|Sample Requirement||Turnaround Time|
EDTA, plain, cytospin
+/- swab for culture
Same working day (cytology)
~48 hours (culture)
Analysis of peritoneal fluid is particularly useful as a diagnostic aid in cases of colic, weight loss and other suspected abdominal disease. It may be of particular value in helping to make the decision for surgical intervention.
To perform a peritoneal tap, the skin over the site of puncture should be clipped and prepared as for surgical intervention. With the horse restrained in the standing position, a 19 gauge, 1.5 or 2.0 inch needle or, following local anaesthesia and a stab incision, a 7.5 cm blunt teat cannula (operator preference) is carefully advanced through the skin at the lowest part of the abdomen and then through the linea alba. If fluid is not immediately forthcoming, the needle may be rotated or the tap may be repeated at other sites.
In foals, prior ultrasound scan examination of the abdomen is recommended to help visualise abnormalities and prevent inadvertent penetration of the intestine. Examination of the ventral midline will help to locate the spleen and to find a ‘pocket’ of peritoneal fluid to guide productive needle puncture. Similarly, if fluid is not obtained in adult horses using the blind technique described above, ultrasonic guidance may be helpful.
A turbid and homogeneously blood stained sample may indicate abdominal vascular embarrassment. A white, turbid fluid may suggest peritonitis. A brown, foul smelling fluid may indicate intestinal rupture or an intestinal tap. A thick and heavily blood stained sample suggests a splenic tap. Total nucleated cell counts >5 x 109/l suggest the presence of peritonitis or an intestinal or peritoneal lesion, which may warrant surgical investigation. Cytological examination may suggest acute or chronic infection, inflammation or neoplasia.