hrct of fibrosing lung disease: problems and pitfalls · hrct pointers to chronic hypersensitivity...
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HRCT of fibrosing lung disease: problems and pitfalls
David M HansellRoyal Brompton Hospital
London UK
ILD Postgraduate Course, Porto - April 2016
• HRCT interpretation of fibrosing lung disease– Basic HRCT signs and their reliability
• Practical HRCT approach to differentiating between fibrosing lung diseases
• Significance of new abnormalities on HRCT in idiopathic pulmonary fibrosis– Focal: nodule or mass
– Diffuse: ground glass opacification
Usual Interstitial Pneumonia
Language used when NOT a definite UIP pattern on CT
• Numerous adjectives beginning
with P….
• Possible, Potential, Permissible, Plausible, Practically, Probable, Portuguese, Perhaps, Presumed, etc.
One radiological classification of UIP
• HRCT Definitely is UIP
– classic UIP pattern
• (n.b. not synonymous with IPF - c.f. chronic HP)
• HRCT Could be UIP
– a fibrosing lung disease, no honeycombing or contradictory (“inconsistent with”) features
• HRCT Definitely not UIP
– clear signs of another diagnosis
Starting point
• Common to all three situations is features of “a fibrosing lung disease” on HRCT
• So, the first step: Does the HRCT show a predominantly fibrosing lung disease?
– What are the HRCT signs of fibrosis?
– How reliable are these HRCT signs?
Which one is a fibrosing lung disease?
UIP on lung biopsy
✓
✗
✗
OP (nitrofurantoin)
Pulmonary oedema
BASICS The HRCT signs of a predominantly fibrotic lung disease:
• Honeycombing
• Traction bronchiectasis
• Volume loss
Reliability of HRCT signs of fibrotic lung disease(++++ = complete certainty)
• Honeycomb pattern
+++(+)
• Traction bronchiectasis
++(+)
• Volume loss
+
++++
Honeycombing
Identification of honeycombing on HRCT - cardinal sign of UIP
• False positive identification
– Severe traction bronchiolectasis
– Centrilobular/paraseptal emphysema e.g. superimposed on NSIP
– Oedema/infection superimposed on emphysema
– Other cystic conditions e.g. Langerhans CH
Lung biopsy: Fibrotic NSIP and centrilobular emphysema
Interobserver variability in the CT assessment of honeycombing in the lungs
• 43 observers (!)
• Honeycombing present definitely yes (5) thro’ definitely not (1)
• Agreement with reference standard moderate κ=0.43-0.58
• In 29% disagreement on presence/absence
• Sources of disagreement: traction bx, cysts and superimposed emphysema
Watadani et al Radiology 2013;266:207
Historically poor: Lynch et al (2005) κ=0.31
Traction bronchiectasis
Identification of traction bronchiectasis on HRCT
• False positive identification
– Within honeycombing
– Dilated bronchi within OP / DAD
– Conspicuous, but not dilated, bronchi within GGO
• “False negative”
– Within honeycombing (advanced)
– Severity of traction reduced if coexistent emphysema
Traction bronchiectasis - identification by CALIPER software:
…differentiation from honeycombing unreliable
• Fibrotic IIPs (UIP and NSIP) – Edey 2011 Eur Radiol
• Rheumatoid Arthritis-related FLD – Kim 2010 Eur Respir J
• Chronic hypersensitivity pneumonitis – Walsh SL 2012 Eur Radiol
• All comers connective tissue disease FLD– Walsh SL 2014 Thorax
Kappas for traction bronchiectasis = 0.58-0.69
Observer agreement for traction bronchiectasis in various FLD
Volume loss
Honeycombing
Traction bronchiectasis
Volume loss
Back to the specifics of a UIP pattern…
UIP pattern
= Unusual Interstitial Pneumonia
Characteristic/Definite UIP pattern on CT
• Subpleural
• Basal
• Honeycombing
Supportive CT features (unofficial)…
• “Propeller blade” cranio-caudal distribution
• Nodular ossifications within fibrosis
• Asymmetric distribution of fibrosis
• Component of pleuroparenchymal fibroelastosis (PPFE)
Supportive/ancillary features of UIP on CT:
• Propeller blade distribution*– Subpleural disease anterior in upper lobes
– Subpleural disease posterior in lower lobes
*so-called because of its lack of resemblance to a propeller
Supportive/ancillary features of UIP on CT:
• Nodular ossification (white spots) in fibrosis
– 29% prevalence (c.f. 8% in non-IPF/UIP) [in press]
• R to L asymmetry of fibrosis [anecdotal]
PleuroparenchymalFibroelastosis (PPFE)
+UIP
Supportive/ancillary features of UIP on CT:
PPFE associated with lower zone UIP in 32% of patients [unpublished data]
UIP pattern(all four features)
Possible UIP pattern(all three features)
Inconsistent with UIP pattern (any one of seven features)
Subpleural basal predominance
Subpleural basal predominance
Upper or mid lung predominance
Peribronchovascular predominance
Reticular abnormality Reticular abnormality Extensive ground glass abnormality (extent > reticular abnormality)
Profuse micronodules (bilateral, predominantly upper lobes)
Honeycombing with or without traction bronchiectasis
Discrete cysts (multiple bilateral, away from areas of honeycombing)
Diffuse mosaic attenuation/air trapping (bilateral in three or more lobes)
Absence of features listed as inconsistent with UIP pattern
Absence of features listed as inconsistent with UIP pattern
Consolidation in broncho-pulmonary segment(s)/lobe(s)
Table 4
Raghu et al AJRCCM 2011;183:788
• Subpleural
• Basal
• Honeycombing
UIP pattern(all four features)
Possible UIP pattern(all three features)
Inconsistent with UIP pattern (any one of seven features)
Subpleural basal predominance
Subpleural basal predominance
Upper or mid lung predominance
Peribronchovascular predominance
Reticular abnormality Reticular abnormality Extensive ground glass abnormality (extent > reticular abnormality)
Profuse micronodules (bilateral, predominantly upper lobes)
Honeycombing with or without traction bronchiectasis
Discrete cysts (multiple bilateral, away from areas of honeycombing)
Diffuse mosaic attenuation/air trapping (bilateral in three or more lobes)
Absence of features listed as inconsistent with UIP pattern
Absence of features listed as inconsistent with UIP pattern
Consolidation in broncho-pulmonary segment(s)/lobe(s)
Table 4
Raghu et al AJRCCM 2011;183:788
Upper or mid lung predominance
Peribronchovascular predominance
Extensive ground glass abnormality (extent > reticular abnormality)
Profuse micronodules (bilateral, predominantly upper lobes)
Discrete cysts (multiple bilateral, away from areas of honeycombing)
Diffuse mosaic attenuation/air trapping (bilateral in three or more lobes)
Consolidation in broncho-pulmonary segment(s)/lobe(s)
• Observer agreement for each of these features?
