Thoracic boundaries

image of Thoracic boundaries
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The thoracic region encompasses vital anatomical structures related to respiration, circulation, digestion and locomotion. Assessing thoracic abnormalities via medical imaging is imperative for accurate diagnosis and optimal case management. This chapter includes a comprehensive overview of normal thoracic anatomy and common congenital, traumatic, infectious, metabolic and neoplastic diseases affecting the thoracic viscera, skeleton, muscles, nerves and body wall in dogs and cats. Relevant imaging features, clinical significance and treatment considerations are discussed for various thoracic disorders.

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8.1 Normal lateral thoracic radiograph of a 1-year-old cat. The costal arch is formed by the union of the costal cartilages of the 9th–11th ribs. The costal cartilages of the 12th ribs do not connect with the costal arch and the 13th ribs lack costal cartilage; both sets are floating ribs.
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8.2 Normal transverse computed tomography image of a mid-thoracic vertebra in a dog. Each rib articulates with the vertebrae at two locations. On each side (bilaterally), the costovertebral joint lies between the rib head and costal fovea, and the costotransverse joint lies between the rib tubercle and transverse process.
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8.3 Normal lateral radiographs of the sternum in (a) a dog and (b) a cat. The sternum comprises eight bones. The cranial sternebra is the manubrium and the caudal is the xiphoid process. The canine sternum is more curved than the feline sternum.
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8.4 Normal lateral radiographs and transverse CT images of the vertebral column in (a) a dog and (b) a cat. The arrangement of the T12 and T13 rib pairs relative to the vertebral bodies and the size of the psoas muscles (*) in cats is such that the caudal lung tips may not extend all the way to the vertebral column on lateral radiographs (arrowed). This normal feline appearance should not be mistaken for a sign of pleural fluid.
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8.5 (a) Lateral and (b) ventrodorsal thoracic radiographs of an adult cat with multiple abdominal masses due to biopsy-confirmed abdominal carcinoma. Unrelated to that diagnosis, the costodiaphragmatic recesses are asymmetrical, the right 12th and 13th ribs articulate with the right side of the T12 vertebral body, the left 12th and 13th ribs are fused and articulate with the left side of the T12 vertebral body, and there is ultrasound-confirmed herniation of the right kidney cranial to the diaphragm (arrowed). This diaphragmatic hernia is presumed to be the result of abnormal development of the diaphragm and adjacent vertebrae, causing enlargement of the space dorsal to the lumbocostal arch. The diaphragmatic margin is normally free ventral to the psoas muscles; here, the pleura encroaches on the renal capsule through this space dorsal to the diaphragm.
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8.6 Normal thoracic radiographs of a dog. (a) On the right lateral view, the right diaphragmatic crus is cranial. (b) On the left lateral view, the left diaphragmatic crus is cranial. (c) On the VD view, both the crura and the cupula are visible. (d) On the DV view, the diaphragm is visible as a single dome. Note the gastric fundus is immediately caudal to the left diaphragmatic crus. On the VD and DV views, the locations of the costodiaphragmatic recesses are bilaterally symmetrical.
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8.7 Normal VD thoracic radiographs of (a) a dog and (b) a cat with poor lung inflation. Note the ribs are angled caudally compared with Figure 8.6cd , which show well inflated lungs with ribs perpendicular to the vertebral column. In (a), the right lung is less inflated with increased opacity. In (b), the pulmonary blood vessel margins are poorly defined.
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8.8 Lateral neck radiograph of a Bulldog with a transitional cervicothoracic vertebra that was an incidental finding of minor consequence. The C7 vertebra has a pair of small ribs that are incompletely fused with the first pair of thoracic ribs.
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8.9 VD radiograph of the thoracolumbar junction in a dog with a transitional thoracolumbar vertebra. At T13, the right rib is normal in size and shape, and the left rib is thick, appearing like a long transverse process. The T13 vertebral body is also abnormal (butterfly vertebra).
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8.10 VD thoracic radiograph of a dog with a solitary aggressive bone lesion of the left third rib. The dorsal aspect of the rib is absent due to severe osteolysis and is surrounded by a soft tissue tumour with indistinct margins.
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8.11 (a) Lateral and (b) DV thoracic radiographs of a cat with nutritional secondary hyperparathyroidism, scoliosis and lordosis. There is generalized osteopenia with reduced contrast between bone and soft tissue, reduced corticomedullary distinction and thin bone cortices. The thoracic vertebral column is misaligned, with right and ventral convexities.
