Crazy-paving appearance at thin-section CT: Spectrum of disease and pathologic findings

PURPOSE: To determine the spectrum of diseases associated with a fine retic ular pattern superimposed on areas of ground-glass opacity (ie, "crazy-pavi ng" appearance) at thin-section computed tomography (CT) and to determine t he underlying pathologic features. MATERIALS AND METHODS: In the in vivo study, the cases of 46 patients (21 m ale, 25 female; age range, 13-82 years) were retrospectively reviewed, with special attention paid to the size and extent of the reticular network. In the in vitro study, the thin-section CT findings in 20 inflated and fixed lungs were precisely correlated with the gross appearance, contact radiogra ph findings, stereomicroscopic views, and histologic findings. RESULTS: In the in vivo study, 15 different diseases were identified, inclu ding alveolar proteinosis, adult respiratory distress syndrome, acute inter stitial pneumonia, diffuse alveolar damage superimposed on usual interstiti al pneumonia, and drug-induced pneumonitis. In the in vitro study, the fine networks at pathologic analysis were due to an alveolar filling process (n = 10), an interstitial fibrotic process (n = 7), or a combination of inter stitial and intraalveolar processes (n = 3). Twelve (60%) cases did not hav e thickening of the interlobular septa within the areas of the crazy-paving appearance. CONCLUSION: The crazy-paving appearance is a nonspecific finding seen in a variety of interstitial and airspace lung diseases.