Pet Factsheets


Peritonitis is the term used to describe inflammation of the peritoneum, the membrane that lines the inner wall of the abdomen and covers most of the abdominal organs. Peritonitis can be very severe in cats and life threatening in many cases.  It is essential to identify and treat the cause as soon as possible.

What causes peritonitis?

The most common cause of peritonitis is bacterial contamination of the abdominal cavity following leakage of gut contents due to perforation of the gastrointestinal tract (bowel). This can be secondary to severe obstruction, such as with a foreign body in the intestine, perforated ulcers or failure of wounds in the intestine or stomach to heal following surgery. Other causes include rupture of other internal organs such as liver, bladder or uterus or external trauma, such as bite wounds. Peritonitis is most severe when bacterial infection is present: septic peritonitis.

Following any surgery involving the stomach or intestine, careful post-operative monitoring for early signs of septic peritonitis is essential. The peak time for development of this complication is 3 to 5 days following the surgery and early detection is vital.


How will my vet diagnose the disease?

An initial diagnosis of peritonitis is based on clinical signs and physical examination. Signs shown include lethargy, loss of appetite, abdominal pain or distention and vomiting. Your vet will then confirm diagnosis by performing abdominocentesis. This technique involves inserting a needle into the abdomen to see if there is any 'free fluid' and, if possible, collect a sample. This is often performed conscious, but may require sedation. The fluid sample can then be tested to identify the type of fluid and to check for bacteria.

X-rays, ultrasound and blood tests are also likely to be performed in order to determine the cause of peritonitis and evaluate the severity of the condition.

Can my cat be treated?

Intensive medical and supportive treatment is necessary both to stabilise the patient before surgery and post-operatively. This consists of fluid therapy to treat the shock, broad spectrum antibiotics, strong painkillers, and nutritional support.

An exploratory laparotomy, which involves a general anaesthetic to surgically open and operate on the abdomen, is required to evaluate the abdominal organs and determine the cause of peritonitis. The underlying condition is identified and addressed, when possible, during the surgery. Abdominal lavage is performed; this consists of profuse flushing of the abdominal cavity with warm sterile saline in order to remove the contaminating material and 'clean' the abdominal cavity as much as possible. In some situations, a drain may be left in the abdomen to allow ongoing drainage post-operatively.

Will my cat get better?

The prognosis depends upon the underlying cause, the severity of the peritonitis and the time of diagnosis, but is generally considered to be guarded.  Even with the best level of care, approximately 50% of cats with septic peritonitis will die, however excellent outcomes can be achieved with a return to normal life.

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