Thorax Flashcards
Inflammatory Disorders
- Cellulitis
- Abscesses
- Osteomyelitis
Thoracic wall cellulitis or abscess can be seen as a sequela to regional infectious inflammatory disease.
Cellulitis manifests as:
- Thoracic wall thickening
- Associated with a loss of fascial plane definition on unenhanced CT images
- Affected regions moderately to markedly enhance following contrast administration
- Lesion margins are poorly defined
Abscesses typically have:
- A fluid‐attenuating center
- As well as a thick surrounding soft‐tissue rim on unenhanced CT images
- Peripherally enhance following contrast administration
Osteomyelitis of the ribs or sternum usually appears as:
- A mixed destructive and productive lesion on CT images
- With moderate to marked, ill‐defined contrast enhancement
Hiatal Hernia
Hiatal hernias include simple sliding hernias as well as less common paraesophageal hernias. Both dogs and cats are affected, and English Bulldogs and Chinese Shar‐Pei dogs are predisposed. Although hiatal hernias are routinely diagnosed using other imaging techniques, such as fluoroscopy, they are occasionally seen in patients undergoing thoracic or abdominal CT for other reasons.
- The cranial displacement of the cardiac region of the stomach through the esophageal hiatus leads to a characteristic stellate pattern produced by the gastric rugal folds o_n transverse CT images_
- On long‐axis images, the gastroesophageal junction is displaced cranially
Thoracic Wall Penetrating Foreign Body (Canine)
5y FS Pointer cross with abrupt coughing episode while outside 5 months previously. Owners noted a small open wound on the chest wall at that time. Currently has a 5‐day history of dyspnea.
- A short, linear, soft‐tissue attenuating opacity is seen in the region of the left caudal lung lobe on survey radiographs (a: arrowhead).
- A soft‐tissue attenuating, linear foreign body (b: arrow) and a small pneumothorax (b: arrowhead) are seen on transverse CT images.
- The full length of the foreign body is best appreciated on a MIP image oriented in the transverse plane (c: arrowheads).
The foreign body was removed via thoracotomy (d: arrow) and was determined to be a carbon fiber or plastic rod that the dog had impaled itself on 5 months previously.
Thoracic Wall Abscess (Canine)
6y MC Golden Retriever with a fluctuant mass of the left ventral body wall.
- The dorsoventral scout view of the thorax shows a large soft‐ tissue mass arising from the left thoracic wall (a).
- A large, ovoid mass is present on the left ventral body wall, deep to the external abdominal oblique muscles and with encroachment internal to the costal margins (b,c: asterisk).
- The central part measures approximately 15 HU on both unenhanced and enhanced CT images (b,c), and the mass has a thick, peripherally enhancing rim (c).
- There is also evidence of diffuse cellulitis more superficially (b,c: arrowhead).
The mass was surgically drained and found to contain purulent material.
Sternal Osteomyelitis (Canine)
18mo MC Doberman Pinscher. Images a and b represent consecutive transverse images of the cranial thorax ordered from cranial to caudal.
- Unorganized bone destruction involving the second sternabral segment (a–d: arrow- head) is evident.
- A pathologic fracture is also present (c: arrowhead).
- A moderate volume of pleural fluid has collected bilaterally in the dependent pleural space (a,b: asterisks).
Bone biopsy confirmed chronic neutrophilic osteomyelitis, and cytology of the pleural fluid revealed suppurative inflammation.
Rib Chondrosarcoma (Canine)
9y FS Greyhound with a left rib mass. Image b represents a magnification of image a.
- There is a moderately well circumscribed destructive and productive mass involving the ventral aspect of the left seventh rib near the costochondral junction (a–c: arrow).
- The mass causes a focal extrapleural sign at its interface with the left parietal pleural and lung margins (b: arrowhead).
- There is minimal enhancement beyond the bone proliferative margin following contrast administration (d).
Excisional biopsy confirmed high‐grade chondrosarcoma.
Diaphragmatic Hernia (Feline)
10y MC Domestic Longhair referred for a cau- dal thoracic mass.
- An ovoid mass is seen in the caudoventral thorax (a,b: arrow), and continuity of liver vasculature across a small window in the diaphragm verifies hepatic origin.
- Transverse images show the appearance of the abdominal (c) and herniated thoracic (d) components of the liver.
The left medial lobe was determined to be herniated through the diaphragm on surgical exploration.
Hiatal Hernia (Feline)
1.5y MC Domestic Shorthair with an esophageal stricture at the level of the heart base.
- A hiatal hernia (arrow) was seen on a thoracic CT examination acquired to evaluate the stricture.
- Gastric rugal folds are clearly delineated on this contrast‐enhanced image (arrowhead).
Gastroesophageal Intussusception (Canine)
5y FS Keeshond with a 7‐month history of coughing and a left cranial lung lobe mass.
- A tubular soft‐tissue mass is present in the region of the caudal esophagus on survey radiographs (a: arrowheads).
- Although the left cranial lung lobe mass is not clearly delineated, there is increased opacity in the cranioventral thorax.
- The leading edge of a gastric intussusceptum is seen on a transverse CT image (b: arrowhead) and has a striated appearance when viewed in long axis (c,d: arrowheads).
- Image d represents a sagittal plane reformation from more thinly collimated images than image c.
The gastroesophageal intussusception was documented and reduced at the time of left cranial lung lobectomy.
Pneumothorax
Pneumothorax most often results from:
- Penetrating injury of the chest wall
- Disruption of the visceral pleura
- Rupture of peripheral pulmonary bulla or subpleural blebs
- Shear injuries of the lung parenchyma
- Penetrating and migrating foreign bodies
- Necrotizing inflammatory and neoplastic lung lesions
- Occasionally, injury to the trachea or esophagus with concurrent involvement of adjacent mediastinal parietal pleura can result in pneumothorax and pneumomediastinum
Plueral Effusion
Classification & Differentials
Pleural effusions result from a variety of disorders and are classified as:
-
Transudative
- Low cellularity - low, the attenuation of the fluid approaches that of water, and these effusions typically range from 0–30 HU
- R-CHF
- Marked hypoproteinemia
-
Modified transudative (e.g. chylous)
- Usually caused by thoracic duct trauma or a disruption of the hydrostatic gradient between the thoracic duct and cranial vena cava, leading to lymphangiectasia and increased lymphatic permeability
- Mediastinal masses may also occasionally result in a chylous effusion by obstructing lymphatic return through the duct
- The composition of the effusion and its chronic contact with pleural surfaces typically results in a low‐grade sterile pleuritis that in turn leads to pleural thickening that is easily detected on CT images
-
Exudative
- Infectious pleuritis or pyothorax may be due to direct penetrating injury or be a sequela of systemic disease
- CT features descriptive of other effusions described above, infectious pleuritis/pyothorax sometimes has a characteristically sedimentary component of relatively high attenuation due to the settling of solids, exudate inspissation, and inflammatory pleural proliferation.
