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What are causes of artifactual unstructured interstitial pattern, and how can you eliminate them when trying to rule in disease?
- underexposure: if you can visualize the thoracic vertebrae well, it is appropriately exposed
- expiration rads: cranially displaced diaphragm and increased contact between cardiac silhouette and diaphragm means it was probably taken during exhalation
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What are the most common causes of non-cavitary structural interstitial patterns? (4) What are some less common causes? (6)
- Primary lung tumor
- Pulmonary metastases
- Granulomas (mycotic pneumonia)
- Thoracic wall lesion- not within lungs, take multiple views to eliminate this possibility
- Less common: traumatic bulla, hematoma, abscess, cyst, mucus in bronchus, lymphosarcoma (uncommon)
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Describe the radiographic appearance of pulmonary metastases. (3)
- non-cavitary (usually) unstructured interstitial pattern
- multiple, round nodules of various sizes
- usually in middle to peripheral aspects of lungs
- [more common than primary lung tumors]
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Describe the radiographic appearance of mycotic pneumonia. (3)
- Disseminated structural interstitial pattern (milliary if nodules are very small)
- nodules are usually the same size
- frequently accompanied by tracheobronchial lymphadenopathy
- [Blasto, Histo, Coccidomycosis]
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Describe the typical radiographic appearance of a primary lung tumor. (4)
- structured interstitial pattern
- usually solitary mess lesion
- usually arise in the periphery
- may be cavitated if communicating with a bronchus
- [bronchogenic carcinomas most common]
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What are 4 other radiographic DDx for a primary lung tumor?
- metastatic tumor
- pulmonary granuloma
- pulmonary abscess (esp if cavitated)
- traumatic cyst (area of lung full of blood- should have Hx of trauma)
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What are the most common differentials for a cavitary structural interstitial pattern? (3) What are some less common causes? (5)
- Paragonimiasis
- Abscess
- Bulla
- Less common: primary lung tumor, pulmonary mets, mycotic granuloma, cyst, bronchiectasis
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Describe the typical radiographic appearance of a pulmonary abscess. (3)
- structured interstitial pattern, often cavitated
- focal, walled-off
- chronic- discrete mass, acute- irregularly margined
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Describe the typical radiographic appearance of a pulmonary bulla. (3)
- cavitated structured interstitial pattern
- spherical, radiolucent area(s)
- smooth, thin-walled
- [congenital, traumatic, rarely infectious]
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What artifact mimics an unstructured interstitial pattern?
underexposure
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How do you differentiate between an unstructured interstitial and an alveolar pattern?
- if you can see the blood vessels around each bronchus- UNSTRUCTURED INTERSTITIAL
- if you cannot see the blood vessels- ALVEOLAR
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What are the differentials for unstructured interstitial and alveolar patterns? (5)
- blood (contusions, hemorrhage)
- pus (aspiration, bronchopneumonia, septic)
- water (cardiogenic or non-cardiogenic edema)
- absence of air (atelectesis- expiration or pleural dz)
- less commonly cells
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Describe "disease in transition".
as bacterial infection worsens, starts with unstructured interstitial pattern that progresses to alveolar pattern; as the lung lobe then recovers, it transitions from alveolar pattern to an unstructured interstitial pattern then back to normal
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What is "geriatric thorax"?
- old-age change
- mild fibrosis, severity depending on amount of pollutants inhaled throughout life, scarring from old lesions
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Describe the radiographic appearance of cariogenic pulmonary edema in dogs. (3)
- unstructured interstitial early, alveolar late/ severe
- secondary to left heart failure- signs of HF (enlarged left heart, rounded cardiac silhouette, enlarged pulmonary veins)
- hilar and perihilar location
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Describe cardiogenic pulmonary edema in cats. (3)
- can look like anything, does not follow typical peri-hilar distribution
- very irregular distribution pattern
- mainly look for cardiac changes
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What are causes of non-cardiogenic pulmonary edema? (7)
- neurologic (head trauma, seizure, electric shock)
- severe allergic reaction
- advanced uremia
- pancreatitis
- irritating inhalants
- drowning
- radiation damage
- [overall, very uncommon]
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Describe the radiographic appearance of non-cardiogenic pulmonary edema.
- distribution is generalized (compared to cardiogenic edema), commonly more peripheral
- heart and pulmonary vein size is normal
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What are potential causes of localized interstitial patterns on thoracic radiographs? (6)
- Partial lobe collapse
- Contusions
- Hemorrhage
- Pulmonary embolism (can also have completely normal looking rads- CT is better)
- Bronchial FB
- Disease in transition
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What are potential causes of localized alveolar patterns on thoracic radiographs? (7)
- Bronchopneumonia
- Edema
- Hemorrhage
- Collapsed lobe (airway obstruction or pleural effusion)
- Primary lung tumor
- Pulmonary metastasis
- Pulmonary infarct
- [remember: exhalation is a type of atelectasis...this is why we take rads on full inspiration]
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Describe the different potential appearances of atelectasis on radiographs.
