Percutaneous sampling of peritoneal fluid with a needle or small catheter, called abdominocentesis (sometimes also known as peritoneocentesis or abdominal paracentesis), is a simple, rapid, and safe diagnostic method. When physical examination or imaging indicates moderate to large amounts of peritoneal effusion in a patient, sampling the fluid for cytologic, microbiological, or biochemical analysis often helps the clinician to quickly make a diagnosis and then to initiate timely and appropriate therapy. Abdominocentesis is most often performed to determine whether a patient needs exploratory celiotomy, particularly for early diagnosis of peritonitis or serious injury.
Before considering abdominocentesis, determine the relative value versus the risk of a blind puncture, particularly when a large vascular abdominal mass, an enlarged vascular organ, or a disorder affecting a distended hollow organ (such as a pyometra) is suspected, or in patients with severe coagulopathies. In these instances, consider ultrasound-guided sample collection if available. Abdominocentesis is best performed after plain radiography unless a rapid diagnosis needs to be made in a deteriorating patient. Free peritoneal air on radiographs may help the clinician identify hollow organ rupture or peritoneal perforation. In a large retrospective study of 129 dogs and cats with intraabdominal injury or disease, abdominocentesis had an overall diagnostic accuracy of 47% in dogs and cats (largely due to false-negative results), compared with 83% for catheter paracentesis, and 95% with diagnostic peritoneal lavage. The clinician must understand that false-negative results are reduced when larger amounts of free fluid are detected within the peritoneal space. False-negative results have also been reported with diseases confined to the retroperitoneal space and conditions resulting in only localized or walled-off fluid pockets. Diagnostic yield can be improved by ultrasound guidance to capture fluid within these pockets.
What You Would Need In General
- Clippers and blades
- Antiseptic scrub
- Sterile surgical gloves
Sampling Equipment
- 18- to 22-gauge 1.5-inch needles or 16- to 18-gauge over-the-needle catheters
- Luer tip syringes (3-12 ml depending on the patient's size and amount of fluid needed for testing)
- Sample containers
- Serum "red-top" tubes (for biochemistry analysis)
- EDTA "purple-top" tubes (for cytology, total protein content, red blood cell and total nucleated cell count)
- Culturettes for bacterial culture
- Glass slides for cytologic evaluation
Step-by-Step: How to perform abdominocentesis
Positioning & Skin Preparation
Abdominocentesis is usually performed in conscious animals with physical restraint. If the patient is intractable, judicious use of chemical sedation should be considered. 1. Clip and prepare the ventral abdominal area for aseptic fluid collection. 2. Infiltrate the proposed sites with a local anesthetic agent if a larger over-the-needle catheter is chosen for sampling. 3. For simple abdominocentesis, stand the patient or position it in sternal recumbency. Access the most dependent site on the abdomen. Alternatively, nonambulatory or unruly patients can be positioned in left lateral recumbency. First puncture the right side to help avoid hemorrhage or contamination of the sample from accidental aspiration of the spleen.