thoracic us cu - for proceedings · pneumothorax •curtain sign •free gas moves ventrally during...
TRANSCRIPT
Claire Underwood MA VetMB PhDSenior Lecturer in Large Animal Diagnostic Imaging
The University of Queensland
Thoracic Ultrasound
Presentation overview
1. Optimising the image
2. Basic technique
3. Advanced technique
4. Disease examples
Optimising the image: Creating an image
• Ultrasound waves• Reflected
• Absorbed
• Scattered
• Transmitted
• Returning waves received by transducer, machine creates an image based on intensity and timing of returning waves
Machine Settings: Frequency
•Higher frequency, better axial resolution, • More attenuation – less depth penetration
•Scan at the highest frequency possible for the required depth
1.5‐5 MHz 5‐8.5 MHz 7.5‐22MHz 5‐7.5 MHz
Equipment for Equine use
• Curvilinear, microconvex and linear probes
1.5‐5 MHz 5‐8.5 MHz 7.5‐22MHz 5‐7.5 MHz
Machine settings: Focus
• Lateral resolution is optimised at the focus depthBest quality image often obtained with just 1 focal zone
Machine settings
• Gain
• Depth
Machine settings: Time Gain Compensation
• Compensates for attenuation of the ultrasound waves asthey travel to increased depths
• must be continually adjusted during a scan in order to obtain the bestimages
• If your machine has an ‘optimize image/ update but’ should be neutral before you press this button. Then adjust after if necessary
Patient preparation
• Best images obtained by• Clipping
• Washing with soap and water
• Wipe with alcohol
• Liberal application of coupling gel
Patient Preparation
• Clip: 17th ‐2nd intercostal spaces•Wash, alcohol, gel
• Sedation usually not required
Equipment
• Range of transducers needed if significant pathology• 7.5‐15 MHz for superficial lung pathology
• 2.5‐5.0 needed for mediastinum or deeper lung pathology
• Linear or curvilinear footprint fits best between ribs
• Rectal probe can be used for superficial lung and ribs
2.5‐5 MHz 5‐8.5 MHz 7.5‐15 MHz 5‐7.5 MHz
Basic Thoracic Ultrasound
Equipment
• Range of transducers needed if significant pathology• 7.5‐15 MHz for superficial lung pathology
• 2.5‐5.0 needed for mediastinum or deeper lung pathology
• Linear or curvilinear footprint fits best between ribs
• Rectal probe can be used for superficial lung and ribs
2.5‐5 MHz 5‐8.5 MHz 7.5‐15 MHz 5‐7.5 MHz
Basic scan technique• 17th ‐2nd intercostal spaces• Label images
• Scan from dorsal to ventral
• Transducer selection
Basic quick scan techniqueAdults:
• Cranioventral caudal to heart fluid • Dorsal‐ free gas
Foal:• Entire thorax
Image orientation
Normal Appearance of Lung and Pleura
• Normal lung• Visceral pleura hyperechoic• Glides smoothly againstparietal pleura with respiration
• Reverberation artifacts
fat
Rib vs lung
Abnormal findings:Comet Tail Artifacts
• Interruption of normal aeration at the surface
• Non‐specific
• Significance depends on history, PE, clinical pathology
Fluid
• Check image quality!
• Ventral up to the same level across the thorax
• Confirm with multiple transducers
Fluid
• Check image quality!
• Ventral up to the same level across the thorax
• Confirm with multiple transducers
• Assess• Echogenicity
• Presence of fibrin
• Free gas
Pericardial Diaphragmatic Ligament
•Normal pleural reflection seen when there is pleural effusion
•Hypoechoic strand in caudoventral thorax
•Should not be mistaken for fibrin
Non‐aerated lung
• Hypoechoic/ anechoic
• Pattern• Ventral
• Diffuse focal areas
• Lung vs fluid
Non‐aerated lung
• Hypoechoic• Compression atelectasis
• Consolidation
• Hepatised lung
• Necrotic lung/Abscess
Pneumothorax
• Curtain sign• Free gas moves ventrally during inspiration
• Easiest to see with pleural fluid (hydropneumothorax)
• Without pleural fluid• Comet tail artifacts or lung consolidation aid identification of lung echo
• Gliding sign is absent in free gas• Scan dorsal to ventral looking forbreak in gas echo
Rib Fractures•Ultrasound often superior to radiography for identifying rib fractures
• Scan in 2 perpendicular planes from dorsal to ventral
•Discontinuation of hyperechoic bony echo•Displaced or non‐displaced
•Overlying hematoma or abscess
Advanced thoracic ultrasound
Basic scan technique• 17th ‐2nd intercostal spaces• Label images
• Scan from dorsal to ventral
• Transducer selection
Technique for Cranial Mediastinum
Under triceps musculature• Right side of thorax
