Pulmonary Parenchyma
Pulmonary Parenchyma Erin Porter, DVM, DACVR Objectives Familiarize ourselves with normal lung anatomy and how to evaluate the lungs radiographically Know where to locate and assess pulmonary arteries and veins Be able to identify the different pulmonary patterns Know common differentials for basic pulmonary patterns Quality Control • Always start with diagnostic quality thoracic radiographs (RL, LL, VD or DV) Quality Control • Always take 3 views • L and R Lat are minimum exam • Lesions in downside lung disappear - even if quite large. 4 4 Pulmonary Parenchyma Three components contribute: A - Air within the small airways and alveoli B - Blood vessels A C - Airway walls • Canine and Feline B – 6 lobes C Lung Lobe Anatomy Dorsal View Lung Lobe anatomy RCa RCr A RCr LCr Cr Seg RM LCr Cr Seg RM LCa A LCr Cr Seg A LCr Cr Seg RCa LCa General Divisions Caudodorsal Cranial Cranioventral Caudal Bronchial Anatomy R Lat Trachea Lt Cranial segment Right Cranial L Lat Lt Caudal segment Pulmonary Vessels • Distinguish lobar arteries and veins – Arteries are dorsal and lateral – Veins are ventral and central (medial) • Cranial lobar vessels: best visualized on laterals • Caudal lobar vessels: best visualized on DV • Size – Lateral – head of 4th rib – VD or DV – cross 9th rib • Must understand pulmonary circulation – Veins toward left heart – Arteries away from right heart Pulmonary Vasculature: Size Left Lateral Projection RIB 4 Proximal 1/3 Pulmonary Vasculature Dorsoventral Projection RIB 9 Pulmonary Vasculature Enlarged pulmonary arteries and veins (overcirculation) • Left to right shunting defect • Arteriovenous fistula • Overhydration • CHF - cats 13 13 Pulmonary Vasculature Enlarged pulmonary arteries • Heartworm disease • Pulmonary hypertension 14 14 Pulmonary Vasculature Enlarged pulmonary veins • Left heart failure 15 15 Pulmonary Parenchyma What to Look For…. • Opacity (Increased or Decreased) • Number Location – Which lung lobe is affected? (focal, multifocal, generalized) – Distribution within each lobe • (peri-hilar, caudodorsal, ventral, cranioventral) • Mediastinal shift • Pulmonary Pattern Differential Diagnosis List – Severity based on all clinical information 1 6 Opacity Increased Opacity – What causes increased pulmonary opacity? • Soft tissue in the air spaces – – – – Blood Pus Water Cells • Enlarged vessels – Pulmonary venous or arterial distention – Pulmonary overcirculation • Mineral – Bronchial mineralization 17 Opacity Decreased – Focal • Regional oligemia: PTE • Bronchial dilation: bronchiectasis • Pulmonary lucency: bulla, pneumatocoele, cavitated lesion – Generalized • Small vessels, heart, CVC: Hypovolemia • Increased thoracic volume: Hyperinflation/air trapping 18 18 Decreased opacity 19 19 Roentgen Signs How to describe any abnormalities….. • • • • • • Location Number Size Shape Margin Opacity Distribution Location/Distribution is FAR more important than the type of pattern in developing a concise, accurate DDx list. 20 Location In general, think… edema bronchopneumonia 2 1 Location Pulmonary Edema (non-cardiogenic) 22 Location Pulmonary Edema (cardiogenic) 23 Mediastinal Shift • Ipsilateral Shift (heart shifted toward lesion) • Contralateral Shift (heart away from the lesion) Pulmonary mass Atelectasis Pulmonary Patterns Four Basic Patterns –Alveolar –Bronchial –Structured interstitial (nodules or miliary pattern) –Unstructured interstitial Other Possibilities –Mass –Vascular Pattern 2 5 Pulmonary Patterns Disease in Transition • Almost all patterns are mixed! • Evaluate relative contributions of each patterns - which is the worse? • Changes over time! 2 6 Pulmonary Patterns Interstitial and alveolar patterns are related • Similar list of differential diagnoses • Attempt to classify differentials by location • • • • • Cranioventral: Bronchopneumonia Caudodorsal: Pulmonary Edema Ventral: Aspiration pneumonia Multifocal: Contusions, Fungal Pneumonia, Mets Diffuse: Lymphoma • Pattern Reflects SEVERITY • Interstitial Alveolar • Which way is it going? Recheck Exam!!!! 27 Alveolar Pattern 5 aspects… • • • • Uniform soft tissue opacity Air bronchograms (±) Border Effacement of heart/diaphragm Will NOT see pulmonary vessels or the serosal walls of the airways • Lobar sign ****Not all have to be present (3/5) 2 8 Alveolar pattern Air Bronchogram • Air filled bronchus surrounded by soft tissue opaque lung Air bronchogram Lobar sign Lobar Sign • Abnormal lung border contrasted with normal lung border • The disease is respecting the lobar border! 2 9 Bronchial Pattern • Major bronchi are normally visible in a central (hilar) position • Always look in the periphery!! • Thickened walls are abnormal (>2 to 3 mm) • RINGS and LINES • Usually generalized disease 3 0 Bronchial Pattern • Small bronchi are visible • "Rings" – End on small airways • "Lines" – Airways moving from central to peripheral position 3 1 3 2 Bronchial Pattern Common Differentials • • • • • Bronchial Wall Mineralization (dogs) Chronic Bronchitis Infectious, allergic, irritant Asthma (cats) Eosinophilic Bronchopneumapathy (dogs) Heartworm disease (in combination with other findings) Bronchial Mineralization 3 4 Structured interstitial • Nodules – Can be subtle – Look over diaphragm and vertebrae • Fake-outs – end on vessels – cutaneous nodules – nipples – ectoparasites – osteomas 3 5 Structured Interstitial Common Differentials • Metastatic Neoplasia • Fungal Pneumonia • Often + TB lymphadenopathy • Benign Pulmonary Osteomas Structured Interstitial 37 Milliary Pattern DDx: • Fungal pneumonia • Metastatic neoplasia 38 Unstructured Interstitial Radiographic Finding: • Increased soft tissue opacity that obscures pulmonary vascular margins • Never mild! • Diagnosis by rule out • Expiration most common cause 3 9 Alveolar and Unstructured Interstitial Common Differentials • • • • • Atelectasis Aspiration pneumonia Bronchopneumonia Pneumonitis Hemorrhage/contusions • Pulmonary edema • Cardiogenic • Non-cardiogenic • Neoplasia • Lymphoma (unstructured interstitial) • Masses (alveolar) Aspiration Pneumonia 41 Beware of Fake Outs – Expiration versus Inspiration – Obesity • Overall increased interstitial opacity secondary to scatter radiation. – Pleural and mediastinal fat accumulation. 42 42 Intra-thoracic Fat Feline – Subpericardial fat can mimic cardiomegaly 43 43 Lateral recumbency (atelectasis) 44 44 Pulmonary Masses • • • • Greater than 3 cm Roundish, uniform soft tissue opacity Air bronchograms (±) Border Effacement with Cardiac Silhouette and Diaphragm • Lobar sign • Can cavitate – Gas filled • Can mineralize (dystrophic) 4 5 Pulmonary Masses 46 Questions?
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