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
