Effusions Lecture 21 Flashcards
In Health what are the body cavities that contain fluid and what does the normal body cavity fluid consist of? Function?
The thoracic (pleural), abdominal (peritoneal), and pericardial cavities contain a small volume of
clear, watery (serous) fluid. This fluid functions to provide lubrication between organs and the body
wall and for diffusion of substances such as electrolytes.
What are the forces involved in body cavity fluid formation?
Rate of fluid formation is dependent on the balance between the opposing oncotic and hydraulic pressures.
Oncotic: water follows solid
Hydraulic: force of flow when fluid encounters resistance IE force your bloodflow is putting on vessels
How is normal cavity fluid formed?
Cavity fluid is formed when plasma exits the arterial capillary bed and enters the interstitial space.
The majority of this fluid is rapidly reabsorbed by venous capillaries and lymphatic vessels. Since
these arterial capillaries are relatively impermeable to proteins, serous fluid in body cavities has a
very low total protein concentration and contains very few cells.
When does effusion occur?
occur when there are changes that promote excess fluid formation or decreased fluid
removal
What are the 4 major mechanisms for effusion formation?
(1) disturbances of fluid circulation: changes in plasma oncotic pressure, hydraulic pressure, lymphatic drainage, or a combination of these factors (These processes generally result in
transudates)
(2) inflammation in a body cavity (This typically results in exudates)
(3) organ rupture (which usually leads to inflammation and/or hemorrhage)
(4) neoplasia
What is the clinical presentation of abdominal (peritoneal) effusions?
- Distended abdomen (+/- palpable fluid wave)
- Exercise intolerance
- +/- respritory difficulty due to pressure on the diaphragm
What is the clinical presentation of thoracic (pleural) effusions?
- increased respiratory rate
- Difficulty breathing esp on inspiration
- Exercise intolerance, weakness
What is the clinical presentation of Pericardial effusions?
- Exercise intolerance, weakness +/- collapse
- Respiratory difficulty
- Muffled heart sounds, weak pulses, jugular distention
- ECG abnormalities
- Usually also abdominal effusion
When collecting fluid samples you must:
be sterile and careful
- sternal recumbency
- Field clipped and prepped
- Sterile gloves
- U/S guidance is often used to help sample fluid
I have done a centesis…now what?
EDTA Tube –> clin path lab and order “Fluid analysis”. you will get TP, Total Nucleated cell count and cytology
Clot (red top) tube–> Clinical bacti and mycology lab, order a bacterial culture. You will get gram stain, culture and susceptibility testing
Heparin Tube–> Clin path lab, Biochemical testing (usually K+, creat, billirubin, triglyceridesm glucose or lactate depending on ddx). Always check with the lab before submitting your sample to make sure you submit
the correct specimen type!
T/F EDTA
results in the best preservation of cells for cytology and prevents clotting of the sample if it has a
high fibrinogen concentration or contains any blood.
True
What if I have to ship the sample to the laboratory?
- Make a direct smear of the fresh fluid, air dry it, &
place in slide holder (do NOT refrigerate)
– Feel free to make a direct smear for yourself to stain and
evaluate! After review, submit with the unstained slide. - Put fluid in EDTA tube ± red-top or heparin tubes
(depending on which assays you will be requesting)
& refrigerate until ship overnight on a cool pack
– EDTA anticoagulant results in best preservation of cellular
morphology for delayed microscopic evaluation
What are the two cytologic analysis options at UTCVM?
Fluid analysis: requireds a tube of fluid and gives you TP refractometry, TNCC, and microscopic evaluation
Cytology: microscopic evaluation only
Microscopic examination should occur ASAP after fluid collection. Cells will degrade and acquire
artifactual changes with storage time, even in EDTA. Also, phagocytic cells (neutrophils and
macrophages) continue “eating” even after they leave the body. Interpretation of intracellular
bacteria or phagocytized cells (erythrophagia, leukophagia) should be done cautiously when
fluid analysis is delayed >24 hours.
