Presenting Signs: Oedema and Ascites

Question 1

1. Define oedema.
2. Oedema on radiograph.

Answer 1

1. Accumulation of fluid in tissue.
   E.g. subcutaneous oedema.
   E.g. pulmonary oedema.
   E.g. oedema of any organ.
2. Makes radiograph hazy and unclear with structures obscured and more difficult to see.

Question 2

Define effusion.

Answer 2

Abnormal accumulation of fluid in a body cavity.
E.g. peritoneal effusion = ascites.
E.g. pleural effusion.
E.g. pericardial effusion.
E.g. joint effusions.

Question 3

Normal fluid transportation in the body.

Answer 3

Blood enters arteriole end of capillary bed and filters out into the interstitial space. Most of this fluid is reabsorbed back into the capillary bed at the venule end but small amount of net filtration mopped up by the lymphatic system and carried back to the heart via this system.

Question 4

What is the serosa made up of?

Answer 4

Mesothelial cells and connective tissue.
Mesothelial cell layer:
- diffusion barrier, transcellular transport.
- synthesise connective tissue and enzymes.
- Respond to cytokines and hormones.
The lymphatics communicate through openings between mesothelial cells.

Question 5

Factors affecting movement of fluid under normal circumstances.

Answer 5

Hydrostatic pressure.
Colloid osmotic pressure.
Endothelial permeability.
Lymphatic function.

Question 6

Why does fluid accumulate?

Answer 6

More filtration occurring than reabsorption.
Increased capillary hydrostatic pressure.
Wider oncotic pressure gradient.
Increased endothelial permeability.
Loss of effective lymphatic drainage.

Question 7

Oedema/effusion clinical signs.

Answer 7

Depend on location of oedema/effusion.
Abdominal distension, fluid thrill.
Dyspnoea, tachypnoea.
Lameness.
Lethargy.
Inappetence.

Question 8

Dx tests for oedema/ascites.

Answer 8

PE.
Blood tests.
Ultrasound:
- abdomen.
- heart.
Radiographs.
Urinalysis - e.g. to look for a PLN&raquo_space; hypoalbuminaemia&raquo_space; ascites.

Question 9

Investigation of the fluid.

Answer 9

If effusion, take sample.
EDTA tube:
- cell counts, cytology, PCV, PCR (virology).
Serum tubes:
- albumin, bilirubin, creatinine, K, triglyceride, glucose, lactate.
Sterile tubes:
- culture (bacteria, fungi).

Question 10

Classification of effusions.

Answer 10

By TP and cell count.
Transudate:
- pure.
- modified.
Exudate:
- septic.
- non septic.
– haemorrhagic, chylous, bilious, malignant

Question 11

Normal pleural/peritoneal fluid.
- vol.
- colour.
- TP. (why?)
- nucleated cell count.
- Cell types.
- purpose.
– in thorax?

Answer 11

Low volume.
Clear, straw-coloured.
TP <2.5g/dL (due to ultrafiltration of blood).
Nucleated cell count usually <1000/microlitre.
Few cells (mesothelial cells, macrophages, lymphocytes, neutrophils).
Lubrication between organs.
– transmission of forces for normal respiration.

Question 12

1. Pure transudate.
   - colour.
   - SG.
   - TS.
   - nucleated cell count.
   - Cells.
2. Why do pure transudates form?

Answer 12

1. Clear, colourless liquid / slightly straw-coloured.
   <1.017.
   <2.5g/dL.
   <1000/microlitre.
   Few cells.
2. Increased hydrostatic pressure. e.g. venous hypertension.
   Decreased osmotic pressure. e.g. hypoalbuminaemia.
   No change in permeability.
   - just fluid leaking out, cells and proteins staying w/in the vasculature.

Question 13

Causes of increased hydrostatic pressure.

Answer 13

Systemic venous hypertension.
- R-sided CHF.
- Portal hypertension (liver disease).
- Occlusion (neoplasia, thrombus).

Question 14

Causes of decreased oncotic pressure.

Answer 14

Hypoproteinaemia - albumin.
– PLE/PLN.
– Liver failure –> not making enough albumin,
– Repeated drainage of effusion.

Question 15

Modified transudate.
- colours.
- SG.
- TP.
- Nucleated cell count.
- cells.

