대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Courtesy

A

Imaging Findings

Initial radiograph showed focal patchy consolidation involving both lower lung zone.
Two weeks later, there was markedly increased extent of consolidation and ground-glass opacity.
On thin-section CT scanning of patients, ground-glass attenuation with patchy consolidation was prominent finding.
Sparing of contiguous lobules gave a geographic or mosaic appearance.
Traction bronchiectasis and architectural distortion were also noted.

Past History

Figure 1: Initial radiograph
Figs. 2-4: Two weeks later.

Discussion

Acute interstitial pneumonia (AIP) is an uncommon interstitial lung disease, first described in 1944 by Hamman and Rich
as acute diffuse interstitial fibrosis of the lungs.
It is the idiopathic variant of adult respiratory distress syndrome (ARDS), responsible for the small subset of patients
that develop ARDS without an associated predisposing factor, such as sepsis or trauma.
Acute interstitial pneumonia has a poor prognosis, with over 50 percent of patients dying within 3 months.

The diagnosis is based on the appropriate clinical presentation, the lack of any precipitating factor for ARDS, and a characteristic open lung biopsy.
The typical clinical presentation of AIP is a previously healthy person, less than 50 years of age,
who presents with acute breathlessness, followed rapidly by respiratory failure.
Breathlessness is preceded by 1 to 2 weeks of a flu-like prodrome, with low-grade fever, myalgia, arthralgia, and fatigue.
Marked gas exchange abnormalities are pretherapeutic interventions.

Pathologically, the findings are distinct from those of other interstitial lung diseases
and are indistinguishable from the organizing stage of diffuse alveolar damage (DAD) seen in ARDS.
There is interstitial fibroblast proliferation, chronic inflammation, and alveolar collapse.
The clinicopathologic picture is distinct from that of idiopathic pulmonary fibrosis (IPF),
though acute exacerbation occurring in patients with IPF have been confused with AIP.

Radiologic Features


The chest radiograph is always abnormal in patients with AIP.
The chest radiographic features of AIP are similar to those of ARDS, with progressive ground-glass attenuation and consolidation,
which may be patchy, but often diffusely involves the mid- and lower zones.

Usually, AIP is distinguishable from cardiogenic edema on the chest radiograph
by the normal size of the heart and vascular pedicle and by the absence of septal lines or peribronchial cuffing.
However, AIP must be distinguished clinically from infection.

On CT scanning of patients with AIP, ground-glass attenuation is invariable, with patchy consolidation being slightly less common.
Sparing of contiguous lobules gives a geographic or mosaic appearance.
Traction bronchiectasis and architectural distortion are common findings in patients imaged at a later stage of their disease.

The temporal course of AIP is divided histologically into exudative, proliferative, and fibrotic phases.
The CT findings of AIP are related to these histologic phases.

Patients that have ground-glass attenuation or consolidation without traction bronchiectasis are either in the exudative or proliferative phase of AIP.
Patients who have traction bronchiectasis are usually in the proliferative or fibrotic phase of their disease.
The presence of honeycombing is indicative of the fibrotic phase of AIP.

The extent of the areas of ground-glass attenuation and traction bronchiectasis increased with the duration of disease.

Reference

1. Lynch DA, Brown KK, Lee JS, et al. Imaging of diffuse infiltrative lung disease. In: Lynch DA, Newell JD, Lee JS. ed. Imaging of Diffuse Lung Disease. Hamilton: BC Decker. 2000:57-140
2. Olson J, Colby TV, Elliott CG. Hamman-Rich syndrome revisited. Mayo Clin Proc 1990;65:1538-48
3. Johkoh T, Muller N, Taniguchi H, et al. Acute interstitial pneumonia: thin-section CT findings in 36 patients. Radiology 1999;211:859

Keywords

Lung, Idiopathic interstitial pneumonia, AIP,