Diagnosis Of Effusions Flashcards
What is an effusion?
An increased amount of fluid in the abdominal or thoracic cavity
What is the clinical significance of finding an effusion?
NOT a disease in itself
Indicative of a pathological process affecting either fluid production and/or removal
May be the only cause of clinical signs
Why should we analyse effusions?
Differentiate between different fluid types to allow further diagnostics
What tubes are required for specific test types?
Collect into EDTA for counts, cytology and protein
Collect into serum tube for biochem tests or culture
Why should a potentially inflammatory fluid be collected into an EDTA tube?
An inflammatory fluid can form a fibrin clot as it has fibrinogen in it
What tests could be run to analyse fluids?
Counts, cytology and protein Biochemistry or culture Total nucleated cell count (TNCC) Cell identification and morphology Protein concentration Other - enzymes (amylase and lipase), urea and creatinine, Cholesterol and triglycerides
Describe normal fluid
Low volume
Clear, straw colour
Ref range total protein, TNCC
Mesothelial cells and macrophages present
What is the normal role of fluid in the abdominal cavity?
In which species would you expect more?
Lubrication of abdominal organs
- forms a film on serosal surfaces
Horses and large animals - can pool due to gravity
How is fluid regulated normally?
Hydrostatic pressure
colloid osmotic pressure/oncotic pressure (albumin)
Permeability of capillary wall
Lymphatic drainage
What are the major classifications of effusions?
Transudate
Modified transudate
Exudate
(Haemorrhage)
What is the main basis of the system for classifying exudates?
TNCC and total protein
Describe a transudate.
What cells might you expect?
Low protein and cellularity
Clear (like water)
Mesothelial cells, macrophages, low numbers non-degenerate neutrophils
How do transudates occur?
Passive movement across membrane
The relationship between hydrostatic and oncotic pressure favours fluid leaving the capillary
What causes transudates?
Decreased colloid osmotic pressure
RAAS activation - more fluid retained therefore increased hydrostatic pressure
When might albumin levels result in a transudate?
RARE - needs to be very low
But hypoalbuminaemia can occur as a result of:
glomerular disease
hepatic disease
GI loss (e.g. protein losing enteropathy)
How can liver disease result in transudate formation?
Hepatic fibrosis/cirrhosis
Portal hypertension and formation of secondary collateral circulation
Local production of vasodilators (NO)
Splanchnic vasodilation and decreased effective blood flow
Compounded by RAAS Na retention and hypertension
Low protein lymph leaks from intestine
Describe a modified transudate.
Yellow to serosanguinous, cloudy
Like transudate + proteins
Mesothelial cells, macrophages, non-degenerate neutrophils, small lymphocytes
What is a mesothelial cell?
Cell that lines serous cavities e.g plura, peritoneum, mediastinum, pericardium
When might you see a modified transudate?
Cardiac disease,
Chylous effusion
Lymphatic obstruction (neoplasia)
How can cardiac disease cause a modified transudate?
Congestion -> increased hydrostatic pressure (esp. in hepatic sinusoids)
Leakage of protein rich lymph from liver
+ Na and fluid retention from RAAS
Describe an Exudate.
High TNCC and protein
Turbid - red, yellow, white
Neutrophils (degenerate or not) and macrophages (+ lymphocytes, eosinophils)
How do exudates occur?
Inflammation of the pleural/abdominal cavity and their linings
Increased capillary permeability, plasma leaks into fluid
Recruitment of inflammatory cells
What can cause an exudate?
Septic (bacteria / non-septic
Long standing modified transudate irritates the lining leading to inflammation
Neoplasia
How can neoplasia cause exudates?
Neoplasia outgrows blood supply
Becomes necrotic leading to the recruitment of inflammatory cells
Describe a non-septic exudate.
What could cause this?
Non-degenerate neutrophils
No bacteria
E.g. FIP (viral)
Describe a septic exudate.
Degenerate neutrophils
Intracellular bacteria
Describe the fluid you would expect to see from a patient with FIP
Variable TNCC
HIGH PROTEIN
Non-degenerate neutrophils and macrophages
Acute phase protein elevation
How can the classification of FIP fluid vary?
Can be classed as an exudate or modified transudate based on the cell count
How can you tell whether haemorrhagic fluid is iatrogenic or not?
Platelets should adhere to the peritoneum almost immediately therefore FEW/NO platelets = fluid
(Platelet clumps present = needle in wrong place OR active bleeding)
How can you tell whether haemorrhage is acute or chronic?
Acute - erythrophagia - macrophages eat RBCs.
Chronic - siderophages and haematoidin - 2-3 days ago
What could you conclude about the bleeding if erythrocytes and siderophages were present?
Bleeding started 2-3 days ago and still happening
Describe a chylous effusion
Opaque and milky (chylomicrons)
Acute- 80% lymphocytes, variable macrophages and neutrophils
Chronic - Mixed population 30-40% lymphocytes, increased neutrophils
Explain the composition of a chronic chylous effusion
If fluid stays in cavity, inflammation occurs
Explain the appearance of a chylous effusion
Chylomicrons
Lymph coming from intestines contains fat from diet in lymph
When would it be necessary to carry out further tests on a chylous effusion?
If animal is off its food
Animal needs to be eating for chylous effusion to be obvious
How can you confirm that an effusion is a chylous effusion?
Higher triglycerides than in serum and lower cholesterol
Formation of ‘cream top’ when refrigerated
Sudan III staining for lipid droplets
Does not separate on centrifugation
Why can mesothelial cells be problematic?
When activated (by inflammation or presence of fluid), look malignant, even thought they’re normal
What fluid would you expect in a case of uroabdomen?
Transudate/modified transudate
Light yellow clear fluid
What fluid would you expect in a case of bile peritonitis?
Modified transudate/ exudate
Green colour
What fluid would you expect in a case of pancreatitis?
Modified transudate / exudate
What volume of peritoneal fluid can normally be collected in a healthy horse ?
3-5 mls
100-300 ml present
Describe normal equine peritoneal fluid.
Pale yellow, clear
50% macrophages, 50% non-degenerate neutrophils
Modified transudate - quite a few cells and inflammatory cells and proteins
Describe a septic exudate in horses.
Yellow, brown, turbid
High TNCC and protein
Degenerate neutrophils, bacteria
Look for plant material and Protozoa - indicates gut wall rupture
Describe a non-septic exudate in horses
Amber, slightly turbid
High TNCC
High protein
High neutrophils
More neutrophils than macrophages
How can you tell if you have performed enterocentesis?
Low cell count
How can you differentiate between enterocentesis and peracute GIT rupture?
Clinical impression
Horses with GIT rupture quill quickly develop CV collapse
