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Lung Consilidation, Ground Glass Shadowing, Obstructive Emphysema, Collateral Air-draft, Mucocoeles, patterns of Collapse, Lung Torsion and Herniation.
Published in Fred W Wright, Radiology of the Chest and Related Conditions, 2022
This sign reflects the point that most anatomical structures bordering the lungs, are not themselves seen, but depend on adjacent air-filled lung for their recognition. This is true for the heart, aorta, diaphragm, IVC or SVC, etc. Thus when the outline of these is obliterated or absent, the sign shows that air-less lung (fluid or solid tumour) is adjacent to the lost anatomical border. This will allow in many instances, the anatomical localisation of the disease process from a single view. On PA views collapse or consolidation of the left upper lobe will obliterate the left cardiac border - the left lower lobe, the left border of the descending aorta, the right middle lobe, the lower right cardiac border, the right lower lobe, the inferior vena cava, the right upper lobe, the ascending aorta and azygos vein, etc. The posterior parts of either side of the diaphragm are also obscured with a non-aerated lower lobe. The normal IVC and the loss of its silhouette are best seen on the lateral view. On a lateral view, a collapsed left lower lobe will often obliterate the posterior margin of the heart and the posterior part of the diaphragm as well as obscure the descending aorta. These points are further shown in Ulus. LOSS OF SILHOUETTE or SILHOUETTE SIGN.
Silhouette Sign
Published in Michael E. Mulligan, Classic Radiologic Signs, 2020
The Felsons (University of Cincinnati, Ohio) stated, ‘With the rapid advances in thoracic surgery, segmental localization of pulmonary disease has assumed greater importance’. [Their method of determining] ‘the exact location of a pulmonary density from the postero-anterior film alone’ [was] ‘based on the premise that an intrathoracic radiopacity, if in anatomic contact with a border of the heart or aorta, [would] obscure that border.’ [They] ‘adopted the term silhouette sign to indicate obliteration of a portion of the cardiovascular silhouette by adjacent disease’ (Figure 1). They tested this premise experimentally and with a study of 84 patients. The sign proved to be very reliable and has withstood the test of time. There has been a lot of discussion about whether this sign should be called a ‘silhouette sign’ or a ‘loss of the silhouette sign.’ The term, silhouette sign, ought to be remembered as it was defined by its originators with fewer arguments about the semantics involved.
Respiratory system and chest
Published in David A Lisle, Imaging for Students, 2012
The silhouette sign refers to loss of visualization of an anatomical structure or margin due to pathology, and is one of the most important principles in chest radiography. The key to understanding the silhouette sign is to remember the five principal densities that are recognized on plain radiographs (see Chapter 1 and Fig. 1.1): air/gas, fat, soft tissue/water, bone and contrast material/metal. The silhouette of an object will be seen with conventional radiography if its borders lie beside tissue of different density. This applies especially in the chest where diaphragms, heart and mediastinal structures are well seen due to their lying adjacent to aerated lung. Should a part of lung lying against any of these structures become non-aerated due to collapse, consolidation or a mass, the outline of that structure will no longer be seen (Fig. 2.12 and Table 2.4).
Molecular detection and genotypic characterisation of Streptococcus pneumoniae isolated from children in Malaysia
Published in Pathogens and Global Health, 2020
Shu Ling Goh, Boon Pin Kee, Kartini Abdul Jabar, Kek Heng Chua, Anna Marie Nathan, Jessie Bruyne, Soo Tein Ngoi, Cindy Shuan Ju Teh
S. pneumoniae (n = 95) were obtained from the collection of cultures from University of Malaya Medical Center (UMMC). These isolates were previously isolated from respiratory specimens (nasopharyngeal swab/secretion) from pediatric patients <12 years of age with LRTI, between the years of 2013 to 2015. Patient’s data showed that children were admitted to UMMC with symptoms of infection (fever, cough and/or runny nose) and signs of LRTI (shortness of breath, tachypnea, recessions, crepitations, and/or rhonchi). Nonetheless, not all patients had the strict definition of pneumonia which is signs of a LRTI with focal or diffuse infiltrates, silhouette sign, pleural effusion, or air bronchogram. All the isolates were recovered on Columbia agar supplemented with 5% horse blood and incubated for 24 h at 37°C, with 5% CO2. This study was approved by the University of Malaya Research Ethics Committee (UMREC) (MECID: 20146–336).