Abdominocentesis

Introduction

The extraction and analysis of fluid from the peritoneum can be useful in assessing the state of the intestines. Abdominocentesis can be a useful diagnostic tool in determining whether the colic patient should go to surgery. It should be performed in every case of recurrent, moderate to severe or persistent colic, chronic weight loss and diarrhea. It should not be performed in the field due to the risks to the veterinarian and horse if the physical examination findings are suggestive of the need for surgery and referral. For normal peritoneal fluid analysis in the horse click here.

Equipment

• Twitch and sedation if necessary
• Clippers and material for a sterile scrub
• Ultrasonography if it is available
• Sterile Gloves
• Sterile 18-gauge to 22-gauge, 1 1/2-inch needles (a #15 scalpel blade is required if using a teat cannlua)
• Sterile syringe
• Sterile gauze
• EDTA tube
• Plain tube
• Sterile vial for culture

Procedure

The best site for abdominocentesis is the most dependent part of the abdomen, midline and usually around 5 cm caudal to the xiphoid. The use of ultrasound for selecting the pockets of peritoneal fluid within the abdomen is ideal as it not only indicates how thick the body wall is but the location of viscera to be avoided. However, peritoneal fluid can still be extracted even if it is not apparent on ultrasound. A right paramedian approach at the most dependent area of the abdomen is the best site if ultrasound is not available. This approach should avoid accidental puncture of the spleen. The selected area should be generously clipped and a sterile scrub performed. At minimum a twitch, or sedation if the horse is more fractious, should be used for restraint. Sterile gloves should be worn to maintain sterility. The veterinarian should stand next to the horse and insert the needle with a quick action through the skin. Then the needle can be gently and carefuly advanced through the linea alba, into the peritoneal cavity. If fluid is present, then drops should be seen in the needle hub. If this is not the case, reposition and twist the needle. Alternatively, a sterile syringe can be attatched and the fluid can be aspirated. Once the fluid is noted, it should be allowed to drop freely into the EDTA and plain tubes for analysis. The fluid may also be submitted for microbiological culture and sensitivity, peritoneal lactate and glucose concentrations if necessary.

Complications

Accidental splenic puncture will contaminate the sample and make analysis difficult. The fluid will be blood-tinged and have a PCV greater than that of the peripheral blood. Accidental puncture and aspiration of the bowel and its contents commonly occurs but does not often cause complications. The risk of this can be minimized using a blunt-tipped cannula. The risk of both scenarios can be minimized by the use of ultrasound guidance. If sterility is broken during the procedure or purulent and septic fluid is removed then there is a risk of cellulitis and abscess formation in the body wall.

Peritoneal Fluid Analysis

For normal and abnormal peritoneal fluid analysis, see peritoneal fluid analysis in horses.

References

• Edwards B. (2009), Diagnosis and Pathophysiology of Intestinal Obstruction, in Equine Gastroenterology courtesy of the University of Liverpool, pp 8-9
• Meuller E, Moore J. N, (2008) Classification and Pathophysiology of Colic, Gastrointestinal Emergencies and Other Causes of Colic, in Equine Emergencies- Treatments and Procedures, 3rd Edition, Eds Orsini J. A, Divers T.J, Saunders Elsevier, pp 102 - 105, 111