Chylothorax and Pyothorax Flashcards
Define chylothoax
The failure of the intestinal lymph to drain normally via the thoracic duct into the venous circulation
What is the most common underlying pathophysiology of a chylothorax?
Idiopathic
What is the success rate of surgery in chylothorax?
40-90%
The thoracic duct returns lymph to the venous circulation from all regions of the body except… (3)
Right thoracic limb, shoulder and cervical regions.
Where does the thoracic duct begin?
Sub lumbar region
Where does the thoracic duct terminate? (2)
Left external jugular vein
Jugulosubclavian angle.
Where is the thoracic duct located in dogs?
Caudal thorax, dorsolateral aorta on RIGHT side
Where is the thoracic duct located in cats?
Caudal thorax, dorsolateral aorta on LEFT side
What are the reported causes of a chylothorax? (9)
-Idiopathic
-Mediastinal or heart-based masses (usually neoplastic)
-Jugular vein/cranial vena cava thrombosis
-Diaphragmatic hernia
-Pericardial effusion
-Congenital abnormalities
-Lung lobe torsions
-Obstruction of cranial mediastinal veins
-Thoracic duct trauma.
What causes the chylothorax?
Increases cranial vena cava hydrostatic pressure, by causing obstruction of the lymphaticovenous junctions and subsequent lymphangiectasia.
Where trauma is the cause of a chylothorax, how do these heal?
Spontaneously
Which dog breed is pre disposed to chylo thorax?
Afghan hound
Which cat breed is pre disposed to a chylo thorax?
Siamese
What are the clinical signs of a chylothorax associated with? What is the common sign if chronic?
- Pleural effusion (e.g., tachypnoea, dyspnoea, lethargy, cough, restrictive breathing pattern etc.).
- Emaciated
What is seen on xrays of a chylothorax?
Pleural effusion
What does a chylothorax yield on thoracocentesis?
Milky coloured fluid
How is a chylothorax definitvely diagnosed?
Comparing triglyceride levels in paired pleural and serum samples
In chyle, serum triglycerides are higher and cholesterol lower compared with serum.
What is the fluid type of a chylothorax?
Modified transudate protein >2.5 g/dL.
What is seen on cytology with a chylothorax?
Initially, lymphocytes and non-degenerate neutrophils predominate (6000-7000 nucleated cells/ul). Later, degenerate neutrophils predominate.
What stain is used for a chylotorax? What does it detect?
Sudan black - chylomicrons
How does the ether clearance test diagnose a chylothorax?
Chylous fluid will clear when potassium hydroxide and ether are added to it.
How is a definitive diagnosis made of a chylothorax?
Lymphangiography immediately before thoracic CT (or, less commonly, radiography), performed by injecting iohexol via ultrasound guidance into the popliteal or mesenteric lymph nodes
How can a chylothorax be medically managed?
Low-fat diet and rutin Intermittent thoracocentesis may be required.
How does changing the diet help a chylothorax?
Low fat diet and rutin - to reduce chylous effusion by decreasing leakage of the lymphatics, increasing protein removal and increasing macrophage number and phagocytosis.
What are the surgical options for a chylothorax? (8)
-Thoracic duct ligation
-Pericardectomy
-Thoracic duct glue embolisation
-Thoracoscopic thoracic duct ligation
-Pleuroperitoneal drainage
-Pleural omentalisation
-Cysterna chyli ablation
-Percutaneous drainage (e.g., Pleural Port).
What is the most common surgical treatment of a chylothorax? How does this work?
Identification and ligation of all the branches of the thoracic duct, which encourages formation of new anastomoses between the lymphatic and venous systems.
What concurrent surgery should be done at the same time as a thoracic duct ligation for chylothorax treatment? why?
Pericardectomy is recommended to decrease right sided pressures, which facilitates anastomotic development.
What surgical approach should be taken for a thoracic duct ligation and pericardectomy for chylothorax treatment? (2)
Open or thoracoscopically
Where is an open surgical thoracic duct ligation approached anatomically in dogs?
RHS - A tenth intercostal thoracotomy is performed
Where is an open surgical thoracic duct ligation approached anatomically in cats?
LHS - A tenth intercostal thoracotomy is performed
In an open approach to thoracic duct ligation, …….. is injected into the ileocaecal (via a paracostal approach) or popliteal lymph node, or an intestinal lymphatic duct is cannulated and methylene blue injected.
Methylene blue
What is the effect of methylene blue injected?
The thoracic duct becomes coloured
Where is the surgical dissection in an open approach to thoracic duct ligation?
All branches are dissected free from the aorta and parietal pleura as far caudally in the thoracic cavity as possible, where the number of branches is likely to be fewer.
Branches are ligated or clipped
How is it confirmed there are no patent branches remaining following a thoracic duct ligation?
Repeat lymphangiography performed fluoroscopically
How can en bloc ligation be performed during a thoracic duct ligation?
En bloc ligation of all structures dorsal to the aorta and ventral to the sympathetic truck (including the azygous vein)
What are possible surgical complications of thoracic duct ligation? (7)
-Pyothorax
-Wound complications
-Haemorrhage
-Recurrence of chylothorax
-Complications associated with the use of methylene blue (e.g., acute renal failure, Heinz body anaemia)
-Lung lobe torsion
-Persistent non- chylous effusions.
