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F. CXR-AIRWAYS, LUNG PARENCHYMA, PLEURA

F. CXR-AIRWAYS, LUNG PARENCHYMA, PLEURA

1. Pleura

  • Pneumothorax: visceral pleural line parallel to thoracic cavity, absence of lung markings (vessels).
    • Views to exaggerate pneumothorax: erect CXR in full expiration, lateral decubitus with suspect side up.
    • On supine film: deep sulcus sign, sharply outlined diaphragm, hyperlucent upper abdomen.
    • Imposters: scapula margin, clothes, wrinkles, lines/tubing, bullous disease. Do not confuse pneumothorax (thin margin, no vessels present beyond it, deep sulcus sign in large pneumothoraces) with skin folds (thick margins, vessels present beyond the margin).
    • Treatment: < 2cm - observe, > 2cm - aspirate. However, small pneumothoraces are improtant if the patient is on positive pressure ventilation as they can grow.

Types of pleural pathology:

  • Haemo-pneumothorax: air-fluid level, no meniscus visible.
  • Tension pneumothorax: ipsilateral diaphragm deprssed, mediastinal contents pushed contralaterally.
  • Pleural effusion: look for the meniscus sign. Collects in the costophrenic angles. If supine - veiling opacity. Empyema can organize into loculations.
  • Sub-pulmonic pleural effusion: with the diaphragm rising up.
  • Apical pleural thickening: focal area of thickening over the apex, can be heavily calcified.
  • Pleural plaques: similar to density of bone. Common posteriorly, laterally & inferior 1/3 of thorax. Metastasis - less dense than bone.
  • Empyema: enhancement of the pleural space & gas within it. Drain the pus before you investigate further with CT.
  • Collapse (associated with large pneumothorax): opacity with no air bronchograms, negative mass effect (displacement of fissure, hilum, mediastinum, elevation of hemidiaphragm, decrease in spacing between the ribs).

2. Lung parenchyma

Collapse:

  • Any collapse will cause negative mass effect, leading to negative mass effect (displacement of fissure, hilum, mediastinum, elevation of hemidiaphragm, decrease in spacing between the ribs).
  • It is difficult but important to differentiate between collapse and consolidation. Both do not occur simultaneously!
  • Lobar collapse: opacity with no air bronchogram, negative mass effect with shift of fissure, hilum, hemidiaphragm.
  • Lung collapse: opacity with whiteout, negative mass effect with mediastinal shift to contralateral side.

Airspace opacities:

  • Differentiate between increased interstitial marking vs. airspace opacification.
  • Consolidation: alveolar pathology (cloud-like/cotton-candy shadowing); no volume loss, air bronchogram, homogeneous airspace opacity. Clears by 6 weeks, if not suspect malignancy.
  • Pulmonary oedema: increased interstitial markings (too many squiggly lines); airspace opacification.
  • Upper lobe venous diversion: (looks like a man putting up his hands saying “Help!”) Process: cardiomegaly ⇒ UL venous diversion ⇒ interstitial oedema ⇒ alveolar oedema ⇒ pleural effusion.
  • Note that interstitial oedema occurs in the peripheries.

Lung volume abnormality:

  • Emphysema: 1. pulmonary hyperinflation, 2. narrowed mediastinum, 3. prominant pulmonary vessels, 4. Reduced peripheral pulmonary vessels, 5. distance to hila/base.

Pathology:

  • Left ventricular failure: 1. increased interstitial marking, 2. Airspace opacification, 3. bilateral pleural effusions.
  • Collapse: 1. CA 2. Mucus plugging. Golden sign of S ⇒ central bronchogenic CA + lobar collapse.
  • Mimics of pulmonary oedema: idiopathic pulmonary fibrosis (honey-combing on CXR or CT), sarcoidosis (bilateral perihilar opacities).


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REFERENCES

1. Goodman, L. and Felson, B. (2015). Felson's principles of chest roentgenology. 3rd ed. Philadelphia, PA: Elsevier, Saunders.
2. Dähnert W. Radiology Review Manual. LWW. (2011) ISBN:1609139437. Read it at Google Books - Find it at Amazon
3. Elizabeth Puddy, Catherine Hill; Interpretation of the chest radiograph, Continuing Education in Anaesthesia Critical Care & Pain, Volume 7, Issue 3, 1 June 2007, Pages 71–75, https://doi.org/10.1093/bjaceaccp/mkm014

Ⓒ A. Manickam 2018

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