Revision 24 for 'Chest x-ray - an approach (summary)'

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Chest x-ray review (basic)

  • this is a basic article for medical students and non-radiologists

Chest x-ray review is a key competency for medical students, junior doctors and other allied health professionals.

Chest radiographs are frequently performed and a fantastic tool for making diagnoses of acute and chronic conditions, as well as acting as a tool for follow up. It is paramount that correct interpretation is performed to ensure that the correct diagnosis is made in a timely fashion.

Be systematic

There are many systematic ways to review a chest x-ray. The important thing isn't to use system X or system Y, it is to get into the habit of having a systematic approach. If you do the same thing every time you look at a chest x-ray, you will be much less likely to make a mistake.

Who, what, why, where, when

Whenever you look at any imaging, ask:

  • who does it pertain to? (John Smith 12 Jan 1952)
  • what are you looking at? (PA chest x-ray)
  • why was it done? (Increased shortness of breath)
  • where was it done? (Emergency)
  • when was it performed? (21 Jun 2014)
Quality

Assessment of the quality of a radiograph allows you to make an assessment about what can be diagnosed using the study. If a chest radiograph is under-inspired and rotated, it is of limited diagnostic use.

  • rotation: medial ends of the clavicles equidistant from the spinous processes
  • inspiration: 10 to 11 posterior ribs on left side
Lines and tubes

The first thing to look at when reviewing a chest x-ray is any additional line or tube on the film. There will often be ECG leads and in some patients, other devices, e.g. pacemaker. Note the position of ET and NG tubes, chest drains or central lines. The fact that these tubes and lines are present gives you additional information about how sick the patient is.

A, B, C, D, E

One of the easiest systems for reviewing a chest x-ray is A, B, C, D, E (using the same headings as ALS (advanced life support):

  • A: airway
  • B: breathing (i.e. the lungs)
  • C: circulation (i.e. cardiomediastinum)
  • D: disability (i.e. fractures and dislocations)
  • E: everything else
Airways

The airways are often overlooked. Start at the top, in the midline the find the trachea. Follow the trachea down in the midline to the carina and then down the right and left main stem bronchi. The angle between the left and right mainstem bronchi shouldn't be much more than 90 degrees.

Read in more depth: airways

Breathing (lungs)

There are a large number of pathological process that can result in abnormality in the lungs that are visible as areas of increased density (white) or increased lucency (black). Compare each size in all 4 zones looking for altered density or focal mass lesions.

Then check around the lungs starting laterally, from the apex down to the costophrenic angle. Does the lung extend to the chest wall, or is there a pneumothorax? After checking the costophrenic angle (is there an effusion?), ensure you can trace the hemidiaphragms to the spine. Finally, check the cardiac borders up to the hilar structures.

Read in more depth: breathing

Circulation (cardiomediastinal)

Assessment of the mediastinum is predominantly about looking at the heart, but it is imperative to remember the other structures in the mediastinum.

Assess the size of the heart, review the aortic knuckle and the upper mediastinal contour. After that, check the pulmonary vessels and the hilar structures. The left hilum is usually higher than the right.

The final thing to look for is a hiatus hernia with a retrocardiac fluid-fluid level.

Read in more depth: circulation

Disability

Check the bony thorax, especially the ribs for any evidence of fracture. If the shoulders have been includes on the film, check the glenohumeral joints and the clavicles.

Pathology
  • rib fractures
  • clavicle fracture
Everything else

At the end of the review, you need to remember to check for other things that don't fall into the A-D categories. This includes free gas within the abdomen (pneumoperitoneum), abnormalities in the soft tissues of the thorax including absent breast shadows.

Pathology
  • pneumoperitoneum
  • mastectomy
  • surgical emphysema
  • pectus excavatum
  • thoracic foreign bodies

Review areas

Double-check the apices (masses, pneumothorax), hila (masses, lymphadenopathy), retrocardiac zone (lobar collapse, hiatus hernia) and below the diaphragm (tubes and free air).

Finally, always compare to old films.

Common pathology

Pneumonia
  • most common cause of death due to infectious diseases
  • higher incidence at the extremes of age
  • streptococcus pneumoniae - most common organism
  • homogenous opacification in lobar pattern
  • characteristic air bronchograms and volume loss
  • more: lobar pneumonia
Lobar collapse
  • due to obstruction; luminal (aspiration, mucous plugging), mural (cancer) or extrinsic (mass compression)
  • RUL: right upper medial opacification, elevated horizontal fissure and right hilum
  • LUL: left hemithorax ‘veil-like’ opacity, elevated left hilum
  • RML: horizontal fissure not visible, ill-defined right heart border
  • RLL: right medial basal triangular opacification, depressed right hilum
  • LLL: left retrocardiac triangular opacification, double cardiac contour, depressed left hilum, loss of descending aortic and left medial hemidiaphragmatic outline
  • secondary signs: elevated hemidiaphragm, crowding of ribs and mediastinal shift towards affected side
  • more: lobar collapse
Pneumothorax
  • air in pleural space
  • categorized as primary spontaneous, secondary spontaneous (underlying lung disease) or iatrogenic/traumatic
  • simple: clearly defined visceral pleural edge paralleling chest wall, peripheral lucency with absent lung markings
  • tension: overexpanded hemithorax, depressed hemidiaphragm, contralateral mediastinal shift
  • more: pneumothorax
Congestive cardiac failure
  • commonly due to left ventricular failure
  • stage 1: redistribution (upper lobe diversion, cardiomegaly)
  • stage 2: interstitial edema (Kerley B lines, peribronchial cuffing, hazy hilar vessels)
  • stage 3: alveolar edema (consolidation, air bronchogram, cottonwool appearance, pleural effusion)
  • more: congestive cardiac failure
Pleural effusions
  • collection of fluid within pleural cavity
  • most commonly due to cardiac failure (transudate) or malignancy (exudate)
  • >200ml fluid required for meniscus at costophrenic angle on erect CXR
  • opaque hemithorax and contralateral mediastinal shift in large volume effusions
  • hydropneumothorax - no meniscus visible
  • more: pleural effusion
Lung carcinoma
  • leading cause of cancer mortality worldwide
  • divided into non-small cell and small cell carcinomas
  • adenocarcinoma most common histological subtype
  • may present as a peripheral rounded or spiculated mass, hilar/perihilar mass, mediastinal widening, lobar collapse or pleural effusion
  • more: lung carcinoma
Pulmonary metastases
  • metastatic spread to lungs via blood or lymphatics
  • most common primaries include breast cancer, colorectal cancer and renal cell cancer
  • peripheral, rounded nodules scattered throughout lungs
  • more: pulmonary metastases
Pneumoperitoneum

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