Silhouette sign

Radiologic sign

Medical condition

Silhouette sign

A) Normal chest radiograph; B) Q fever pneumonia affecting the right lower and middle lobes. Note the loss of the normal radiographic silhouette (contour) between the affected lung and its right heart border as well as between the affected lung and its right diaphragm border. This phenomenon is called the silhouette sign
Differential diagnosis| right middle lobe syndrome

In radiology, the silhouette sign refers to the loss of normal borders between thoracic structures.[1] It is usually caused by an intrathoracic radiopaque mass that touches the border of the heart or aorta.[2] In other words, it is difficult to make out the borders of a particular structure - normal or otherwise - because it is next to another dense structure, both of which will appear white on a standard X-ray.[3] It may occur, for example, in right middle lobe syndrome, where the right heart margin is obscured, and in right lower lobe pneumonia, where the border of the diaphragm on the right side is obscured, while the right heart margin remains distinct.[2] Silhouette sign is very useful in localizing lung lesions as all structures forming cardiac silhouette are in contact with a specific portion of the lung.

## References

[edit]

1. ^ Silouette Sign, 2008, Family Practice Notebook, LLC. Retrieved 9 February 2010.
2. ^ a b The silhouette sign and possible mechanisms, Ian Maddison Nov 1994, revised Nov. 2007. Retrieved 9 February 2010.
3. ^ Corne; et al. (2002). Chest X-Ray Made Easy. Churchill Livingstone. ISBN 978-0-443-07008-2.

## Further reading

[edit]

* The Silhouette Sign Revisited, Vernon J. Louw, Adrian Schmidt, Chris T. Bolliger. Lung Unit, Department of Internal Medicine, Tygerberg Hospital, Cape Town, South Africa.

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Signs and symptoms relating to the respiratory system

Auscultation|

* Stethoscope
* Respiratory sounds
* Stridor
* Wheeze
* Crackles
* Rhonchi
* Stertor
* Squawk
* Pleural friction rub
* Fremitus
* Bronchophony
* Death rattle
* Elicited findings
* Percussion
* Pectoriloquy
* Whispered pectoriloquy
* Egophony

Breathing|

| Rate|

* Apnea
* Prematurity
* Dyspnea
* Hyperventilation
* Hypoventilation
* Hyperpnea
* Tachypnea
* Hypopnea
* Bradypnea

|

Pattern|

* Agonal respiration
* Biot's respiration
* Cheyne–Stokes respiration
* Kussmaul breathing
* Ataxic respiration

Other|

* Respiratory distress
* Respiratory arrest
* Orthopnea/Platypnea
* Trepopnea
* Aerophagia
* Asphyxia
* Breath holding
* Mouth breathing
* Snoring

Other|

* Chest pain
* In children
* Precordial catch syndrome
* Pleurisy
* Nail clubbing
* Cyanosis
* Cough
* Sputum
* Hemoptysis
* Epistaxis
* Silhouette sign
* Post-nasal drip
* Hiccup
* COPD
* Hoover's sign
* asthma
* Curschmann's spirals
* Charcot–Leyden crystals
* chronic bronchitis
* Reid index
* sarcoidosis
* Kveim test
* pulmonary embolism
* Hampton hump
* Westermark sign
* pulmonary edema
* Kerley lines
* Hamman's sign
* Golden S sign

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Radiologic signs

Cardiovascular|

* Aortic unfolding
* Dense artery sign
* Halo sign

Respiratory|

* Air crescent sign
* Deep sulcus sign
* Golden S sign
* Hampton hump
* Kerley lines
* Peribronchial cuffing
* Sail sign of the chest
* Silhouette sign
* Steeple sign
* Thumbprint sign
* Traction bronchiectasis
* Tree-in-bud sign
* Westermark sign

Urogenital|

* Canga's bead symptom

Musculoskeletal|

* Crescent sign
* Fabella sign
* Fat pad sign/Sail sign of the elbow
* Osteopathia striata

Gastrointestinal|

* Cupola sign
* Double bubble
* Endoexoenteric
* Football sign
* Hampton's line
* Hot quadrate sign
* Mumoli's sign
* Omental cake
* Pneumatosis intestinalis
* Rigler's sign
* Sentinel loop

Neurological|

*   * Hyperdense middle cerebral artery

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