This document discusses differentials and radiological signs of conditions presenting with a unilateral hypertransradiant hemithorax. It provides two mnemonics, SAFE POEM and CRAWLS, listing potential causes such as rotation, pneumothorax, emphysema, bullous lung disease, Swyer-James syndrome, pulmonary embolism, and abnormalities of the chest wall or contralateral lung. For each condition, the document describes associated radiographic findings and example images. It aims to educate radiologists on evaluating and differentially diagnosing this common pediatric chest x-ray finding.

1. Radiographic signs and
differentials of conditions
presenting with
hypertransradiant hemithorax
Prepared by; Joyce F. Mwatonoka
MD5
April 2017

2. Objectives
• Introduction
• Differentials and their radiological signs

3. Introduction
• Transradiancy or Radiolucency indicates
greater transparency to X-ray photons ie
ability of material of relatively low atomic
number to allow most x-rays to pass through
them producing dark images on x-ray film

4. Cont…
• Hypertransradiant means increase in
transradiancy of the lung field
• Unilateral hyperlucent hemithorax - when
one side of the chest is more lucent (black)
than the other on a frontal chest radiograph

5. Normal Vs Unilateral Hypertransradiant
CXR

6. Cont…
• It is a common pediatric chest radiographic
finding
• When evaluating a patient with this finding it
is important to note whether the apparent
unilateral hyperlucent hemithorax is truly too
lucent or if the contralateral hemithorax is too
opaque

7. Cont…
• Unilateral hypertranslucent hemithorax has
many potential causes; but it may be a result
of rotation away from an optimal position
(technical problem) or because of a pathology

8. 1. Rotation
• The side towards which the patient
turns/rotates is hyperlucent due to shorter
distance of tissues from x ray source and
hence increased x ray transmission;
• Irrespective of whether the CXR has been
taken AP/PA

9. Unilateral hypertranslucent hemithorax
due to patient rotation

10. Cont…
• One can assess patient’s rotation by observing
the clavicular heads (sternoclavicular joints)
and determine whether they are equidistance
from the spinous process of the thorasic
vertebrae bodies

11. 2.Pathology
• There are many different conditions which
may present with unilateral hypertransradiant
hemithorax
• Two mnemonics;
a) SAFE POEM
b) CRAWLS

12. a) SAFE POEM
• S: Swyer-James syndrome
• A: agenesis (pulmonary)
• F: fibrosis (mediastinal)
• E: effusion (pleural effusion on the contralateral
side)
• P: pneumonectomy/pneumothorax
• O: obstruction
• E: embolus (pulmonary)
• M: mucous plug

13. b) CRAWLS
• C: contralateral lung increased density,
e.g. supine unilateral pleural effusion,
unilateral diffused pleural thickening
• R: rotation
• A: air, e.g. pneumothorax
• W: wall, e.g. chest wall mass
mastectomy, polio, Poland syndrome

14. Cont…
• L: lungs e.g.
airway obstruction; foreign body,
endobronchial tumor, extrinsic masses such as
an enlarged nodes/heart
emphysema
unilateral lung transplantation for pulmonary
emphysema
Swyer-James syndrome

15. Cont…
unilateral large bullae
large pulmonary embolus
Pulmonary agenesis
• S: Scoliosis

16. Contralateral lung increased density
• Here the lucent side is normal and the
opposite side is abnormally radiopaque
• Commonest cause is supine radiograph in
pleural effusion

17. Supine radiograph in pleural effusion
• A minimal volume of 175 mL is required to
produce notable change on the supine
radiograph
• The opacity first projects over the lower lung
zones, then the entire hemithorax as the fluid
increases

18. AP supine view of the chest in a 60-year-old man with right-sided effusion.
There is asymmetric density with increased haziness in the lower Rt
hemithorax (blue arrow). Note that the pulmonary vascular structures are not
obscured or silhouetted by the vague density but, rather, are still visible
through it (open arrow)

19. Pneumothorax
• Visible visceral pleural edge seen as a very thin, sharp
white line
• No lung markings are seen peripheral to this line
• The peripheral space is radiolucent compared to
adjacent lung
• The lung may completely collapse
• Mediastinal shift in a tension pneumothorax
• Subcutaneous emphysema and pneumomediastinum
(retrosternal space >2.5cm) may also be present

