A clinincal evaluation of abdominal paracentesis in the horse.

Abstract: This paper evaluates the usefulness of abdominal paracentesis as a diagnostic aid in abdominal disease in the horse and in particular considers whether or not it can be effectively utilised as an indication for surgical intervention in cases of colic. The results are based upon peritoneal fluid samples collected from 20 normal horses and from 20 cases of colic and peritonitis. Peritoneal fluid was collected from standing horses by inserting a bovine teat cannula into the horses abdomen through the linea alba after desensitisation of the skin on the ventral midline with local anaesthetic. Usually, from 3-5 ml of fluid could be collected from a normal horse. This was either clear or cloudy white or yellow in colour and contained 3310 +/- 703 leucocytes/ml consisting of 63.81% neutrophils, 1.4 +/- 1.3% monocytes, 13.5 +/- 4.3% mesothelial cells and 21.25% +/- 6.2% lymphocytes. Protein content was 1.29 +/- .4g/100ml. Changes in the volume, colour, cellular constituents and protein content of fluid, characterised abdominal disease. In cases of colic, discolouration of the abdominal fluid was found to be the most consistent, reliable and useful indication of bowel necrosis. This in turn indicated the need for urgent surgical intervention rather than conservative treatment. Discolouration commenced early in the course of the disease even while the segment of bowel involved was still viable. Increased volume of fluid, elevated leucocyte count (statistically significant at the 5% level), increased neutrophil percentage and elevated protein levels were less useful criteria for determining the integrity of the bowel. Similar changes from the normal were also found in cases of peritonitis. Here, however, microscopic examination of cells in a smear of the fluid was more useful, as phagocytosis and abnormal cell types indicating infection or inflammation could be seen readily, and a diagnosis based upon these findings. It was concluded that abdominal paracentesis, although no substitute for thorough clinical examination, was a valuable diagnostic aid for abdominal conditions of the horse.