• Can image from left if enough pathology to displace heartcaudally
• In horse’s axilla, 3rd intercostal space • Leg forward• Angle towards opposite point of shoulder
Through the triceps musculature
Sonographic Appearance of Mediastinum
• Cranial Mediastinum• Can often see lung through triceps musculature
• Presence of fat is a normal finding: homogeneous, hypoechoic
lung
fat
triceps
Abnormal Sonographic Appearance of Mediastinum
• Cranial Mediastinum• Echoic mediastinal septum best seen when fluid present
• Thymus: can be seen in neonates up to 2 year olds, may bedifficult to distinguish from adjacent fat
Cranial mediastinal abscess
• Hypoechoic
• Monitor
• Care! other differentials
• Thymic hyperplasia• Fat• Pulmonary parenchyma
• Pleural effusion
Cranial mediastinal abscess
Non‐aerated lung
• Hypoechoic• Compression atelectasis
• Consolidation
• Hepatised lung
• Necrotic lung/Abscess
Compression Atelectasis
• Compression of lung by fluid, air or abdominal viscera
• Non‐bulging
• Hypoechoic
• Linear air echoes in medium/ larger airways
• Floats in fluid
Pulmonary Consolidation
• Non‐compressed lung• Filled with fluid and cells• Does not float• No air in small airways
• Hypoechoic and wedge‐shaped
Pulmonary Consolidation
•Air bronchograms in larger airways
•Fluid bronchograms => hepatized appearance
Air bronchogram Fluid bronchogram
Severe pulmonary damage/necrosis
• Loss of normal architecture
• Bulging appearance• Gelatinous with respiratory movement
• Hypoechoic to anechoic• Cavitated areas
• Progress to abscess or bronchopleural fistula
Pulmonary Abscesses• Anechoic-hypoechoic cavitated area lacking pulmonary vessels or bronchi• Dorsal hyperechoic gas cap• May be encapsulated• Serial evaluation
Pulmonary Abscesses
6 months later
Specific pulmonary pathologies:Rhodococcus Pneumonia
Rhodococcus Pneumonia
Can also see…..
Prominent bronchointerstitialpattern
Miliaryalveolar/interstitial pattern (rare)
Rhodococcus Pneumonia
RhodococcusPneumonia
• If ARDS, pulmonary edema appears as multiple coalescing comet tails
• May see largecavitated abscesses
Pleuropneumonia
• Characterize and quantify fluid• Identify site for drainage
• Identify necrosis, abscesses, bronchopleural fistula• Affects prognosis and length of treatment (cost)
Pleuropneumonia: Fluid
Echogenicity varies with cellularity, types of cells, amount of protein, and free gas present
Fluid level can be described relative to point of shoulder; monitor fluid accumulation
Pleuropneumonia: Fluid
Gas bubbles from anaerobes, chest tube, or bronchopleuralfistula
Pleuropneumonia: Fibrin
Shaggy or smooth layer of hypoechoic material on parietal and visceral pleural surfaces
Pleuropneumonia: Fibrin Loculations
Lacey fibrin and fluid; lung is tethered to parietal pleura by fibrin strand
Thick coating of fibrin on parietal pleura of thoracic wall and diaphragm with fluid pocket; lung is adhered to diaphragm
Pleuropneumonia: Fibrin Loculations
Bronchopleural Fistula
• Bronchus and pleura communicate
• Creates pneumothorax• Dorsal gas cap
• Gas within fluid• DDx Anaerobic infection/introduced gas from chest tube
Prognosis for Pleuropneumonia
• Survival for fibrinous pneumonia 52%, with loculations 40%, mostreturn to performance if survive
• Survival for anaerobic pneumonia 32‐41%, few return to performance
•Treatment days longer for horses with pleural fluid, fibrin loculations, free gas, necrosis or abscess
Reimer et al JAVMA 1989
Not all sonographic abnormalities are bacterial…
Interstitial lung disease
• Pulmonary fibrosis
• Diffuse granulomatous disease
• Fungal pneumonia
• Viral pneumonia
• Pulmonary edema
• Neoplasia
• Coalescing comet tail artefacts/ multiple hypoechoic lesions in pulmonary parenchyma
• Cannot differentiate using U/S
Interstitial Lung Disease
Pulmonary Edema
• Left heart failure•ARDS• Coalescing comet tail artifacts
Thoracic Neoplasia
•Primary Pulmonary• Granular Cell
•Pleural• Mesothelioma• Carcinomatosis• Hemangiosarcoma
•Mediastinal• Lymphosarcoma• Melanoma• Hemangiosarcoma
Diaphragmatic hernia
Conclusions
• Preparation key
• Basic quick evaluation• Fluid
• Non‐aerated lung
• Pneumothorax
• Thorough thoracic US• Fluid type/ additional pathologies (BPF)
• Consolidation/necrosis/abscess
• Fibrin/ adhesions
• Cranial mediastinum
• Non‐infectious pathologies
• Always consider findings in conjunction with the clinical picture