RESPIRATORY SYSTEM. System examination

Transcription

1 RESPIRATORY SYSTEM System examination Remove pluck. Cut on the medial side of the mandibles close to the bone. Remove the tongue manually and pull down and back. Hyoid bone should be cut with shears to release the tongue and larynx for removal. The tongue and thymus are removed (asterix). Leave the heart attached for best evaluation of vessels supplying the respiratory tract. Leave the lungs attached to the diaphragm as a fixation point to enable the trachea and oesophagus to be pulled tight when opening. The larynx and trachea are opened with shears through the roof of the larynx between the arytenoid cartilages (arrows) and examined. Image = opened larynx and trachea of bovine calf with multiple Lumpy skin disease (Capripox) nodules in the larynx and trachea. 1

2 Open the rest of the trachea, bronchial bifurcation and secondary bronchi cutting through the dorsal soft tissue between the free ends of the tracheal rings with scissors. Image = Bovine with heartwater (Ehrlichia ruminantium) frothy oedema fluid in distal trachea. Incise the tracheobronchial lymphnode (arrow) and examine. Image = enzootic pneumonia in a pig (Mycoplasma hyopneumonia) with hemorrhagic tracheobronchial lymphadenitis. Diaphragm attachment of the heart and lungs, is resected and the heart and lungs turned over to examine the vessels of the lung for emboli (arrow). Remove heart (see cardiovascular system). Image = Babesiosis in a cat (Babesia felis) 2

3 Lungs are palpated to evaluate for nodules, masses or areas of consolidation. Remember the 3 P s of pneumonia evaluation palpation, palpation, palpation!!! Impression smears of the cut surface of any presumed pneumonic focus are made and stained with Diff-Quick. The presence of bacteria, inflammatory cells and phagocytosis of bacteria by inflammatory cells, are hallmark features of a bacterial pneumonic process. Cytological impression smear from the lung of a dog with Nocardia asteroids. Note the free lying and phagocytosed bacteria (arrows) and cellular component of macrophages and individual neutrophils. 3

4 Examine distribution of lung lesions o Diffuse affects the entire lung (80-90%) or a multifocal major part of it. o Locally extensive large confluent area/s involing adjacent lobules. o Focal or Multifocal Examine the nasal cavity by splitting the skull open longitudinally along the nasal septum to reveal the nasal turbinates. Image = opened nasal cavity of a horse with strangles (Streptococcus equi subspp equi), retropharngeal lymphnode abcess (arrow) 4

5 Comparative Pathology Avians: Syrinx (arrow) should always be examined for evidence of any necrotic plugs. Common site for necrotic plaques of respiratory aspergillosis. Air sacs thoracic and abdominal. Thoracic airsacs (asterix) and abdominal airsacs (diamonds) frequently involved with important respiratory pathogens. Image = fungal plaques in abdominal airsacs (Aspergillus spp). Equines: Open and examine the guttural pouch. These diverticulae of the auditory tubes are commonly involved in respiratory infections due to their ommunication with the nasal passages. Image = fibrinonecrotic empyema due to strangles (Streptococcus equi subspp equi). 5

6 Sample collection a. Histopathology Include sample of tracheobronchial lymphnode. Collect samples from affected as well as unaffected from the various lobes. Always a good procedure to include material close to the main-stem bronchus as well as the periphery of the lung tissue.tissue blocks should not exceed 1cm 2 dimensions to ensure good fixation. If trachea is sampled, cut out individual tracheal rings for fixation. Collect rings from proximal, mid and distal trachea. Immerse in 10% buffered formalin. Ensure that there is adequate formalin for fixation. Guide = 1 part tissue to 9 parts formalin. 6

7 b. Microbiology (Bacterial / Fungal culture, Virus Isolation, PCR) Aseptic collection of lung tissue from affected areas into sterile containers. Always consider collection of the tracheobronchial lymphnode in a separate sterile container. Never mix multiple organs in a single container. In avians tracheal swabs and air sac swabs are commonly employed for culture and PCR analysis due to the nature of important avian respiratory pathogens (Mycoplasmas, respiratory viruses, fungi). Further Reading 1. Evans, H E & delahunta Guide to the dissection of the dog. 6 th edn. Elsevier Saunders, St Louis. 2. GlaxoSmithKline Respiratory Collection Protocol of the laboratory dog. Charles River Laboratories. 3. King J M, Roth, L, Dodd, D C & Newson, M E The Necropsy Book. 4 th edn, Charles Louis Davis Foundation of Comparative Pathology, Washington. 4. Maxie, M G Pathology of Domestic Animals. 5 th edn. Saunders Elsevier, St Louis. 5. McGavin, M D & Zachary, J F Pathologic Basis of Veterinary Disease. 4 th edn. Mosby Elsevier, St Louis. 6. Shivaprasad, H L Pathology of Birds An overview. Charles Louis Davis Foundation of Comparative Pathology, Washington. 7