Chest X Ray Interpretation

Introduction

• Postero-anterior(PA): The ideal chest-xay. A procedure using ionising radiation passing through the chest from posterior to anterior (PA) to an x-ray plate. The patient places arms around the x-ray plate so scapula are pulled laterally. The cardiac shadow is smaller than with an AP
• Antero-Posterior (AP): In portable X-rays, the rays pass from anterior to posterior (AP) and this is more practical in sick patients but it magnifies the heart and quality is reduced.
• Lateral (LAT): can see posterior mediastinum and lung fields. Helps to define consolidation, collections and foreign bodies in the thorax. However CT is the more usual test to delineate opacities

Anatomy

Landmarks

Landmarks

Normal

Posterior Anterior CXR: patient needs to be able to stand or sit up so difficult if ill. The chest presses on the film cartridge (well it's all digital now). Best diagnostic quality.

Lateral CXR - rarely done now as CT used for exact placement of lesions

AP chest - the film goes behind the patient who can lie back. Done when the patient is ill. There is cardiomegaly and often poor inspiration and the diagnostic quality is reduced. Useful looking for gross pathology

ABBCDE Format of looking at CXR

• Check name and hospital number
• Check date on CXR

Positioning

• Postero-Anterior Film
  • The normal CXR is a Postero-Anterior (PA) - the direction of the X-ray beams
  • The patient stands or may sit with their chest against the X-ray film plate.
  • This is the standard and best view for lung and cardiac and thorax pathology
  • Should be done in full inspiration
  • Pneumothorax may be seen better in maximal expiration
• Anteroposterior films
  • Most commonly as the portable CXR - the film is placed behind the patient
  • The heart is magnified and so can lead to misdiagnosis of cardiomegaly
  • Usually poorer quality
• Imaging
  • Is it rotated - look at symmetry of medial ends of clavicles
  • Is it adequately penetrated - can I see vertebrae behind heart

Interpretation

• Check name, dob, date of CXR
• Check orientation - markers for left/right
• Check if AP or PA film (should be marked). PA means X-rays pass from behind onto a radiographic plate against the patient's sternum. It is the best CXR to get.
• See if it erect or supine and check rotation by comparing medial ends of clavicle
• Adequate penetration should enable vertebral bodies to be well seen
• Female - look for breast shadow and more importantly absence of one due to mastectomy
• Lung fields - look for vascular markings. Absence of any markings at periphery look for a Pneumothorax
• Describe lesions as upper zone, mid zone and lower zone and then go on to decide if you can identify lobe involved though a lateral may well be needed for this

• A-airway
  • Trachea - midline
  • Bronchi
• B-bone
  • Ribs and lytic lesions and fractures
  • Clavicles - fracture
• B-breasts
  • Absent shadow may suggest mastectomy
• C-cardiac
  • Cardiomegaly if = 0.5 overall chest diameter
  • Situs inversus
• D- diaphragm
  • Blunting of angles due to effusion
  • Pneumoperitoneum
  • Normal air bubble under the left-handed hemidiaphragm.
• E&F- equal (lung) fields
  • Bats wing pulmonary oedema
  • Alveolar shadowing
  • Pleural effusion
  • Opacities
  • Pneumothorax - lack of lung markings
• G- gastric bubble
• H- hilum and mediastinum
  • left side should be higher than the right
  • Check both should be same size
  • Unilateral enlargement
    • Lymphadenopathy
    • Tuberculosis
    • Lung cancer
  • Bilateral Lymphadenopathy
    • Sarcoidosis
    • Tuberculosis
    • Lymphoma

Common CXRs in the exam

• Lobar Consolidation
• Pneumothorax
• Pulmonary oedema
• Fibrosing lung disease
• Pleural effusion
• Lobar Collapse
• Pneumonectomy
• Neoplastic lesion - mass
• Tuberculosis
• Hilar enlargement
• NG tube in oesophagus or bronchus
• Central line / Pacemaker
• Endotracheal tube

Normal CXR despite breathless ill patient

• Asthma, COPD
• Pulmonary embolism
• Early pneumonia
• Pneumocystis pneumonia - looks like LVF
• Left lower lobe collapse
• Fume inhalation but may develop ARDS with LVF picture
• Diabetic ketoacidosis

Things that can be missed when the film initially appears normal

• Upper zone: Small apical PTX, Pancoast tumour
• Retrocardiac : Hiatus hernia, neural tumour, vertebral disease
• Cardiac : Calcification of valves
• Skeletal: Cervical rib, Secondary deposits due to tumour
• Gas: Look for air under the diaphragm and mediastinal air (pneumomediastinum)
• Others: absent breast shadow from mastectomy

Fibrosis predominately affecting the upper zones

• Tuberculosis, Fungal, Sarcoidosis
• Extrinsic allergic alveolitis
• Coal worker's pneumoconiosis/progressive massive fibrosis
• Silicosis, Ankylosing spondylitis, Histiocytosis

Fibrosis predominately affecting the lower zones

• Idiopathic pulmonary fibrosis (Cryptogenic fibrosing alveolitis) , Asbestosis
• Connective tissue disorders e.g. RA, SLE, SSc
• Drug-induced: Amiodarone, Bleomycin, methotrexate

Bilateral Hilar lymphadenopathy

• Tuberculosis, Sarcoidosis, Berylliosis
• Lymphoma, Carcinoma, Leukaemia
• Histoplasmosis, Coccidioidomycosis

Causes of an opaque hemithorax on CXR

• Pleural effusion, Consolidation, Collapse
• Massive tumour, Fibrothorax
• Combination of above lesions
• Pneumonectomy, Lung agenesis

Lung cavitation

• Malignancy - Carcinoma squamous cell, Melanoma, Cervical carcinoma, Sarcoma metastasis
• Rheumatology Wegener?s, Rheumatoid lung (Caplan's syndrome)
• Vascular/septic emboli
• Infection TB (important finding as suggests active disease and infectivity), fungal (coccidio, aspergillosis, cryptosporidium, nocardia), bacterial (esp. GNR, staph, strep) , Hydatid cyst, Lung abscess
• Congenital lesions, such as a bronchogenic cyst or communicating sequestration

Lung abscess

Consolidation

Severe Pulmonary oedema

Pneumothorax

Pleural effusion

Air under diaphragm

Bilateral hilar lymphadenopathy classed as Stage 1 sarcoidosis.

Idiopathic Pulmonary Fibrosis Finger clubbing

Right Upper lobe Mass (Pancoast Tumour)