Author: Tim Milligan

This image shows a pulmonary nodule in the right upper lung. Differential diagnosis of pulmonary nodules includes:

1. Malignancy (primary or metastatic)
2. Benign neoplasm: hamartoma, bronchial adenoma
3. Granuloma
4. Simulated: nipple, bone lesion, skin lesion, foreign body, artefact

Less common causes include:

1. Abscess
2. Infarct
3. Loculated pleural effusion
4. Organized pneumonia
5. Sarcoidosis
6. Cystis disease
7. Vascular lesions

Pulmonary Edema – Reticulonodular Pattern
Reticulonodular Patterns: A combination of reticular and nodular patterns.

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Pulmonary Edema: Pulmonary edema is a redistribution of vascular fluid into the interstitium first, and then possibly the alveoli. The causes can be cardiogenic, renal failure, or due to respiratory conditions like ARDS.
Peribronchial Cuffing: Normal bronchi do not have the circumferential thickening depicted in the image below.

Kerly lines result fomr thickened connective tissue planes occurring as a result of pulmonary edema or carcinomatosis.

Kerly A Lines: Radiate towards hila in mid- and upper-lung zones, 3-4 cm long, smaller than vascular markings (not useful)
Kerly B Lines: Horizontal, <2 cm long an d1 mm thick, at periphery of lung, reach lung edge (very useful)
Kerly C Lines: Thickened interlobular septa

Pulmonary Edema – Indistinct Pulmonary Vasculature
Cardiogenic and overflow states can lead to pulmonary vessel distension.

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Reticular patterns: Thin, well-defined linear densities, often in net-like or “honeycomb” arrangement.

Reticulonodular patterns: A combination of reticular and nodular patterns.

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Nodular patterns: Multiple, discrete, nodular densities, <5 mm diameter.
Right image depicts a close up of the pathology.

Kerly lines result fomr thickened connective tissue planes occurring as a result of pulmonary edema or carcinomatosis.

Kerly A Lines: Radiate towards hila in mid- and upper-lung zones, 3-4 cm long, smaller than vascular markings (not useful)
Kerly B Lines: Horizontal, <2 cm long an d1 mm thick, at periphery of lung, reach lung edge (very useful)
Kerly C Lines: Thickened interlobular septa

Interstitial disease is a pathological process involving the interlobular connective tissue (i.e. scaffolding of the lung).

Differential diagnosis of interstitial disease includes:

1. Pulmonary edema (which can move into the alveoli)
2. Collagen disease (fibrosis)
3. Sarcoidosis
4. Pneumoconiosis
5. Metastatic disease (from the lymphatics)
6. Inflammatory conditions (viral/interstitial pneumonia)