Reference values for equine peritoneal fluid

Twenty horses, aged one to 17 years (mean age 6 years), presented for elective destruction and subsequently found at autopsy to have no significant peritoneal alterations, were used to determine a variety of reference values for peritoneal fluid. Samples were collected ante mortem or within 1 h post mortem. Each cavity contained 100 to 300 ml of usually clear, pale yellow fluid which in a clinical refractometer showed a mean specific gravity 1.010 (range 1.0081-1.0116) and mean (+/- standard deviation) total protein 7.7 +/- 3.6 g/litre. The mean total nucleated cell count (+/- sd) was 4.33 +/- 2.5 x 10(9)/litre (range 1.5-10.1 x 10(9)/litre) and, proportionally, polymorphonuclear leucocytes averaged 45.2 per cent, mononuclear phagocytes 47 per cent, lymphocytes 7.8 per cent, eosinophils 0.7 per cent and basophils and mast cells zero. Eosinophils were not usually seen but 6 samples had 1 to 5 per cent. The peritoneal fluid chemical profile (mean +/- sd) was: Aspartate aminotransferase (AST) 118.9 +/- 46.9 iu/litre; alkaline phosphatase (AP) 56.0 +/- 52.7 iu/litre; lactate dehydrogenase (LDH) 143.0 +/- 106.1 iu/litre; total bilirubin (TB) 8.0 +/- 6.2 mumol/litre; total protein (TP) (biuret method) 14.2 +/- 6.8 g/litre; urea nitrogen (BUN) 6.1 +/- 1.1 mmol/litre; glucose 7.7 +/- 1.8 mmol/litre; inorganic phosphate (IP) 1.4 +/- 0.5 mmol/litre; calcium 2.0 +/- 0.2 mmol/litre. TP, BUN, glucose and IP were closely correlated with levels in paired serum samples.