Chest X-Ray Interpretation for the Internist

Theresa Cuoco, MD Medical University of South Carolina February 22, 2012

Disclaimer: I am NOT a radiologist!

Why do we need to know?

 To direct care while awaiting an “official read”  Low level radiation for the patient  Easily available and noninvasive  Relatively inexpensive

Objectives  Basics of technique  Type of film and the “tions”  Identification of structures on a “normal” CXR  Alveolar vs interstitial, lobar anatomy, silhouette sign, air bronchograms, and patterns of lung disease  The mediastinum, pleura, and heart  Systematic approach to interpretation  Cases

Technique  PA and lateral  AP  Which is preferred and why?

 Lateral film – left side of chest against x-ray cassette  Decubitus films

Which is which?

The “tions”  IdentificaTION  InspiraTION  PenetraTION  RotaTION

Inspiration vs Expiration Any indications for an expiratory film?

Penetration A Heavy light exposure causes the film to be black (A) Little light exposure causes the film to be white (B) B

Rotation

Normal Anatomy

The Normal Chest X-Ray

Alveolar vs Interstitial  Alveolar = air sacs   Radiolucent Blood, mucous, tumor, or edema in alveoli obscure normal anatomy: “airless lung”  Interstitial = vessels, lymphatics, bronchi, and connective tissue   Radiodense Interstitial disease: prominent lung markings with aerated lungs

Lobar Anatomy Anterior Posterior

Lobar Anatomy – Lateral Views Right Left

The Silhouette Sign  There are 4 basic radiographic densities  Gas, fat, soft tissue (water), and metal (bone)  Anatomic structures are recognized on x-ray by their density differences  Two substances of the same density in direct contact can’t be differentiated  Loss of the normal radiologic silhouette (contour) is called the “silhouette sign”

Localizing Lesions Where is the silhouette sign?

Localizing Lesions

Localizing Lesions A B

Localizing Lesions A B

Localizing Lesions  Obscured L heart border = lingula  Aortic knob obliterated = left upper lobe  Right lung base w heart border seen = right lower lobe  Right lung base w heart obscured = right middle lobe  Descending aorta obscured = left lower lobe  EXCEPTIONS:    Pseudosilhouette of diaphragm in underpenetrated film Right heart border my overlap spine Heart obscures anterior left diaphragm on lateral

The Air Bronchogram  When lung is consolidated and bronchi contain air, the dense lung delineates the air-filled bronchi  Visualization of air in the intrapulmonary bronchi is called the “air bronchogram sign”  Abnormal finding  Can be seen in:  PNA, edema, infarction  Chronic lung lesions

NO Air Bronchograms…  In pneumonia if bronchi are filled with secretions  If cancer obstructs a bronchus  Interstitial fibrosis  Asthma/emphysema (hyperinflation)

What do you see?

Lung and Lobar Collapse  When a whole lung collapses, the trachea deviates TOWARD the side of collapse (due to volume loss)

Fissures  Formed by 2 visceral pleural layers  Demarcate the boundaries of the lobes  Shift of fissures is best sign of lobar collapse

Which lobes have collapsed?

Minor fissure is elevated – RUL partially collapsed Heart has moved to right and silhouette sign of right diaphragm – indicated RLL collapse

Hilar Displacement  The left hilum is normally slightly higher than the right  Hilar depression indicates collapse of lower lobe  Hilar elevation indicates collapse of upper lobe

Patterns of Lung Disease Pearls  Pulmonary markings are more visible in interstitial disease  Generalized interstitial markings = linear (reticular)  Discrete/focal thickening = nodular  Homogeneous or patchy consolidation = alveolar  Focal consolidation < 3cm = nodule  Focal consolidation > 3cm = mass  Heavy calcification generally = benign

What is the pattern?

A: Focal/linear B: Diffuse/nodular C: Alveolar

The Mediastinum

The Mediastinum  I: Anterior Mediastinum   Heart Retrosternal clear space  5 T’s  II: Middle Mediastinum  Esophagus   Arch and descending aorta Trachea  III: Posterior Mediastinum  Paravertebral area  Lymph nodes in all 3!

The Pleura  The posterior costophrenic angle is the deepest and only seen on the lateral film  The lateral film is more sensitive for detection of small pleural effusions  How much fluid can be seen on a radiograph?

 Erect PA: 175 mL  Erect lateral: 75 mL  Decubitus: >5 mL  Supine: Several hundred mL

What do you see?

The Heart  The horizontal width of the heart should be less than ½ the widest internal diameter of the thorax

Left and Right Ventricular Enlargement  Left ventricular enlargement   Frontal: LHB moves laterally and cardiac apex inferolaterally Lateral: LHB moves inferoposteriorly  Right ventricular enlargement   Frontal: RHB further right Lateral: Contacts lower half of sternum (instead of lower 3 rd )

Cephalization  Enlargement of the upper lobe vessels  “Vascular redistribution”  “Kerley B” lines: interstitial edema thickening the interlobular septa causing short lines perpendicular to the pleural surface

Systematic approach  ABCDE       Airway Bones and breasts Cardiac and costophrenic Diaphragm Edges and extrathoracic Fields (lung fields and failure)  ATMLL (“Are There Many Lung Lesions?”)     Abdomen Thorax – bones and soft tissues Mediastinum Lungs – unilateral and bilateral

Cases

Young man with cancer

Young man without symptoms

ICU patient with fever, WBC

Two older women with cough

Dyspnea with sudden CP & fever