Pulmonary Parenchyma
Erin Porter, DVM, DACVR
Objectives
 Familiarize ourselves with normal lung anatomy and
how to evaluate the lungs radiographically
 Know where to locate and assess pulmonary arteries
and veins
 Be able to identify the different pulmonary patterns
 Know common differentials for basic pulmonary
patterns
Quality Control
• Always start with diagnostic quality
thoracic radiographs (RL, LL, VD or DV)
Quality Control
• Always take 3 views
• L and R Lat are minimum exam
• Lesions in downside lung disappear - even
if quite large.
4
4
Pulmonary Parenchyma
Three components contribute:
A - Air within the small airways and alveoli
B - Blood vessels
A
C - Airway walls
• Canine and Feline
B
– 6 lobes
C
Lung Lobe Anatomy
Dorsal View
Lung Lobe anatomy
RCa
RCr
A
RCr
LCr
Cr Seg
RM
LCr
Cr Seg
RM
LCa
A
LCr
Cr Seg
A
LCr
Cr Seg
RCa
LCa
General Divisions
Caudodorsal
Cranial
Cranioventral
Caudal
Bronchial Anatomy
R Lat
Trachea
Lt Cranial
segment
Right
Cranial
L Lat
Lt Caudal
segment
Pulmonary Vessels
• Distinguish lobar arteries and veins
– Arteries are dorsal and lateral
– Veins are ventral and central (medial)
• Cranial lobar vessels: best visualized on laterals
• Caudal lobar vessels: best visualized on DV
• Size
– Lateral – head of 4th rib
– VD or DV – cross 9th rib
• Must understand pulmonary
circulation
– Veins toward left heart
– Arteries away from right heart
Pulmonary Vasculature: Size
Left Lateral
Projection
RIB 4
Proximal 1/3
Pulmonary Vasculature
Dorsoventral
Projection
RIB 9
Pulmonary Vasculature
Enlarged pulmonary arteries and veins (overcirculation)
• Left to right shunting
defect
• Arteriovenous fistula
• Overhydration
• CHF - cats
13
13
Pulmonary Vasculature
Enlarged pulmonary arteries
• Heartworm disease
• Pulmonary hypertension
14
14
Pulmonary Vasculature
Enlarged pulmonary veins
• Left heart failure
15
15
Pulmonary Parenchyma
What to Look For….
• Opacity (Increased or Decreased)
• Number Location
– Which lung lobe is affected? (focal, multifocal,
generalized)
– Distribution within each lobe
• (peri-hilar, caudodorsal, ventral, cranioventral)
• Mediastinal shift
• Pulmonary Pattern
Differential Diagnosis List
– Severity
based on all clinical information
1
6
Opacity
Increased Opacity
– What causes increased pulmonary opacity?
• Soft tissue in the air spaces
–
–
–
–
Blood
Pus
Water
Cells
• Enlarged vessels
– Pulmonary venous or arterial distention
– Pulmonary overcirculation
• Mineral
– Bronchial mineralization
17
Opacity
Decreased
– Focal
• Regional oligemia: PTE
• Bronchial dilation: bronchiectasis
• Pulmonary lucency: bulla, pneumatocoele, cavitated
lesion
– Generalized
• Small vessels, heart, CVC: Hypovolemia
• Increased thoracic volume: Hyperinflation/air trapping
18
18
Decreased opacity
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19
Roentgen Signs
How to describe any abnormalities…..
•
•
•
•
•
•
Location
Number
Size
Shape
Margin
Opacity
Distribution
Location/Distribution is
FAR more important
than the type of pattern
in developing a
concise, accurate DDx
list.
20
Location
In general, think…
edema
bronchopneumonia
2
1
Location
Pulmonary Edema
(non-cardiogenic)
22
Location
Pulmonary Edema
(cardiogenic)
23
Mediastinal Shift
• Ipsilateral Shift (heart shifted toward lesion)
• Contralateral Shift (heart away from the lesion)
Pulmonary mass
Atelectasis
Pulmonary Patterns
Four Basic Patterns
–Alveolar
–Bronchial
–Structured interstitial (nodules or miliary pattern)
–Unstructured interstitial
Other Possibilities
–Mass
–Vascular Pattern
2
5
Pulmonary Patterns
Disease in Transition
• Almost all patterns are mixed!