**Look at the Routine Fluid Analysis Section of Notes for More info on each
Why do we classify effusions?
- Help you think about mechanisms!
– Altered fluid circulation
– Inflammation
– Rupture of an organ
– Neoplastic - Mechanisms help narrow differential diagnoses!
- A few caveats:
– Interpret fluid data in light of entire clinical picture
– Some fluids can’t be neatly classified
– Fluid characteristics may change over time - The more chronic –> the more inflammatory
What 2 laboratory parameters are used to classify effusions?
Protein levels and cellularity
Describe the mechanisms for transudate formation.
Decreased oncotic pressure due to hypoalbuminemia
- Usually needs to be severe (<1.5 g/dL)
- EX: Protein losing nephropathy
Increased hydraulic pressure due to venous congestion, or venous obstruction (e.g., space-occupying lesion [tumor, granuloma], thrombus, organ
torsion).
- When the hydraulic pressure gradient exceeds the oncotic pressure gradient fluid is pushed out of the capillary lumen and into the interstitium at a rate that
exceeds lymphatic drainage, leading to fluid accumulation in tissues and body cavities. Another EX is R Sided HF.
Lymphatic Obstruction due to blockage or dysfunction of lymphatic vessels.
- If fluid formation outpaces fluid removal, effusion results
- Space occupying mass like a tumor
although in most cases
hypoalbuminemia alone will not cause transudation
Are the mechanisms of transudate formation mutually exclusive?
NO, often more than one
mechanism is at work in the same patient.
Why do some transudates have higher protein concentrations than other transudates?
Transudates are divided into low or high protein categories.
Not all capillaries are created equal! Some capillaries have large fenestrations, and some have
small fenestrations.
- Low protein transudate –> capillaries with small fenestrations. Typically very low cell counts and TP.
- High protein transudate –> capillaries with large fenestrations (hepatic sinusoids, lung)
Examples of Low protein transudate causes.
- End-stage liver failure (hepatic cirrhosis): this forms due to decreased albumin production by
the liver (decreased plasma oncotic pressure) and portal hypertension secondary to hepatic
fibrosis and high-resistance blood flow (increased plasma hydraulic pressure). There will
often be other biochemical evidence of hepatic insufficiency (hypoglycemia, low urea,
hypocholesterolemia)
Protein-losing disorders:
- Protein-losing nephropathy: Glomerular disease can result in the loss of large
amounts of albumin in the urine (decreased plasma oncotic pressure) and sodium
retention in the kidney (increased hydraulic pressure)
- Protein-losing enteropathy: Albumin loss through the gut can result in marked and
chronic hypoalbuminemia. Impaired lymphatic drainage (lymphangiectasia) is also
often present in protein-losing enteropathies.
Examples of High protein transudate causes
- High-protein transudates develop due to increased plasma hydraulic pressure within capillary beds
that are more permeable to protein loss (hepatic sinusoids, lungs) - Most common pathologies resulting in high-protein transudates are:
- Congestive heart failure: Decreased cardiac output can lead to venous congestion in
multiple organs, including liver and lungs - Portal hypertension can result in increased hydraulic pressure within the hepatic sinusoids, a
highly fenestrated capillary bed
What is the expected predominant cell type(s) in transudates?
All transudates have low cell counts. But depending on protein content, they are subclassified as either low-protein transudates or high-protein transudates
mostly mononuclear cells (macrophages and mesothelial cells with fewer lymphocytes), low
numbers of neutrophils. Variable amount of hemodilution.
Gross appearance: colorless to pale yellow
Difference between high and low protein transudate?
Low:
- Color: colorless, clear
- TP<2.5
- TNCC<1500
- Predominant cell type: Mononuclear cells
(macrophages, small
lymphocytes)
- May also see: Mesothelial cells and low # of neutrophils
High:
- Color: light yellow, clear
- TP>/equal to 2.5
- TNCC: <5000
- Predominant cell type: Mononuclear cells
(macrophages, small
lymphocytes)
- May also see: Mesothelial cells and variable # of neutrophils
Describe the mechanisms for exudate formation.
