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==Overview==
==Overview==
*High resolution computed tomography (HRCT) is helpful for patients with an atypical clinical presentation or atypical findings on chest radiograph. A baseline HRCT scan in patients with radiographic findings of silicosis is usually obtained to document the presence and extent of nodules, emphysema, and other silica-related abnormalities that may progress in the future.
*High resolution computed tomography ([[HRCT]]) is helpful for patients with an atypical clinical presentation or atypical findings on chest radiograph. A baseline HRCT scan in patients with radiographic findings of silicosis is usually obtained to document the presence and extent of [[nodules]], [[emphysema]], and other silica-related abnormalities that may progress in the future.
==CT==
==Computed Tomography scan ==
A [[CT scan]] can also provide a mode detailed analyses of the nodules, and can reveal cavitation due to concomitant mycobacterial infection. However, HRCT is usually not necessary in simple silicosis unless atypical clinical or radiographic features are noted (eg, fever, spiculated nodules, a single nodule of substantially larger size than the others)[74,75]
*A [[CT scan]] can also provide a mode detailed analyses of the [[nodules]], and can reveal [[cavitation]] due to concomitant mycobacterial infection. In the diagnosis of silicosis, HRCT scans are superior to [[chest X-rays]],  both  for  the  early  detection  of  the  initial phases of the disease and for the identification of [[PMF]].<ref name="pmid18545821">{{cite journal| author=Lopes AJ, Mogami R, Capone D, Tessarollo B, de Melo PL, Jansen JM| title=High-resolution computed tomography in silicosis: correlation with chest radiography and pulmonary function tests. | journal=J Bras Pneumol | year= 2008 | volume= 34 | issue= 5 | pages= 264-72 | pmid=18545821 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=18545821  }} </ref>
The typical HRCT findings in simple silicosis are bilateral, symmetric, centrilobular, and perilymphatic nodules with sharp margination (image 5). These nodules calcify in 10 to 20 percent of patients.
*The typical [[CT|HRCT]] findings in simple silicosis are
HRCT is superior to conventional chest radiography for documentation of conglomerate lesions and emphysematous changes associated with complicated silicosis (image 6) [68-71,76-78]
:*Bilateral,
The HRCT findings consist of numerous bilateral centrilobular nodular opacities, focal ground glass opacities, and patchy areas of consolidation [54]. In a small series that compared pulmonary alveolar proteinosis (PAP) and acute silicosis, the most common HRCT finding in PAP was “crazy paving”, while the most common finding in acute silicosis was dependent consolidation and nodular calcification [55].
:*Symmetric,
 
:*[[Centrilobular]], and perilymphatic nodules
Hilar lymph node enlargement may be apparent on HRCT, which is a typical feature of silicosis, but not of PAP [53]. In a series of 13 patients, calcified lymph nodes were noted on HRCT in 11 (85 percent) [54].  
:*With sharp [[margination]].
 
:*These nodules calcify in 10 to 20 percent of patients.
Although pleural effusions are unusual, pleural thickening appears to be common, especially among patients with more severe disease. In a series of 110 patients with biopsy proven silicosis followed for a mean of 14 years, pleural effusions were noted in 12 patients (11 percent), but pleural thickening was present in 64 patients (58 percent) [79].
*However, [[CT|HRCT]] is usually not necessary in simple silicosis unless [[fever]] or  atypical radiographic features such as [[spiculated]] nodules, a single nodule of substantially larger size than the others are noted <ref name="pmid7795742">{{cite journal| author=Talini D, Paggiaro PL, Falaschi F, Battolla L, Carrara M, Petrozzino M et al.| title=Chest radiography and high resolution computed tomography in the evaluation of workers exposed to silica dust: relation with functional findings. | journal=Occup Environ Med | year= 1995 | volume= 52 | issue= 4 | pages= 262-7 | pmid=7795742 | doi= | pmc=PMC1128205 | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=7795742  }} </ref><ref name="pmid21355064">{{cite journal| author=Meijer E, Tjoe Nij E, Kraus T, van der Zee JS, van Delden O, van Leeuwen M et al.| title=Pneumoconiosis and emphysema in construction workers: results of HRCT and lung function findings. | journal=Occup Environ Med | year= 2011 | volume= 68 | issue= 7 | pages= 542-6 | pmid=21355064 | doi=10.1136/oem.2010.055616 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21355064  }} </ref>.  
 
