Differentiating theCauses of an Opacified

Hemithorax

William Hering 2002

Three Major Causes + 1

1. Atelectasis of an entire lung2. A large pleural effusion3. Pneumonia of an entire lung4. And a fourth cause:

n Post-pneumonectomy – removal ofan entire lung

Atelectasis of the Lung

• Atelectasis of an entire lung = loss ofvolume of the affected lung

• Visceral and parietal pleura do NOTseparate from each other

• There is a shift of heart andhemidiaphragm toward side ofopacification (toward side of volume loss)

Atelectasis of the right lung

The right hemithorak is opaque.

The shift of trachea & heart toward the side of opasification

Pleural Effusion

• If an effusion (whatever the fluid is) fillsthe entire hemithorax

• It acts like a mass

• Pushing the heart and trachea away fromthe side of opacification

Pneumonia

• The hemithorax is opaque and there isno shift of the heart or trachea

• There may be an air bronchogram signpresent

Post-Pneumonectomy

• When the entire lung is removed, there isvolume loss on the pneumonectomizedside

• The hemithorax eventually fibroses andbecomes opaque

• Clues: There is frequently a resected fifthrib and/or surgical clips

Important Points

• In atelectasis, there is s shift toward theside of the opacification

• In pleural effusion, there is a shift awayfrom the side of the opacification

• In pneumonia, there is no shift• In pneumonectomy, the 5th rib is usually

absent

Which is this?

Which is this?

Which is this?

Recognizing A Pleural Effusion

Normal Anatomy

• Visceral pleura is adherent to the lung

• Space between visceral and parietalpleura is a potential space

• Infoldings of visceral pleura formfissures

• Loose connective tissue beneathvisceral pleura = subpleural space

Normal Physiology

• Normally there are 2-10 cc of fluid inthe pleural space

• Each hour, as much as 100cc of fluid isproduced, mostly at parietal pleura

• Fluid drains mostly to visceral pleuraand via lymphatics

Pleural Effusion-Types

• Transudate

• Exudaten Empyeman Hemothoraxn Chylothorax

Specific Types of Effusions

• Hemothoraxn Fluid hematocrit > 50% blood hematocrit

• Empyema = exudate containing pus.

• Chylothorax = ↑triglycerides or cholesteroln Obstruction or rupture of lymphatic vessels

Side-specificity

Mostly left-sidedn Pancreatitisn Dressler’s syndromen Distal thoracic duct obstruction

Mostly right-sidedn Heart failuren Abdominal disease related to liver or ovaryn Proximal thoracic duct obstruction

Appearances of Pleural Effusions

• Subpulmonic effusion• Blunting of Costophrenic angle• Meniscus sign• Layering• Loculated• Laminar effusion• Opacified hemithorax• Air-fluid levels

Subpulmonic Effusion• Usually less than 300-350cc

• Accumulates at base of lung betweenvisceral and parietal pleura

• Causes apparent lateral displacement ofhighest part of hemidiaphragm

• Flat-edge sign on lateral

• Increased distance between stomachbubble and base of lung

Subpulmonic Pleural EffusionOn the frontal film, the highest point of the apparent right hemidiaphragmis displaced laterally (it is usually in the center). On the lateral film, there

is a flat edge where the effusion meets the major fissure

Blunting of the CP Angle

• Normally there are 2-10cc of fluid in thepleural space

• When >75cc accumulate, the posteriorcostophrenic (CP) sulci, seen on thelateral film, become blunted

• When 200-300cc accumulate, the CPsulci on the frontal film become blunted

Normal costophrenic angle BluntingWhen 200 – 300 cc of fluid accumulate in the pleural space, usually costophrnenic angle

become blunted ( the same person )

Meniscus Sign

• Pleural fluid tends to rise higher along itsedge producing a meniscus shapemedially and laterally

• Usually only lateral meniscus can be seen

• The meniscus is a good indicator of thepresence of a pleural effusion

Meniscus Sign

Effect of Position - Layering

• Supine Erect

Loculated Effusion

• Occurs 2 adhesions which formbetween visceral and parietal pleura

• Adhesions more common with blood(hemothorax) and pus (empyema)

• Loculated effusions have unusualshapes or positions in thoraxn E.g. remain at apex on erect films

Loculated Effusion

• A loculated effusin (lenticular form )in the thoracic cavity.• Loculated empyema

Laminar Effusion

• A laminar effusion collects in the looseconnective tissue between the lung andthe visceral pleura

• It is not usually free-flowing

• It usually occurs with CHF orlymphangitic spread of malignancy

• A laminar effusion collectsbetween the lung and thevisceral pleura in the looseconnective tissue of thesubpleural space

•Laminar effusions areusually seen with CHF orlymphangitic spread oftumor

Opacified Hemithorax

• If an effusion fills the entire hemithorax, itacts like a mass

• There is displacement of the heart andtrachea away from the side of opacification

• In atelectasis of an entire lung, the heartand trachea are pulled toward the side ofopacification

Hydropneumothorax

• If both a pneumothorax and a pleuraleffusion occur together, it is called ahydropneumothorax

• A hydropneumothorax is usually due totrauma, surgery, bronchopleural fistula

• It is characterized by an air-fluid level inthe hemithorax

• A straight edge,indicative of a fluidinterface, in thiscase an air-fluidinterface, is seen onthe right.

• In order to have anair-fluid level in thepleural space, theremust be apneumothoraxpresent.

Important Points• Pleural effusions are transudates or

exudates

• It takes from 200-300cc to blunt thecostophrenic sulcus on the frontal view

• The meniscus is the classic shape of aneffusion on a frontal film

• Pleural effusions shift the mediastinalstructures away from the side opacified