Understanding Atelectasis: Causes, Signs, and Types

1. Atelactasis By Don Wynn

14. Atelectasis • Greek = incomplete stretching • Definition: diminished gas within the lung associated with reduced lung volume and radiologic signs

15. Signs of Atelactasis • Direct • Indirect

16. Direct Signs • Displacement of fissures • Increased opacification of the airless lobe. • Crowding of pulmonary vessels

17. Indirect Signs • Displacement of hilar structures (Katan’s triangle sign) • Cardiomediastinal shift toward the side of collapse • Narrowing of ipsilateral intercostal spaces • Elevation of the ipsilateral diaphragmatic leaflet (Juxtaphrenic peak sign)

18. Indirect Signs • Compensatory hyperexpansion and hyperlucency of the remaining aerated parts of the lung • Obscuring of structures adjacent to the collapsed lung, such as the diaphragm, heart, or pulmonary vessels.

20. Types of Atelactasis • Obstructive • Nonobstructive

21. Types of Atelactasis • Obstructive • Blockage of an airway. • Air retained distal to the occlusion is then resorbed from nonventilated alveoli. Over time, the affected regions become totally airless.

22. Obstructive Atelectasis • Causes: • 1). Bronchogenic carcinoma (always a consideration in patients with histories of persistent atelectasis, recurrent atelectasis, or recurrent pneumonia with failure of complete clearing after treatment) • 2). Bronchial carcinoid (above considerations also apply here) • 3). Metastases to the bronchi: most commonly renal cell carcinoma, breast carcinoma, melanoma, adenocarcinoma of the colon, sarcomas

23. Obstructive Atelectasis • Causes: • 4). Lymphoma (usually late stage and accompanied by hilar and mediastinal lymphadenopathy) or other causes of bulky adenopathy • 5). Tuberculosis • 6). Left atrial enlargement from mitral stenosis (left lower-lobe atelectasis) • 7). Foreign body obstruction • 8). Mainstem bronchus intubation

24. Types of Atelactasis • Nonobstructive • Causes: • Loss of contact between the parietal and visceral pleura, • Parenchymal compression, • Loss of surfactant, • Replacement of lung tissue by scarring or infiltrative disease.

25. Types of Atelactasis • Mechanisms of Atelactasis • Relaxation • Compressive • Adhesive • Cicatrization • Replacement • Rounded

26. Types of Atelactasis • Relaxation • Contact between the parietal and visceral pleurae is eliminated. • 1). Pleural effusion 2). Pneumothorax 3). Hydrothorax, hemothorax 4). Diaphragmatic hernia 5). Pleural masses (including metastases and mesothelioma)

27. Types of Atelactasis • Compressive • Chest wall, pleural, intraparenchymal masses, or loculated collections of pleural fluid lead to a diminution in lung volume below the usual resting volume. • It has much in common with relaxation atelectasis, but is distinguished by local, rather than generalized, collapse.

28. Types of Atelactasis • Compressive • Causes: • peripheral tumor compressing adjacent normal lung, • extensive air trapping (as seen in bullous emphysema, lobar emphysema, interstitial emphysema, or bronchial foreign body obstruction)

29. Types of Atelactasis • Adhesive • Induced by surfactant dysfunction. • Decreased production or inactivation of surfactant leads to alveolar instability and collapse. • Respiratory distress syndrome of premature infants, ARDS, acute radiation pneumonitis, PE and lung contusion.

30. Types of Atelactasis • Adhesive • In the appropriate clinical setting, PULMONARY EMBOLISM MUST ALWAYS BE CONSIDERED in the patient with SUBSEGMENTAL atelectasis AND PLEURAL EFFUSION. Induced by surfactant dysfunction.

31. Types of Atelactasis • Cicatrization • Diminution of volume as a sequel of severe parenchymal scarring. • Etiologies include: • granulomatous disease, • late sequelae of TB, • necrotizing pneumonia, • radiation • pneumoconioses • Collagen vascular diseases (e.g., scleroderma, rheumatoid lung)

32. Types of Atelactasis • Replacement • Occurs when the alveoli of an entire lobe are filled by tumor, such as bronchioloalveolar cell carcinoma, with ensuing loss of volume.

33. Types of Atelactasis • Rounded • Also called folded lung or Blesofsky syndrome • A distinct form of atelectasis associated with pleural disease, particularly following asbestos exposure

34. MRI • Can distinguish between obstructive and nonobstructive atelectasis. • Obstructive atelectasis displays high signal intensity on T2-weighted images due to proton-rich mucus accumulation.

35. MRI • Nonobstructive atelectasis shows low signal intensity on T1 and T2 images • The use of MRI in diagnosing atelectasis is still experimental, and more experience needs to be accrued

36. RUL Collapse • Elevation of the right hilum and the minor fissure • Convex upward • Collapse lobe tends to shift cephalad and medially

39. Right Upper Lobe Atelactasis • This configuration of the minor fissure is called the S-sign of Golden and indicates a probable neoplastic etiology for the obstructive atelectasis. • A juxtaphrenic peak indicates loss of volume in the upper lobe and can be a helpful sign of upper lobe atelectasis.

41. RUL Atelactasis • Medial collapse of the right upper lobe can occasionally mimic a right paratracheal mass • Lateral collapse lead to a peripheral mass-like opacity that mimics a loculated pleural effusion. • Right middle and lower lobes hyperexpand superiorly and medially rather than laterally.

43. RML Atelactasis • Greater tendency to collapse because of: 1) decreased collateral ventilation 2) a long thin curved bronchus 3) Possible compression by a collar of enlarged lymph nodes at bronchus origin

44. RML Atelactasis • Chronic RML Atelactasis • RML syndrome • Frequently nonobstructive • Accompanied by scarring and bronchiectasis • Often found in elderly women

45. RML Atelactasis • Total collapse has little impact on appearance of surrounding structures • Absent contour of right heart border • A small triangular opacity pointing laterally

48. RML Atelactasis • On CT scan, the atelectatic right middle lobe presents as a triangular opacity with its apex pointing laterally and with its medial contour apposed against the right heart border. • This has been called the "tilted ice cream cone" appearance

50. RLL Atelactasis • Tethered to the mediastinum by the hilar structures and the inferior pulmonary ligament. • Visibility of major fissure – early sign of RLL collapse on frontal X-ray • Forms a triangular opacity that obscures the lower lobe pulmonary artery.