Thoracic cavity

Question 1

According to Frykfors von Hekkel 2020 in Vet Surg what factors were associated with increased mortality following thoracic dog bite wounds? What factors were associated with likelihood of exploration and length of hospitalization?

Answer 1

Presence of pleural effusion and positive bacterial culture.

Presence of pneumothorax, flail chest and rib fractures were associated with likelihood of exploration.

The level of wound management correlated to length of hospitalization.

Question 2

According to Kanai 2020 in Vet Surg, was VATS with en bloc thoracic duct ligation or conventional clipping associated with better long term resolution of chylothorax?

Answer 2

En bloc ligation (85%) compared to 20% with conventional clipping.

Anesthesia time, operation time, time until pleural effusion resolution were also significant better for EB-TDL.

Question 3

In a study by Dickson 2021 in JAVMA, which two lung lobes were bullous lesions most likely to be identified in surgical treatment of spontaneous pneumothorax? What was the recurrence rate post-operative?

Answer 3

Left cranial (33%), and right cranial (24%).

Recurrence rate was 13%, with recurrence much more likely before 30 days post-operative. Recurrence after 30 days was rare (3%).

Question 4

In a study by Mayhew 2023 in JAVMA, what was the resolution rate for chylothorax following thoracoscopic TDL alone in the absence of constrictive pericardial pathology? Chylous redistribution was predominantly by retrograde flow to what structure?

Answer 4

94% resolution with TDL alone (88% with TDL/P).

Chylous redistribution was predominantly by retrograde flow to the lumbar lymphatic plexus. Continued flow was observed in 5/17 dogs, but only 1 of these developed recurrence.

Question 5

In a study by Howes 2020 in JSAP what was the 2 year survival rate for patients undergoing surgery for spontaneous pneumothorax? What was the recurrence rate post-operatively?

Answer 5

2 year survival was 88%.

Recurrence rate was 14% (with a median time to recurrence of 25 days). Increased risk of recurrence was observed with giant breed dogs and with increasing bodyweight.

Question 6

In a study by Marks 2024 in JSAP, what was the perioperative mortality rate for cats undergoing surgical excision of thymic epithelial tumours (thymoma)? What was the MST? What was the only significant prognostic factor for survival?

Answer 6

The perioperative mortality rate was 11%.

The MST was 897 days.

Masaoka-Koga stage was the only significant prognostic factor for survival (stage III and IV tumours associated with an increased risk of death).

Recurrence often occurred late in the disease course (median 564 days).

Question 7

In a study by Kanai 2024 in VRU, what was the most common side of the thoracic duct on CTLA in dogs with idiopathic chylothorax? What proportion of dogs had bypass (or sleeping duct) formation post-operative?

Answer 7

Right sided in 10/12, left side in 1/12, bilateral in 1/12.

Sleeping ducts were identified in 4/14 dogs post-operative. These may be a source of ongoing chylous effusion although this was not identified in this cohort.

Question 8

In a study by Guarnera 2023 in VRU, what percentage of cats showed contrast enhancement of the thoracic duct on CT 10 minutes following IV contrast administration?

Answer 8

83% (cisterna chyli also highlighted in 91%, point of anastomosis of the thoracic duct with the venous circulation only evident in 66% of cats).

Question 9

In a study by Racette 2022 in JVECC, at what median fluid production rate were thoracostomy tubes removed in dogs? What was associated with a higher median fluid production at the time of tube removal (2)? What increased the risk of pleural effusion within 2 weeks following tube removal (2)?

Answer 9

0.09 ml/kg/hr. Rate of fluid production at the time of tube removal was not associated with the detection of pleural effusion within 2-weeks. Only 4% of patients needed reintervention.

Presence of pre-operative pleural effusion, and median sternotomy rather than lateral thoracotomy were associated with higher fluid production at the time of tube removal.