- Pleural membranes are often markedly thickened and may be highly contrast enhancing.
- Small volumes of free gas may be seen because of the presence of gas‐forming organisms or penetrating injury.
- Rarely, foreign bodies initiating a pyothorax can be seen within the effusion
-
Hemorrhagic
- Frank blood has attenuation of 40–50 HU on CT images, although mixed hemorrhagic effusions may be less dense than this
- Trauma
- Bleeding masses
- Anticoagulant poisoning
- Bleeding diathesis
- Increased vascular permeability of compromised tissue
The volume of effusion is variable and may be diffusely distributed, unilateral, or regionally compartmentalized
CT lymphangiogram
CT lymphangiography
CT lymphangiography is performed to visualize thoracic duct anatomy, to define location and character of chyle leakage, and to preoperatively plan for thoracic duct ligation. Iodinated contrast medium is injected either directly into a popliteal lymph node or into a mesenteric lymph node using ultrasound guidance, and thoracic CT is performed after the thoracic duct is fully opacified. The normal lymphangiogram reveals one or more thoracic duct branches coursing next to the thoracic aorta and entering the cranial vena cava. Near this junction, a variable number of smaller lymphatic branches are seen that connect with the cranial mediastinal lymph nodes.
In patients with thoracic duct injury or obstruction, extravasated contrast medium may be seen dispersing within the mediastinum.
In other patients, a proliferation of many small lymphatic vessels in the cranial mediastinum is indicative of lymphangiectasia from lymphatic flow obstruction.
The transverse view of the thoracic duct on CT images provides a means of accurately determining the number of parallel branches and their location relative to the aorta in anticipation of surgical ligation
Pleural Effusion with Lung Lobe Torsion (Canine)
9y MC Bernese Mountain Dog with hemothorax resulting from heparin administration for an unrelated medical problem.
- The ventrodorsal radiograph reveals pleural effusion and an ill‐defined mass in the region of the right middle lung lobe (a).
- Images b and c are the same images optimized for viewing aerated lung and soft tissues, respectively.
- There is moderate pleural effusion distributed in the dependent part of the pleural space (b,c: asterisk) and an enlarged, malpositioned right middle lung lobe with CT features consistent with lobar torsion (c: arrows).
A right middle lung lobe torsion was confirmed surgically.
Chronic Chylous Pleural Effusion (Feline)
8y FS Domestic Shorthair with 1‐month history of rapidly progressive increased respiratory effort.
- A lateral radiograph (a) reveals a large volume of pleural effusion and rounding of the lung margins consistent with chronic pleural thickening and reduced compliance.
- CT images also document the pleural effusion and restricted pulmonary inflation (b,d–f). A CT image optimized for viewing aerated lung reveals multiple focal regions of atelectasis (d: arrows).
- Contrast‐enhanced images also highlight uniform visceral and parietal pleural thickening and enhancement, all of which are consistent with pleuritis (c,e,f: arrows).
Analysis of fluid from thoracocentesis confirmed chylous effusion. Clinical diagnosis was chronic chylothorax with restrictive pleuritis.
Abnormal Thoracic Duct Lymphangiogram (Canine)
11y Australian Cattle Dog with thyroid carcinoma and associated thrombi involving the left jugular and brachiocephalic veins and cranial vena cava. Images a–c are oriented with the dog in dorsal recumbency.
- Moderate dependent pleural effusion (a: asterisks) and multiple small parallel branches of the caudal thoracic duct are seen (a: arrow) following ultrasound‐guided contrast medium injection into a jejunal lymph node.
- More cranially, extravasated contrast medium surrounds the descending aorta (b: arrow), the brachiocephalic trunk, and the left subclavian artery (c: arrows).
- A sagittally oriented maximum intensity projection (MIP) image (d) reveals widespread extralymphatic dispersal of contrast medium in the cranial mediastinum.
Thrombi were confirmed surgically as the source of lymphatic duct obstruction.
Pleuritis and Pleural Foreign Body (Canine)
2y MC Belgian Malinois.
- Thoracic radiographs revealed a focal left caudal pulmonary infiltrate and pleural fissure lines (a: arrow).
- Thoracic CT confirmed the presence of a small pleural fluid volume (b: arrowheads) and a focal lesion consisting of a peripheral consolidating pulmonary component and an adjacent pleural component (b: arrow).
Presumptive diagnosis was focal foreign‐body pneumonia and pleuritis from migrating plant awn. The diagnosis was confirmed by bronchoscopy and partial lung lobectomy performed 3 days following the CT scan.
Mesothelioma (Canine)
11y FS Golden Retriever with coughing, dyspnea, and weight loss. Representative images include ventral and dorsal recumbent images acquired cranial (a–c) and caudal (d–f) to the heart.
- An ill‐defined mass extends the length of the ventral thorax on the sternal recumbent unenhanced images (a,d: asterisk; d: L = liver).
- A small volume of dependent pleural fluid is also present, which partially obscures the mass.
- The mass is more clearly seen on the dorsal recumbent unenhanced images (b,e: asterisk), and incorporation of adipose tissue contributes to a heterogeneous attenuation caudally (e).
- Comparable contrast‐enhanced images reveal uniform enhancement of the soft‐tissue component of the mass (c,f).
- Dependent pleural fluid is again seen (e,f: arrows).
Cytologic evaluation of the pleural effusion was interpreted as mild mesothelial proliferation. Tissue biopsy of the mass revealed mesothelioma.
Pleural Fibrosis (Canine)
8y FS Shiba Inu with a retrobulbar mass. CT was performed as a metastasis‐screening test.
