Peritonitis is inflammation of the peritoneum, the membrane that lines the abdominal cavity. Peritonitis may be short- or longterm, local or diffuse. Most commonly it occurs due to contamination (for example by perforation of the abdominal cavity by a foreign object, the splitting open of an abdominal wound closure, or the rupture of the intestine due to a foreign object or compromised intestinal wall), but it also may be caused by infectious agents such as viruses or bacteria.

Signs vary depending on the type and cause of peritonitis. Abdominal pain (colic) may be generalized and severe. The affected horse may guard the abdomen, walk with a stiff gait, or lie down and roll. Diarrhea or constipation may be noted, along with fever and loss of appetite. Abdominal distention, which may not be easily seen, is usually due to an accumulation of fluids and other material in the abdomen. Distention may be accompanied by bleeding, blood poisoning, paralytic obstruction of the intestines, shock, and adhesions. Jaundice may be present in generalized gallbladder peritonitis.

Common Causes of Peritonitis in Horses
Traumatic perforation or injury to the abdomen Leakage of material from damaged intestines  Leakage from damaged spleen, liver, or umbilical organs Injury caused by infections, chemical toxins, or parasites Rupture of the intestines, stomach, or rectum

Diagnosis of peritonitis can be difficult due to the nonspecific signs. Your veterinarian will likely use a combination of signs, x-rays or ultrasonography, rectal examination, and examination of peritoneal fluid (obtained from the abdomen) to make a diagnosis.

The first priority of treatment is to stabilize the consequences of peritonitis (for example, changes in electrolytes, acid-base imbalance, fluid loss, and blood clotting abnormalities), In addition, your veterinarian will want to identify the source of inflammation or infection and correct or remove it. Antibiotics are usually needed. Replacement fluids, electrolytes, plasma, or whole blood may be necessary to maintain heart output.

Once the horse is stabilized, surgery is done to explore the abdomen and to repair any defects. Your veterinarian will follow this with a thorough rinsing of the abdominal cavity with a saline solution, antiseptic, or antibiotics. Antibiotics are continued after surgery. Nutritional support with intravenous feeding may be needed, as many horses with peritonitis will not eat after surgery. In animals with blood poisoning and shock, fluids and electrolytes are crucial elements of treatment, especially for horses during the first 24 to 72 hours after surgery. Peritonitis caused by infection is frequently fatal, despite intensive treatment.

Last full review/revision July 2011 by Otto M. Radostits, CM, DVM, MSc, DACVIM (Deceased); Delores E. Hill, PhD; Barton W. Rohrbach, VMD, MPH, DACVPM; Charles J. Issel, DVM, PhD; Max J. Appel, DMV, PhD; David A. Ashford, DVM, MPH, DS; Daniela Bedenice, DrVetMed, DACVIM, DACVECC; Farouk M. Hamdy, DVM, MSc, PhD, MPA (Deceased); Kenneth R. Harkin, DVM, DACVIM; Johnny D. Hoskins, DVM, PhD; Eugene D. Janzen, DVM, MVS; Jodie Low Choy, BVMS; John E. Madigan, DVM, MS; Dale A. Moore, MS, DVM, MPVM, PhD; J. Glenn Songer, PhD; Joseph Taboada, DVM, DACVIM; Charles O. Thoen, DVM, PhD; John F. Timoney, MVB, PhD, Dsc, MRCVS; Ian Tizard, BVMS, PhD, DACVM; Brian J. McCluskey, DVM, MS, PhD, DACVPM; Bert E. Stromberg, PhD; Peter J. Timoney, MVB, MS, PhD, FRCVS