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8.12 Lateral radiograph of a cat with severe diffuse osteosclerosis (presumed osteopetrosis). The ribs and vertebral bodies maintain a normal shape and are of homogeneous mineral opacity with absent corticomedullary distinction and trabecular markings.
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8.13 Lateral thoracic radiograph of a dog with degenerative remodelling. The costal cartilages are mineralized, and the costochondral junctions have irregular well defined margins. No rib lysis is detected. The dog also has ossifying pulmonary metaplasia, another degenerative change. All these findings are incidental and of minor consequence.
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8.14 VD thoracic radiograph of a dog with a wide left fourth intercostal space secondary to a chronic displaced rib fracture and lung herniation into the body wall.
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8.15 DV thoracic radiographs of (a) a cat with severe bilateral pneumothorax secondary to generalized restrictive pleuritis and (b) a Dobermann with left-sided congestive heart failure. Both animals have a pathological ‘barrel chest’ conformation due to maximal expansion of the thoracic cavity by different mechanisms.
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8.16 DV radiograph centred on the diaphragm of an obese cat with substantial bilaterally symmetrical fat within the body wall. The opaque body wall musculature is laterally displaced but remains well defined from the fat.
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8.17 Normal lateral thoracic radiograph of a dog with obliquely oriented skin folds in the ventral part of the thorax. In this example, the skin folds produce multiple alternating opaque and lucent bands that are positive and negative summation shadows of the skin with the rest of the thorax. These lines may be distinguished from intrathoracic abnormalities because they extend beyond the margins of the thoracic cavity (they extend caudally over the abdomen and cranioventrally over the axilla).
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8.18 Lateral radiograph of a cat centred on the xiphoid region. Wet hair from ultrasound gel summates with the ventral thoracic and abdominal fat and could be mistaken for body wall swelling or peritoneal fluid but extends beyond the skin margin.
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8.19 DV thoracic radiograph of a dog with an acute traumatic left rib fracture. Associated with the fracture, there is a focal soft tissue swelling that displaces the visceral pleura medially and has oblique margins that gradually taper towards the body wall (i.e. an extrapleural sign).
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8.20 (a) Lateral and (b) VD thoracic radiographs of a dog with extensive body wall gas from a tracheal rupture secondary to severe bite wounds. The gas extends throughout the superficial fascia of the neck and thorax, visceral fascia of the ventral neck, and mediastinum.
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8.21 (a) Left lateral, (b) right lateral and (c) VD thoracic radiographs of a dog with bite wounds. (a, b) On the lateral views, body wall gas creates confusing apparent lung pathology (arrowed). (c) This can be accurately localized to the left body wall on the orthogonal view.
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8.22 (a, b) Transverse thoracic CT images of a cat with major trauma causing herniation of body wall fat into the right pleural cavity through a large rent in the thoracic body wall (arrowed). The cat also has a tension pneumothorax (*), rib fractures (not shown), and gas dissection through the superficial and deep fasciae of the body wall.
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8.23 Lateral thoracic radiograph of a cat with nine sternebrae (rather than eight). This finding is an incidental congenital developmental anomaly of minor consequence.
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8.24 (a) DV and (b) VD thoracic radiographs of a dog. In (a), bilateral displacement of the diaphragm is suspected, but diaphragm location is normal in (b).
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8.25 Normal (a) right lateral and (b) DV thoracic radiographs of a Dachshund. Note the short vertebral bodies, barrel chest conformation and internal curvature of the rib cage at costochondral junctions.
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8.26 (a) DV thoracic radiograph and (b) dorsal CT image of a Bulldog with incomplete fusion of the T1 spinous process (spina bifida occulta).
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8.27 Dorsal CT image (bone window) of a Bulldog with sternal dysraphism, a midline defect. This patient also had pulmonic stenosis but no other midline fusion defect.
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8.28 (a) Lateral and (b) VD radiographs of the thoracolumbar vertebral column in a neurologically normal French Bulldog with short, wedge and butterfly-shaped vertebrae, narrow intercostal spaces, fusion of spinous processes and mild scoliosis.
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8.29 Lateral thoracic myelogram of a dog with congenital developmental kyphosis. The mid-thoracic vertebral column has malformed vertebral bodies and a focal dorsal convexity with attenuation of contrast material within the subarachnoid space at the level of the lesion, consistent with extradural spinal cord compression.