Answer 15

• Yellow - serosanguinous.
• 1.017-1.025.
• 2.5g/dL-5g/dL.
• 1000-10000/microlitre.
• low numbers of mesothelial cells, macrophages, neutrophils, mature lymphocytes, RBCs.
  – may see atypical cells if neoplastic process.

Question 16

1. Why do modified transudates form?
2. Why is modified transudate the most common kind of effusion we see?

Answer 16

1. Increased permeability of vessel wall to cells and proteins.
2. A chronic pure transudate&raquo_space; enough inflammation&raquo_space; increased permeability will occur&raquo_space; transudate becomes modified overtime.

Question 17

Causes of modified transudate.

Answer 17

Increased hydrostatic pressure.
R-sided CHF.
Vasculitis.
Neoplasia.
Post surgery.
Organ torsions.

Question 18

Exudate appearance.
SG.
TP.
Nucleated cell count.
Cell types.
What if exudate is septic?

Answer 18

Turbid - red, yellow, white.
>1.025.
>3g/dL.
>5000/microlitre.
Mostly neutrophils and macrophages +/- atypical cell (if neoplasia).
May see intracellular bacteria - CULTURE!

Question 19

Why does exudate form?

Answer 19

Increased permeability.
Inflammatory cells.
Lymphatic drainage reduced.

Question 20

How does exudate form?

Answer 20

Local inflammatory response to foreign material (exogenous, neoplastic, endogenous).
Cytokines, oxidants, proteases - increase mesothelial and endothelial permeability.
Influx of inflammatory cells.
Leak of protein into tissue.
Obstruction of lymphatics, decreasing drainage.

Question 21

Causes of septic exudate.

Answer 21

GI leakage, penetrating wounds.
FBs.
Urogenital tract.
Respiratory tract.
Haematogenous spread.
Intracellular bacteria on cytology (contamination on slide!)

Question 22

Causes of non septic exudates.

Answer 22

Pancreatitis: intra-abdominal inflammation.
FIP: coronavirus, protein-rich effusion, straw-gold, hazy.
Vessels: haemorrhagic effusion.
Lymphatic: chylous effusion.
Organs: urine, bile.

Question 23

Haemorrhagic effusion.
- appearance.
- SG.
- TP.
- cell count.
- PCV.
- If platelets present… if not…
- secondary to …. if not, what?
- cytology.

Answer 23

Closely resemble peripheral blood (RBCs, neutrophils, lymphocytes).
>1.025.
>3g/dL.
>1000/microlitre.
>10%.
If platelets present, may see blood clots (splenic aspiration, venepuncture, acute severe haemorrhage). Usually no platelets so no clotting as clotting factors usually used up before sampling.
Secondary to blunt trauma, or coagulopathy/neoplasia.
Buffy coat and sediment.

Question 24

Cause of chylous effusion.
Appearance.
SG.
TP.
Cell count.
Cell types.
Triglyceride.
Cholesterol.
Causes.

Answer 24

Impaired lymphatic drainage from GIT into caudal vena cava.
Opaque, milky.
>1.017.
>2.5g/dL.
Variable.
Lymphocytes (neutrophils, variable macrophages).
Triglyceride more than in serum at >100mg/dL.
Cholesterol less than in serum.
Cardiac disease, lung lobe torsion, trauma, mass lesions (compression of lymph drainage), idiopathic.

Question 25

Uroabdomen.

Answer 25

Acute uroperitoneum: pure transudate.
Inflammatory response develops.
Creatinine and urea in effusion > blood.

Question 26

Bilious effusion associated with?
Appearance.
SG.
TP.
Cell types.
Bilirubin.
Causes.

Answer 26

Gall bladder injury.
Green, orange, yellow.
>1.025.
>3g/dL.
Neutrophils, macrophages containing golden, green, black brown pigment from bile.
Bilirubin in effusion > in serum.
Trauma, cholangitis, pancreatitis, surgery, concurrent bacterial infection: poor Px.

Question 27

Effusion w/ exfoliation of cells.

Answer 27

Neoplastic or reactive mesothelial cells: highly cellular effusions.
Carcinomas, mesotheliomas, round cell neoplasms (lymphoma, MCT, malignant histiocytosis).
Can also get activation of mesothelial cells due to chronic effusions.