Effusions and Fluid Analysis Flashcards
Peritoneal, pleural and pericardial cavities are lined by ?
Mesothelium
How is movement of the mesothelium facilitated?
Contain serous fluid
Describe the serous fluid
This fluid is an ultrafiltrate of blood
- Low cellularity
- Low total protein
Describe the pathophysiology of fluids in the body
Volume of fluid present depends upon equilibrium between:
- Hydrostatic pressure of blood
- Oncotic pressure of blood (proteins)
- Permeability of vessels
Define effusion
Effusion: any accumulation of fluid in a body cavity
- Indicative of a pathological process
- Rate of fluid formation»_space; Rate of fluid removal
What are the two classifications of effusions based on protein, cell count and cytology?
Transudate
Exudate
Define transudate
Effusion usually caused by imbalances of hydrostatic and/or oncotic pressure
Define exudate
Effusion usually caused by increased vascular permeability due to inflammation – higher protein much more cellular fluid
How are effusions classified based on aetiology and composition?
Haemorrhagic
Chylous
Pseudochylous
Neoplastic
Analysis of effusions is based on what characteristics?
- Colour
- Turbidity: clear or opaque
- Odour
- Cell counts and total protein
- Microscopic examination
- Biochemistry depending on the case
Describe haemorrhagic effusions and their causes
- Heavily blood-stained Caused by: - True cavity haemorrhage: vessel disruption - Iatrogenic blood contamination - Splenic tap
How will a sample appear if it has been Iatrogenically contaminated?
- Initially clear then bloody or vice-versa
- Swirling of blood
- Should form clot
- Supernatant clear
- Can seen platelets
- No erythrophagocytosis
What are the causes of true body cavity haemorrhage?
Bleeding tumour
Coagulopathy
Trauma
Describe the features and cytological appearance of a true body haemorrhage
- Fluid does not clot
- Supernatant often haemolysed due to RBC degradation in cavity
- Microscopy:
Erythrophagocytosis (RBC removed by macrophages)
No platelets
How can abdominal haemorrhage be investigated?
- Coagulation profile / haematology
- Ultrasound abdomen to detect masses
- Look for neoplastic cells on the cytology slide
What is chyle?
Chylomicron-rich lymph
What are chylomicrons and their functions?
- TG-rich lipoproteins absorbed from the intestine
- Transport of dietary lipid
- Enter lymphatics, then the blood via thoracic duct
- BIG so make fluid opaque (milky)
Describe the features of a chylous effusion
- Milky fluid (white, opaque)
- Protein often >25g/l*
- Cell count very variable
- Cytology mainly lymphocytes, but can be mixed
- Neutrophils increase with chronicity
- High [triglyceride] (> serum): over 1.13 mmol/L -> chyle
How does a chylous effusion form?
Formed due to lymphatic drainage impairment or lymphatic leakage
- Lymphatic drainage impairment or lymphatic leakage
What are the causes of a chylothorax?
Heart disease
Trauma/surgery
Neoplasia
Idiopathic
How is pseudochyle different to chyle?
- Looks similar grossly
- BUT not high in triglycerides
- White colour due to cell debris, protein and cholesterol
- Uncommon
Describe the features of (Low protein) Transudate
- Clear, colourless
- Protein < 25 g/l
- Cell count < 1.5 x109/l
- Few cells
- Mainly monocytes and macrophages
- Lymphocytes
- Mesothelial cells
- Few neutrophils
What is the pathophysiology of (Low protein) Transudate formation?
Decreased oncotic pressure due to low serum protein
Low protein fluid leaks out of vessels
What are the causes of transudates?
- Decreased oncotic pressure - Severe hypoalbuminaemia
- Portal hypertension
- Over hydration
- Cardiac failure
- Thrombi in major vessels (acute phase)
What are the 3 causes of hypoalbuminaemia
- Protein losing enteropathy
- Protein losing nephropathy
- Reduced protein production in liver disease
How can transudates be further investigated?
- Biochemistry (plasma/serum): Albumin, Creatinine
- Urinalysis (check for proteinuria) - Urine protein:creatinine ratio
- Imaging
- Look for GI or renal disease
Describe the features of High protein (modified) transudates
- ‘Modified’: more protein and cells than pure transudate but not as much exudate
- Colourless to amber or pink
- Clear (low cell count)
- Protein > 25 g/l
- Cell count < 5.0 x109/L
What is the pathophysiology of High protein (modified) transudates
Increased hydrostatic pressure
(Higher protein) fluid pushed out
How does a High protein (modified) transudates appear on cytology?
- Low cellularity (usually higher than pure transudates)
- Mixed population of cells
- More neutrophils than transudate
What are the causes of modified transudates?