The risk of pleural effusion within 2 weeks of tube removal was increased by the presence of pre-operative pleural fluid, or in cases with lung lobe torsion or chylothorax.

Question 10

In a study by Morris 2019 in Vet Surg, which side of the flank was preferable for laparoscopic approach to the cisterna chyli?

Answer 10

Left side as the vena cava made the right sided approach more challenging.

Question 11

In a study by Johnson 2023 in JVIM, what were the most common bacterial isolates from pyothorax in the cat v. dog?

Answer 11

Actinomyces common in both species. Pasteurella more commonly isolated in cats, E.coli in dogs.

Anaerobes were more commonly isolated in cats. Cats were more likely to have higher numbers of bacterial isolates.

Penetrating injury to the thorax was the primary cause of pyothorax in both dogs and cats (75%, respectively).

Question 12

What is the volume of pleural fluid in the dog and cat?

Answer 12

Dog: 0.1 ml/kg
Cat: 0.3 ml/kg

Question 13

Is the left or right pleural cupula larger?

Answer 13

The left (extends father cranially).

Question 14

What are the portions of the parietal pleura?

Answer 14

Costal, mediastinal, diaphragmatic.

Question 15

What is the vascular supply to the parietal and visceral pleura?

Answer 15

Parietal: arterial supply is via the pericardial, intercostal and diaphragmatic arteries. Venous drainage is via the internal thoracic veins and azygous.

Visceral: arterial supply is via the pulmonary circulation (pulmonary and bronchial arteries), and drainage is via the bronchial veins.

Question 16

Label the lymph nodes of the thoracic cavity.

Answer 16

Question 17

What are the parietal and visceral lymph nodes of the thoracic cavity?

Answer 17

Visceral: mediastinal (receive efferents from a large number of sources) and bronchial (pulmonary and tracheobronchial).

Mediastinal nodes on the left drain into the thoracic duct or left tracheal trunk, right side drain into the right tracheal trunk or lymphatic duct. Bronchial nodes drain to the mediastinal nodes.

Parietal: sternal nodes. Drain into the right lymphatic duct or thoracic duct (on the left). Receive efferent drainage from the ribs, sternum, serous membranes, thymus and adjacent muscles.

Question 18

The thoracic duct acts as the primary return of lymphatics for which parts of the bdoy?

Answer 18

Majority of the body, except for the right thoracic limb, shoulder and cervical region (right lymphatic duct).

Question 19

What is the location of the cisterna chyli?

Answer 19

Ventral to the 1st-4th lumbar vertebrae on the right dorsolateral surface of the aorta, caudal to the celiac and cranial mesenteric arteries.

Typically located surgically through a left paracostal approach. The left kidney is retracted medially, and the cisterna chyli is visualized on the surface of the aorta dorsal to the left kidney and caudal to the liver.

Question 20

On which side of the thoracic cavity does the thoracic duct travel in dogs and cats?

Answer 20

Dogs: right (crossing to the left at the 5th or 6th thoracic vertebra).
Cats: left.

Question 21

Where does the thoracic duct terminate?

Answer 21

The left external jugular vein or jugolusubclavian angle.

Question 22

At what age does the thymus start to involute?

Answer 22

4-5 months

Question 23

What is the vascular supply of the thymus?

Answer 23

Arterial: internal thoracic artery.
Venous: Parallels the arteries.

Question 24

What is the lymphatic drainage of the thymus?

Answer 24

The sternal lymph nodes

Question 25

Label important structures in the following diagram.

Answer 25

Question 26

What forces does intrapleural pressure need to overcome for lung expansion during inspiration?

Answer 26

Airway resistance and elastic recoil of the lungs.

Question 27

What is the functional residual capacity of the lungs?

Answer 27

The volume of air remaining in the lung at the end of normal exhalation (~45 ml/kg). This represents the point at which all forces, including collapse of the lungs and expansion of the chest cavity, are in passive equilibrium

Question 28

What determines minute ventilation?

