RADIOLOGY, PREGNANCY, INFECTION AND TREATMENT: LEARNING RADIOLOGY

Pneumothorax

Presence of air in the pleural space Anatomy Visceral pleura is adherent to lung surface There is no air in the pleural space normally The introduction of air into the pleural space separates the visceral from the parietal pleura In contradistinction, the visceral and parietal pleura usually do not separate from each other in obstructive atelectasis Pathophysiology Either from disruption of visceral pleura Or, trauma to parietal pleura Clinical findings Acute onset of Pleuritic chest pain Dyspnea (in 80-90%) Cough Back or shoulder pain Etiologies Penetrating trauma Blunt trauma May be due to rib fracture May be caused by increased intrathoracic pressure May lead to bronchial rupture “Fallen lung sign” (ptotic lung sign) -- hilum of lung is below expected level within chest cavity Persistent pneumothorax with functioning chest tube Iatrogenic Tracheostomy Central venous catheter attempt or insertion Mechanical ventilation May occur in up to 25% of patients maintained on PEEP May be bilateral or under tension Thoracic irradiation Spontaneous pneumothorax Most common etiology Cause Rupture of subpleural blebs in apical region of lung Age 20-40 years M:F = 8:1 Especially in patients who are tall and thin Smokers Prognosis Recurrence in 30% on same side Recurrence in 10% on contralateral side Treatment Simple aspiration (success in >50%) Tube thoracostomy (effective in 90%) Other causes of a pneumothorax Neonatal disease Meconium aspiration Respirator therapy for hyaline membrane disease Malignancy Primary lung cancer Lung metastases, especially from osteosarcoma Also pancreas, adrenal, Wilms tumor Pulmonary infections Tuberculosis Necrotizing pneumonia Coccidioidomycosis Hydatid disease Pertussis Acute bacterial pneumonia Staphylococcal septicemia AIDS (Pneumocystis carinii, Mycobacterium tuberculosis, atypical mycobacteria) Complication of pulmonary fibrosis Histiocytosis X Idiopathic Cystic fibrosis Sarcoidosis Scleroderma Eosinophilic granuloma Interstitial pneumonitis Rheumatoid lung Idiopathic pulmonary hemosiderosis Pulmonary alveolar proteinosis Biliary cirrhosis Asthma or emphysema Produce a second peak incidence of pneumothorax from 45-65 years of age Due to rupture of peripheral emphysematous areas “Catamenial pneumothorax” is a recurrent spontaneous pneumothorax that occurs during menstruation and is associated with endometriosis of the diaphragm R >> L Marfan’s syndrome Ehlers-Danlos syndrome Pulmonary infarction Lymphangiomyomatosis and tuberous sclerosis Incidence of pneumothorax is particularly high in lymphangiomyomatosis and histiocytosis X Types of pneumothorax Closed pneumothorax = intact thoracic cage Open pneumothorax = "sucking" chest wound Tension pneumothorax Accumulation of air within pleural space due to free ingress and limited egress of air Pathophysiology: Intrapleural pressure exceeds atmospheric pressure in lung during expiration (check-valve mechanism) Frequency In 3-5% of patients with spontaneous pneumothorax Higher in barotrauma (mechanical ventilation) Simple pneumothorax –no shift of the heart or mediastinal structures Imaging findings in pneumothorax Must see the visceral pleural white line Very thin white line that differs from a skin fold by its thickness Absence of lung markings distal or peripheral to the visceral pleural white line Not evidence enough to say there is a pneumothorax only if there are no lung markings seen No lung markings will be seen with bullous disease Bullae have a concave surface facing the chest wall Pneumothorax almost always has a convex surface facing the chest wall Displacement of mediastinum and/or anterior junction line Deep sulcus sign On frontal view, larger lateral costodiaphragmatic recess than on opposite side Diaphragm may be inverted on side with deep sulcus Total / subtotal lung collapse This is passive or compressive atelectasi Collapse of SVC or IVC due to decreased systemic venous return and decreased cardiac output Tension hydropneumothorax Sharp delineation of visceral pleural by dense pleural space Mediastinal shift to opposite side Air-fluid level in pleural space on erect chest radiograph Radiographic signs in upright position White margin of visceral pleura separated from parietal pleura Usually seen in the apex of the lung Absence of vascular markings beyond visceral pleural margin May be accentuated by an expiratory film in which lung volume is reduced while amount of air in pneumothorax remains constant so that relative size of pneumothorax appears to increase Radiographic signs in supine position Anteromedial pneumothorax (earliest location) Outline of medial diaphragm under cardiac silhouette Deep sulcus sign Decubitus views of the chest may demonstrate a pneumothorax on the side that is non-dependent Left lateral decubitus view for right-sided pneumothorax Right lateral decubitus view for left-sided pneumothorax Subpulmonic pneumothorax (second most common location) Hyperlucent upper abdominal quadrant Deep lateral costophrenic sulcus Sharply outlined diaphragm in spite of parenchymal disease Visualization of anterior costophrenic sulcus Visualization of inferior surface of lung Apicolateral pneumothorax (least common location) Visualization of visceral pleural line Posteromedial pneumothorax (in presence of lower lobe collapse) Lucent triangle with vertex at hilum V-shaped base delineating costovertebral sulcus Pneumothorax outlines pulmonary ligament Pitfalls in diagnosis Skin fold Thicker than the thin visceral pleural white line Air trapped between chest wall and arm Will be seen as a lucency rather than a visceral pleural white line Edge of scapula Follow contour of scapula to make sure it does not project over chest Overlying sheets Usually will extend beyond the confines of the lung Hair braids Prognosis Resorption of pneumothorax occurs at a rate of 1.25% per day (accelerated by increasing inspired oxygen concentrations)

Left pneumothorax-deep sulcus sign., Lucency at left costophrenic angle which projects well below the costophrenic angle on the opposite side is the "Deep sulcus sign" indicating the presence of a pneumothorax on a supine radiograph of the chest (Bullet is seen overlying the heart)

Thoracic Radiology: The Requisites Dahnert 4^th Edition