20. Types

21. Visible visceral pleura in
pneumothorax

22. Upright CXR demonstrating right pneumothorax.
Note the clear visceral pleural line (white
arrows) and the lucency in the right chest

23. White arrows indicate the visceral pleural
margin in this expiration view of a patient with
bilateral pneumothoraces

24. Lateral CXR of pneumomediastinum

25. Pneumomediastinum

26. Pneumomediastinum and subcutaneous emphysema
associated with pandemic (H1N1) influenza

27. Tension pneumothorax

28. Tension pneumothorax

29. Emphysema
• Pulmonary hyperlucency
• Low set flat diaphragm
• Increased anterior posterior diameter (barrel
chest)
• Vertical heart

30. PA chest x-ray showing lung hyperinflation
in a patient with COPD (emphysema)

31. Increased AP diameter

32. Giant Bullous
• Bullae is an air-filled space in the lung
parenchyma due to destruction of alveolar tissue,
distal to terminal bronchiole
• Giant bulla = bulla >1/3 of the hemithorax size
and compression of adjacent lung parenchyma
• Bullae + emphysema = bullous emphysema (can
be congenital or complication of COPD)
• Their rupture cause pneumothorax and
atelectasis

33. Cont…
• VLS (vanishing lung syndrome)/Idiopathic
giant bullous emphysema
• Characterized by giant emphysematous bullae,
which commonly develop in the upper lobes
and occupy at least one-third of a hemithorax
• Most affected patients smoke cigarettes

34. Radiographic features
• Can be non-specific
• Bullae occupy > 1/3 of the affected
hemithorax (vary in size 1-20 cm)
• May have compress effect to adjacent
structures (lung parenchyma atelectasis,
invert the ipsilateral diaphragm or
contralateral displacement of the
mediastinum)

35. CXR shows a large lucent area in the right upper
zone extending to the middle zone

36. Cont…

37. Swyer James Syndrome
• Swyer-James-MacLeod syndrome /Bret
syndrome, is a rare lung condition that
manifests as unilateral hemithorax lucency as
a result of postinfectious obliterative
bronchiolitis
• It typically follows a viral respiratory infection
such as adenoviruses or Mycoplasma
pneumoniae infection in infancy or childhood,
and post-transplant patients

38. Radiographic features
• Hyperlucency of the involved lung or lobe
• Decreased vascularity
• Small hilum
• Decreased volume of the involved lung or lobe
• Air trapping on the expiratory radiographs

40. Inspiratory and expiratory CXR

41. Foreign body aspiration
• Foreign body radiopaque in 6-20%
• Obstructive emphysema/induced
hyperinflation (check valve effect) - expiratory
CXRs are more sensitive
• Atelectasis
• Pneumonia

42. X-ray chest shows a radio-opaque foreign body
(piece of sharpener blade) inhaled accidentally
by a 3-year-old child

43. Increased Lt lung volume and hyperlucency, and
mediastinum shift to the right on expiratory CXR

44. Cont…

45. Cont…

46. Large pulmonary embolus
• Dyspnoea, chest pain, and haemoptysis have
been described as a classic triad in PE
• Westermark's sign: regional oligaemia
• Fleishner sign: enlarged pulmonary artery (20%)
• Hampton hump: peripheral wedge of airspace
opacity
• Pleural effusion (35%)
• Knuckle sign

47. Cont…

48. Cont…

49. Other radiological features of PE

50. Cont…

51. Mastectomy
Hyperlucent left lung compared to right because of
the reduced soft tissue

52. Mastectomy

53. Poland syndrome
• It’s a rare birth defect characterized by
underdevelopment or absence of the chest
muscle (pectoralis) on one side of the body,
and usually also webbing of the fingers
(cutaneous syndactyly) of the ipsilateral hand

54. Poland syndrome

55. Cont…

56. References;
• Chest Radiology the Essentials 2nd Edition
• A-Z of Chest Radiology 2007
• Radiopaedia
• Medscape
• Google images

57. Thank you for your
attention!