protein levels >3mg/dL, a nucleated cell count >1000/microliter, and characteristics including erythrophagocytosis, inflammatory response, does not clot, and PCV lower than peripheral blood?

hemorrhagic effusion

What can cause hemorrhagic pleural effusion?

trauma, coagulopathies, neoplasia (hemangiosarcoma), lung lobe torsion

What tests should be initially performed in cases of hemorrhagic pleural effusion?

activated clotting time and platelet count

What type of pleural effusion can result in most effusion types and fluid may contain exfoliated neoplastic cells but difficult to establish diagnosis based on cytology since inflammation causes metaplastic changes in mesothelial cells which are hard to distinguish from neoplastic cells?

neoplastic effusion

What is the only neoplasia reliably identified in neoplastic effusion?

lymphoma

What can be seen on this cytology of pleural effusion?

lymphoma

What condition is defined as an accumulation of air in the pleural space via leaks from lung or through extra-thoracic entry?

pneumothorax

What type of pneumothorax develops if air leaks through functional “one way valve” lesion in the lungs?

tension pneumothorax

What can lead to extrathoracic entry of air into the pleural space resulting in pneumothorax?

thoracic wall trauma, iatrogenically through a chest tube, or during abdominal surgery if the diaphragm is not intact

What can cause pneumothorax of pulmonary origin?

blunt chest wall trauma

rupture of cavitary lung lesions —> cysts, bullae, blebs, necrotic neoplastic tissue, abscesses, etc

What is the primary differential of mediastinal masses?

neoplasia (commonly lymphoma)

others may include thymoma, thyroid carcinoma, parathyroid carcinoma, and chemodectoma

non-neoplasia masses may include abscesses, granulomas, hematomas, and cysts

How do mediastinal masses cause inspiratory distress?

displacement of lung tissue or secondary to pleural fluid accumulation

What imaging modality is indicated to evaluate underlying causes of pleural effusion?

ultrasound

What does TFAST stand for?

thoracic focused assessment with sonography for trauma

What ultrasound exam provides rapid, minimally stressful assessment of pleural space for fluid or air?

TFAST

What imaging modality is more sensitive than radiography for assessing the thorax, is useful for evaluating the extent of masses and increases the likelihood of finding cavitary lesion in spontaneous pneumothorax?

CT

What is your diagnosis based on this thoracic CT?

lung retracted from the pleural lining due to a pneumothorax

What procedure is indicated for collection of fluid or air from pleural space in the dog or cat?

thoracocentesis

What are possible complications of a thoracocentesis?

lung laceration, hemothorax, iatrogenic pyothorax

Where would you insert the needle for a thoracocentesis?

7th intercostal space, 2/3 distance from costochondral junction to spine

What procedure is indicated for treatment of pyothorax and accumulating pneumothorax?

chest tube

What are potential complications of a chest tube?

pneumothorax caused by leaking apparatus or poor handling technique

Where/How should you place a chest tube?

burrowed SQ from 10th intercostal space to 7th intercostal space then inserted into pleural space at 7th intercostal space directed cranially