000 Position Lower Lung Diseases

Lower Lung Fields

Most Common Causes of Lower Lobe Lung Disease

Category	Disease	CT Characteristics	Key Features
Aspiration-Related Acinar Nodules Ground Glass Nodules and consolidation Post Trauma Axial CT following trauma and resuscitative attempts in a 37 year old female shows 2-5mm solid and ground glass nodules in both the upper lobes. A focus of consolidation in the right upper lobe posteriorly could reflect a hematoma or aspiration . w There is evidence of subpleural sparing with a more central distribution. These findings are consistent with hemorrhagic foci of acinar shadows or acinar nodules following trauma Ashley Davidoff MD TheCommonVein.net 137267 301Lu	Aspiration Pneumonitis / Pneumonia	– Dependent lower lobe airspace opacities – Tree-in-bud opacities (bronchiolar involvement) – Can progress to necrotizing pneumonia	– Common in stroke patients, alcoholics, GERD – Often due to anaerobic bacteria
Inflammation & Immune-Related CT UIP and Honeycomb Lung CT scan in the axial plane through the lung bases of an 84 year old female with UIP showing the typical changes of honeycomb lung in the periphery of both lung bases, and in this instant more prominent at the right base Ashley Davidoff MD TheCommonVein.net 136453	Usual Interstitial Pneumonia (UIP) / Idiopathic Pulmonary Fibrosis (IPF)	– Reticular opacities & traction bronchiectasis – Honeycombing in subpleural regions – Lower lobe & peripheral predominance	– Fibrotic lung disease with poor prognosis – UIP pattern also seen in rheumatoid arthritis & asbestosis
Inflammation & Immune-Related NSIP 71-year-old female presents with a history of scleroderma, ILD, hypothyroidism and dcSSc CT of the lower lobes in the axial plane, shows bronchovascular changes with some volume loss in a background of extensive ground glass changes with traction bronchiectasis and irregular thickening of the interlobular septa. Subpleural sparing is noted at the right base The fissures show irregular thickening as well. Air-fluid level is noted in the dilated esophagus Ashley Davidoff MD TheCommonVein.net 196Lu 136612	Nonspecific Interstitial Pneumonia (NSIP)	– Ground-glass opacities – Mild reticulation & traction bronchiectasis – Subpleural lower lobe predominance	– More homogeneous than UIP – Associated with connective tissue diseases (e.g., Scleroderma, Sjögren’s Syndrome)
Inflammation & Immune-Related Hypersensitivity Pneumonitis Head Cheese Sign 70-year-old female presents with dyspnea CT performed in expiration shows multicentric foci of differing densities that include ground glass (seen on inspiration images) normal, and mosaic attenuation with air trapping and prominent centrilobular nodules These findings confirm small airway disease and in the appropriate clinical context are consistent with hypersensitivity pneumonitis (HP) Ashley Davidoff MD TheCommonvein.net 135792c 144Lu	Chronic Hypersensitivity Pneumonitis (HP)	– Ground-glass opacities & centrilobular nodules – Fibrotic changes in chronic cases – Headcheese sign (mosaic attenuation)	– Caused by long-term organic antigen exposure (e.g., bird droppings, mold) – Progresses to fibrosis if untreated
Inflammation & Immune-Related Asbestosis and Shaggy Heart Border Axial CT in a 72-year-old man with asbestosis demonstrating predominant lower lung zone involvement, with a ‘shaggy’ heart border, reticular changes, and early honeycombing. Fibrotic changes are notable in the lingula and middle lobe, suggesting segmental involvement. Additional findings include thickening of the right lower lobe subsegmental airways, architectural distortion, and pleural calcifications in the posteromedial right lower lung. These findings are characteristic of asbestosis, an interstitial lung disease resulting from prolonged asbestos exposure.” Editorial Comment: This case highlights the hallmark features of asbestosis, including lower lobe-predominant fibrosis, reticular interstitial changes, tractional bronchiectasis, and a ‘shaggy’ heart border due to pleural and parenchymal fibrosis. Pleural plaques serve as a telltale sign of prior asbestos exposure, supporting the diagnosis. The involvement of the lingula and middle lobe suggests a more diffuse fibrotic process. Early honeycombing is worrisome for progressive fibrosis and warrants clinical correlation and follow-up imaging to assess disease progression. Ashley Davidoff TheCommonVein.com (47078)	Asbestosis	– Lower lobe-predominant fibrosis – Pleural plaques (pathognomonic) – Honeycombing in advanced cases	– Chronic inflammation due to asbestos fiber exposure – Dose-dependent with a latency of 20-40 years – High risk for mesothelioma
Inflammation & Immune-Related	Desquamative Interstitial Pneumonia (DIP)	– Diffuse ground-glass opacities, lower lobe predominance – Mild interstitial thickening – No honeycombing	– Strong smoking association – Smoker’s macrophages fill alveoli
Inflammation & Immune-Related	Chronic Bronchitis & Smoker’s Bronchiolitis	– Bronchial wall thickening – Lower lobe-predominant peribronchiolar inflammation – Air trapping (mosaic attenuation on expiratory CT)	– Chronic smoking-related airway disease – May precede COPD development
Inflammation & Immune-Related	Drug-Induced Lung Disease (Nitrofurantoin, Amiodarone, Methotrexate, Bleomycin, etc.)	– Lower lobe predominant ground-glass opacities – Fibrosis & reticulation in chronic cases – Hyperattenuation (iodine deposition in Amiodarone toxicity)	– Nitrofurantoin & Methotrexate mimic NSIP – Bleomycin toxicity can resemble UIP
Mycobacterial Infections	Atypical Mycobacterial Infection (MAC/NTM, e.g., Lady Windermere Syndrome)	– Bronchiectasis & tree-in-bud opacities – Lower lobe predominant in some cases – Centrilobular nodules	– More common in elderly females (“Lady Windermere Syndrome”) – Often associated with bronchiectasis
Cryptogenic Organizing Pneumonia (COP) Follicular Bronchiolitis CT Follicular Bronchiolitis, (aka Bronchiolitis Obliterans), Centrilobular Nodules, Air Trapping, Ground Glass Opacities (GGO) in Upper Lobes 70-year-old female former smoker with long standing history of RA presents with chronic dyspnea. Axial CT of the chest at the level of the aortic arch reveals centrilobular nodules, ground-glass opacities, and mosaic attenuation (likely due to air trapping in this context) and bronchial wall thickening. In the context of a patient with rheumatoid arthritis a diagnosis of follicular bronchiolitis is likely. However radiologically fibrotic hypersensitivity pneumonitis (HP) is included in the differential diagnosis Ashley Davidoff MD TheCommonVein.net 132Lu 136652	Formerly known as BOOP (Bronchiolitis Obliterans Organizing Pneumonia)	– Patchy lower lobe consolidations – Peribronchovascular & subpleural involvement	– Can mimic infectious pneumonia but nonresponsive to antibiotics – Responds well to steroids