- Heterogeneous pleural thickening is present involving visceral pleura of multiple lung lobes bilaterally (a,b: arrowheads).
- There is no suggestion of a pleural effusion component, which suggests pleural changes are inactive.
- Pleural thickening was thought to represent residual pleural fibrosis from previous inflammatory disease.
Mediastinal Neoplasia
- Thymoma and other solid neoplasms
- Lymphoma
Thymoma and other solid mediastinal neoplasms
Thymomas are variable in size but can be quite large, occupying a significant volume in the cranial thorax and causing cranial lung lobe displacement and atelectasis as well as displacement of the heart, mediastinal blood vessels, and the cranial thoracic esophagus and trachea. Because of the orientation of the ventral recess of the cranial mediastinum, which is often positioned to the left of midline, large thymomas often extend caudally primarily along the left hemithorax. Thymomas can have a cystic center with a thick and internally irregular parenchymal margin on CT images, and solid components have a moderate to intense heterogeneous pattern of contrast enhancement. Thymomas can also be associated with development of megaesophagus in some patients.
A number of other mediastinal neoplasms have been reported, including thyroid carcinoma, carcinomas of other origin, sarcomas, and round cell tumors. Imaging features of these neoplasms may be similar to those described for thymomas but vary depending on cell type.
An important reason for imaging cranial mediastinal neoplasms is to determine the presence and extent of vascular invasion, which can determine operability and prognosis. With CT imaging, vascular luminal defects representing local tumor extension are best seen on images acquired shortly after contrast administration while intravascular contrast medium concentration is high. However, if images are acquired too quickly, intravascular contrast concentration may be nonuniform because of inadequate recirculation, which can create pseudo‐filling defects. Intraluminal tumors appear as relatively hypoattenuating masses surrounded by hyperattenuating blood (Figures 4.3.10, 4.3.11). Filling defects can also result from tumor‐associated thrombi, which usually cannot be distinguished from tumor invasion.
Lymphoma
Lymphoma in the mediastinum may involve the thymus or the mediastinal lymph nodes, the latter often resulting in marked nodal enlargement with affected lymph nodes retaining their normal shape. Lymph nodes are normally soft‐tissue attenuating on unenhanced CT images and may have a uniform or mildly heterogeneous pattern of moderate contrast enhancement
Paraesophageal Abscess
Paraesophageal abscesses preferentially involve the caudal thoracic esophagus, intimately involve the esophageal wall, and are presumably caused by penetrating foreign bodies. Paraesophageal abscesses are generally well‐delineated, fluid‐filled, spheroid to ellipsoid masses arising in the mediastinum. The esophagus appears as a thin soft‐tissue attenuating crescent associated with part of the abscess margin on transverse CT images. Abscesses are fluid attenuating on unenhanced CT images and peripherally contrast enhance. The flattened esophageal mucosa has a characteristic curvilinear pattern of contrast enhancement conforming to the curvature of the abscess. Additional imaging features associated with mediastinitis may also be present. The adjacent lung lobes can sometimes be atelectatic as a result of encroachment by the mass.
Esophageal Neoplasia
Neoplasia of the esophagus is rare and includes:
- Carcinoma
- Sarcoma (associated with Spirocerca lupi infection)
- Leiomyoma/leiomyosarcoma
- Lymphoma
Imaging features depend on the size and location of the mass. Obstruction may be a sequela with resulting esophageal dilation cranial to site of the neoplasm. Neoplasms may be solid or heterogeneous on CT and MR images and typically appear as an eccentric or circumferential mass. The intensity and pattern of contrast enhancement are variable.
Normal Cranial Mediastinum
CT images are of three different dogs. The cranial mediastinum contains major arteries and veins, sternal and mediastinal lymph nodes, and a variable amount of fat. Normal features include the:
- Cranial vena cava (a–c: large arrowhead)
- Left subclavian artery (a–c: small arrows)
- Brachiocephalic trunk (b,c: large arrow)
- Common carotid and right subclavian arteries (a: brackets)
- Sternal and cranial mediastinal lymph nodes (a,b: small arrowhead).
- The thymus may also be visible in young animals (c: asterisk).
Cranial Mediastinal Cyst (Feline)
17y MC Domestic Shorthair with pelvic mass. The thoracic CT examination was performed for cancer staging.
- There is a well‐defined ovoid mass in the cranial mediastinum (a: arrow).
- The mass is of uniform fluid density, has an average attenuation of approximately 5 HU, and does not enhance following contrast administration (b: arrow).
Mediastinal ultrasonography further documented the presence of a thin‐walled, anechoic cyst (c: arrow).
Mediastinal Hematoma (Canine)
10y MC Golden Retriever with a cranial mediastinal mass discovered on a recent thoracic radiographic examination.
- There is a large, well‐defined, ovoid mass in the cranial mediastinum.
- The mass is heterogeneously attenuating and has a thin peripheral rim of enhancement following contrast administration.
Excisional biopsy revealed a chronic organizing hematoma with necrosis of entrapped adipose tissue. This latter finding explains the heterogeneity of the mass on CT images.
Mediastinal Mycotic Granulomatous Lymphadenopathy (Canine)
4y FS Labrador Retriever with a 1‐week his tory of coughing and fever and a rapid decline in clinical condition.
- The sternal (a: arrow head), cranial mediastinal (a: arrow), and tracheobronchial (b: arrowheads) lymph nodes are markedly enlarged and heterogeneously attenuate.
The dog was confirmed to have a systemic Aspergillus deflectus infection.
Thrombus of the Jugular Vein (Canine)
7y FS Labrador Retriever with thoracic limb lameness and lethargy. Transverse images a–d were acquired through the cranial thorax and thoracic inlet and are ordered from caudal to cranial.
- A cranial mediastinal mass was detected on thoracic radiographs.
- There is a large, well‐defined soft‐tissue attenuating mass in the cranial mediastinum (a: asterisk).
- The mass engulfs the cranial vena cava (a: arrow) and the branches of the brachiocephalic trunk (a: arrowhead).
- Cranial to the mass, the paired brachiocephalic veins are seen, and a large central contrast filling defect is present in the left vein (b: arrowhead).
- Further cranial, the filling defect persists (c: arrowhead) at the level of the convergence of the jugular and subclavian vein (c: arrow).