Answer 28

Tidal volume and respiratory frequency (breaths per minute).

Question 29

In which direction is the movement of fluid across the pleural space?

Answer 29

Typically occurs from the parietal pleural to the visceral pleura, based on predominant hydrostatic and colloid osmotic pressures.

Question 30

What is the most important function of the thymus?

Answer 30

Maturation and selection of T-cells. Lymphoid stem cells produced in the liver migrate to the thymus, become thymocytes and then mature T-cells.

Question 31

What are some potential causes of increased pleural fluid production?

Answer 31

Right sided congestive heart failure (increased systemic hydrostatic pressure), hypoalbuminemia (decreased colloid osmotic pressure), inflammatory conditions increasing vascular permeability, lymphatic obstruction.

Question 32

What is the effect of increased pleural fluid on CVP?

Answer 32

Increased CVP. If severe has been reported to cause cardiac tamponade.

Question 33

What are the classifications of pleural fluid types?

Answer 33

Pure transudate, serosanguineous (modified transudate), sanguineous, inflammatory, chylous, neoplastic.

Question 34

What are the most common causes of a pure transudate pleural effusion?

Answer 34

Hypoproteinemia, congestive heart failure (although this often results in a modified transudate).

Question 35

What are the most common causes of a serosanginous pleural effusion?

Answer 35

Lung lobe torsion, diaphragmatic hernia and hepatic entrapment, pericardial effusion and right sided heart failure, neoplasia, idiopathic pleuritis.

Question 36

What are the most common causes of a sangineous pleural effusion?

Answer 36

Trauma, coagulopathy, acute lung lobe torsion, neoplasia (i.e. chemodectoma invading the great vessels of the heart, hemangiosarcoma).

Question 37

Is chylous pleural effusion and transudate, modified transudate, or exudate?

Answer 37

Typically a modified transudate (protein 2.5-4 g/dL, cell counts <7000/uL, SG <1.032).

Question 38

How is chylous pleural effusion diagnosed?

Answer 38

1. Higher trigylcerides and lower cholesterol compared to serum. 2. Observation of chylomicrons on cytology (Sudan black staining) . 3. Ether clearance test results. Lymphocytes predominate on cytology of early chylous effusions, which may progress to degenerative neutrophils because of intrapleural inflammation.

Question 39

What are the mechanisms behind pleural fluid accumulation in instances of intrathoracic inflammation?

Answer 39

Increased fluid production due to vasodilation and greater vascular permeability, increased oncotic pressure in the intrapleural space, thickening of the pleura.

Question 40

What is the most common source of pyothorax in the cat? What is a risk factor for development of this disease?

Answer 40

Parapneumonic spread secondary to viral upper respiratory tract infection. There is an increased risk in multicat households. Most infections are polymicrobial and commonly include anaerobes. Fluid should be evaluated for Actinomyces and Nocardia.

Question 41

Are inflammatory pleural effusions modified transudates or exudates?

Answer 41

Can be either. If septic is typically exudative with a very high nucleated cell count.

Question 42

What are some causes of pleural effusion secondary to neoplastic disease?

Answer 42

Inflammation, vessel and lymphatic obstruction, hypoalbuminemia, increased intrapleural oncotic pressure, erosion of vessels.

Question 43

What is paradoxical breathing?

Answer 43

Sinking of the flanks when the ribs elevate during inspiration, and bulging of the flanks when the ribs depress. Typically associated with pleural disease.

Question 44

What is a typical stance for a patient with severe pleural disease?

Answer 44

Abduction of the elbows and extension of the neck.

Question 45

What volume of intrapleural air is tolerated in healthy dogs without clinical signs?

Answer 45

45 ml/kg

Question 46

What imaging techniques can be used for the assessment of pleural disease?

Answer 46

1. Radiography: can detect as little as 100 ml or pleural fluid in the dog, and 50 ml in the cat. 2. Ultrasonography. 3. CT

Question 47

What are signs of pleural effusion on thoracic radiographs?

