Page 809 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

784 CHAPTER 4

VetBooks.ir Abdominocentesis of total protein or specific gravity (SG) can provide
Visual examination of the fluid plus determination
Abdominocentesis is often utilised to assist in deter-
mining whether colic surgery or euthanasia is indi-
neal fluid is clear to slightly yellow in colour. Total
cated; however, it can also be useful in the evaluation adequate information in most cases. Normal perito-
of fever of unknown origin or evaluation of perito- protein level should be <25 g/l (2.5 g/dl). The fluid
neal effusion. Although often advocated in chronic may be dark yellow or orange and turbid with perito-
weight loss, chronic diarrhoea and chronic inflam- nitis or compromised intestinal viscera (Fig. 4.116).
matory disease, its usefulness in these conditions is Bloody or red-tinged fluid should be interpreted
questionable. with caution, as iatrogenic bleeding may discolour a
The preferred site is approximately 10 cm caudal normal sample. A high packed cell volume (PCV) is
to the xiphoid and 5–10 cm to the right of midline. suggestive of splenic puncture and determination of
The area should be clipped and surgically prepared. total protein content of the supernatant is not reliable
An 18-gauge, 1.5-inch needle is adequate for most in such cases. Intestinal contents may be evident as
horses. A larger needle may be required for very fat dark, flocculent, foul-smelling fluid. Enterocentesis
animals and those with ventral oedema. Occasionally, is possible, particularly when a needle is used. If
a change in resistance or ‘pop’ may be felt when the enterocentesis does occur, then rapid initiation of
peritoneum is entered, or fluid may flow spontane- therapy with a broad-spectrum antimicrobial (such
ously (Fig. 4.115). A small volume (1–2 ml) of air can as tetracycline or trimethoprim/sulphonamide) via
be aseptically injected into the needle to dislodge a single intravenous dose is indicated. Further anti-
any tissue that may be blocking flow. If no fluid is microbial therapy is not typically required beyond
obtained, a second needle can be inserted 3–6 cm a single dose, but the patient should be monitored
from the first. Alternatively, a teat cannula can be closely for signs of peritonitis, such as fever. If
used. The area should be infiltrated with 2% lido- abdominocentesis fluid is suggestive of rupture of
caine and a stab incision made through the skin and an intestinal viscus, sampling should be repeated at
superficial tissue. Controlled force should be used to one or more distant sites. Ultrasonography may also
enter the peritoneal cavity. Abdominocentesis will be useful to distinguish rupture as a large volume of
not always yield fluid and this is not an abnormal or free fluid is typically seen in such cases unless the
unexpected finding. horse is severely hypovolaemic.

4.115 4.116

Fig. 4.115 Free-flowing
abdominal fluid during
abdominocentesis.

Fig. 4.116 Serosanguineous
abdominal fluid from a horse
with a strangulating small-
intestinal lesion.