- Further cranial, the jugular veins appear normal (d: arrowhead).
- The thymoma (e: asterisk) and the intraluminal filling defect (e: arrowhead) are clearly depicted on a dorsal reformatted image.
Fine‐needle aspiration biopsy confirmed a diagnosis of thymoma. The composition of the filling defect was not determined, but it was thought to represent either thrombus or caval invasion by the thymoma.
Esophageal Stricture (Canine)
2y FS Border Collie with regional megaesophagus. Images a–d are ordered from cranial to caudal.
- The cranial thoracic esophagus is markedly enlarged, appears flaccid, and contains a mix of fluid and gas (a,b,e: arrowheads).
- The esophagus contracts and appears smaller in diameter than expected in the midthorax (c: arrowhead).
- The caudal thoracic esophagus appears normal (d: arrowhead).
- No extramural cause for the obstruction was identified on the remainder of the CT examination.
An esophagram and endoscopic examination confirmed an esophageal stricture at the level of esophageal contraction seen on CT (f: arrow).
Paresophageal Abscess (Canine)
5y FS Dalmation with lethargy, vomiting, and respiratory distress. Thoracic radiographs revealed a caudal thoracic mass.
- There is a well‐defined, encapsulated, fluid‐attenuating (approx. 35 HU), ovoid mass within the caudodorsal mediastinum (a: arrow).
- The gas‐containing esophagus is seen as an eccentrically located crescent‐shaped structure adjacent to the mass (a: arrowhead).
- The thick peripheral capsule of the mass moderately enhances following contrast administration, but the central part of the mass remains unchanged (b–d).
- The right middle lung lobe is volume depleted with associated increased attenuation (c: arrowhead).
- The mass is fluid filled and thick walled on ultrasound examination (e).
A definitive diagnosis of chronic encapsulated paraesophageal bacterial abscess was based on excisional biopsy.
Pericardial Neoplasia
Neoplasms that can cause a pericardial mass or hemorrhagic/malignant pericardial effusion include:
- Cardiac hemangiosarcoma
- Chemodectoma
- Mesothelioma
- Lymphoma
- Rhabdomyosarcoma
- Fibrosarcoma
Hemorrhagic pericardial effusion from erosive right atrial hemangiosarcoma is reported to be the most common cause of pericardial effusion in dogs. As with exudative effusions, hemorrhagic and malignant effusions can be highly cellular and will therefore have a density somewhat greater than a transudative effusion on CT images.
The CT imaging appearance of neoplastic peri cardial masses will vary depending on cell type, complexity, and vascularity, but they often appear as mural and/or intraluminal masses that are isoattenuating compared to myocardium and enhance following contrast administra tion.
Cardiac MR has been compared to transthoracic and transesophageal echocardiography for evaluation of pericardial effusion caused by cardiac neo plasia. Cardiac MR did not improve diagnostic accuracy but did yield additional anatomical information. Imaging technique consisted of dark blood, steady‐state free procession cine, unenhanced and contrast‐enhanced T1‐ weighted imaging, and delayed inversion recovery prepped imaging. MR features included mixed T1 inten sity, T2 hyperintense mural masses that variably enhanced following contrast administration.
Peritoneopericardial Diaphragmatic Hernia (Feline)
Adult MC Maine Coon with chronic cough and suspected peritoneopericardial diaphragmatic hernia based on previous thoracic radiographs. Images a and b are at slightly different levels in the sagittal plane.
- Part of the liver is cranially displaced into the pericardial sac, causing encroachment on, and cranial displacement of the heart (a–c: arrow).
- The defect in the diaphragm (b: arrowheads) and characteristic branching hepatic vasculature can be seen (a,c: arrowhead).
Echocardiography confirmed the presence of herniated liver in the pericardial sac.
Pericarditis (Canine)
1.5y FS Chihuahua with acute respiratory distress.
- A moderate pericardial effusion is present, associated with uniform thickening and contrast enhancement of the epicardium (a,b: arrowhead) and pericardium (a,b: arrow).
- The average attenuation of pericardial fluid was approximately 15 HU both before and after contrast administration.
Cytologic analysis revealed marked suppurative inflammation with a mixed population of bacteria. A clinical diagnosis of pericarditis was made, and a partial pericardiectomy was performed.
Normal Cardiac Anatomy
3y F clinically normal Beagle. Images a–i were acquired with contrast primarily in the chambers and vessels of the left side of the heart. Images k–q (next page) were acquired following a delay in which contrast material enhances structures of both the left and right side of the heart. Images a–d and j–l were acquired in the transverse plane and are ordered from cranial to caudal. Images e–f and m–n were acquired in the dorsal plane and are ordered from dorsal to ventral. Image g was acquired in a long oblique plane approximating the long axis of the heart. Images h–i and p–q were acquired in the sagittal plane and are ordered from left to right.
- The left atrium and right ventricle in image q appear to be contiguous as a result of partial volume effect from image collimation and the tangential orientation of the image plane in relation to the myocardial wall.
Pulmonic Stenosis (Canine)
2y M English Bulldog. Sequential sagittal images show the right ventricle (a: RV), the pulmonic valve (a,b: arrow), and main pulmonary trunk (a,b: PT). A marked poststenotic pulmonary arterial dilatation is best seen in image B. Also seen are the descending aorta (a: DA), cranial (c: CrV) and caudal (c: CaV) vena cava, and the right atrium (c: RA). Transverse and dorsal plane images highlight the right ventricle (d–g: RV), pulmonary trunk (e: PT), the right (f: RPA) and left (f: LPA) pulmonary arteries, the ascending (d–f: AA) and descending (d–f: DA) aorta, the right atrium (d: RA), the right auricular appendage (f: RAA), and the left ventricle (g: LV).
- The pulmonic valve appears stenotic (e: arrow), and a poststenotic dilatation of the pulmonary trunk is evident immediately dorsal to the valve.
- Marked right ventricular myocardial hypertrophy is seen in all images.
Right‐to‐left Patent Ductus Arteriosis (Canine)
11mo M Pomeranian with chronic, nonprogressive exercise intolerance.
- A large patent ductus (a–c: arrow) is seen arising from the pulmonary trunk (a–c: PT) and merging with the origin of the descending aorta (a–d: DA).