Answer 47

Interlobar fissure lines; retraction of the lung borders from the chest wall; and loss of detail, cardiac silhouette, or diaphragmatic line.

Question 48

What are potential complications associated with CT guided aspiration of intrathoracic lesions?

Answer 48

Pneumothorax (0-27%) and hemorrhage (30%). Normally resolve without intervention.

Question 49

What radiographic view is best used for visualization of the left pulmonary cupula, and differentiation between cranial mediastinal and apical pulmonary lesions?

Answer 49

Ventrodorsal view

Question 50

What testing should be performed on pleural fluid obtained by thoracocentesis?

Answer 50

Cytology, TNCC, RBC count, SG, TP, triglyceride and cholesterol concentrations, amylase and lipase (if pancreatitis suspected), aerobic/anaerobic +/- fungal culture.

Question 51

What are some additional parameters that might help in differentiating modified transudate and exudative pleural effusions?

Answer 51

Pleural fluid lactate to serum concentrations (cats), C-reactive protein concentrations (dogs).

Question 52

At what intercostal spaces is thoracocentesis typically performed?

Answer 52

Fluid: ventral third of the 7th-9th intercostal spaces. Air: dorsal third of the 7th-9th (or middle of the thorax if laterally recumbent).

Question 53

Why should thoracostomy tubes not be placed too far into the cranial extent of the mediastinum?

Answer 53

This area of the chest is narrow and can result in obstruction of the fenestrations.

Question 54

Describe the placement of a thoracostomy tube.

Answer 54

Question 55

How many crossings should be placed on a finger trap suture to ensure security of a thoracostomy tube?

Answer 55

Question 56

How are small-bore wired-guided chest drains (i.e. MILA) placed?

Answer 56

Modified Seldinger technique.

Question 57

What are the two options for drainage from a thoracostomy tube?

Answer 57

1. Intermittent. 2. Continuous.

Question 58

How is the level of suction controlled in a continuous suction system?

Answer 58

Controlled at the level of the atmospheric vent. Usually maintained between 5-10 cmH2O.

Question 59

What are some complications associated with thoracostomy tubes?

Answer 59

Occur in 22% of cases. Discharge around the tube, accidental removal, blockage, accidental displacement, subcutaneous emphysema. Leakage around the tube may be less likely if a metal trochar rather than Carmalt forceps is used to tunnel under the latissimus dorsi during placement.

Question 60

What guideline of thoracostomy tube fluid production is traditionally used to removal?

Answer 60

2 ml/kg/day. More recently values of 3 ml/kg/day for dogs and 5 ml/kg/day for cats has been described. Ultimately, tube removal should likely be based on multiple clinical parameters as well as fluid production levels.

Question 61

Describe the location of thoractomy for access to various structures of the thorax.

Answer 61

Question 62

What are the two described thoracoscopic approaches to the thorax?

Answer 62

1. Intercostal (lateral or sternal). 2. Paraxiphoid transdiaphragmatic.

Question 63

What are some potential complications associated with thoracoscopy?

Answer 63

Port site metastasis, need for conversion secondary to hemorrhage, limited visualization due to adhesions.

Question 64

What are the most common causes of death following thoractomy?

Answer 64

Mortality rates of 6-22% have been reported. Euthanasia due to disease was the most common cause of death. Other less common causes include hemorrhage, cariopulmonary arrest, and postoperative pneumothorax.

Question 65

What are some factors associated with non-survival in patients undergoing thoracotomy?

Answer 65

Pre-operative oxygen requirement, use of neuromuscular blocking agents during anesthesia, surgical duration (>180 minutes), blood product use.

Question 66

Are wound complications more common after intercostal thoracotomy or median sternotomy?

Answer 66

Median sternotomy. Overall rate of wound complications for thoractomy was 22-71%.

Question 67

What are some thoracic injuries commonly associated with thoracic bite wounds?

