- Understanding normal anatomy is key before being able to understand what is abnormal
- Anatomy review
- Visceral pleura hugs the lungs (forms fissures), parietal pleura lines chest wall
- Lobes of the lung: right lung has upper, middle, and lower lobes, left lung has upper and lower lobes
- Fissures: right lung has horizontal/minor fissure and oblique major fissure, left lung has one huge oblique major fissure
- Invisible or fine white lines, if thickened may represent excess fluid from a process such as congestive heart failure
- Trachea -> carina -> main bronchus -> lobar (secondary) bronchi -> segmental (tertiary) bronchi -> subsegmental bronchi -> bronchioles -> secondary lobules (centrilobular artery and bronchus) -> respiratory bronchioles -> alveoli
- Cannot usually see bronchi on chest x-ray
- Conduction zone = trachea, bronchi, bronchioles, terminal bronchioles
- Respiratory zone = respiratory bronchioles, alveolar ducts, alveoli
- Lung parenchyma = alveoli, ducts, and respiratory bronchioles
- Type 1 pneumocytes do gas exchange, type 2 pneumocytes produce surfactant, alveolar macrophages ingest and process debris
- Hemidiaphragms: left is obscured by heart, on lateral radiograph can follow the right hemi all the way across
- Left main pulmonary artery arches over the left main bronchus
- The right pulmonary artery will be anterior and inferior to the bronchus/left pulmonary artery on lateral radiograph
- Each pulmonary artery may appear as slightly opaque compared to the lumen of the bronchus
- Pulmonary vessel markings taper peripherally and will show up as white lines thicker at the base of the lung
- Lungs have supply from pulmonary arteries and bronchial arteries (from aorta)
- Pulmonary veins drain into left atrium
- Innervation: parasympathetic from vagus, sympathetic from thoracic ganglia
- Lymph drainage goes to hilum
- Physiology: parasympathetic causes vasoconstriction, bronchoconstriction, gland secretion, sympathetic does opposite and opens things up
- Lateral radiograph is important to view areas of the lung that may not be obviously abnormal on frontal view
- Normal features of lateral radiograph:
- Space behind the sternum (lack of could point to mediastinal masses)
- Absence of a major shadow from the hila (presence could point to sarcoidosis)
- Consistent height of vertebrae
- Sharp posterior (requires less fluid to visualize) costophrenic angles (blunted/opacity filled could point to pleural effusion)
- Continuous right hemidiaphragm (and slightly higher)
- As with all studies/indications, when looking at an image, do not forget to look at all of the structures in field of view; even if you are reading a chest x-ray to rule out pneumonia/pneumothorax, remember to view all of the other structures, such as the thoracic vertebrae!
References: Herring's Learning Radiology, Radiopaedia, Mandell's CORE Radiology