- The proximal segment of the left pulmonary artery (b,c: arrowhead) can also be seen at its origin from the pulmonary trunk on sagittally oriented images.
- Although the ductus is not seen in image d because of superimposition from the origin of the descending aorta, the division of the pulmonary trunk into the left (d: LPA) and right (d: RPA) pulmonary arteries is clearly seen.
- Right ventricular myocardium (a–c: RVM) is also hypertrophic.
Persistent Right Aortic Arch (Canine)
14mo Cocker Spaniel with chronic regurgitation. Images a and b are from a normal dog and are ordered from cranial to caudal. Images c and d are from the dog with the persistent right aortic arch and are at approximately the same anatomic level as a and b, respectively.
- The cranial thoracic esophagus is markedly dilated with fluid and gas (c: Es)
- The aortic arch (c: AAr) is located to the right of the trachea, causing tracheal displacement and luminal narrowing (c,d: Tr).
- Although the ligamentum arteriosum is not directly identified, its presence is implied by the location of the esophagus (c,d: Es) relative to the aorta (c,d: AAr,AA,DA) and the pulmonary trunk (d: PT) and the presence of megaesophagus cranial to the obstruction.
Left Cardiac Chamber Enlargement from Mitral Valve Insufficiency (Canine)
10y MC German Shepherd cross with lethargy and pleural effusion.
- Left atrial (a,b: LA) and ventricular (a,b: LV) chamber enlargement is evident on enhanced transverse and long‐axis images of the heart.
- Moderate pleural effusion is also present (a,b: asterisk).
Echocardiographic examination confirmed moderate left atrial and ventricular enlargement and mitral valve regurgitation. Although the right atrium and ventricle (a,b: RV) were deemed to be of normal size, tricuspid valvular degeneration was also evident. The cause for pleural effusion was thought to be right ventricular failure.
Hypertrophic Cardiomyopathy (Feline)
8y FS Domestic Shorthair. A computed tomography examination was performed on this cat to evaluate a mediastinal mass and pleural effusion. Hypertrophic cardiomyopathy was previously diagnosed by echocardiography.
- There is moderate generalized cardiomegaly (a–c).
- On contrast‐enhanced images, the left ventricular chamber is small (b,c: LV), and there is marked myocardial hypertrophy of the left ventricular septal and free walls (b,c: arrows), which are hypoattenuating relative to the ventricular chamber.
- A pleural effusion is also present (a–c: asterisk).
Cardiac ultrasound findings were summarized as marked concentric hypertrophy of the left ventricular and papillary muscles.
Presumptive Right Atrial Hemangiosarcoma (Canine)
10y MC German Shepherd cross with 3‐month history of exercise intolerance.
- There is a heterogeneously enhancing mass filling the lumen of the right atrium (arrowheads). Echocardiography confirmed the presence of a right atrial mass with extension into the cranial and caudal vena cava.
- Pleural effusion is also present in the dependent thorax (asterisk).
The mass was thought to represent a right atrial hemangiosarcoma based on imaging appearance and location.
Chemodectoma (Canine)
9y M Rottweiler with recent onset frequent regurgitation.
- There is a large, irregularly margined and mildly contrast‐enhancing mass (a,b: arrowheads) immediately dorsal to the ascending aorta (a,b: AA).
Surgical biopsy of the mass confirmed a diagnosis of malignant carotid body tumor (chemodectoma).
Pulmonary Thromboembolism (Canine)
5y FS Cattle Dog cross with progressive cough following heartworm disease treatment. Images b and c have been reformatted in oblique planes paralleling the path of the right and left pulmonary artery, respectively.
- Contrast‐enhanced CT images acquired during the vascular phase reveal discrete hypoattenuating filling defects within the right (b) and left (c) pulmonary arteries, consistent with chronic pulmo- nary thromboembolism (a–c: arrowheads).
- The dog also had concurrent metastatic carcinoma resulting in multiple pulmonary masses and nodules and thoracic lymphadenopathy (a–c).
Aortic Mineralization (Canine)
8y MC Border Collie. A thoracic CT examination was performed to evaluate the cause of recent‐onset pleural effusion.
- Circumferential mural mineralization of the ascending aorta was seen as an incidental finding (arrowheads).
Aortic Thrombosis (Canine)
11y FS German Shepherd cross with rapidly progressive L4–S2 myelopathy.
- The midabdominal aortic lumen is T1 and T2 hyperintense and markedly and uniformly contrast enhances, indicating blood pooling due to flow obstruction (a–f: arrow).
- Immediately caudally, there is an irregularly shaped intraluminal mass that is of mixed T1 and T2 intensity representing an aortic thrombus (a–c: arrowhead).
Ultrasound confirmed a caudal abdominal aortic flow obstruction that extended to, and included, the trifurcation (g: arrowhead).
Vena Cava Atresia with Aneurism and Thrombosis (Canine)
10mo F English Bulldog with history of collapsing episodes following physical exertion.
- Following contrast administration through a catheter placed in the saphenous vein, contrast medium pools in the caudal abdominal vena cava (a: arrowhead).
- In the mid abdomen, the vena cava diameter is markedly enlarged, and the lumen remains unenhanced (b: arrowhead).
- A large number of distended veins result from venous recruitment as an alternate venous return path (b: arrows).
- Following a short delay, image c was acquired at the same anatomic level as image b, revealing nearly complete obstruction of the vena cava at this level, with only a thin rim of contrast medium visible (c: arrowhead).
- Image d was acquired cranial to images b and c and reveals no demonstrative vena cava at this level.
- Descending aorta (d: arrow), portal vein (d: arrowhead).
- The size of the caval thrombus is best appreciated in image e (arrowheads).
Given the age of the patient and duration of clinical signs, this was thought to represent atresia of the vena cava with secondary thrombosis.
Normal Trachea and Bronchi (Canine)
The normal canine trachea should have a height:width ratio close to 1.0 (a: arrow). Mainstem bronchi should originate symmetrically at the carina (b: arrows). The origin of the lobar bronchi in the normal, well‐inflated lung are easily detected (c: arrowheads), and bronchi can be followed through five or six genera tions, depending on image resolution and image collimation. The normal thoracic trachea can sometimes deviate to the right as a result of displacement by the aorta (c: arrow) or other cranial mediastinal structures. The average normal canine bronchial:arterial ratio is approximately 1.45 and should not exceed 2.0 (d: a = artery; b = bronchus; v = vein).