Increased intravascular hydrostatic pressure in liver or lung (venous congestion):
- Congestive heart failure
- Thrombi or neoplasia
Also:
- Non-exfoliating neoplasia
- Lung lobe/ splenic torsion
- Occasionally feline infectious peritonitis
Describe the appearance and features of exudates
- Turbid (due to lots of cells)
- Yellow/brown/bloody
- High nucleated cell count
- High protein
- Mostly neutrophils: Inflammation (e.g. pleuritis, peritonitis, pericarditis)
Describe the pathophysiology of exudates
Increased vessel permeability
High protein, cellular fluid leaks out
Describe septic exudates and its cause
- Intracellular organisms
- But not always visible
- Absence of organisms does not rule out sepsis
- Often degenerate neutrophils (karyolysis & karyorrhexis)
Describe non-septic exudates and its cause
- Non-degenerate neutrophils
- Lower numbers of hypersegmented neutrophils and pyknotic cells
What are the causes of septic exudates?
- Penetrating wound
- Foreign body
- GI perforation or ischaemia
- Haematogenous route
Describe the effect of gut contamination on a sample
Smelly
Brown
Bits of plant material
Free bacteria
What are the causes of non-septic exudates?
- Ruptured gall bladder
- Ruptured urinary bladder
- Necrotic tumour
- Pancreatitis
- FIP*
Describe the fluid sample that would be taken in the case of feline infectious peritonitis
- Yellow sticky fluid
- High protein -> froths
- Moderate cellularity
- Globulin:albumin ratio
A:G low in FIP
A:G< 0.4 then FIP likely
A:G> 0.8 NOT FIP
Describe how the cytology of an FIP case would look
- Abundant proteinaceous background
- Cells mainly neutrophils
- Fewer macrophages
What are some further tests used for FIP diagnosis?
- Immunohistochemistry of fluid pellet for coronavirus and/or PCR
- Serology
- Can measure alpha 1-acid glycoprotein = Acute phase protein
- No single test definitively diagnostic (except for histology)
Describe bile peritonitis and how it occurs
- Ruptured gall bladder / bile duct
- Trauma
- Following obstruction
- Chemical peritonitis
+/- secondary infection
What colour is the fluid from bile peritonitis?
Green
Describe how the cytology from bile peritonitis would look
- Neutrophils
- Macrophages with green pigment
- [Bilirubin] fluid higher than [bilirubin] plasma
The concentration of which substance changes if there’s a ruptured bladder?
[Creatinine] fluid > [Creatinine] plasma
Usually at least twice
How would fluid from a ruptured bladder case appear? How does it change?
- Urea equalises between fluid and plasma so may be similar (or higher)
- Fluid starts as transudate (very low protein because diluted by urine)
- Urine -> irritant -> changes to exudate
What are the effects of neoplastic effusions
- Compression of blood vessels and lymphatics -> increased hydrostatic pressure and/or abnormal vasculature
- Increased vessel permeability
- Inflammation
- Necrosis
- Haemorrhage
- Cell exfoliation
Name 3 tumours that can cause neoplastic effusions
Lymphoma
Adenocarcinoma
Mesothelioma
What are some pitfalls in diagnosing neoplasias?
- Mesothelial cells found in all effusions
- Shed off pleura / peritoneum
- Can become reactive and look like tumour cells!
Describe the appearance of reactive mesothelial cells
- Eosinophilic fringe or brush-boarder
- May be multinucleated
- May contain prominent multiple nucleoli or variable shapes and sizes
- May phagocytose cells and particulate matter
What are the indications for using arthrocentesis?
- Joint disease of unknown aetiology
- Diseases in multiple joints
- Suspected infective arthritis
- Pyrexia of Unknown Origin
- Monitoring therapeutic response
Describe the normal appearance of synovial fluid
Clear, pale yellow
Describe the appearance of synovial fluid during inflammation
Yellow turbid
What does uniformly bloody synovial fluid suggest?
Haemarthrosis
What does clear then bloody synovial fluid suggest?
Contamination
What are the main principles when handling a sample
- Make smear immediately
- Note viscosity
- Collect into EDTA and sterile plain tube
- Always send fresh smear with sample
Describe all of the normal features of synovial fluid
Clear pale yellow
Very viscous
Hypocellular
Protein background
How does synovial fluid appear grossly and on cytology when there has been trauma
Grossly red
Low viscosity due to effusion
Red cells
Some neutrophils
How would the cytology of synovial fluid in the case of osteoarthritis appear?
- Cellularity normal or mildly increased
- Predominantly mononuclear
- Can see osteoclasts (rarely)
How would the cytology of synovial fluid in the case of inflammatory arthropathy appear?
- Viscosity reduced
- Cellularity increased
- Increased cell count
- Mainly neutrophils
- Degenerative change rarely evident if infective
How would the cytology of synovial fluid in the case of septic arthritis
- Usually monoarticular
- Penetrating wound
- Haematogenous spread (rare)
- Often we do not see bacteria and culture is negative
