Gamal Rabie Agmy, MD, FCCPProfessor of Chest Diseases, Assiut UniversityERS National Delegate of Egypt
The definition of atelectasis is loss of air in the alveoli;alveoli devoid of air (not replaced).A diagnosis of atelectasis requires the following:1-A density, representing lung devoid of air2-Signs indicating loss of lung volumeAtelectasis
1-Absorption AtelectasisWhen airways are obstructed there is no furtherventilation to the lungs and beyond. In the earlystages, blood flow continues and gradually theoxygen and nitrogen get absorbed, resulting inatelectasis.Types of Atelectasis:
2-Relaxation AtelectasisThe lung is held close to the chest wall because of thenegative pressure in the pleural space. Once thenegative pressure is lost the lung tends to recoil dueto elastic properties and becomes atelectatic. Thisoccurs in patients with pneumothorax and pleuraleffusion. In this instance, the loss of negativepressure in the pleura permits the lung to relax, dueto elastic recoil. There is common misconception thatatelectasis is due to compression.Types of Atelectasis:
3-Adhesive Atelectasis :Surfactant reduces surface tension and keeps thealveoli open. In conditions where there is loss ofsurfactant, the alveoli collapse and becomeatelectatic. In ARDS this occurs diffusely to bothlungs. In pulmonary embolism due to loss of bloodflow and lack of CO2, the integrity of surfactantgets impaired.Types of Atelectasis:
Types of Atelectasis:4-Cicatricial Atelectasis–Alveoli gets trapped in scar andbecomes atelectatic in fibroticdisorders
.5-Round AtelectasisAn instance where the lung gets trapped bypleural disease and is devoid of air.Classically encountered in asbestosis.Types of Atelectasis:
Generalized1-Shift of mediastinum: The trachea and heart gets shiftedtowards the atelectatic lung.2-Elevation of diaphragm: The diaphragm moves up andthe normal relationship between left and right side getsaltered.3-Drooping of shoulder.4-Crowding of ribs: The interspace between the ribs isnarrower compared to the opposite side.Signs of Loss of Lung Volume:
Movement of FissuresYou need a lateral view to appreciate the movement ofoblique fissures. Forward movement of oblique fissure inLUL atelectasis. Backward movement in lower lobeatelectasis.Movement of transverse fissure can be recognized in thePA film.Signs of Loss of Lung Volume:
Movement of HilumThe right hilum is normally slightly lower than the left.This relationship will change with lobar atelectasis.Signs of Loss of Lung Volume:
Compensatory HyperinflationCompensatory hyperinflation as evidenced by increasedradiolucency and splaying of vessels can be seen with thenormal lobe or opposite lung.Signs of Loss of Lung Volume:
Alterations in Proportion of Left andRight LungThe right lung is approximately 55% and left lung 45%. Inatelectasis this apportionment will change and can be aclue to recognition of atelectasis. .Signs of Loss of Lung Volume:
Hemithorax AsymmetryIn normals, the right and left hemithorax are equal in size.The size of the hemithorax will be asymmetrical andsmaller on the side of atelectasisSigns of Loss of Lung Volume:
Signs of Loss of Lung Volume:GeneralizedShift of mediastinum: The trachea and heart gets shifted towards the atelectatic lung.Elevation of diaphragm: The diaphragm moves up and the normal relationship between leftand right side gets altered.Drooping of shoulder.Crowding of ribs: The interspace between the ribs is narrower compared to the opposite side.Movement of FissuresYou need a lateral view to appreciate the movement of oblique fissures. Forward movement ofoblique fissure in LUL atelectasis. Backward movement in lower lobe atelectasis.Movement of transverse fissure can be recognized in the PA film.Movement of HilumThe right hilum is normally slightly lower than the left. This relationship will change with lobaratelectasis.Compensatory HyperinflationCompensatory hyperinflation as evidenced by increased radiolucency and splaying of vesselscan be seen with the normal lobe or opposite lung.Alterations in Proportion of Left and Right LungThe right lung is approximately 55% and left lung 45%. In atelectasis this apportionment willchange and can be a clue to recognition of atelectasis.Hemithorax AsymmetryIn normals, the right and left hemithorax are equal in size. The size of the hemithorax will beasymmetrical and smaller on the side of atelectasis
Atelectasis Right LungHomogenous density right hemithoraxMediastinal shift to rightRight hemithorax smallerRight heart and diaphragmatic silhouette are not identifiable
Atelectasis Left LungHomogenous density left hemithoraxMediastinal shift to leftLeft hemithorax smallerDiaphragm and heart silhouette are not identifiable
Left Lower Lobe Atelectasis• Inhomogeneous cardiac density• Left hilum pulled down• Non-visualization of left diaphragm• Triangular retrocardiac atelectatic LLL
Atelectasis Left Lower LobeDouble density over heartInhomogenous cardiac density Triangular retrocardiac densityLeft hilum pulled downOther findings include:Pneumomediastinum
Atelectasis LeftUpper LobeMediastinal shift to leftDensity left upper lung fieldLoss of aortic knob and left hilarsilhouettesHerniation of right lungAtelectatic left upper lobeForward movement of leftoblique fissure "Bowing sign"
Atelectasis Left UpperLobeHazy density over leftupper lung fieldLoss of left heartsilhouetteTracheal shift to leftLateralA: Forward movement ofoblique fissureB: Herniated right lungC: Atelectatic LUL
LateralMovement of oblique and transversefissuresAtelectasis Right Upper LobeHomogenous density right upper lungfieldMediastinal shift to rightLoss of silhouette of ascending aorta
LateralMovement of oblique and transversefissuresAtelectasis Right Upper LobeHomogenous density right upper lung fieldMediastinal shift to rightLoss of silhouette of ascending aorta
RML AtelectasisVague density in right lower lung field, almost normalRML atelectasis in lateral view, not evident in PA view
Vague density in right lower lung field (almost a normal film).Dramatic RML atelectasis in lateral view, not evident in PA view. Movement oftransverse fissure.Other findings include: Azygous lobe
Atelectasis Right Lower LobeDensity in right lower lung fieldIndistinct right diaphragmRight heart silhouette retainedTransverse fissure moved downRight hilum moved down
Adhesive AtelectasisAlveoli are kept open by the integrity of surfactant. When there is lossof surfactant, alveoli collapse. ARDS is an example of diffuse alveolaratelectasis.Plate-like atelectasis is an example of focal loss of surfactant.