Bronchial Dysplasia (Canine)
6mo F Miniature Pinscher with chronic cough, exercise intolerance, and recent onset of dyspnea. Images c–e are representative CT images in the cranial (c) and middle (d,e) thorax. Images d and e are at the same level and are lung and soft‐tissue windowed, respec tively.
- The left lung is atelectatic (a,b), but primary and lobar bronchi are air‐filled and clearly delineated (b: arrows).
- Compensatory right lung hyperinflation results in a left‐sided mediastinal shift (b).
- Mainstem bronchi are displaced dorsally and to the left in the cranial thorax (c,f: arrowheads).
- Smaller air bronchograms are present further caudally (d: arrows), and atelectatic lung contrast enhances (e: arrow) indicating unimpeded parenchymal perfusion.
- Evaluation of the entire CT examination revealed that only the right middle lung lobe was inflated.
- The right middle lobar bronchus can be seen (d: arrowhead).
- The mainstem bronchial lumina are malformed and par tially occluded (g).
Microscopic evaluation of surgically excised lung revealed malformation of large and small airways consistent with congenital bronchial dysplasia.
Barotrauma (Canine)
Adult dog with immune‐mediated mega esophagus and pneumonia.
- There is a uniform cuff of perivascular gas surrounding the pulmonary arteries. (a,b: arrowheads).
The dog had been under positive‐pressure ventilation while under anesthesia, which was thought to have caused alveolar or small airway rupture leading to the perivascular gas dissection.
Feline Bronchial Disease (Feline)
6y FS Domestic Shorthair with chronic cough.
- Representative CT images of the middle and caudal thorax are ordered from cranial to caudal and reveal widespread airway thickening (a–c: arrowheads).
- There is also regional consolidation or atelectasis of dependent lung (a: arrows).
Bronchoscopy documented bronchial wall edema, bronchospasm, and copious mucus within lobar bronchi (d). Bronchoalveolar lavage cytology interpreta tion was eosinophilic inflammation with mod erate epithelial hyperplasia.
Feline Bronchial Disease with Luminal Obstruction (Feline)
11y MC Domestic Shorthair with chronic cough. Thoracic radiographs show a heavy generalized bronchial pattern (a,b: arrowheads). There are also multiple pulmonary masses or regions of consolidation, best seen in the right cranial lung lobe (a: arrow).
- On CT images, in addition to documenting bronchial wall thickening, the masses are revealed to be large bronchial luminal concretions of inspissated airway exudates (c,d: arrows), the largest of which involves the right cranial lobe bronchus.
- An arborizing concretion in the right caudal lung lobe typifies the “tree‐in‐bud” pattern (e: arrowhead).
- The bronchial branching pattern is clearly defined on a thinly collimated image (f: arrowhead).
Bronchoscopy findings included mucosal hyperemia and stenosis and occlusion of multiple bronchi. Bronchoalveolar lavage cytology was suppurative inflammation with mild chronic hemorrhage.
Focal Bronchiectasis (Canine)
8y FS Labrador Retriever with prior history of plant awn foreign body pneumonia and a recent history of cough. Ill‐defined alveolar infiltrates are present in the left caudal lung lobe on an initial radiographic examination (a: arrowheads). The CT examination was performed 12 days following the radiographic study, and the dog was on antibiotic therapy during that interval. Image b is a representative 1 mm collimated CT image of the caudal thorax, and image c is a magnified view of image b.
- Regional arborizing bronchial dilation is evident in the periphery of the left caudal lung lobe (b,c).
- Bronchial lumen enlargement is accompanied by bronchial wall thickening, but no significant pulmonary infiltrates or luminal exudates are evident.
Microscopic evaluation following lung lobectomy revealed interstitial fibrosis consistent with resolution of pneumonia. The bronchiectasis was presumed to be an end‐stage result of the previous bronchopneumonia.
Bronchial Foreign Body (Canine)
4y F Bearded Collie with cough and recent‐onset lethargy and fever due to pyothorax. The dog was treated and improved but cough persists.
- Sequential CT images of the right caudal lung lobe show thickening of the caudal lobar bronchus (a: arrowhead) and a complex linear foreign body more peripherally (b: arrowhead).
- The foreign body is soft‐tissue attenuating and is well defined because of surrounding gas.
Surgery revealed an approximately 7 cm long plant fragment, thought to be an evergreen frond that originated in the distal right caudal lobar bronchus, penetrated the pulmonary parenchyma, and terminated in the pleural space. Excisional lung biopsy confirmed chronic catarrhal, suppurative bronchitis, and pleuropneumonia.
Tracheal Osteochondroma (Canine)
2y FS Bernese Mountain Dog with stridor.
- There is a sessile soft‐tissue mass that arises from the ventral tracheal wall and appears to be primarily intraluminal (a: arrow).
- The mass proves to be of mixed soft‐tissue and mineral opacity on unenhanced CT images (b,c) and mildly enhances following contrast administration (d).
- CT imaging confirms the mass is well defined and is restricted to the ventral tra cheal wall.
Bronchoscopic evaluation supports the radiographic and CT imaging findings (e). Biopsy confirmed the mass to be an osteochondroma.
Tracheobronchial Carcinoma (Feline)
11y MC Domestic Shorthair with 2‐month history of weight loss, lethargy, and coughing.
- Volume depletion of the left lung is associated with compensatory hyperinflation of the right lung (a).
- A moderately enhancing soft‐tissue attenuating mass is present at the level of the origin of the left mainstem bronchus (c: arrows) and extends into the right mainstem bronchial lumen (b: arrow).
- The heterogeneous appearance of the atelectatic left lung is due to contrast‐enhanced lung parenchyma surrounding fluid‐filled airways or fluid bronchograms (c,d: arrowheads).
- The intraluminal component of the mass is clearly identified bronchoscopically (e).
The microscopic diagnosis from excisional biopsy was bronchial carcinoma.
Tracheal Lymphoma (Feline)
8y FS Domestic Shorthair with 1‐month his tory of stridor.
- On a CT image cranial to the mass, the trachea has a normal ovoid appear ance and is thin walled (a: arrow).
