Back

BODY CAVITY EFFUSIONS

First broadcast on www.provet.co.uk  

This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

Accumulation of fluid within a body cavity is a common clinical finding which may be associated with a variety of diseases. Characterisation of the fluid helps with the differential diagnosis.

Aspiration and laboratory identification of fluid from a body cavity is a commonly used  diagnostic aid. The following table (modified after MacWilliams et al, Proceedings NAVC Jan 2000) summarises the different fluid characteristics and differential diagnosis :

  Normal Transudate Exudate
Volume of fluid Very small amount Large amount Variable amount
Appearance of fluid Clear and colourless Clear and colourless or red-tinged Turbid and white-yellow.
Protein content <2.5 g/dl <2.5 g/dl >3.0g/dl
Total number of nucleated cells (TNCC) <3000 / mL <1500 / mL >5000 /mL
Cell types present Mixed  cells: Lymphocytes Macrophages Mesothelial cells Monocytes Mixed cells: Lymphocytes Macrophages Mesothelial cells Monocyte Inflammatory cells: Eosinophils Lymphocytes Macrophages Neutrophils (majority)
Cause 1 NA Hypoproteinaemia Inflammation
Cause 2 NA Venous or lymphatic obstruction/congestion Organ perforation or rupture
Cause 3 NA   Neoplasia with inflammation or necrosis

Hypoproteinaemia (serum albumin less than 1.0g/dl) may occur with:

  • Severe protein loss :
    • Intestinal malabsorption 
    • Proteinuria
  • Liver disease
  • Overhydration

Venous or lymphatic obstruction/congestion may be due to :

  • Cardiac Failure - right heart failure. Fluid is clear to red-tinged with increased protein (2.5-4.5 g/dl) and only a slightly increased TNCC (neutrophils, lymphocytes and macrophages). This fluid is called a modified transudate.
  • Lymphangiectasia
  • Atelectasis
  • Obstruction due to a mass

Inflammation may be due to infection caused by  :

  • Bacteria
  • Fungi
  • Protozoa
  • Viruses eg Feline Infectious Peritonitis. Clear to yellow-orange fluid. Turbid. Total nucleated cell count (TNCC) 500-20000/ mL. Protein content 3.5-7.0 g/dl

and by 

  • Fluid leakage from organs
  • Neoplasia . 
    • Lymphoma results in white to yellow, clear or turbid fluid accumulation. TNCC varies. Large hyperchromatic lymphoblasts with evidence of mitosis are present.

Fluids originating from a perforated or ruptured organ include :

  • Haemorrhage - trauma to blood vessels, thrombocytopenia, clotting defects
    • blood may appear in a sample due to contamination during collection of the fluid
    • If fluid has a high platelet count - blood presence is most likely due to contamination or active haemorrhage is going on.
    • Post-trauma a large number of red blood cells and few leukocytes are present.
  • Gastrointestinal perforation - leakage of secreted fluids, digestive enzymes, chyme or faeces lead to peritonitis. 
  • Chyle - milky-white fluid sometimes with blood tinge. Chyle contains higher triglyceride and lower cholesterol than serum. Causes :
    • Obstruction of thoracic duct - neoplasia or granulomas
    • Injury leading to rupture or perforation of the thoracic duct. May be associated with diaphragmatic hernia.
    • Cardiovascular disease
    • Vomiting
    • Chronic coughing 
  • Bile - causes peritonitis.  Yellow-orange to green fluid and turbid fluid.
  • Urine - ruptured bladder, ureters, renal injury. Azotaemia may be present. Little inflammation caused. Fluid is clear, light yellow and contains few cells, unless inflammation was present before rupture.
  • Ruptured gravid uterus
  • Ruptured uterus with pyometra
  • Ruptured cysts

Last updated : January 2016