Felis ISSN 2398-2950

Peritoneal: effusion

Contributor(s): Yvonne McGrotty


  • Accumulation of fluid within the peritoneal cavity.
  • Cause: fluid may be blood, chyle, bile, urine, exudate, transudate or modified transudate.
  • Signs: abdominal distension, respiratory distress related to pressure on diaphragm
  • Diagnosis: ultrasonography, radiography and abdominocentesis.
  • Treatment: treatment of underlying cause where possible.
  • Prognosis: guarded overall, may be successfully managed.
    Follow the management tree for Peritoneal Effusion Peritoneal effusion.



  • Fluid type reflects underlying pathophysiology:
    • Neoplasia (hepatic, splenic, intestinal, lymphoma)
    • Trauma Abdomen: trauma (bite wound, RTA (HBC - hit by car), ruptured spleen).
    • Cardiac disease    →   right sided heart failure.
    • Pericardial disease Pericardial disease. Resulting in right-sided CHF and subsequent ascites.
    • Foreign body- resulting in peritonitis Peritonitis.
    • Bladder rupture Bladder: trauma rupture resulting in uroabdomen.


  • Accumulation of fluid within the peritoneal cavity by a variety of mechanisms.


  • Trauma, ruptured spleen or neoplasia bleeding into abdominal cavity.
  • PCV of effusion is similar to that of blood and has similar white cell number.
  • Usually doesn't clot due to rapid loss of fibrin (in contrast to inadvertent aspiration from blood vessel).


  • True chylous effusion is usually caused by abnormal or obstructed lymph channels:
    • Lymphangiectasia.
    • Inflammation or obstruction of flow, eg neoplasia, right-sided heart failure.
    • Lymphoproliferative disease affecting mesenteric lymph nodes.


  • Introduction of bacteria into peritoneal space, eg bite wound, foreign body, intestinal perforation, rupture of pyometra.
  • Migration of WBCs    →   abdominal cavity, or inflammatory conditions affecting peritoneum, eg neoplasia.


  • Due to imbalance of absorption and filtration of fluid across peritoneal lining.
  • May be due to:
    • Increase of capillary hydrostatic pressure.
    • Portal hypertension.
    • Hypoalbuminaemia.

Modified transudate

  • Long-standing transudates which have increased protein and cells secondary to peritoneal inflammation.
  • May be due to:
    • Hepatic disease.
    • Right-sided congestive heart failure.
    • Abdominal neoplasia.


  • Acute to chronic.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Levin G M, Bonczynski J J, Ludwig L L et al (2004) Lactate as a Diagnostic Test for Septic Peritoneal Effusions in Dogs and Cats. J Am Anim Hosp Assoc 40 (5), 364-371 PubMed.
  • Bonczynski J J, Ludwig L L, Barton L J et al (2003) Comparison of Peritoneal Fluid and Peripheral Blood pH, Bicarbonate, Glucose, and Lactate Concentration as a Diagnostic Tool for Septic Peritonitis in Dogs and Cats. Vet Surg 32 (2), 161-6 PubMed.
  • Tyler R D & Cowell R L (1989) Evaluation of pleural and peritoneal effusions. Vet Clin North Am Small Anim Pract 19 (4), 743-768 PubMed.