- Caudally, a poorly defined, moderately enhancing mural mass encompasses approximately 75% of the tracheal wall circumference and distorts the tracheal lumen (b,c: arrows; c is a magnifica tion of b).
A comparable bronchoscopic view of the mass (d) is consistent with the CT findings. Cytologic diagnosis was lymphoma.
Tracheal Malacia (Canine)
9y FS Yorkshire Terrier with previously documented tracheal collapse.
- The caudal cervical tracheal lumen (a: arrow) is flattened and less than 50% of the cross‐sectional area of the midcervical (b: arrow) and intrathoracic (c: arrow) trachea.
Endoscopic examination confirmed dynamic bronchial (d: arrow heads) and tracheal (not shown) collapse.
Lung Lobe Atelectasis (Feline)
4y MC Abyssinian cat with chronic respiratory disease. Images a and b are representative 1 mm collimated transverse images of the midthorax at the level of the left cranial (a) and right middle (b) lobar bronchi, respectively. Image c is an oblique long‐axis reformatted image highlighting the right middle lung lobe.
- The left cranial lobar bronchus is aerated and in its normal position (a: arrow), but the lung lobe is volume depleted and of increased attenuation as a result of atelectasis (a: arrowheads).
- Similar findings are seen involving the right middle lobar bronchus (b,c: arrows) and lung (b,c: arrowheads).
- The oblique view clearly defines the path of the right middle lobe bronchus (c: arrow).
- The intermediate attenuation surrounding the atelectatic right middle lung lobe is pleural/pericardial fat.
Multiple lobe atelectasis was secondary to chronic inflammatory pulmonary disease. Cultures from bronchial secretions documented a diagnosis of Mycoplasma pneumonia.
Emphysema (Feline)
1.5y Domestic Shorthair with respiratory distress and radiographic evidence of pneumothorax.
- There is evidence of bilateral pneumothorax and multiple focal areas of atelectasis.
- Aerated lung appears somewhat more lucent than expected given the severity of the pneu- mothorax, and peripheral parenchyma attenuation averaged below −925 HU.
Other specific morphologic features of emphysema were not seen on CT images, but the gross postmortem image of the lungs reveals pronounced emphysematous changes and bullae in multiple lung lobes (c: arrowheads). Microscopic features were consistent with congenital terminal bronchiolar dysplasia leading to emphysema and bulla formation.
Right Middle Lung Lobe Torsion (Canine)
4y F Afghan Hound with chylous pleural effusion and increasing respiratory effort. Images d and f are lung and soft‐tissue windowed images, respectively, acquired at the level of the right middle lung lobe bronchus. Image e is a magnified view of image d.
- There is moderate pleural effusion (a–c) and increased right lung lobe density and volume (c: arrows) on survey thoracic radiographs.
- The right middle lobar bronchus tapers abruptly near its origin (d,e: arrow), consistent with lung lobe torsion.
- Right middle lobe volume is increased because of congestion but is necrotic centrally with a characteristic emphysematous appearance (f: arrows).
- Although contrast medium was not administered, torsional vascular occlusion would most likely prevent contrast enhancement of the affected lung lobe.
- On ultrasound examination, the lung lobe is surrounded by hypoechoic fluid and is partially aerated centrally (g).
At the time of surgery the devitalized lung lobe had a hepatized appearance (h). Right middle lung lobe torsion was confirmed and lobectomy was performed. Microscopic findings were consistent with widespread infarction due to vascular compromise.
Interstitial Pneumonia (Feline)
12y FS Ragdoll with progressive respiratory signs.
- Radiographic findings include diffuse bronchointerstitial infiltrates that coalesce to alveolar infiltrates ventrally (a: arrowheads) and marked bronchiectasis (a: arrow).
- CT images confirm the presence of generalized bronchiectasis and alveolar infiltrates involving the left cranial, right cranial, and left and right caudal lung lobes (b–d).
Bronchoalveolar lavage revealed moderate suppurative inflammation without evidence of infectious agents. Postmortem examination documented bronchiectasis and severe, diffuse and acute interstitial pneumonia with fibrin exudation, alveolar histiocytosis, and septal fibrosis (e). Infectious agents were not detected on either routine or special stains.
Eosinophilic Bronchopneumopathy (Canine)
4y MC Rottweiler with 3‐month history of cough and recent progression to dyspnea and tachypnea, which has been unresponsive to cough suppressants and antibiotics. Image b is representative of the caudal thorax in a lung window, and image c is a contrast‐enhanced image at approximately the same level as image b.
- Radiographs revealed opacification of the accessory and dependent regions of the caudal lung lobes, consistent with consolidating alveolar infiltrates or pulmonary masses (a).
- CT images reveal pulmonary masses in the accessory and dependent regions of the caudal lung lobes (b: asterisks).
- Ground‐glass to alveolar infiltrates are also present in the nondependent regions of the caudal lung lobes (b: arrows).
- Patent airway lumina are evident within the masses in image b, and a complex grape cluster appearance in image C is indicative of additional thick‐walled, fluid‐filled airways incorporated within consolidated lung parenchyma.
Lung biopsy revealed severe, diffuse, chronic eosinophilic bronchitis with eosinophilic granulomas. Microbial cultures were negative, and the dog responded to immunosuppressive doses of steroids but eventually developed severe bronchiectasis. (Same dog as in Figure 4.5.10 with end-stage bronchiectasis.)
Endogenous Lipid Pneumonia (Feline)
9y Domestic Shorthair with respiratory distress following thoracotomy and lung lobectomy for removal of a lung tumor.
- There is a diffuse reticulated interstitial to alveolar pattern throughout all lung fields (a,b).
- Average lung attenuation was approximately −250 HU.
- A right‐ sided pneumothorax is present as a sequela of right caudal lung lobectomy (a).
Postmortem examination revealed severe diffuse lipid pneumonia characterized by flooding of alveoli by large numbers of macrophages containing lipid droplets, confirmed by Oil Red O staining. There was also extensive pleural and septal fibrosis. Review of lung tissue from the lung lobectomy performed 6 days prior to postmortem examination showed no evidence of alveolar histiocytes. In this patient, the endogenous lipid pneumonia was thought to be associated with acute respiratory distress syndrome following thoracotomy.