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8.30 Lateral radiographs of the thoracolumbar vertebral column in (a) a normal dog and (b) a Pug with articular process dysplasia. In (b), from T10–T12, the caudal articular processes are small or absent and the intervertebral disc spaces are narrow ventrally.
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8.31 Lateral thoracic radiograph of a young Labrador Retriever with pectus excavatum. The congenital developmental sternal malformation caused mild displacement of the cardiac silhouette without cardiovascular dysfunction.
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8.32 Lateral thoracic radiographs of a 13-year-old Yorkshire Terrier with progressive dyspnoea for 3 months that acutely decompensated due to laryngeal obstruction (epiglottic retroversion, swelling). (a) Thoracic radiographs on the day of decompensation demonstrated acquired pectus excavatum. (b) The sternum was normal 3 days prior.
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8.33 Lateral radiograph centred on the xiphoid region in a French Bulldog with pectus carinatum (ventral displacement of the caudal sternum).
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8.34 (a) Lateral cervicothoracic radiograph and (b) myelogram of a dog with neurological deficits due to ‘Wobbler’ syndrome (cervical spondylomyelopathy). At T1–T3, the vertebral canal is narrow with diffuse attenuation of contrast material in this region, consistent with vertebral stenosis. Vertebral stenosis may cause extradural spinal cord compression or predispose the spinal cord to injury following minor trauma.
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8.35 (a) Lateral and (b) VD cervical radiographs of a juvenile cat with mucopolysaccharidosis. The vertebral bodies and arches are thick, the vertebral endplates are irregular, the intervertebral disc spaces are narrow and the articular process joints are poorly defined due to bridging bone.
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8.36 VD thoracic radiograph focused on the right costal region in a dog with recent vehicular trauma. The dog has multiple acute traumatic rib fractures, body wall gas and lung contusion. The rib fractures are subtle, arranged in a line, and characterized by discontinuous margins and abnormal angulation.
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8.37 Lateral thoracolumbar radiographs of a dog with acute trauma. (a) Slight radiographic underexposure allows for detection of the fracture line in the T13 spinous process. (b) Slight obliquity and increased exposure better demonstrates the reduced size of the T13–L1 intervertebral foramen and collapse of the T13–L1 intervertebral disc space, suggestive of annular rupture and possible intervertebral disc herniation.
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8.38 Lateral thoracic radiograph of a cat with a presumed (unwitnessed) traumatic sternal dislocation.
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8.39 Lateral thoracolumbar radiographs of (a) a normal juvenile dog and (b) a juvenile dog with a T13 compression fracture following vehicular trauma. (b) The T13 vertebral body is short due to overriding fracture margins, and the ventral cortical margin is irregular and discontinuous.
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8.40 VD thoracic radiographs centred on the (a) left and (b) right costal regions in a dog with unilateral trauma. There is body wall asymmetry, with (a) the left body wall having normal thickness and well defined musculature. (b) The right body wall is swollen with wispy soft tissue within the fat and poorly defined musculature.
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8.41 (a) Lateral and (b) VD trunk radiographs of a dog with traumatic herniation of intestine into the right thoracic body wall, which is severely swollen. Within the thoracic cavity, the right hemithorax has diffuse soft tissue opacity that was not present on referral radiographs from the same day and, thus, was attributed to progression of traumatic lesions, though not further localized to the pleural cavity or lung. Note the left humeral fracture on the lateral view.
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8.42 (a) VD and (b) lateral thoracic radiographs of a dog with multiple traumatic fractures at various stages of healing due to repeated episodes of abuse. The acute fractures have well defined angled margins (arrowed). The chronic (healing) fractures show bridging callus (arrowheads).
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8.43 (a) Transverse and (b) dorsal back CT images (bone window) of a dog with a T13 vertebral body fracture. CT is more sensitive than radiography for subtle bone fractures that may determine whether the vertebral column is likely to be stable. CT can also provide information about neural injury, although MRI is more accurate.
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8.44 (a) Lateral and (b) VD thoracic radiographs centred on the left costal region in a cat with chronic cough secondary to severe lower airway disease. Note the chronic remodelling rib fractures.
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8.45 Lateral radiographs of the thoracic vertebral column in two dogs with discospondylitis. The imaging signs can range from (a) obvious to (b) subtle and are characterized by lysis of adjacent vertebral endplates, an active periosteal response and variable intervertebral disc space width.
