In a normal healthy horse, there is a small amount (about 50cc) of clear, sterile pale yellow peritoneal fluid that lubricates the very large and complicated intestine, and other organs in the abdominal space.

Peritonitis is infection of this huge and complicated space, usually with bacteria. Infection results in the fluid increasing in volume, and turning cloudy, indicating a large increase in the number of infection fighting cells (inflammatory White Blood Cells) in the fluid.

Peritonitis can result from a variety of causes including wounds into the abdominal space and blood borne infections. It can also be a complication of colic surgery.

Vets use systemic antibiotics to fight this infection, however sometimes these are not enough. There is simply too much infectious material in the cavity and the resulting septic "stew" must be diluted, drained and flushed away. In this case, we perform an abdominal lavage.

HOW IT WORKS

In the standing horse, a large abdominal (or chest) sterile plastic drainage tube is placed into the abdomen. The horse is usually sedated for the procedure. The site, which is usually on the lowest, front part of the belly, is clipped and surgically prepared.

A local anesthetic numbs the skin at the selected site. A skin incision is made surgically and the abdominal wall is separated to allow the placement of the tube into the abdominal space. The abdominal wall is 3-6cm thick, depending upon the horse. Most chest drainage tubes come with a sharp poker that sits within them (a stylette), which is held within the tube during placement. This keeps it rigid and allows it to penetrate the wall. The stylette is removed once the tube is in place.

In most cases, the tube is sutured in place to maintain drainage and act as a portal for repeated flushing.

Excessive pus is initially drained out. Large quantities (10 liters on average) of sterile intravenous fluids are placed into the abdomen through the tube. They are allowed to sit in the abdomen for a short period of time before being drained. This may be repeated.

In many cases, the tube is left in place (often with a one-way valve known as a Heimlich Valve) allowing the procedure to be repeated later. The procedure may be repeated once or even twice daily until it is believed that the infection is under control or cleared.