Relaxation AtelectasisThe lung is held in apposition to the chest wall because of negative pressurein the pleura. When the negative pressure is lost, as in pneumothorax orpleural effusion, the lung relaxes to its atelectatic position. The atelectasis isa secondary event. The pleural problem is primary and dictates otherradiological findings.
Round AtelectasisMass like densityPleural basedBase of lungsBlunting of costophrenic anglePleural thickeningPulmonary vasculature curvinginto the densityEsophageal surgical clips
Round AtelectasisMass like densityPleural basedBase of lungsBlunting of costophrenic angle, pleural thickeningPulmonary vasculature curving into the density
BronchiectasisLeft lung atelectasis due to mucus pluggingMucus plugs suctioned with bronchoscopyBronchogram done after bronchoscopySaccular bronchiectasis in bronchogram below
BronchogramBronchograms are rarely done nowadays. The need for itdisappeared with the invention of the fiberopticbronchoscopy and high resolution CT scan. View theseimages to get a greater understanding of a threedimensional view of a bronchial tree..
BronchogramBronchograms are rarely done nowadays. The need for it disappeared with theinvention of the fiberoptic bronchoscopy and high resolution CT scan.
Number:Multiple bilateral cavities would raisesuspicion for either bronchiogenous orhematogenous process. You should consider:Aspiration lung abscessSeptic emboliMetastatic lesionsVasculitis (Wegeners)Coccidioidomycosis, tuberculosis
Location:• Classical locations for aspiration lung abscessare superior segment of the lower lobesposterior segments of upper lobes.• Tuberculous cavities are common in superiorsegments of upper and lower lobes or posteriorsegments of upper lobes.• When a cavity in anterior segment isencountered, a strong suspicion for lung cancershould be raised. TB and aspiration lungabscess are rare in anterior segments. Cancerlung can occur in any segment.
Wall Thickness:• Thick walls are seen in:– Lung abscess– Necrotizing squamous cell lung cancer– Wegeners granulomatosis– Blastomycosis
Wall Thickness:• Thin walled cavities are seen in:• Coccidioidomycosis• Metastatic cavitating squamous cellcarcinoma from the cervix• M. Kansasii infection• Congenital or acquired bullae• Post-traumatic cysts• Open negative TB
Contents:• The most common cause for air fluid level islung abscess. Air fluid levels can rarely beseen in malignancy and in tuberculouscavities from rupture of Rasmussensaneurysm.• A fungous ball should make you consideraspergillosis. A blood clot and fibrin ball willhave the same appearance.• Floating Water Lily: The collapsed membraneof a ruptured echinococcal cyst, floats givingthis appearance.
Lining of Wall:The wall lining is irregular and nodular inlung cancer or shaggy in lung abscess
Evolution of Lesion:Many times review of old films to assess theevolution of the radiological appearance ofthe lesion extremely helpful. Examples• Infected bullae• Aspergilloma• Sub acute necrotizing aspergillosis• Bleeding from Rasmussens aneurysm in atuberculous cavity
Associated Features:Ipsilateral lymph nodes or lyticlesions of the bone is seenwith malignancy
BullaDefinition•Thin-walled–less than 1 mm•Air-filled space•In the lung> 1 cm in size and up to 75% of lung•Walls may be formed by pleura, septa,or compressed lung tissue.•Results from destruction, dilatation andconfluence of airspaces distal to terminalbronchioles.
•Bullous disease may be primary or associatedwith emphysema or interstitial lung disease.• Primary bullous lung disease may be familialand has been associated with Marfans, EhlersDanlos, IV drug users, HIV infection, andvanishing lung syndrome.•Bullae may occasionally become very largeand compromise respiratory function. Thushas been referred as vanishing lung syndrome,and may be seen in young men.
Pneumatocele is a benign air containing cyst of lung, withthin wall < 1mm as bulla but with different mechanism Infection with staph aureus is the commonest cause ( lesscommon causes are, trauma, barotrauma) lead to necrosisand liquefaction followed by air leak and subpleuraldissection forming a thin walled cyst.
•Honeycombing is defined as multiple cysts < 1cm in diameter,withwell defined walls, in a background of fibrosis, tend to formclusters and is considered as end stage lung .•It is formed by extensive interstitial fibrosis of lung with residualcystic areas.
A cyst is a ringshadow > 1 cm indiameter and up to10 cm with wallthickness from 1-3mm.