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8.46 Lateral radiograph of the sternum in a German Shepherd Dog with locally extensive polyostotic sternal osteomyelitis and sternal dislocation, characterized by lysis and an active periosteal response. This patient also had discospondylitis secondary to aspergillosis (not shown).
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8.47 (a) Lateral and (b) VD thoracic radiographs of a dog with asymmetrical polyostotic aggressive bone abnormalities secondary to systemic coccidioidomycosis fungal infection. The bone abnormalities are consistent with osteomyelitis and are primarily proliferative. Thoracic lymphadenopathy is not detected. On the VD view, the two large cranial abnormalities are associated with an extrapleural sign.
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8.48 VD thoracic radiograph centred on the left costal region of a dog with a solitary primary bone neoplasm that arises from a rib and involves adjacent ribs (locally extensive polyostotic). The neoplasm forms a large mass-like tumour that is centred on the rib, extends medially into the thoracic cavity, extends laterally to form a bulge on the skin surface, and extends cranially and caudally displacing the adjacent ribs. The main rib affected has extensive osteolysis and an amorphous periosteal response. The adjacent displaced ribs are sclerotic or have a periosteal reaction.
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8.49 Lateral radiographs of the thoracic vertebral column in a dog with a solitary primary bone neoplasm that arises from a vertebra. (a) Initially, the abnormality is subtle, mostly affecting the vertebral body and characterized by lysis and poorly defined cortical margins. (b) After 1 year of radiation therapy, the mass is progressive with extensive periosteal proliferation and progressive lysis extending into the vertebral arch, and the vertebral body is short due to a pathological compression fracture. CT confirmed that the neoplasm has spread ventrally into the adjacent lung, causing pneumothorax. Note the contrast with the ventral soft tissue portion of the tumour.
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8.50 (a) Lateral and (b) VD radiographs of the thoracolumbar vertebral column in a dog with a solitary primary bone neoplasm that arises from a vertebra. The neoplasm forms an expansile bone lesion that affects both the vertebral body and arch. Notice the outward displacement and thinning of the cortices with moth-eaten lysis. The vertebral body is also short. (b) Loss of the pedicles can be observed on the VD view.
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8.51 (a) VD and (b) oblique collimated VD thoracic radiographs in a dog with a palpable body wall mass. (a) The full extent of the rib involvement is not appreciated on the VD view. (b) The oblique view reveals that the neoplasm forms a mass-like tumour that extends medially producing an extrapleural sign, causes the skin to bulge laterally, and displaces the adjacent ribs cranially and caudally. In addition, the tumour is characterized as a locally extensive polyostotic aggressive bone lesion. Note the severe lysis and extensive palisading periosteal response that were not apparent on the initial radiograph.
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8.52 A lateral back radiograph in a dog with a pathological compression fracture secondary to a lytic, non-proliferative aggressive bone tumour. The vertebral body is short, which could be confused with a vertebral malformation if the subtle signs of an aggressive bone tumour and fracture were not observed.
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8.53 Orthogonal close-up thoracic radiographs of a dog with (a) pulmonary metastasis characterized by multiple generalized random soft tissue nodules and (b) rib metastasis characterized by a subtle solitary aggressive bone lesion (arrowed). It is important not to mistake the normal costochondral junction (arrowhead) for an expansile bone abnormality.
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8.54 Lateral (a) back and (b) thoracic radiographs in a dog with multiple myeloma. (a) There are numerous moth-eaten lytic defects in the lumbar vertebrae. (b) The findings are more subtle but include moth-eaten lysis of T9, thin cortices in the ribs with heterogeneous trabecular bone and multiple pathological rib fractures with variable signs of healing. (c) The orthogonal view allows further characterization of the rib fractures.
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8.55 Lateral thoracic radiograph of a dog with locally extensive polyostotic aggressive bone lesions involving multiple sequential ribs, due to a large malignant body wall neoplasm that extends into the thoracic cavity, displacing and compressing the cardiopulmonary structures.
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8.56 Lateral thoracic radiograph of a dog that has difficulty swallowing due to a longus colli rhabdomyosarcoma. In the dorsal part of the cranial mediastinum, immediately ventral to the vertebral column, the neoplasm forms a round soft tissue mass-like tumour that summates with the dorsal aspect of the trachea. Bone involvement is not detected. See also Figure 8.58 .