Define pyothorax
The development of purulent fluid within the pleural cavity, usually secondary to an infectious agent.
What is the most common type of infection in a pyothorax?
Bacterial and mixed
What is the success outcome for a pyothorax?
86%
What is the cause of a pyothorax?
Often - unidentified
What are common causes of a pyothorax? (5)
- Penetrating wounds from the external environment (e.g., cat bite);
- Penetration via the airways/oesophagus (e.g., inhaled grass seed or perforated oesophageal foreign body);
- Haematogenous spread;
- Extension of infection from neighbouring regions (e.g., discospondylitis, pneumonia, pulmonary abscessation). Parapneumonic spread may be one of the more common causes;
- Thoracic surgery
What bacteria is most common in a dog pyothorax?
E. Coli
What bacteria is most common in a cat pyothorax?
Pasturella
Clinical signs of a pyothorax (9)
Often clinically unwell - ESPECIALLY CATS
Dyspnoea
-Tachypnoea
-Pyrexia
-Lethargy
-Cough
-Abnormal lung sounds
-Visible wounds/scars
-Variable signs of cardiovascular collapse/shock.
Pyothorax thoracocentesis:
a) Gross
b) Cytology
c) Biochemistry
a) opaque and turbid
b) nucleated cell count > 7000/ul, degen neutrophils with intracellular bacteria, sulphur granules
c) protein >3.5g/dL
What is seen on hematology with a pyothorax?
Inflammatory leucogram, Left shift, toxic neutrophils
What is seen on biochemistry with a pyothorax? (4)
Hypoalbumin
Hyperglobulin
Hypoglycaemia
Axotaemia
What is seen on thorax x-rays with a pyothorax?
Pleural effusion, mass lesion, pneumothorax, pleural thickening, focal interstitial/alveolar pattern
What is seen on thoracic CT with a pyothorax?
Pleural effusion, mass lesion, pneumothorax, pleural thickening, focal interstitial/alveolar pattern - FB visual, LN enlarge, pericardial thickening and mediastinal effusion
What is seen on thoracic ultrasound with a pyothorax?
Pleural effusion, mass lesion, foreign material, fibrosing pleuritis
What is sulphur granules in thoracocentesis suggestive of? (2)
Nocardia sp
Actinomyces sp
What is the first stage of treatment in an unwell patient with a pyothorax?
Stabilisation is indicated in the first instance. Patients may require intravenous crystalloids/colloids/dextrose, oxygen supplementation and/or warming, in addition to antibiotic provision.
Which patients with a pyothorax don’t benefit from medical stabilisation first?
Those benefiting from immediate surgery - FB or lung lobe abscess
What does non surgical management consist of for a pyothorax?
Uni- or bilateral thoracostomy tube placement in order to regularly lavage and evacuate the pleural space.
Which thoracostomy tube is used in a pyothorax?
Trochar or small bore thoracostomy tube
Why is repeat needle thoracocentesis for a pyoderma not optimal? (4)
- Not effective for complete drainage of pleural space
- Does not allow pleural lavage
- Risk of lung laceration
- Less tolerated
What ABx as first line for a pyothorax? What length of course?
Ampicillin and metronidazole
6weeks
How is the thoracic cavity drained in a pyothorax?
Fluid type and amonunts?
Isotonic, body-temperature crystalloids every 8 hours. I prefer to use 10-20ml/kg boluses, which is instilled into the chest tube. The fluid is delivered slowly, with respiratory rate/effort monitored for compromise, and if there are concerns, fluid is removed and smaller boluses used subsequently.
How many times in the thoracic cavity drained and flushed for a pyothorax?
Once the fluid has been instilled, it is withdrawn and the volume retrieved recorded. The installation is repeated until the fluid returned is as clear as it can be. The volume of fluid retrieved before lavage begins, and the total volume of lavage fluid required (until it is returned clear) are both recorded.
What is critical to be monitored during a pyothorax treatment? (4)
PCV
Total protein
Albumin
Nutritional status
When is surgical required in a pyothorax? (3)
- A lesion is identified on initial imaging which requires resection (i.e., a mediastinal or pulmonary lesion);
- Actinomyces spp. is isolated;
- Non-surgical management has failed (persistent effusion beyond 3-7 days).
What is the most common approach to surgical pyothorax?
Median sternotomy
What is performed during open surgery of a pyothorax?
Lesion resected or debrided using stapler of vessel sealing device
Thoracic omentalisation has been reported as successful
What % of patients has n underlying cause found for a pyothorax?
18%
1 year following treatment in dogs, what % were free of disease following:
A. Medical management?
B. Surgical management?
A. 25%
B. 78%
What is the mortality rate of dogs with pyothorax as a complication following thoracotomy?
67%
What bacteria was often cultured from a pyothorax following thoracotomy?
MRSA
What is the survival of a pyothorax in cats?
48.8% - 66.1%
What is the recurrence rate in cats with a pyothorax?
5.8%
Pyothorax complications (6)
- Death
- Sepsis
- Disseminated intravascular coagulation
- Recurrence, treatment failure
- Thoracostomy tube complications
- Surgical wound infection/complications.