Answer 67

Rib fractures (46% to 88%), pneumothorax (34% to 67%), pulmonary contusions (52% to 67%), and pleural effusion (16% to 22%).

Question 68

What factors were negatively associated with survival following thoracic trauma in cats?

Answer 68

Flail chest, pleural effusion, diaphragmatic hernia. Overall survival was 63%.

Question 69

Is spontaneous or traumatic pneumothorax more common in dogs and cats?

Answer 69

Traumatic, secondary to penetrating injury to the thoracic cavity.

Question 70

What are some potential causes of spontaneous pneumothorax?

Answer 70

Pulmonary bullae, subpleural blebs, or emphysema (68% of dogs); pulmonary neoplasia (11% of dogs and 14% of cats); pleuritis; migrating plant material; pulmonary abscessation; feline asthma/inflammatory airway disease (the most common etiology in cats); chronic pneumonia; heartworm disease; or lungworm infection.

Question 71

What dog breed is at increased risk of spontaneous pneumothorax?

Answer 71

Siberian huskies.

Question 72

What is the treatment for pneumomediastinum?

Answer 72

Drainage of any concurrent pneumothorax and treatment of the underlying disease. Prognosis is typically good.

Question 73

What are the physiologic sequelae of tension pneumothorax?

Answer 73

Supra-atmospheric pressures in the pleural space with significant V/Q mismatch and decreased venous return, with subsequent tachypnea, tachycardia, shock and death.

Question 74

What percentage of dogs with pneumothorax have bilateral disease?

Answer 74

89%. In 31% of cases pulmonary bullae could be identified.

Question 75

How is pneumomediastinum identified on radiography?

Answer 75

Visualization of mediastinal air pockets and the azygos vein and delineation of the inner and outer aspects of the tracheal wall.

Question 76

What is an autologous blood patch?

Answer 76

Used for medical sealing of pneumothorax. Injection of 5-10 ml/kg of the patient's blood into the pleural space, followed by 10-20 ml of saline. The tube is capped for 4-hours, after which gentle aspiration is applied to check for ongoing pneumothorax.

Question 77

When is surgery indicated for patients with pneumothorax?

Answer 77

Continued or repeated air accumulation within a 5-day period, identification of a source of leakage or an abnormality within the chest. Mortality rates for dogs treated surgically for spontaneous pneumothorax (3-12%) lower than for dogs treated conservatively (50-53%).

Question 78

What is the most common cause of chylothorax?

Answer 78

Idiopathic, associated with lymphangiectasia. Other causes include; cardiomyopathy, mediastinal masses (e.g., lymphosarcoma, thymoma), dirofilariasis, blastomycosis, jugular vein or cranial vena cava thrombosis, diaphragmatic hernia, pericardial effusion, congenital anomalies, lung lobe torsion, heart-based tumors, trauma.

Question 79

What are some blood work changes that may occur secondary to chylothorax?

Answer 79

Lymphopenia, hyponatremia, hyperkalemia (typically secondary to chronic drainage).

Question 80

Why does fibrosing pleuritis occur secondary to chylothorax?

Answer 80

Inflammatory induced changes to the mesothelial cells, and decreased fibrinolysis due to a dilutional effect of pleural fluid on plasminogen activator.

Question 81

What diagnostics should be performed in the work-up of chylothorax?

Answer 81

CBC/biochem, urinalysis, heartworm test, thoracic radiographs, abdominal radiographs and ultrasound, CT, echocardiography, pleural fluid analysis, pleural fluid culture and susceptibility testing. Lymphangiography is required for definitive diagnosis (either radiographic or CT).

Question 82

What are the options for performing lymphangiography for the diagnosis of chylothorax?

