Interpretation of Imaging Chapter 4: Embedding High-Resolution Computed Tomography (HRCT) Into Clinical Practice

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Hello, and welcome back to the Interstitial Lung Disease Explainer Video Series. I am Dr Joseph Mammarappallil, a cardiothoracic radiologist at The Duke Medical Center. This series focuses on interpreting high-resolution computed tomography, or HRCT, specifically in diagnosing and characterizing progression in interstitial lung diseases, or ILDs. In this video, you will learn how to recognize key imaging patterns, understand their clinical implications, and integrate radiology findings into multidisciplinary care. 

Let’s review the hallmark HRCT findings used to evaluate fibrotic lung disease. 

We’ll look at four defining features: reticulation, traction bronchiectasis, honeycombing, and ground-glass opacities. Then, we’ll review a few case examples with a variety of features. 

Here you can see reticulation, which manifests as a network of fine, linear opacities giving the lung a mesh-like pattern. These lines represent thickened interlobular and intralobular septa due to fibrosis. 

The pattern is usually subpleural and basilar in distribution, characteristic of UIP. 

When reticulation is accompanied by traction bronchiectasis or honeycombing, it denotes irreversible fibrotic remodeling rather than inflammatory change.

Here is an example of classic traction bronchiectasis.  

Note the dilated, irregular bronchi extending toward the pleural surface. This results from fibrotic contraction pulling outward on bronchial walls, leading to distortion and widening.

When this finding is peripheral and basilar, it indicates established architectural distortion, strongly favoring UIP. 

Traction bronchiectasis thus makes a fibrotic, non-reversible process, distinct from inflammatory airway dilatation. 

This image shows honeycombing; stacked cystic airspaces, typically 3–10 mm in diameter, with thick, well-defined walls. 

The cysts are subpleural and basal, often arranged in multiple contiguous layers. 

Honeycombing reflects end-stage fibrotic destruction and irreversible architectural distortion. 

It’s important to distinguish this from traction bronchiectasis, which appears more tubular and irregular. 

Here, we see ground-glass opacities. These are areas of hazy increased attenuation through which bronchial and vascular markings remain visible. 

Ground glass opacities indicate partial alveolar filling, interstitial thickening, or a mix of both. 

When isolated, ground glass opacities often signify active or reversible inflammation. 

Now let’s review case examples with mixed features. This image shows the classic UIP pattern: basal, subpleural reticulation with traction bronchiectasis and honeycombing. 

Traction bronchiectasis shows dilated, distorted bronchi, and the thick-walled, stacked cysts indicate honeycombing. 

Together, these features confirm irreversible fibrosis and the heterogeneous “patchwork” appearance typical of UIP.

Here we see UIP progression over time. In 2008, early disease shows only fine reticulation at the lung bases. 

By 2011, coarser reticulation, new honeycombing, and traction bronchiectasis appear. 

These changes reflect advancing fibrosis and architectural distortion, the hallmark of progressive UIP. 

In early-stage NSIP, we see ground-glass opacities with minimal reticulation, representing inflammation or mild fibrosis. 

In the later, fibrotic stage, the pattern becomes more diffuse, with increased reticulation and traction bronchiectasis indicating architectural distortion. 

Unlike UIP, honeycombing is uncommon. Fibrosis appears more uniform and symmetric in NSIP. 

The key takeaway is that HRCT brings clarity to the clinical picture of ILD. With the support of multidisciplinary colleagues, even complex scans become manageable. This structured approach not only guides diagnosis and monitoring but also creates a clear clinical story that supports ongoing management decisions. 

ACR – American College of Rheumatology 

ATS – American Thoracic Society 

CHEST – American College of Chest Physicians 

CTD-ILD – Connective Tissue Disease–Related Interstitial Lung Disease 

DLCO – Diffusing Capacity of the Lung for Carbon Monoxide 

ERS – European Respiratory Society 

FVC – Forced Vital Capacity 

GGO – Ground-Glass Opacity 

HRCT – High-Resolution Computed Tomography 

ILD – Interstitial Lung Disease 

IPF – Idiopathic Pulmonary Fibrosis 

JRS – Japanese Respiratory Society 

LIP – Lymphocytic Interstitial Pneumonia 

MDD – Multidisciplinary Discussion 

NSIP – Nonspecific Interstitial Pneumonia 

OP – Organizing Pneumonia 

PFTs – Pulmonary Function Tests 

SARDs – Systemic Autoimmune Rheumatic Diseases 

UIP – Usual Interstitial Pneumonia

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