Original subtitles

in this lecture we will review chest

radiographic findings of pulmonary edema

hydrostatic pulmonary edema can be

classified as cardiogenic or non

cardiogenic cardiogenic edema is

commonly due to left heart failure or

mitral valve disease while non

cardiogenic edema is most often the

result of volume overload or renal

failure the mechanism of cardiogenic

edema is illustrated on this slide left

heart failure results in decreased

cardiac output which raises left atrial

pressure this pressure is transmitted in

retrograde fashion to the pulmonary

veins and ultimately increases pulmonary

capillary pressure we remember that

fluid is retained in the intravascular

space due to a delicate balance between

the intravascular capillary and osmotic

pressure and the surrounding pressures

in the interstitial space when capillary

pressure increases or plasma colloid

pressure decreases the gradient favours

movement of fluid from the capillaries

into the interstitial space cardiogenic

edema can be divided into three stages

from least to most severe based on the

degree of capillary pressure elevation

these are redistribution interstitial

edema and alveolar edema redistribution

is characterized by cephalization of

pulmonary blood flow distension of the

pulmonary arteries and veins enlarging

the hilar shadows and an increased size

of the pulmonary artery relative to the

bronchus this is pulmonary venous

hypertension without interstitial edema

and in the acute heart failure setting

is typically associated with pulmonary

capillary wedge pressure of 12 to 17

millimeters mercury with increase in

pulmonary capillary wedge pressure fluid

transit Eights into the interstitial

space resulting in interstitial edema

manifesting as septal lines

peribronchial cuffing and vascular and

distinctness on chest radiographs with

continued increase in the capillary

wedge pressure

exceeding 25 millimeters of mercury

fluid moves from the interstitial space

into the air space resulting in alveolar

edema seen as peri hilar or dependent

bilateral symmetric air space opacities

on the chest x-ray

this is an example of the earliest stage

of edema redistribution we can see

dilated upper zone vessels known as

cephalization enlarged hilar shadows and

a vessel two bronchus ratio greater than

one the mantra old films are your

friends is illustrated in this case the

changes of redistribution are subtle and

more easily detected when a baseline

exam is available for comparison here is

that same case on the right next to the

patient's baseline normal exam on the

Left chest radiologists often describe

lung findings in relation to the

secondary pulmonary lobule it is the

smallest unit of lung delimited by

connective tissue septa and ranges in

diameter from 1 to 2.5 centimeters in

size it is the unit of lung evaluated at

HRC T relevant to our discussion today

pulmonary lymph attics are located

around the central ovular core

structures the lobular bronchial and

arteriole in the interlab Euler septa

and in the sub plural inner system when

fluid transit Eights from the capillary

to the interstitial it fills the spaces

illustrated in yellow first resulting in

smoothly thickened septal lines also

known as curly B lines the findings of

interstitial edema include widening of

the vascular pedicle reflecting

distension of the superior vena cava and

increasing circulating blood volume

distension of the as igus vein can be

used as a manometer of the mediastinum

fluid exiting the lymphatics into the

interstitial space result in septal

lines peribronchial cuffing and fissure

'el thickening with cardiogenic edema

the cardiac silhouette will often be

enlarged reflecting chamber dilation

pleural effusions are frequently present

as the lymphatics in the outer third of

the lung drain to the pleural space this

patient presented to the emergency room

with shortness of breath and vague chest

discomfort after consuming a large bag

of potato chips while watching the NFL

playoffs we see sternal wires and bypass

graft markers indicating prior coronary

artery bypass surgery

as you search for abnormalities remember

our mantra old films are your friends we

see on this exam findings of expanded

circulating blood volume including

widening of the vascular pedicle width

and as a guest distension

additionally septal thickening and

peribronchial cuffing are present

characteristic findings of interstitial

edema there is a small right pleural

effusion as well on the lateral

examination in a different patient we

can often identify fish oil thickening

mistakenly referred to as fluid in the

fissure but is it really fluid in the

fissure if it was in the pleural

potential space shouldn't it follow a

gravitational distribution it is

actually fluid in the subfloor

interstitial that is on the side of the

visceral pleura associated with the lung

