16/04/2026
Peritonitis in the Horse
Brian S. Burks, DVM
Diplomate of the American Board of Veterinary Practitioners®
394 Fox Road
Apollo, PA 15613
(724) 727-3481
www.foxrunequine.com
Peritonitis is inflammation of the lining of the peritoneal cavity, which is a space between the body wall and the viscera of the abdomen. It is similar to the pleura and pericardial sac, and lines the body wall and the abdominal organs; the peritoneal cavity is within the abdomen. It is caused by mechanical, chemical, or infectious insult. It may be acute or chronic, diffuse or local, primary or secondary, and either septic or non-septic. Most commonly, peritonitis is acute, diffuse, and septic, often secondary to gastrointestinal disease.
Inflammation liberates many mediators that result in loss of vascular integrity and influx of inflammatory cells, protein, red blood cells and electrolytes into the peritoneal cavity. These are to help limit the infection but can result in adhesions or abscessation if the disease becomes chronic. Disease may be mild to severe, causing hypovolemic and septic shock, leading to death.
Most cases of equine peritonitis are secondary to GI disturbance: perforation of intestine or the stomach, intestinal ischemia, abscess of the intestinal wall, duodenitis-proximal jejunitis, parasitism, etc. Re**al tears, uterine tears, castration, and abdominal surgery can also lead to peritonitis. It may also be due to trauma, such as foaling or breeding; mesenteric abscess, bile stones, and others. In foals, peritonitis can be due to ruptured urinary bladder or urachus, infection of the umbilical stump, and septicemia.
Some horses will develop peritonitis due to hematogenous spread or immunocompromise.
Clinical Signs
The clinical signs of peritonitis in the horse can be variable, but include fever, colic, depression, anorexia, diarrhea, and weight loss. They sometimes may suffer from shock. There may be altered GI motility, distended abdomen, splinted abdomen, or a distended viscus with fibrin palpated per re**um. Secondarily, horses may develop diarrhea or laminitis
Diagnosis
Definitive diagnosis of peritonitis is based on fluid collected during abdominocentesis. A cannula or needle is inserted into the peritoneal space to collect some of the small amount of fluid normally present. With severe peritonitis, this fluid may be voluminous, and may be noted upon abdominal ultrasonography. Ultrasound is also used to look for peripheral abscesses.
Peritoneal fluid cell count and protein are measured, and the gross color and turbidity are noted. Normal peritoneal fluid has few cells and little protein; it is also clear and pale yellow/straw colored. Cytology may reflect a septic process when looking at white blood cell type and number. There may be bacteria and/or plant material present. Culture of the fluid should be performed to help tailor antimicrobial therapy, but fewer than 30% of cases have positive bacterial growth.
Biochemistry analysis of serum may reveal hypoproteinemia or hyperproteinemia. Antibody levels may be increased, normal, or decreased. The complete blood count often shows an elevation in white blood cells, especially neutrophils, though they may also be decreased. Serum amyloid A and fibrinogen are usually elevated.
Treatment
Therapy of equine peritonitis begins with identification of the cause and correcting it, if possible. In some cases, this may mean an exploration of the abdominal cavity. In many cases supportive care is critical, including correction of fluid and electrolyte deficits. Anti-inflammatory medication is also warranted; inflammation of the peritoneum can lead to adhesions between two pieces of bowel, causing a kink obstruction.
Broad spectrum antibiotic therapy is also critical. This may be based on the most likely bacterial cause, depending upon the age of the hose, and etiology of the peritonitis. In cases with large amounts of fluid and/or fibrin apparent with ultrasound, abdominal lavage can be helpful. It will remove cells, fibrin, foreign materials, and bacterial products from the peritoneal cavity. This is always done at the end of any abdominal exploratory surgery to help reduce the incidence of adhesions. Lavage can also be done in the standing horse by infusing fluids from the top of the abdomen, walking the horse around to mix the fluid and wash toward the bottom, and draining via the ventral abdomen.
Peritonitis is a life-threatening disease. Upward of 90% of GI ruptures do not survive. Other causes are associated with a 60% recovery rate.
Fox Run Equine Center
www.foxrunequine.com
(724) 727-3481