Less Common Causes of Lower Lobe Lung Disease

Category	Disease	CT Characteristics	Key Features
Neoplasm (Malignant, Benign)	MALT Lymphoma (Extranodal Marginal Zone B-Cell Lymphoma)	– Lower lobe nodules or consolidation – Air bronchograms common – Patchy ground-glass opacities (GGO)	– Most common pulmonary lymphoma – Can arise from chronic antigenic stimulation (e.g., Sjogren’s, chronic infections)
Neoplasm (Malignant, Benign)	Castleman’s Disease (Multicentric Variant)	– Lower lobe-predominant lymphadenopathy – Interlobular septal thickening – Patchy ground-glass opacities	– Multicentric form more commonly affects lungs – Associated with HHV-8 (in HIV patients) – Can mimic lymphangitic spread of carcinoma
Idiopathic	Lymphoid Interstitial Pneumonia (LIP)	– Diffuse or lower lobe-predominant ground-glass opacities (GGO) – Thin-walled cysts (varied sizes) – Mild interstitial thickening & nodularity	– Associated with Sjogren’s syndrome, HIV, & autoimmune diseases – Can progress to fibrosis or MALT lymphoma

Key Takeaways:

Aspiration remains the most common lower lobe disease, especially in stroke patients and those with GERD.
Fibrotic diseases (UIP/IPF, NSIP, Hypersensitivity Pneumonitis) dominate immune-related lower lobe pathology.
Asbestosis is reclassified as an inflammatory disease due to chronic irritation from asbestos fibers.
Chronic bronchitis, smoker’s bronchiolitis, and DIP are now included as common smoking-related lower lobe diseases.
Drug toxicity (Nitrofurantoin, Amiodarone) mimics interstitial lung disease.
Mycobacterial infections (MAC) affect lower lobes in “Lady Windermere Syndrome”.
COP (BOOP) mimics pneumonia but is steroid-responsive.
Less common causes include malignancies (MALT lymphoma, Castleman’s) and lymphoproliferative diseases (LIP).