Answer 82

1. Pre-operative popliteal or ultrasound guided mesenteric lymphangiography: 1 ml/kg of Iohexol is injected into the popliteal prior to CT. Visualization of the thoracic duct normally occurs within 2-13 minute. 2. Intraoperative: direct catheterization of a mesenteric lymphatic vessel via a paracostal approach. Can be combined with injection of methylene blue to aid in thoracic duct visualization. After injection of iodinated contrast (1 ml/kg diluted 1:1 with saline) intra-operative fluoroscopy can be performed, or the patient can be moved from theatre for radiography or CT.

Question 83

What are surgical options for treatment of chylothorax?

Answer 83

1. Thoracic duct ligation (open vs. thoracoscopic) 2. Pericardiectomy (open vs. thoracoscopic) 3. Cisterna chyli ablation 4. Thoracic duct embolization 5. Pleurodesis 6. Decortication 7. Pleuroport placement 8. Pleuroperitoneal shunt placement 9. Omentalization

Question 84

Which intercostal space is usually approached for thoracic duct ligation?

Answer 84

The tenth on the right (dogs) or left (cats).

Question 85

How can thoracic duct visualization be improved at the time of surgery?

Answer 85

Injection of methylene blue into a mesenteric (particularly the ileocecal) lymph node, popliteal lymph node, or catheterized intestinal lymphatic. Typically only 0.2ml is required, takes 10 minutes for visualization to occur, and lasts for 60 minutes.

Question 86

What are some complications associated with injection of methylene blue?

Answer 86

Heinz body anemia, renal failure.

Question 87

What is en bloc ligation of the thoracic duct?

Answer 87

Ligation of all the structures dorsal to the aorta and ventral to the sympathetic trunk, including the azygous vein if required.

Question 88

What are some potential complications associated with thoracic duct embolization?

Answer 88

Distant, nontarget (i.e. pulmonary artery) embolization and persistent pleural effusion.

Question 89

When performing thoracoscopic thoracic duct ligation where are the ports placed?

Answer 89

Lateral recumbency: telescope port mid to dorsal third of the eighth or ninth intercostal space. Instrument ports 7th/8th and 9th/10th. Sternal: ventral portion of the dorsal third of the right tenth intercostal space for the initial port, with additional ports based off visualization of the thorax.

Question 90

What is subtotal pericardiectomy?

Answer 90

Removal of the pericardium ventral to the phrenic nerves.

Question 91

What are the surgical approaches to pericardiectomy?

Answer 91

1. Intercostal thoracotomy. 2. Median sternotomy. 3. Trandiaphragmatic. 4. Thoracoscopic (transxiphoid, intercostal).

Question 92

Is more complete pericardiectomy achieved with a transxiphoid or intercostal thoracoscopic approach to the thorax?

Answer 92

Transxiphoid. Pericardial window can also be performed instead of subtotal pericardiectomy with similar results.

Question 93

What is the resolution rate of idiopathic chylothorax following thoracoscopic TDL and pericardiectomy?

Answer 93

86% (40% for non-idiopathic cases).

Question 94

What is the success rate of concurrent TDL and CCA?

Answer 94

88%

Question 95

What are surgical approaches to the cisterna chyli?

Answer 95

1. Ventral midline. 2. Left paracostal (single right paracostal approach has also been described in dogs for concurrent TDL and CCA). 3. Laparoscopic.

Question 96

What is pleurodesis?

Answer 96

Obliteration of the pleural space by stimulation of adhesion formation between the visceral and parietal pleura. Use has not been proven in dogs.

Question 97

What is decortication?

Answer 97

Removal of the visceral pleura. Has been attempted in patients with severe fibrosing pleuritis secondary to chylothorax, but results in significant parenchymal damage and may increase morbidity and mortality.

Question 98

What are complications associated with the treatment of chylothorax?

Answer 98

Persistent chylothorax, persistent nonchylous pleural effusion, lung lobe torsion, pneumothorax.

Question 99

What are the reported resolution rates for various treatment combinations for chylothorax?