Necrotizing Pleuropneumonia (Canine)
12y FS Golden Retriever being treated for pneumonia and pneumothorax. Thoracostomy catheters were placed prior to acquiring the imaging studies. Representative CT images (b,c,e) are ordered from cranial to caudal. Image f represents a thinly collimated magnification of image c.
- Radiographs revealed consolidating alveolar infiltrates in multiple lobes (a), which were more pronounced in the dependent regions of the lung (best seen on lateral radiographs, not included here) and consistent with bronchopneumonia.
- There are generalized interstitial infiltrates with ground‐glass appearance in all visible lung lobes (b,c,e: black arrow), which coalesce into alveolar infiltrates in dependent regions of the lungs (b,c,e: black arrowheads).
- Mild pneumothorax is present bilaterally (c: white arrows).
- The right thoracic wall emphysema is a sequela of thoracostomy catheterization.
Pleural fluid cytology was interpreted as marked suppurative inflammation, and microbial culture yielded large numbers of hemolytic E. coli. Gross postmortem examination revealed lung discoloration and volume loss with palpable regions of consolidation (d).
Foreign Body Pneumonia (Canine)
3y FS German Shorthair Pointer with chronic cough and more recent onset of weight loss and lethargy.
- Interstitial to alveolar infiltrates are present involving multiple lung lobes on thoracic radiographs (a), and there is an ill‐defined mass in the periphery of the left caudal lung lobe (b: arrowheads).
- Peripheral consolidating alveolar infiltrates with air bronchograms are present in multiple lung lobes on CT images and appear to be centered on distal airways (d: arrowheads).
- Ground‐glass opacity surrounds the larger lesions (e: arrowheads).
The peripheral and multifocal distribution of alveolar infiltrates is characteristic of pneumonia induced by migrating plant awn foreign bodies lodged in distal airways. Multiple plant awns were detected (c: arrowhead). Representative image of a bronchoscopically retrieved plant awn (from a different patient) (f). Bronchoalveolar lavage revealed septic suppurative inflammation with intracytoplasmic organisms.
Pyogranulomatous Pneumonia (Feline)
13y FS Domestic Shorthair with progressive cough and weight loss. Images b and e are magnifications of a and d, respectively.
- Radiographs reveal widespread, irregularly margined and coalescing nodules of varying size in all lung lobes (a,b).
Bronchoalveolar lavage cytology was interpreted as pyogranulomatous inflammation. The underlying cause of the pyogranulomatous pneumonia was not determined but thought to be infectious. Tests for feline coronavirus, Toxoplasma gondii, Dirofilaria immitis, Mycoplasma, bacteria, and fungal organisms were all negative.
Coccidioides immitis Mycotic Pneumonia (Canine)
7y MC Dachsund with progressive increase in respiratory effort, weight loss, and diminished activity of 1‐month duration.
- There is consolidation of the entire left lung and coalescing alveolar infiltrates in the right lung on thoracic radiographs (a,b).
- On CT images, the central tracheobronchial lymph node is markedly enlarged (c: arrow), causing compression and abaxial displacement of the mainstem bronchi (c: arrowheads).
- The left lung is consolidated with persisting air bronchograms (d).
- Multifocal, partially coalescing, and poorly margined alveolar infiltrates are present in the right lung lobes and appear to be centered on airways in many instances (e).
On bronchoscopic examination, the carina has an abnormal blunted shape, and mucosa appears inflamed with regions of frank hemorrhage (f). Bronchoalveolar lavage cytology revealed pyogranulomatous inflammation, and a Coccidioides immitis titer was positive. Postmortem examination confirmed disseminated pyogranulomatous pneumonia with numerous intralesional fungal spherules.
Cavitary Bronchoalveolar Carcinoma (Canine)
11y FS Shepherd/Doberman Pinscher cross with no clinical signs referable to pulmonary disease.
- A well‐demarcated cavitary mass is seen in the right caudal lung lobe on survey radiographs (a: arrow).
- The cavitary nature of the pulmonary mass is also evident on CT images (b: arrow), and the presence of a meniscus indicates that part of the soft‐ tissue attenuating component is fluid that has distributed in the dependent part of the mass (b: arrowhead).
Pathologic diagnosis following lung lobectomy was bronchoalve- olar carcinoma.
Bronchoalveolar Carcinoma (Canine)
11y M Australian Shepherd with no clinical signs referable to pulmonary disease.
- There is a large well‐demarcated soft‐tissue mass in the dorsal aspect of the left caudal lung lobe on survey radiographs (a,b: arrows).
- The soft‐ tissue attenuating mass is also seen on rep- resentative CT images (c,d: large arrows).
- Some airways are left relatively undisturbed (c: arrowhead), while others are compressed and displaced (d: arrowheads).
- Ground‐glass opacities are present at the periphery of the mass (c: small arrow).
Pathologic diagnosis following lung lobectomy was locally inva- sive well‐differentiated bronchoalveolar car- cinoma. The ground‐glass infiltrates seen on CT images likely reflected the local tumor invasion.
Histiocytic Sarcoma (Canine)
10y M Labrador Retriever with increased respiratory effort and cough. Representative CT images are ordered from cranial to caudal.
- There are multiple well‐demarcated bronchocentric soft‐tissue attenuating pulmonary masses of variable size seen in the left cranial (a,b: arrows) and right middle (c: arrows) lung lobes.
- There is also partial atelectasis of the dependent part of the right cranial and middle lung lobes, likely associated with lateral recumbency during transport to the CT room while under anesthesia (a,c: arrowheads).
Postmortem examination confirmed a diagnosis of histiocytic sarcoma.
Pulmonary Fibrosis (Canine)
9y MC Doberman Pinscher with a right caudal lung lobe adenoma.
- There is a moderate unstructured interstitial pattern in the caudodorsal lung field on thoracic radiographs (a).
- CT images of the caudal lung lobes reveal unstructured and linear regions of increased attenuation that are located primarily in the subpleural regions of the lung (b,c).
- A thin‐walled bulla is also present in the right caudal lobe (b) and is considered an incidental finding.
Right caudal lung lobectomy was performed to remove the pulmonary mass (not shown). Pathologic diagnosis of the unstructured and linear hyperattenuating lung lesions described above was marked multifocal to coalescing chronic inter- stitial fibrosis. The inciting cause for the fibrosis was not determined but was thought likely to be due to a previous inflammatory insult.