• Evaluate relative contributions
of each patterns - which is the
worse?
• Changes over time!
2
6
Pulmonary Patterns
Interstitial and alveolar patterns are related
• Similar list of differential diagnoses
• Attempt to classify differentials by location
•
•
•
•
•
Cranioventral: Bronchopneumonia
Caudodorsal: Pulmonary Edema
Ventral: Aspiration pneumonia
Multifocal: Contusions, Fungal Pneumonia, Mets
Diffuse: Lymphoma
• Pattern Reflects SEVERITY
• Interstitial
Alveolar
• Which way is it going? Recheck Exam!!!!
27
Alveolar Pattern
5 aspects…
•
•
•
•
Uniform soft tissue opacity
Air bronchograms (±)
Border Effacement of heart/diaphragm
Will NOT see pulmonary vessels or the serosal walls of the
airways
• Lobar sign
****Not all have to be present (3/5)
2
8
Alveolar pattern
Air Bronchogram
• Air filled bronchus
surrounded by soft
tissue opaque lung
Air bronchogram
Lobar sign
Lobar Sign
• Abnormal lung
border contrasted
with normal lung
border
• The disease is
respecting the lobar
border!
2
9
Bronchial Pattern
• Major bronchi are normally
visible in a central (hilar)
position
• Always look in the periphery!!
• Thickened walls are abnormal
(>2 to 3 mm)
• RINGS and LINES
• Usually generalized disease
3
0
Bronchial Pattern
• Small bronchi are visible
• "Rings"
– End on small airways
• "Lines"
– Airways moving from
central to peripheral
position
3
1
3
2
Bronchial Pattern
Common Differentials
•
•
•
•
•
Bronchial Wall Mineralization (dogs)
Chronic Bronchitis
Infectious, allergic, irritant
Asthma (cats)
Eosinophilic Bronchopneumapathy (dogs)
Heartworm disease
(in combination with other findings)
Bronchial Mineralization
3
4
Structured interstitial
• Nodules
– Can be subtle
– Look over diaphragm and vertebrae
• Fake-outs
– end on vessels
– cutaneous nodules
– nipples
– ectoparasites
– osteomas
3
5
Structured Interstitial
Common Differentials
• Metastatic Neoplasia
• Fungal Pneumonia
•
Often + TB lymphadenopathy
• Benign Pulmonary
Osteomas
Structured Interstitial
37
Milliary Pattern
DDx:
• Fungal pneumonia
• Metastatic
neoplasia
38
Unstructured Interstitial
Radiographic Finding:
• Increased soft tissue opacity that
obscures pulmonary vascular
margins
• Never mild!
• Diagnosis by rule out
• Expiration most common cause
3
9
Alveolar and Unstructured
Interstitial
Common Differentials
•
•
•
•
•
Atelectasis
Aspiration pneumonia
Bronchopneumonia
Pneumonitis
Hemorrhage/contusions
• Pulmonary edema
• Cardiogenic
• Non-cardiogenic
• Neoplasia
• Lymphoma (unstructured
interstitial)
• Masses (alveolar)
Aspiration Pneumonia
41
Beware of Fake Outs
– Expiration versus
Inspiration
– Obesity
• Overall increased interstitial
opacity secondary to scatter
radiation.
– Pleural and mediastinal fat
accumulation.
42
42
Intra-thoracic Fat
Feline
– Subpericardial fat
can mimic
cardiomegaly
43
43
Lateral recumbency (atelectasis)
44
44
Pulmonary Masses
•
•
•
•
Greater than 3 cm
Roundish, uniform soft tissue opacity
Air bronchograms (±)
Border Effacement with Cardiac
Silhouette and Diaphragm
• Lobar sign
• Can cavitate – Gas filled
• Can mineralize (dystrophic)
4
5
Pulmonary Masses
46
Questions?