Answer 99

TDL alone: 50-59% (dogs), 14-53% (cats). TDL + SP: 55-100% (dogs), 80% (cats). TDL + pericardial window: 83-86% TDL + CCA: 63-88% TDL + SP + omentalization: 57-77%

Question 100

What options exist for patients with recurrent effusion following surgical management of chylothorax?

Answer 100

1. Glucocorticoids (if non chylous). 2. If duct missed or recanalized based on CT lymphangiogram, repeat surgical intervention can be performed. 3. Percutaneous drainage system (PleuralPort). 4. Pleuroperitoneal shunts (active or passive). 5. Medical management (low-fat diet and rutin supplementation).

Question 101

What are complications associated with the use of PleuralPorts?

Answer 101

Obstruction is the most common complication. Can be treated with tissue plasminogen activator. Flushing with hepanarized saline after use is also recommended.

Question 102

What is the difference between active and passive pleuroperitoneal shunts?

Answer 102

Active: fenestrated one way catheter with a valve placed over the ribs. The valve is pumped daily with each compression moving 1ml of fluid. Passive: synthetic mesh sewn into a defect in the diaphragm. Will generally become occluded by omentum, fibrous tissue or liver.

Question 103

What are some complications associated with active pleuroperitoneal shunts?

Answer 103

High rate of complications. Kinking, infection, dislodgement, lack of owner compliance, discomfort, obstruction, pyothorax, and peritonitis reported.

Question 104

What is the proposed MOA of rutin?

Answer 104

Decreased lymphatic leakage, increased protein removal, increased macrophage phagocytosis.

Question 105

What are some complications associated with chronic long-term drainage of chylous effusion?

Answer 105

1. Fibrosing pleuritis. 2. Dehydration. 3. Loss of lipids, proteins and fat soluble vitamins. 4. Compromised immune system (lymphocyte depletion).

Question 106

What are some potential causes of non-septic peritonitis?

Answer 106

Canine hepatitis, leptospirosis, canine distemper, feline infectious peritonitis, and feline upper respiratory infections.

Question 107

What were risk factor for development of pyothorax for dogs undergoing thoracic surgery?

Answer 107

Diagnosis of idiopathic chylothorax, preoperative intrathoracic biopsy, and preoperative thoracocentesis.

Question 108

What are the most common bacterial isolates from pyothorax?

Answer 108

Dogs: Pasteurella (22%), Nocardia (19%), E.coli. Cats: Pasteurella (63%), Nocardia (13%). Anaerobes are present in 60% of dogs, and 89% of cats.

Question 109

How much more likely to fail was medical rather than surgical management of canine pyothorax?

Answer 109

5.4 times. Medical management tends to be more successful in cats.

Question 110

What are non-surgical management options for pyothorax?

Answer 110

Antimicrobials, oxygen, IV fluid support, therapeutic thoracocentesis (bilateral chest tubes and lavage every 8-hours is recommended), patient warming, dextrose. Antimicrobials are administered for 6-8 weeks.

Question 111

What empirical antimicrobial therapy is recommended for use in pyothorax or dogs and cats?

Answer 111

Penicillin or ampicillin in cats and a combination of metronidazole and cefoxitin, enrofloxacin, or trimethoprim-sulfonamide in dogs.

Question 112

What are indications for surgical treatment of pyothorax?

Answer 112

Identification of a primary cause that requires surgical resection (e.g., foreign body, lung lobe abscess), failure of appropriate medical management, persistence of effusion beyond 3 to 7 days, and thoracostomy tube complications.

Question 113

Is recurrence of pyothorax more likely in dogs treated medically or surgically?

Answer 113

Medically (25% at 1-year compared to 78% for surgical treated dogs).

Question 114

What are some potential complications associated with pyothorax?

Answer 114

Death, DIC, abdominal effusion, thoracostomy tube complications. Overall rate of successful treatment 48-86%.

Question 115

What factors were predictive of survival in cats undergoing treatment for pyothorax?