*In complicated silicosis [[CT|HRCT]] is superior to conventional chest radiography for documentation of conglomerate lesions and [[emphysematous]] changes. The [[CT|HRCT]] findings consist of  
●FDG-PET scan – Fluorine-18-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) scans are often used to differentiate benign from malignant lung lesions. However, FDG-PET is often positive in PMF in the absence of malignancy or infection. The uptake of PMF lesions on FDG-PET scans was evaluated in a series of nine patients with 14 masses, ranging in size from 1.2 to 6.4 cm in maximum diameter [80]. The maximal standard uptake value (SUV) ranged from 3.1 to 14.6 and mean SUV ranged from 1.4 to 8.5. An SUV exceeding 2.5 is generally considered highly suggestive of malignancy or active inflammation. (See "Computed tomographic and positron emission tomographic scanning of pulmonary nodules", section on 'Positron emission tomography (PET)'.)
:*Numerous bilateral centrilobular nodular opacities,  
 
:*Focal [[ground glass opacities]], and  
Bronchoscopy — Flexible bronchoscopy has a limited diagnostic role in chronic silicosis, and, for most patients, bronchoscopy to confirm the diagnosis is not indicated. However, bronchoscopic washings, brushing, or bronchoalveolar lavage may be used to obtain samples for microbiologic studies and cytology when infection and/or malignancy are in the differential diagnosis based on the imaging results. In general, transbronchial biopsy is avoided in chronic silicosis due to the presumed risk for pneumothorax and the small sample size.
:*Patchy areas of [[consolidation]] <ref name="pmid18029877">{{cite journal| author=Marchiori E, Souza CA, Barbassa TG, Escuissato DL, Gasparetto EL, Souza AS| title=Silicoproteinosis: high-resolution CT findings in 13 patients. | journal=AJR Am J Roentgenol | year= 2007 | volume= 189 | issue= 6 | pages= 1402-6 | pmid=18029877 | doi=10.2214/AJR.07.2402 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=18029877  }} </ref>.
 
:*Hilar lymph node enlargement may be apparent on [[CT|HRCT]], which is a typical feature of silicosis, but not of [[PAP|pulmonary alveolar proteinosis]].  
Diagnosis — The diagnosis of acute silicosis is based upon the history of an acute, high dose silica exposure, imaging findings of diffuse nodular and patchy consolidative opacities, a milky, lipoproteinaceous bronchoalveolar lavage effluent, and exclusion of other potential explanations (infection, pulmonary edema, alveolar hemorrhage, eosinophilic pneumonia, primary pulmonary alveolar proteinosis). A lung biopsy is not necessary in the setting of a definite exposure history and these characteristic findings.
*In a small series that compared [[pulmonary alveolar proteinosis]] (PAP) and acute silicosis, the most common [[CT|HRCT]] finding in PAP was “crazy paving”, while the most common finding in acute silicosis was dependent consolidation and nodular calcification<ref name="pmid21211921">{{cite journal| author=Souza CA, Marchiori E, Gonçalves LP, Meirelles GS, Zanetti G, Escuissato DL et al.| title=Comparative study of clinical, pathological and HRCT findings of primary alveolar proteinosis and silicoproteinosis. | journal=Eur J Radiol | year= 2012 | volume= 81 | issue= 2 | pages= 371-8 | pmid=21211921 | doi=10.1016/j.ejrad.2010.12.012 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=21211921  }} </ref>.  
 
*Although [[pleural effusions]] are unusual in silicosis, pleural thickening appears to be common among patients with more severe disease<ref name="pmid16040925">{{cite journal| author=Arakawa H, Honma K, Saito Y, Shida H, Morikubo H, Suganuma N et al.| title=Pleural disease in silicosis: pleural thickening, effusion, and invagination. | journal=Radiology | year= 2005 | volume= 236 | issue= 2 | pages= 685-93 | pmid=16040925 | doi=10.1148/radiol.2362041363 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=16040925  }} </ref>.
Once lipoproteinaceous fluid has been obtained by BAL or observed on biopsy, other causes of alveolar proteinosis or lipidosis are usually identified by history of inhalational exposure (eg, titanium, indium-tin oxide, or aluminum), testing for GM-CSF antibodies, lipid-laden macrophages in bronchoalveolar lavage fluid (suggest lipoid pneumonia), stains and/or cultures obtained from bronchoscopy (eg, Pneumocystis jirovecii or Nocardia), or presence of leukemic cells in the peripheral blood. (See "Diagnosis and treatment of pulmonary alveolar proteinosis in adults", section on 'Evaluation and diagnosis' and "Clinical presentation and diagnosis of Pneumocystis pulmonary infection in HIV-infected patients", section on 'Bronchoalveolar lavage' and "Clinical manifestations and diagnosis of nocardiosis" and "Aspiration pneumonia in adults", section on 'Lipoid pneumonia'.)


