How to perform abdominocentesis and interpret abdominal fluid in equine patients.

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

Animals: 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.

Methods: 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).

Results: 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.

Clinical Relevance: 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.