DOI: 10.1148/radiol.2433041835
(Radiology 2007;243:905-906.)
© RSNA, 2007
The Crazy-paving Sign1
Chang Hyun Lee, MD
1 From the Department of Radiology and Institute of Radiation Medicine, Seoul National University College of Medicine, Clinical Research Institute, Seoul National University Hospital, 28 Yeongon-dong, Jongno-gu, Seoul 110-744, Korea. Received October 26, 2004; revision requested October 29; revision received January 10, 2005; final version accepted February 2.
Address correspondence to the author (e-mail: chlee{at}radiol.snu.ac.kr).
 |
APPEARANCE
|
|---|
The crazy-paving sign is a pattern seen on thin-section computed tomographic (CT) images of the lungs. It is characterized by a reticular pattern superimposed on ground-glass opacity (1) (Figure). The term crazy-paving is used because the sign resembles the appearance of paths made with broken pieces of stone or concrete.
View larger version (160K):
[in this window]
[in a new window]
[Download PPT slide]
|
Alveolar proteinosis in a 47-year-old man. Transverse thin-section CT image demonstrates bilateral areas of ground-glass opacity with reticulation, which is caused by smoothly thickened inter- and intralobular septa.
|
|
|
EXPLANATION
|
|---|
In the crazy-paving sign, ground-glass opacity may reflect the presence of airspace or interstitial abnormalities; the lines of reticular opacities may represent interlobular septal thickening, thickening of the intralobular interstitium, irregular areas of fibrosis, or a preponderance of an airspace-filling process at the periphery of lobules or acini (2).
|
DISCUSSION
|
|---|
The crazy-paving sign was initially recognized in patients who had pulmonary alveolar proteinosis (1). Pulmonary alveolar proteinosis manifests as filling of the alveoli by a proteinaceous material that is positive at periodic acid–Schiff staining and is rich in lipids, in association with an inflammatory response in the adjacent interstitium (3). It is believed that pulmonary alveolar proteinosis results from an abnormality of surfactant production, metabolism, or clearance by type II alveolar cells and macrophages (4). Most cases are idiopathic. Some result from exposure to silica (silicoproteinosis) or occur in association with hematologic disorders, such as lymphoma or leukemia and, occasionally, with human immunodeficiency virus infection (4).
The linear network or reticular pattern in the crazy-paving sign is believed to result from a thickening of the interlobular septa, while areas of ground-glass opacity result from partial alveolar filling processes (1,5). Interlobular septal thickening can be seen from interstitial fibrosis, but the presence of areas of reticular opacity does not necessarily represent interstitial abnormalities (2). Kang et al (6), using the findings of a single case, suggested that the network in the crazy-paving sign in alveolar proteinosis may result from an accumulation of periodic acid–Schiff-positive material in the airspaces adjacent to the interlobular septa rather than to thickening of the septa. Therefore, when there is a slight increase in the severity of the alveolar filling process at the borders of unit structures such as acini or secondary pulmonary lobules, the networks in the crazy-paving sign can also be caused purely by airspace disease (2).
The crazy-paving sign may also be seen in patients with a variety of other diseases (2,7). The differential diagnosis of crazy-paving sign includes Pneumocystis carinii pneumonia, mucinous bronchioloalveolar carcinoma (8), sarcoidosis, lipoid pneumonia (9), adult respiratory distress syndrome (7), and pulmonary hemorrhage syndromes (10). In a prospective study of patients showing the crazy-paving sign, a variety of causes were identified (7). These included P carinii pneumonia, alveolar proteinosis, usual interstitial pneumonia, pulmonary hemorrhage, acute radiation pneumonitis, adult respiratory distress syndrome, and drug-induced pneumonitis. Of these, P carinii pneumonia was most common.