==References==
==References==
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Latest revision as of 15:36, 8 June 2016

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Aparna Vuppala, M.B.B.S. [2]

Overview

  • High resolution computed tomography (HRCT) is helpful for patients with an atypical clinical presentation or atypical findings on chest radiograph. A baseline HRCT scan in patients with radiographic findings of silicosis is usually obtained to document the presence and extent of nodules, emphysema, and other silica-related abnormalities that may progress in the future.

Computed Tomography scan

  • A CT scan can also provide a mode detailed analyses of the nodules, and can reveal cavitation due to concomitant mycobacterial infection. In the diagnosis of silicosis, HRCT scans are superior to chest X-rays, both for the early detection of the initial phases of the disease and for the identification of PMF.[1]
  • The typical HRCT findings in simple silicosis are
  • Bilateral,
  • Symmetric,
  • Centrilobular, and perilymphatic nodules
  • With sharp margination.
  • These nodules calcify in 10 to 20 percent of patients.
  • However, HRCT is usually not necessary in simple silicosis unless fever or atypical radiographic features such as spiculated nodules, a single nodule of substantially larger size than the others are noted [2][3].
  • In complicated silicosis HRCT is superior to conventional chest radiography for documentation of conglomerate lesions and emphysematous changes. The HRCT findings consist of
  • In a small series that compared pulmonary alveolar proteinosis (PAP) and acute silicosis, the most common HRCT finding in PAP was “crazy paving”, while the most common finding in acute silicosis was dependent consolidation and nodular calcification[5].
  • Although pleural effusions are unusual in silicosis, pleural thickening appears to be common among patients with more severe disease[6].

References

  1. Lopes AJ, Mogami R, Capone D, Tessarollo B, de Melo PL, Jansen JM (2008). "High-resolution computed tomography in silicosis: correlation with chest radiography and pulmonary function tests". J Bras Pneumol. 34 (5): 264–72. PMID 18545821.
  2. Talini D, Paggiaro PL, Falaschi F, Battolla L, Carrara M, Petrozzino M; et al. (1995). "Chest radiography and high resolution computed tomography in the evaluation of workers exposed to silica dust: relation with functional findings". Occup Environ Med. 52 (4): 262–7. PMC 1128205. PMID 7795742.
  3. Meijer E, Tjoe Nij E, Kraus T, van der Zee JS, van Delden O, van Leeuwen M; et al. (2011). "Pneumoconiosis and emphysema in construction workers: results of HRCT and lung function findings". Occup Environ Med. 68 (7): 542–6. doi:10.1136/oem.2010.055616. PMID 21355064.
  4. Marchiori E, Souza CA, Barbassa TG, Escuissato DL, Gasparetto EL, Souza AS (2007). "Silicoproteinosis: high-resolution CT findings in 13 patients". AJR Am J Roentgenol. 189 (6): 1402–6. doi:10.2214/AJR.07.2402. PMID 18029877.
  5. Souza CA, Marchiori E, Gonçalves LP, Meirelles GS, Zanetti G, Escuissato DL; et al. (2012). "Comparative study of clinical, pathological and HRCT findings of primary alveolar proteinosis and silicoproteinosis". Eur J Radiol. 81 (2): 371–8. doi:10.1016/j.ejrad.2010.12.012. PMID 21211921.
  6. Arakawa H, Honma K, Saito Y, Shida H, Morikubo H, Suganuma N; et al. (2005). "Pleural disease in silicosis: pleural thickening, effusion, and invagination". Radiology. 236 (2): 685–93. doi:10.1148/radiol.2362041363. PMID 16040925.

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