Colic - Peritoneal Fluid Analysis

Assessing the pertioneal fluid can give information about the disease process in the very early stages. Some disease processes such as peritonitis and enteritis produce changes in the peritoneal fluid before the onset of clinical signs. This allows for the early diagnosis of the disease which will favour an improved prognosis for the patient. Strangulating obstructions produce changes in the peritoneal fluid within a few hours of the obstruction occurring. Horses with an intussusception may have normal peritoneal fluid initially as the peritonitis that develops is localised to the portion of entraped bowel.

Peritoneal fluid should be assessed for colour, turbidity, specific gravity, total nucleated cell count and examined under the microscope for cytology. Normal peritonel fluid is clear to yellow in colour and has a specific gravity of 1.005 mg/dl. The fluid becomes yellow or white and increasingly turbid when there is more protein or cells in it. The initial changes seen in the fluid during gastrointestinal disease are a serosanguinous appearance and an increased red blood cell count and total protein level. The fluid becomes yellow or white and increaingly turbid when there is more protein or cells in it. When the affected portion of bowel becomes ischaemic and necrotic, it leaks cells into the peritoneal fluid. White to yellow, cloudy fluid or exudate will be high in white blood cells. This is seen in septic peritonitis. Red, brown or green fluid can indicate rupture of the gastrointestinal tract and plant material may be present in the sample. A dark red sample may indicate accidental splenic or vessel puncture. The sample will have a higher Packed Cell Volume (PCV) than the peripheral blood if it has been obtained from the spleen, and the same PCV as the peripheral blood if it has come from a vessel.

A high nucleated cell count indicates a ruptured bowel but this is not always the case. Sometimes the nucleated cell count is normal in a case of bowel rupture because the cells may have been lysed in the fluid.

A sample from the fluid should be stained with Wright's and/or Gram stain and examined under the microscope. The sample should be examined for the presence of bacteria (intracellular or extracellular), plant material, cellular appearance, a white blood cell count and a differential cell count. Cases of septic peritonitis will have samples with predominantly toxic and degerate neutrophils.

The fluid can be assessed for glucose and lactate level. A sample with a glucose concentratio higher than that of the peripheral blood indicates septic peritonitis. If the peritoneal lactate concentration is higher than the peripheral blood concentration then intestinal infarction is likely.

Peritoneal Fluid Analysis and Intraabdominal Disorders

Clinical Condition	Appearance	Total Protein (g/dl)	Total Nucleated Cells/L	Cytology
Normal	Clear - Yellow	< 2.0	< 7.5 x109	20 - 80% mononuclear cells, 40 - 80% neutrophils
Non-strangulating Obstruction	Clear - Yellow, Slightly turbid	< 3.0	< 3.0 - 15.0 x 109	Mostly neutrophils (preserved)
Strangulating Obstruction	Red - Brown, Turbid	2.5 - 6.0	5.0 - 50.0 x 109	Mostly neutrophils (degenerate)
Proximal Enteritis	Yellow - Red, Turbid	3.0 - 4.5	< 10.0 x 109	Mostly neutrophils (preserved)
Bowel Rupture	Red - Brown - Green, Turbid with or without particulate matter	5.0 - 6.5	20 - 150 x 109	> 95% neutrophils ( severely degenerate), intracellular or extracellular bacteria, with or without particulate matter
Septic Peritonitis	Yellow - White, Turbid	> 3.0	20.0 - 100.0 x 109	Mostly neutrophils (degenerate)
Accidental Enterocentesis	Brown - Green, with or without paticulate matter	Variable	< 1.0 x 109	Free bacteria, plant material, few cells
Intraabdominal haemorrhage	Dark red	Similar TPP to peripheral blood	White Blood Cell Count increases with time	PCV less than peripheral blood, erythrocytophagia, few if any platelets
Post-celiotomy	Yellow - Red, Turbid	Variable	Variable	Mostly neutrophils (moderate degeneration), no intracellular bacteria

Colic - Peritoneal Fluid Analysis Learning Resources
Flashcards Test your knowledge using flashcard type questions	Cytology Q&A 15

References

• Meuller E, Moore J. N, (2008) Classification and Pathophysiology of Colic, Gastrointestinal Emergencies and Other Causes of Colic, in Equine Emergencies- Treatments and Procedures, 3rd Edition, Eds Orsini J. A, Divers T.J, Saunders Elsevier, pp 103 - 105