- Unstructured interstitial pattern most common (esp if only a little of the gas is removed from the lobe)
- Alveolar pattern also possible (esp if all or most of the air is removed)
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What are potential causes of atelectasis? (3 general, 6 specific)
- Incomplete aeration: film made during expiration, prolonged recumbency
- Airway obstruction: internal blockage (FB), external compression (tumor)
- Increased intrapleural pressure: pneumothorax, pleural effusion
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How might pulmonary hemorrhage appear radiographically?
- interstitial or alveolar
- look for other signs of trauma (as trauma is the most common cause....coagulopathy also possible)- rib fractures, pleural effusion, neumothorax, diaphragmatic hernia
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What are some causes of generalized alveolar pattern on thoracic radiographs? (5)
- severe bronchopneumonia
- severe edema
- severe pulmonary contusions
- near-drowning
- smoke inhalation (as in house fire, not cigarette smoke)
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What are the possible radiographic appearances of bacterial pneumonia? (3)
- early- unstructured interstitial pattern, later- alveolar pattern [once you start treatment and it starts resolving, goes back to interstitial]
- bronchial pattern- if spread via airways, lobar sign
- hematogenous spread- patchy, multifocal distribution around vessels
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What are the most common locations for bronchopneumonia and aspiration pneumonia? (3)
- [cranioventral lung lobes]
- right cranial lung lobe
- right middle lung lobe (ESP WITH MEGAESOPHAGUS- most common location for aspiration pneumonia with megaesophagus)
- left cranial lung lobes
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How does aspiration pneumonia appear radiographically?
- unstructured interstitial pattern or alveolar pattern
- depends on the amount of fluid aspirated and the nature of the aspirated material
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The distribution of aspiration pneumonia depends on...
- patient position at time of aspiration
- passive aspiration--> right cranial and right middle lobes most common
- forceful aspiration--> right caudal most common
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What are the causes of a bronchial pattern on thoracic radiographs? (4)
- bronchial mineralization
- allergic bronchitis
- chronic bronchitis
- peribronchial cuffing (esp with bronchopneumonia)
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Describe allergic bronchitis in cats? (4)
- feline asthma
- peribronchial infiltrate of eosinophils and mononuclear cells
- if severe, can get interstitial edema
- if chronic, can get permanent interstitial fibrosis
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What are the causes of viral bronchitis in dogs and cats?
- Dogs- tracheobronchitis
- Cats- upper respiratory disease
- [not usually seen radiographically unless complicated by bacterial infection]
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What are the pathological aspects of bronchiectasis?
- loss of normal bronchial tapering
- changes in bronchial epithelium, mucus characteristics, ciliary function--> these lead to predisposition for chronic bacterial infections
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It is common to have __________ with bronchiectasis because...
chronic bacterial infections/ bronchopneumonia; changes in bronchial epithelium and mucociliary elevator.
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What are causes of diffuse hyperlucency on thoracic radiograph? (5)
- overexposure
- hypovolemia
- air trapping
- emphysema (usually accompanied by bronchial thickeing)
- overinflation (increased tidal volume, upper airway obstruction, iatrogenic)
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What are causes of focal pulmonary mineralization? (6)
- bronchial mineralization
- pulmonary osteomas
- granulomas
- histoplasmosis
- primary lung tumor
- aspirated barium sulfate
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What are causes of diffuse pulmonary mineralization? (4)
- hyperadrenocorticism (cushings)
- hyperparathyroidism
- chronic uremia
- idiopathic
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How many radiographs are usually needed to make a complete thoracic series on an adult horse?
usually 4
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Describe bacterial pneumonia in large animals. (4)
- usually bilateral
- ventral distribution most common
- interstitial or alveolar pattern
- abscesses/ granulomas more common than in small animals
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You see multiple, "fluffy" soft tissue opacity masses that are sometimes cavitated in the lungs of a foal; top differential?
Rhodococcus pneumonia
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Describe COPD (heave's) in horses. (4)
- Radiographic abnormalities only seen in advanced disease
- air trapping- you can see this by making inspiration and expiration projections (will look the same because gas is not leaving the lungs, hence "trapped")
- reticulated interstitial pattern
- +/- bronchiectasis
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How does hypovolemia appear radiographically? (3)
- pulmonary vessels very small
- lack of vascular markings
- microcardia
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