Johkoh et al (2) reported 46 patients showing the crazy-paving sign on thin-section CT images, the most common causes included adult respiratory distress syndrome (n = 8), bacterial pneumonia (n = 7), acute interstitial pneumonia (n = 5), and, despite its rarity, alveolar proteinosis (n = 5). Others were drug-induced pneumonitis (n = 3), radiation pneumonitis (n = 3), pulmonary hemorrhage (n = 3), chronic eosinophilic pneumonia (n = 2), diffuse alveolar damage superimposed on usual interstitial pneumonia (n = 2), cardiogenic edema (n = 2), mycoplasma pneumonia (n = 2), obstructive pneumonia (n = 1), tuberculosis (n = 1), P carinii pneumonia (n = 1), and bronchiolitis obliterans organizing pneumonia (n = 1). Also, the highest prevalence of crazy-paving sign in this study was seen in pulmonary alveolar proteinosis (100%), diffuse alveolar damage (67%), acute interstitial pneumonia (31%), and adult respiratory distress syndrome (21%) (3).
In summary, the crazy-paving sign can be seen primarily in airspace, interstitial, or mixed diseases. Although the causes of this sign are frequently indistinguishable at radiologic evaluation, differences in the location of the characteristic attenuation in the lungs, as well as the presence of additional radiologic findings, the patient's history, and the clinical manifestation, can often be useful in suggesting the appropriate diagnosis (10).
|
FOOTNOTES
|
|---|
Author stated no financial relationship to disclose.
|
References
|
|---|
- Murch CR, Carr DH. Computed tomography appearances of pulmonary alveolar proteinosis. Clin Radiol 1989;40:240–243.[CrossRef][Medline]
- Johkoh T, Itoh H, Müller NL, et al. Crazy-paving appearance at thin-section CT: spectrum of disease and pathologic findings. Radiology 1999;211:155–160.[Abstract/Free Full Text]
- Rosen SH, Castleman B, Liebow AA, Enzinger FM, Hunt RTN. Pulmonary alveolar proteinosis. N Engl J Med 1958;258:1123–1142.[Medline]
- Wang BM, Stern EJ, Schmidt RA, Pierson DJ. Diagnosing pulmonary alveolar proteinosis: a review and an update. Chest 1997;111:460–466.[CrossRef][Medline]
- Godwin JD, Müller NL, Takasugi JE. Pulmonary alveolar proteinosis: CT findings. Radiology 1988;169:609–613.[Abstract/Free Full Text]
- Kang EY, Grenier P, Laurent F, Müller NL. Interlobular septal thickening: patterns at high-resolution computed tomography. J Thorac Imaging 1996;11:260–264.[Medline]
- Murayama S, Murakami J, Yabuuchi H, Soeda H, Masuda K. "Crazy-paving appearance" on high resolution CT in various diseases. J Comput Assist Tomogr 1999;23:749–752.[CrossRef][Medline]
- Tan RT, Kuzo RS. High-resolution CT findings of mucinous bronchioloalveolar carcinoma: a case of pseudopulmonary carcinoma. AJR Am J Roentgenol 1997;168:99–100.[Free Full Text]
- Franquet T, Giménez A, Bordes R, Rodriguez-Arias JM, Castella J. The crazy-paving pattern in exogenous lipoid pneumonia: CT-pathologic correlation. AJR Am J Roentgenol 1998;170:315–317.[Abstract/Free Full Text]
- Rossi SE, Erasmus JJ, Volpacchio M, Franquet T, Castiglioni T, McAdams HP. "Crazy-paving" pattern at thin-section CT of the lungs: radiologic-pathologic overview. RadioGraphics 2003;23:1509–1519.[Abstract/Free Full Text]
This article has been cited by other articles:
|
|
|
|
 
A. A. Frazier, T. J. Franks, E. O. Cooke, T.-L. H. Mohammed, R. D. Pugatch, and J. R. Galvin
From the Archives of the AFIP: Pulmonary Alveolar Proteinosis
RadioGraphics,
May 1, 2008;
28(3):
883 - 899.
[Abstract]
[Full Text]
[PDF]
|
|
|
|
|
|
|
A. K. Saxena, R. Agarwal, and C. Hyun Lee
It Is Time to Move: Pneumocystis Jirovecii, Not Pneumocystis Carinii
Radiology,
March 1, 2008;
246(3):
985 - 986.
[Full Text]
[PDF]
|
|
|
TOP
APPEARANCE
EXPLANATION