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8.57 Thoracic ultrasound images of a dog with an extensive body wall neoplasm that has pleural extension. The transducer was placed on the costal region. (a) Normal ribs are observed. (b) The neoplasm forms a mass-like tumour in the body wall and causes severe rib lysis and periosteal proliferation. Normal ribs have smooth, concave, hyperechoic margins whereas the mass is characterized by disorganized mineral and soft tissue.
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8.58 Sagittal cervicothoracic CT image of the same dog as in Figure 8.56 . The longus colli mass, which is less discernible on the initial radiograph, is confirmed by contrast-enhanced CT obtained for radiation therapy planning.
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8.59 (a) Lateral and (b) VD thoracic radiographs of a dog with multiple endocrinopathies leading to diffuse osteopenia, pathological fractures and severe narrowing of the intervertebral disc spaces.
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8.60 (a) Transverse and (b) dorsal CT images of the scapular regions of a dog with hypertrophic osteopathy secondary to a thoracic mass (not shown). Both scapulae have bilaterally symmetrical, smooth, continuous periosteal proliferation.
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8.61 Lateral back radiograph of a Dachshund with a calcified T11–T12 intervertebral disc that has herniated dorsally and summates with the intervertebral foramen (arrowed), and several non-displaced calcified discs (arrowheads).
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8.62 (a) Transverse and (b) sagittal back CT images of a dog with intervertebral disc herniation. CT allows for image reconstruction in multiple planes, is more accurate than radiography at identifying disc herniation and more precise for describing the location of displaced disc material, which is necessary for surgical planning. CT is especially helpful when the displaced disc is calcified. MRI is also excellent for evaluating intervertebral disc disease.
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8.63 Sagittal back CT images of a dog with intervertebral disc herniation. Images obtained using (a) a soft tissue and (b) a bone window. CT can provide information about non-mineralized intervertebral disc herniation. There is a difference in conspicuity of the displaced disc material in the two images.
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8.64 Lateral back radiograph of a dog with incidental/minor consequence spondylosis deformans, characterized as a smooth, well defined enthesopathy bridging intervertebral disc spaces. The enthesopathy occurs where the annulus fibrosus attaches to the apposing vertebral bodies.
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8.65 Lateral back radiograph of a dog with incompletely bridging spondylosis deformans and intradiscal vacuum phenomenon, indicative of intervertebral disc degeneration.
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8.66 Lateral back radiograph of a dog with continuous flowing bone across more than four intervertebral disc spaces (consistent with a diagnosis of disseminated idiopathic skeletal hyperostosis) as well as signs of vertebral osteoarthrosis, worse at L2–L3 and L3–L4.
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8.67 (a) Lateral and (b) VD thoracic radiographs of a cat with a solitary cavitated pulmonary mass. (a) The mass partially summates with the diaphragm, signifying its pulmonary origin. (b) The mass produces border effacement with the cranial margin of the diaphragm and could be mistaken for a diaphragmatic mass or abscess.
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8.68 Lateral thoracic radiograph in a dog with pleural and peritoneal (‘bicavitary’) fluid, which causes border effacement of the ventral half of the diaphragm.
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8.69 Right lateral trunk radiograph centred on the diaphragm of a dog with pneumoperitoneum caused by rupture of a large hepatic abscess. The caudal margin of the diaphragm is variably contrasted by a large amount of peritoneal gas. The left diaphragmatic crus is contrasted by gas between the diaphragm and stomach/emphysematous liver (arrowed). The border of the right diaphragmatic crus is effaced by the liver (i.e. normal). The cupula (ventral dome) of the diaphragm is partially contrasted by gas between the diaphragm and liver abscess.
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8.70 Lateral (a, b) preoperative and (c) postoperative trunk radiographs of a dog with chronic diaphragmatic hernia caused by diaphragmatic rupture. (a, b) Preoperatively, there is border effacement of portions of the diaphragm (cranial margin) due to intestinal herniation into the thoracic cavity. There is also severe gastric enlargement due to gastrointestinal obstruction. (c) Postoperatively, the cranial border of the diaphragm is well defined and contrasted by pulmonary gas (i.e. normal).