Answer 115

Increased survival with increased heart rate and WBC counts and decreased respiratory rate.

Question 116

What is the treatment for caudal mediastinal abscessation?

Answer 116

Exploration via median sternotomy or intercostal thoracotomy. Abscess drainage, debridement, lavage +/- omentalization.

Question 117

What are the most common causes of malignant pleural effusion?

Answer 117

Mesothelioma and carcinoma. Thymoma and lymphoma cause effusion less commonly.

Question 118

What is the prognosis for patients with malignant pleural effusion?

Answer 118

Poor (MST of 15 days, compared to a MST of >785 days for inflammatory conditions).

Question 119

How are malignant pleural effusions diagnosed?

Answer 119

1. Cytology rarely useful due to the regular presence of reactive mesothelial cells. 2. Imaging (radiography, ultrasound, CT) for detection of mass lesions. 3. Frequently only diagnosed on thoracoscopic sampling of the pleura and mediastinal tissue (multiple biopsies recommended).

Question 120

What is the most common type of thymic mass in dogs and cats?

Answer 120

Dogs: Thymoma, Cats: Lymphoma.

Question 121

Which breeds of dog are most commonly affected by thymoma?

Answer 121

Golden retrievers and labradors.

Question 122

What are some common paraneoplastic syndromes associated with thymoma in dogs and cats?

Answer 122

Hypercalcemia, myasthenia gravis (up to 47% of dogs and may cause megaesophagus and regurgitation). Additional nonthymic tumours are identified in 27% of dogs.

Question 123

Compression of the cranial vena cava by a thymic tumour results in what clinical sign?

Answer 123

Cervical venous distension and edema of the head, neck and thoracic limbs (caval syndrome).

Question 124

Are most thymomas localized?

Answer 124

Yes, spread to other organs is uncommon.

Question 125

How can thymoma and lymphoma be differentiated on cytologic sampling of thymic tumours?

Answer 125

1. Lymphocytes are common in both diseases, but thymomas may be more likely to have epithelial cells. 2. Flow cytometry.

Question 126

What causes myasthenia gravis?

Answer 126

Increased circulating antibodies against acetylcholine receptors, resulting in failure of nerve transmission at the NMJ.

Question 127

How is myasthenia gravis diagnosed?

Answer 127

1. Acetylcholine receptor antibody titres. 2. Tensilon test using edrophonium chloride (0.1 mg/kg IV). Atropine should be available prior to testing in case of vagal response.

Question 128

What vessel is most commonly affected by cranial mediastinal masses?

Answer 128

Cranial vena cava, followed by the internal thoracic arteries and axillary vein.

Question 129

What are complications associated with resection of thymoma?

Answer 129

Aspiration pneumonia, hemorrhage, infection, hypocalcemia, seroma formation, persistent signs of myasthenia gravis, DIC, and tumor recurrence (17%).

Question 130

What is the MST for patients undergoing resection of thymoma?

Answer 130

Dogs: 790 days. Cats: 1825 days.

Question 131

What factors might affect survival time in dogs undergoing resection of thymoma?

Answer 131

High grade tumours, presence of second non-thymic tumour. Varied results for whether megaesophagus and concurrent aspiration pneumonia are predictive of survival. Hypercalcemia and phrenic nerve transection not associated with survival.

Question 132

What percentage of patients undergoing radiation therapy for thymoma have complete remission?

Answer 132

20% (MST is 248 days for dogs, 720 days for cats).

Question 133

What percentage of dogs with thymic lymphoma have concurrent hypercalcemia?

Answer 133

25%

Question 134

Does thymic lymphoma more commonly affect younger or older animals as compared to thymoma?

Answer 134

Younger

Question 135

What is the MST for patients with mediastinal carcinoma (thyroid carcinoma, neuroendocrine carcinoma)?

Answer 135

243 days

Question 136

What is the treatment for benign mediastinal cysts?

Answer 136

Surgical excision if the patient is clinically affected.