Due to inflammation of the pleural or peritoneal surface
- Inflammation (“serositis”) –>vascular and mesothelial permeability –> leaky vessels &
mesothelium –> exudation of
fluid, protein, & cells. - Inflammatory stimulus can be sterile or infectious
- Chemokines attract nflammatory cells
- Resulting effusion –> high cellularity, high
protein
When someone says a animal has “septic effusion” what does that mean? and can it ever be non-septic?
Yes it can be non-septic.
Septic can mean either “a patient have sepsis” OR it is used to mean “containing bacteria” (but NOT necessarily implying the clinical syndrome of sepsis)
Septic exudates refer to those with infectious, usually bacterial, causes.
EX: Gastrointestinal tract leakage
What is the classic findings of septic effusions?
- High cellularity effusion (exudate)
- Neutrophilic inflammation
- Degenerate (karyolytic) neutrophils
- Bacteria phagocytized by neutrophils &/or
macrophages - Positive bacterial culture –> GOLD
STANDARD
What is the expected predominant cell type(s) in exudates?
High cellularity and protein
Neutrophils (may be degenerative if septic effusion)
Mononuclear cells, mesothelial cells, microorganisms
TP>2.5
TNCC>5000
Variable (yellow to tan to red), turbid to cloudy to opaque in color.
What are some biochemical biomarkers of septic effusion?
Glucose:
- May help ID septic effusion
- Usually fluid glucose < plasma glucose (because cells and bacteria in fluid are consuming the glucose)
Lactate:
- May help ID septic effusion (anaerobic metabolism of neutrophils) OR strangulating obstruction (poor perfusion produces more lactate)
- Usually fluid lactate > plasma lactate
Effusion [lactate] > 4.2 mmol/L was 72%
SN & 84% SP for diagnosis of septic
peritonitis
What are the categories of special effusions?
- Vessel/Organ
rupture/leakage
a. GI tract rupture/leakage
b. Urine (uroabdomen)
c. Chyle (chylous effusion)
d. Bile (bile peritonitis)
e. Blood (hemorrhagic
effusion) - Neoplastic effusions
- Pericardial effusion
We just had a vessel/organ leak or rupture. What will we see?
Oftens ee exudate or a hemorrhagic effusion.
If GI tract rupture (especially lower), expect mixed bacteria and debris
We just had a GI rupture what is the suspected appearance, what will we see on microscope and what might be the cause?
COlor: variable, often opaque, brown to tan and odiferous
Mixed bacteria and debris suggesting ingesta or feces
Marked neutrophilic inflammation. Neutrophils may be degenerate and typically contain phagocytosed bacteria of mixed morphology
Rupture of organ due to trauma or other diseases
What biochemical tests will be do to confirm GI rupture?
+/- Glucose or lactate to help support septic effusion
This is not needed if cytology shows obvious bacterial infection or gut leakage!
Lactate and glucose measurements on effusion fluid should be done shortly after collection as cells in the effusion consume glucose and produce lactate
What is the appearance of a Uroabdomen?
Uroabdomen appearance is
highly variable
May look like a transudate
(acute/early) due to large volume of low-protein fluid (urine)
May look like an exudate
(late/chronic) due to urine irritating peritoneal surfaces
Might not fit neatly into a
category based on TNCC and
TP
We suspect uroabbdomen. What are some specific microscopic features, biochemical tests to confirm and the likely cause?
- Cause: urinary tract rupture due to stone, cancer. Or Trauma
- Microscopic fts: crystals typically found in urine (not always tho) Sperm in males, and if pt has UTI then microorganisms
- Tests to confirm: [creatinine], [potassium]> 2x plasma *caution: Do not measure [potassium] on effusion in EDTA tube
o Potassium may also be increased in the fluid compared to plasma, especially early. Sodium and
chloride concentrations may be lower in the fluid than in plasma.
o Since potassium (and sodium and chloride) equilibrate with plasma over time, the more chronic
the effusion is, the smaller the differences in electrolyte concentrations between fluid and
plasma will be.