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8.71 (a) VD, (b) DV, (c) left lateral and (d) right lateral thoracic radiographs of a cat with chronic diaphragmatic rupture. (a, b) The left side of the diaphragm and cardiac silhouette are effaced due to cranial displacement of abdominal viscera and fat into the left pleural cavity. (c, d) The ventral portion of the diaphragm is not detected, and the different soft tissue and fat opacities are more easily discerned; the cardiac silhouette is contrasted by herniated fat in the ventral aspect of the thorax. In (c), the spleen is visible between the cardiac silhouette and diaphragm. In (d), the cardiac silhouette and trachea are dorsally displaced by the herniated content.
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8.72 Thoracic ultrasound images of the same cat as in Figure 8.71 , confirming diaphragmatic rupture by identifying herniation of (a) the pancreas and (b) the spleen within the thorax. Shadowing artefacts from the ribs can also be seen.
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8.73 Ultrasound image of the liver, gallbladder and diaphragm of a dog. In the upper right part of the image (near field), the normal liver, gallbladder (arrowhead), and diaphragm can be identified. The diaphragm is the curvilinear hyperechoic line. In the bottom left part of the image, the liver and gallbladder are artefactually duplicated and displayed in the far field as a mirror image (arrowed).
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8.74 (a) Lateral thoracic radiograph and (b) non-contrast-enhanced thoracic CT image of a dog with a diaphragmatic hernia and unknown history of trauma. (a) The signs of diaphragmatic hernia are subtle and additional testing is needed. Herniated fat in the caudoventral aspect of the thorax produces a vague increased opacity with a distinct oblique cranial border that summates with the heart and lungs. In addition, the cranial border of the diaphragm is defined. (b) CT reveals that fat and small intestine have herniated through a rent in the diaphragm and are in the right pleural cavity adjacent to the heart.
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8.75 (a) Lateral and (b) VD thoracic, and (c) lateral abdominal radiographs of a juvenile dog with vomiting associated with PPDH. The cardiac silhouette is severely enlarged, globoid, and has a heterogeneous opacity due to abnormally located abdominal content, primarily intestines. In addition, the cranioventral margin of the diaphragm is effaced on all views and in the midline in (b). (c) There is reduced abdominal content and the small intestine is enlarged, consistent with obstruction of the small bowel. There is an incidental umbilical hernia (arrowhead) that is of minor consequence. The granular tubular material (arrowed) may be faeces in the colon or foreign material in the small intestine.
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8.76 (a) Lateral and (b) VD thoracic radiographs, and (c) transverse and (d) sagittal contrast-enhanced thoracic CT images (soft tissue window) of a 9-year-old dog with nasal discharge. (a, b) Thoracic radiography was performed to test for pulmonary metastasis, which was negative, and incidentally the diaphragmatic contour was noted to be lobular cranioventrally and in the midline. (c, d) During CT, the abnormal diaphragmatic contour was attributed to congenital PPDH. The liver and gallbladder (*) are in the right ventral aspect of the pericardial sac. The portion of liver within the thorax (arrowed) and the portion of the liver in the abdomen (arrowhead) have normal and comparable contrast enhancement, indicating no vascular compromise.
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8.77 (a) Left lateral, (b) right lateral and (c) DV thoracic radiographs of a Bulldog with a sliding hiatal hernia (type 1). (a) Caudodorsal to the heart and summating with the caudal mediastinum, there is a focal soft tissue opacity with a cranially convex margin. In addition, the oesophageal lumen contains a small amount of gas dorsal to the cardiac silhouette. The soft tissue opacity was attributed to herniation of the stomach through the oesophageal hiatus. (b, c) The hernia was considered sliding or intermittent because the same opacity was not observed on the other views.
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8.78 (a) Transverse and (b) dorsal contrast-enhanced thoracic CT images (soft tissue window) of a cat with a hiatal hernia identified by the intrathoracic location of the stomach (arrowed). The stomach is in the dorsal aspect of the caudal mediastinum and to the left of the aorta. The herniated stomach also displaces the aorta (*) to the right.
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8.79 Lateral thoracic radiograph of an 18-month-old Domestic Shorthaired cat with muscular dystrophy, demonstrating an undulating diaphragm and mild cardiomegaly.
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8.80 (a) Left lateral, (b) right lateral and (c) VD thoracic radiographs of a dog with right phrenic nerve paralysis, indicated by cranial displacement of the right diaphragmatic crus on all views.
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8.81 M-mode ultrasound images of the left diaphragmatic crus using a transabdominal approach. (a) Normal diaphragmatic motion is depicted. (b) Poor and (c) absent diaphragmatic motion are demonstrated, due to phrenic nerve dysfunction.
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