23 June 2021

Vet advice: peritonitis explained — plus one pony’s miracle recovery

Vet advice: peritonitis explained — plus one pony’s miracle recovery

Problems with the horse’s stomach can sometimes be attributed to peritonitis, an inflammation of the abdominal cavity. Vet Leona Bramall MRCVS from Oakhill Equine Vets in Preston discusses what peritonitis is and how to treat it.

When 12-year-old Freddie was referred for veterinary assessment, his owner described him as not being ‘quite right’ for the past 48 hours. They reported that the grey gelding appeared quieter than usual, tending towards being a little depressed, alongside a reduced appetite and fewer droppings than normal. On examination, Freddie’s heart and breathing rates were mildly increased and his gut sounds were reduced. He had a fever of 39.5C.

Given Freddie’s history, a rectal examination was undertaken. This revealed no abnormal findings. As a result, anti-inflammatory drugs were administered, and a blood sample was taken for analysis.


Blood work revealed a low white blood cell count, which can result from white blood cells leaving the blood stream to fight infection. Serum amyloid A, an inflammatory marker, was also high, and a number of other parameters pointed towards mild dehydration. It was advised that Freddie was admitted to our hospital for further investigations and treatment as necessary.

On admission, abdominal ultrasonography was performed, which revealed an increased amount of free fluid in Freddie’s peritoneal cavity. No other abnormalities were noted on ultrasonography. A sample of the peritoneal fluid was subsequently obtained and analysis revealed a high white blood cell count.

A diagnosis of peritonitis was made.

What is peritonitis?

Peritonitis refers to inflammation of the peritoneal cavity, which is the medical term used to describe the abdominal cavity. In very simple terms it can be likened to a balloon, filled with a small amount of fluid, in which the abdominal organs sit. The fluid contained within the cavity — peritoneal fluid — acts as a lubricant, reducing friction during movement of the abdominal organs.

What are the signs?

The clinical signs displayed by an affected horse depend on the cause, duration and severity of the disease. In certain cases, the diagnosis is reached very quickly whereas in others, peritonitis is a less clear diagnosis.

If there is a penetrating injury to the horse’s abdominal wall, a secondary peritonitis is highly likely. Other cases are harder to diagnose, especially those with primary peritonitis, where the diagnosis is ascertained after performing a series of diagnostic tests.

  • As a general rule, horses with peritonitis will present with a history of being off colour and with a reduced appetite.
  • When examined these horses normally have a fever (a temperature greater than 38.5°C), increased heart and breathing rates, may be dehydrated and have evidence of toxaemia.
  • Affected horses may also show signs of pain when the external abdominal wall is palpated and may be reluctant to move.
  • Signs of colic can also be apparent, especially in those cases that occur secondary to a gastrointestinal cause.

What causes it?

Freddie made a full recovery after his treatment

In equine patients, the majority of peritonitis cases can be categorised as either primary or secondary peritonitis. Primary peritonitis is a spontaneous disease process without an obvious inciting cause, whereas in cases of secondary peritonitis a cause is identified.

Secondary peritonitis can occur when the external abdominal wall is breached following trauma. As a result, bacteria gain entry into the once sterile peritoneal cavity, resulting in a bacterial infection. Secondary peritonitis can also occur following perforation of the gastrointestinal tract or reproductive tract (namely the uterus as a consequence of traumatic foaling).

Other causes of secondary peritonitis include spread of bacteria to the peritoneal cavity from the blood stream (septicaemia), spread of infection from the urinary tract or uterus, from an intraabdominal abscess, from an infected umbilical cord in foals, as a complication of the gelding process, parasites (worms), certain viral infections and finally, neoplasia (cancer).

How is it diagnosed?

Compatible clinical signs will raise suspicions that a patient may have peritonitis, but the diagnosis is confirmed following a number of diagnostic tests, namely blood work, abdominal ultrasonography and analysis of a sample of fluid obtained from the peritoneal cavity.

Affected patients will normally have an abnormal (either high or low) white blood cell count, increased free fluid in the peritoneal cavity on ultrasound examination and peritoneal fluid analysis will reveal a high white blood cell count in addition to high protein levels.

How is it treated?

Treatment Freddie was started on broad spectrum, intravenous and oral antimicrobials, and he continued on the anti-inflammatory therapy on his livery yard. Intravenous fluid therapy was also initiated due to Freddie’s mild dehydration and reluctance to drink.

Treatment for peritonitis is based on intravenous antibiotic and anti-inflammatory therapy in addition to managing toxaemia if present. Correcting dehydration and maintaining hydration is achieved through the use of intravenous fluid therapy. In non-responding cases, placement of an abdominal drain to facilitate lavage and/or surgical exploration and subsequent treatment may be indicated.

Prognosis ultimately depends on the cause of the peritonitis, severity of the clinical signs and initial response to treatment. Cases occurring secondary to gastrointestinal tract rupture carry a grave prognosis.

How is Freddie now?

In Freddie’s case, he responded well to the treatment initiated and within 24 hours his temperature stabilised and remained normal thereafter. During this timeframe his demeanour, appetite — and in turn faecal output — also improved.

Serial repeat abdominal ultrasound and peritoneal fluid examinations revealed a gradual normalisation and Freddie was discharged after seven days to continue his treatment and rehabilitation at home. He has recovered fully and is back in work.

Main image = stock image/Shutterstock

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