How to perform abdominocentesis and interpret abdominal fluid in equine patients

To describe and demonstrate the collection of abdominal fluid from a standing, sedated equine patient.

1 healthy university-owned animal was used for abdominocentesis demonstration. Images from various clinical cases from the University of Illinois Veterinary Teaching Hospital are shown.

Under standing sedation, a 10 X 10-cm area is clipped and aseptically prepared on the most dependent portion of the abdomen to the right of midline. One to 2 mL of 2% lidocaine is instilled subcutaneously and into the abdominal musculature at the abdominocentesis site. A stab incision is made through the skin and external rectus sheath with a No. 15 blade, and the blade is rotated 180°. A teat cannula is placed into the incision, and pressure is applied to penetrate the peritoneum. The teat cannula is rotated as necessary to achieve fluid. Alternatively, an 18-gauge, 1.5-inch needle can be inserted through the skin in the ventral abdomen in the center of the aseptically prepared area (no lidocaine block or incision needed).

Abdominal fluid is collected in a red top tube for stall side parameters (lactate and total protein) or culture and a purple top tube for cytologic evaluation. Normal fluid is straw-colored and clear, with a total protein < 2 g/dL and L-lactate < 2 mmol/L (or similar to peripheral L-lactate), and has a nucleated cell count < 500 cells/µL.

Abdominal fluid is a useful diagnostic tool to investigate conditions of the equine abdomen. When used in conjunction with other diagnostic procedures, abdominocentesis helps guide treatment and referral decisions in colic patients.