• Extent at which these abnormalities become significant?
Column 3 as a checklist to differentiate UIP from “others”
• Not basal
• Bronchocentric
• GGO > reticular
• Nodules
• Cysts
• Mosaicism (lobules)
• Consolidation
Much of Column 3 is a checklist of features that differentiate UIP from CHP…
• Mosaicism (lobules)
• Not basal
• Bronchocentric
• Nodules
• GGO > reticular
• Cysts
• Consolidation
NSIP
HP
LIP
DIP/
RB-ILD
UIPOP
LIP
DIP/
RB-ILD
NSIP
HP
UIP
OP
LIP
DIP/
RB-ILD
NSIP
HP
UIP
OP
HRCT pointers to chronic hypersensitivity pneumonitis:
• Lobules of decreased attenuation in spared (non-fibrotic) lung
• Occasional septal thickening may be a bit more obvious than in other fibrotic IIPs
• x3 distributions of fibrosis: UZ, LZ or random - sometimes vague/subtle bronchocentricity if UZ
• Coexistent subacute changes - indistinct relatively low attenuation centrilobular nodules (rare)
Lobules of decreased attenuation in spared lung
Chronic HP
UIP
Septal thickening in chronichypersensitivity pneumonitis
Unusual distribution of fibrosis, particularly vague bronchocentricity when upper lobe predominant:
n.b. Bronchocentricity, when present,
is much more subtle than the
bronchocentric fibrosis in sarcoidosis
BAL lymphocytosis 27%
MDT diagnosis of Chronic HP
UIP on lung biopsy
MDT diagnosis of IPF
Coexisting chronic and subacute features of HP (rare)
Summary scheme for HRCT of fibrosing lung disease:
• Is it a fibrosing lung disease (3 signs)?
• If yes, is it classical/definite UIP?
• If no, what are the choices?
HRCT differential diagnosis of fibrosing lung disease:
• Usual interstitial pneumonia (UIP)
• Non-specific interstitial pneumonia (NSIP)
• Chronic hypersensitivity pneumonitis
• Fibrotic sarcoidosis
• Fibrosing variant of organizing pneumonia
For non-definite UIP, list in order of prevalence/importance:
• Non-honeycomb UIP -v- Chronic HP
• Fibrosing variant of OP
• Idiopathic NSIP
• Fibrotic sarcoidosis
www.diagnoseIPF.com
A practical guide to the CT imaging of fibrosing lung disease
New abnormality on background of fibrosing lung disease
• Focal - nodule/mass
• Diffuse - ground glass opacification (“grey lung”)
Focal abnormality on a background of fibrosing lung disease
• Considerations:
–Condensation of fibrosis
• ?PPFE component (not often OP)
– Lung cancer
• x8 relative risk, 5-15% prevalence
• Often masked by background fibrosis
– Tuberculosis
• Atypical manifestations: often focal
Probable PPFE - monitor
Lung cancer
Reactivation TB(!)
New “grey lung” on background of fibrotic IIP - what’s happening?
Progressive fibrosis versus incipient acute exacerbation
Interval?
One year
6 weekslater
Differential diagnosis for rapid onset “grey lung” on background of fibrotic IIP:
• Acute exacerbation of IPF/UIP
• Supervening heart failure (oedema)
• Opportunistic infection (PCP/CMV)
• Drug reaction – esp. novel drugs
• (Spurious – expiratory CT)
• (Spurious – contrast in CTPA)
3 weeks later
Acute Exacerbation
Pulmonary oedema
Pneumocystis pneumonia
Expiratory CT
CTPA (contrast)
Ideal:Pre-contrast HRCT (limited sections)
Summary• “Is it fibrosing lung disease or not?” is the
crucial first question
• CT differentiation between UIP and other fibrosing lung diseases can be difficult but the main distinction is UIP -v- CHP
• Not all new nodules in IPF patients are lung cancer
• Be aware of differential diagnosis of supervening ground glass opacification in IPF