Fundamentals of HRCT - Reticular opacitites

Question 1

what are the 3 types of reticular opacities seen on HRCT

Answer 1

interlobular septal thickening, honeycombing, INTRAlobular septal thickening

Question 2

describe the anatomy of the secondary pulmonary lobule

Answer 2

separated by the interlobular septa (which carries the veins and lymphatic systems). the lobular bronchiole and artery are centrilobular in locatoin

Question 3

when interlobular septal thickening is the predominant finding, what is the next framework/finding that helps guide diagnosis?

Answer 3

smooth ist vs nodular ist vs irregular ist

smooth ist = pulm edema or lymphangitic spread. rarely - lympoprolif, amyloid, PVOD, lymphangiomatosis
nodular ist = sarcoid, lymphangitic spread, lymphoprolif, amyloid
irregular ist = fibrotic

Question 4

what are the characteristics of honeycombing?

Answer 4

• BLACK ie airfilled without any anatomy inside (vessels, bronchi, septations)
• thick walls (thin = cyst)
• 3-10 mm in diameter
• must have subpleural involvement
• layering/cluster should be visible
• do not branch
• associated w/ other fibrotic features - traction brx, irregular reticulation, volume lost

Question 5

what is the differential for the diseases with honeycombing? (9)

Answer 5

IPF, CTD-ILD (RA), drug fibrosis, asbestosis,chronic HP, sarcoid, NSIP, pneumoconiosis, post-ARDS fibrosis

Question 6

what are the HRCT findings that are consistent with UIP? (3 + and 6 negative)

Answer 6

honeycombing, other signs of fibrosis (traction bcx, irreg reticulations), subpleural and basilar predominance

ABSENCE of GGOs, consolidation, cysts, airtrapping, upper lobe predominance, micronodules

Question 7

ddx for UIP

Answer 7

IPF, CT-ILD (RA), asbestos, drugs

Question 8

what are some differences between honeycombing and paraseptal emphysema? (4)

Answer 8

PSE is usually one layer, can be larger, not associated with fibrosis, upper lobes > lower lobes

Question 9

what is intralobular interstitial thickening?

Answer 9

thickening of the interstitum within pulmonary nodules - causes reticulation. relatively nonspecific

Question 10

what is the differential for fibrotic disease in the upper lobes? (6)

Answer 10

sarcoid, prior TB , prior fungal, radiation fibrosis, pneumoconioses, AS

note idiopathic pnas involve the costophrenic angle

Question 11

what is the differential for fibrotic disease in the lower lobes? (5)

Answer 11

IPF, CT-ILD, drugs, asbestos, aspiration

Question 12

what is the differential for subpleural involvement? (5)

Answer 12

ipf, ct-ild, drugs, asbestosis, ards