parenchyma we can think of it as a

septal line sandwich in the two layers

of visceral pleura the granddaddy of all

curly lines here is a lateral chest

radiograph and the corresponding

sagittal CT scan note the thickened

septal lines perpendicular to the

thickened fissures demonstrating at

contiguity of the interstitial space

filled with transit data fluid another

characteristic feature of edema is rapid

clearance after treatment in this

patient who presented with interstitial

edema there is rapid return to normal

after administration of lasix and

associated diuresis let's return to our

schematic representation of the

secondary pulmonary lobule with

increased capillary pressure the fluid

transiti overwhelms the lymphatics and

interstitial space ultimately filling

the alveolar space remember this is a

transudate and readily distributes in

the air spaces based on position and

gravity this patient presented with an

acute ST segment elevation myocardial

infarction and the chest radiograph

reveals symmetric bilateral parry hilar

airspace opacity there is also blunting

of the right costophrenic angle

consistent with a small pleural effusion

this parry hilar airspace distribution

has been termed a batwing edema pattern

occurring with rapid increases in the

left-sided cardiac pressure often before

the cardiac chambers have had time to

dilate

this CT illustrates the exquisite

gravity dependent distribution of early

alveolar edema remember the patient is

supine for a CT exam note the

accompanying septal lines and fish oil

thickening of concomitant interstitial

edema in the non-dependent lung this

patient presented with an alveolar edema

pattern which cleared rapidly after

medical therapy and placement of an

intra-aortic balloon counterpulsation

device the inflation deflation cycle of

the intra-aortic balloon functions to

decrease after load just prior to

systole by deflating the balloon and to

push blood back toward the heart to

augment coronary artery perfusion by

inflating the balloon in diastole let's

look at several examples of non

cardiogenic edema this is one of the few

mnemonics that I like because it makes

sense non cardiogenic edema the mnemonic

is not cardiac and it is a fairly

comprehensive list of the myriad causes

of non cardiogenic pulmonary edema here

is a 19 year old patient who presented

with acute renal failure and non

cardiogenic edema note the widened

vascular pedicle and distended as igus

vein there is bilateral symmetric

airspace opacity and small pleural

effusions with a normal-sized cardiac

silhouette the contrast chest CT in this

same patient reveals a gravitational

distribution of this alveolar edema with

small bilateral pleural effusions note

the interstitial edema with septa lines

in the non-dependent portion of the

lungs this example is a 23 year old

woman who presented with septic shock

and circulatory collapse due to

meningococcus emia she required

aggressive resuscitation with 11 liters

of fluid to maintain her pressure

resulting in over hydration edema there

is a diffuse white out of both lungs

with sparing of the costophrenic angles

a common feature of edema as she

responded to antibiotic therapy and

diuresis her chest radiograph rapidly

cleared over a 24 hour period let's

review one last extremely important

concept we've been discussing the

manifestations of pulmonary edema and in

some instances discussing the size of

the heart

in practice radiologists most often use

the term enlargement of the cardiac

silhouette why is that it is important

to remember other structures may

contribute to the shadow

besides the heart here's a PA and

lateral chest x-ray in a patient at

baseline you can disregard the retained

bullet fragment indicated by the arrow

in the left chest soft tissues patient

came back to the hospital with chest

pain and this examination reveals an

enlarged cardiac silhouette is it a

large heart remember that the heart is

enclosed in a pericardial sac that is

generally so thin is to not contribute

substantially to the size of the cardiac

silhouette and is not seen as a separate

structure at conventional radiography

because it is soft tissue density and so

is the myocardium that is unless the

space fills up with fluid in which case

the mediastinal fat in the epicardial

fat becomes separated by a visible layer

of fluid resulting in a laminar

appearance on the lateral exam a fat

fluid and fat this is the so-called

epicardial fat stripe sign or Oreo

cookie sign so in this lecture we

reviewed the two major categories of

hydrostatic edema the three stages of

edema increasing in severity from stage

1 redistribution stage to interstitial

edema and stage 3 alveolar edema these

stages roughly correlate with wedge

pressure and finally we've just seen

that in large cardiac silhouette may be

a big heart or adjacent structures such

as a pericardial effusion