An effusion that is milky to lactescent grossly is most consistent with what type of effusion?
Chylous effusion! Occurs due to leakage or rupture of lymphatics draining the intestines .
Can occur in the thorax (thoracic duct) OR abdomen. Cardiovascular disease may also cause chylous thoracic
effusions, especially in cats.
May look like a “strawberry milkshake” if contaminated with blood during sampling
What confirmatory test can you preform if you suspect a chylous effusion? What are the special microscopic features of it?
microscopic features: Highly vacuolated, light purple background with a predominance
of small lymphocytes
Test: Paired plasma (or serum) and fluid triglyceride (TG)
concentrations. [TG]fluid > [TG]plasma supports a chylous effusion. Usually, a [TG]fluid > 100 mg/dL is also supportive of a chylous effusion.
Variable numbers of neutrophils may be
present with chronic chylous effusions, due to irritation of the cavity surface by the chyle and/or
inflammation induced by repeated sampling or drainage attempts (iatrogenic).
What is a bile peritonitis effusion appearance?
Usually an exudate secondary to free bile causing inflammation of the peritoneal surface. Fluid may be green-tinged to yellow-orange in color. Bile is caustic and very pro-inflammatory – these effusions are typically exudates with marked neutrophilic inflammation.
What is a bile peritonitis effusion special microscopic features and what testing do we do to confirm?
- Presence of bile in the smear background (and possibly
phagocytosed by inflammatory cells) - Bile can either appear as green-black material or as wispy to amorphous, pale lavender to blue-gray material (so called “white bile”).
- Testing: A fluid total bilirubin concentration at least 2x higher than that in the plasma
Potential causes of bile peritonitis?
Biliary tract rupture, inflammation, or trauma (e.g., hit-by-car); pressure necrosis
secondary to a gallbladder mucocele or cholelithiasis.
What is the appearance if a hemorrhagic effusion?
Grossly bloody and opaque. Fluid often does not clot if left in a red-
top tube.
What are some things you will see on the microscope in hemorrhagic effusions?
like a blood smear, except that platelets typically are
not observed (consumed during the hemorrhage). Macrophages containing phagocytosed RBCs
and/or RBC breakdown products (hemosiderin, hematoidin) may be seen (the more chronic the effusion, the more likely you are to see these). Mesothelial cells are also commonly seen, especially in pericardial effusions.
What biochemical test should you do to confirm hemorrhagic effusion?
not applicable.
A packed cell volume (PCV) of the fluid will be equal to or greater than the peripheral blood PCV in the case of major vessel or organ rupture. The PCV of a hemorrhagic effusion will often be >10%, and in general, if the PCV of the fluid is greater than 3%, then hemorrhage is contributing to the effusion. Minor iatrogenic hemorrhage associated with fluid collection should not result in a PCV >3%.
What are potential causes of hemorrhagic effusion?
Trauma or disease (neoplasia, amyloidosis, etc.) leading to vessel or organ
rupture; congenital or acquired coagulopathy (e.g., anticoagulant rodenticide intoxication).
An effusion that is grossly bloody with a PCV >10% is most consistent with what type of
effusion?
Hemorrhagic effusion!!
What is the appearance of a neoplastic effusion?
variable but typically just contains a bunch of neoplastic cells.
What are the microscopic features of neoplastic effusions? Tests to confirm?
Cells with features of malignancy and will vary depending on causes
Tests: No biochemistry. Flow, PARR, special stains like immunocytochemistry
What is the typical appearance of pericardial effusion?
often hemorrhagic but can be transudate
What are special feactures of pericardial effusions on the microscope and what tests do we do to confirm?
- similar to hemorrhagic effusion plus mesothelial cells
- Testing? not applicable
Causes of pericardial effusions?
Idiopathic pericarditis, heart-based neoplasm, atrial rupture, etc. Neoplastic cells rarely observed in hemorrhagic pericardial effusions due to heart-based tumors.
