Peritonitis - Cats and Dogs

Signalment

• No breed predisposition.
• No sex predilection.
• No specific age distribution.

Description

Peritonitis is defined as the inflammation of the peritoneum. The inflammatory process leads to vasodilation, cellular infiltration, pain and adhesion. This can be classified into primary or secondary peritonitis.

Primary peritonitis occurs spontaneously without pre-existing pathology in the abdomen. In cats, this form of peritonitis is associated with feline infectious peritonitis.

Secondary peritonitis occurs as the result of a pathological condition in the abdomen. This can be further classified into septic or non-septic peritonitis. Septic peritonitis results from free bacteria in the peritoneal cavity. This can be caused by perforation of the gastrointestinal tract due to foreign bodies, necrosis, intussusception, neoplasia, foreign bodies or dehiscence. Peritonitis as a result of wound dehiscence is most likely to occur 3-5 days post-operatively. Septic peritonitis is the most common form that occurs in dogs. Non-septic, also known as chemical peritonitis, may be the result of leakage of bile, urine or pancreatic enzymes. Non-septic peritonitis can however cause septic peritonitis, for example in cases where septic urine is present.

Diagnosis

Clinical Signs

• Abdominal pain
• Depressed
• Vomiting
• Diarrhoea
• Hypotension and shock
• Hypothermia or hyperthermia

Laboratory Tests

Haematology

• Leucocytosis; predominantly neutrophilia ± left shift or neutropaenia
• Haemoconcentration
• Hypoproteinaemia

Biochemistry

• Hypoglycaemia - possible sepsis
• Increased lactate concentration
• Azotaemia
• Hypokalaemia
• Metabolic acidosis

Diagnostic Imaging

Radiography

• Abdominal radiography may reveal free gas in the abdomen. This is highly suggestive of peritonitis. The visceral details are loss. If radiograph is taken with the patient standing, a fluid line may be seen.
• Thoracic radiograph should be assessed for signs of metastatic disease.

Ultrasonography

• This is sensitive to detect free fluid in the abdomen.
• Possible causes such as abscesses of organs or rupture of gall bladder can be identified.
• It can be used to assist abdominocentesis.

Histopathology

• Abdominal fluid can be collected for laboratory analysis via abdominocentesis. The fluid should be stained for intracellular bacteria and assessed for:
  • amylase and lipase for pancreatitis
  • bile for biliary leak
  • creatinine for urine
  • glucose (<2.8 mmol/l) and lactate (>5.5 mmol/l) for sepsis

Treatment

It is vital to identify cases which require emergency surgical intervention. Any of the following is a major indication:

• positive for intracellular bacteria.
• free gas visible in the abdominal radiograph.
• presence of penetrating injuries in the abdomen.

Medical

Fluid therapy

• Aggressive fluid therapy with crystalloid and colloid should be given on initial presentation to improve haemodynamic parameters.
• Fluid therapy is also very important in the postoperative period. Both crystalloid and colloid should be continued until the patient is normotensive. However, if hypotension continues, a vasopressor such as vasopressin should be considered.
• Supplementaion of glucose and potassium may be needed.
• If severe metabolic acidosis is present, bicarbonate may be given.
• Septic peritonitis can cause disseminated intravascular coagulation (DIC) and therefore plasma can be given to replace clotting factors.

Antimicrobial

• Broad spectrum antibiotics should be given, preferably following culture and sensitivity test. Escherichia coli, Clostridium spp. and Enterococcus spp. are most commonly isolated.

Surgery

This may be indicated if the cause of peritonitis is undetermined or intestinal rupture or intestinal obstruction or mesenteric avulsion is suspected. Abdominal lavage is controversial due to the possibility of dissemination of infection. It is indicated in cases of generalised peritonitis but care has to be taken in cases of localised peritonitis. As much of the fluid used for lavage has to be drained as it will hinder the body’s immune system otherwise.

Prognosis

Guarded. Peritonitis is a multifactorial disease and the consequence is fatal in most cases. A rapid diagnosis and treatment may improve the prognosis.

References

• Fossum, T. W. et. al. (2007) Small Animal Surgery (Third Edition) Mosby Elsevier
• Nelson, R.W. and Couto, C.G. (2009) Small Animal Internal Medicine (Fourth Edition) Mosby Elsevier.
• Tilley, L. P. & Smith, F. W. K. (2007) Blackwell's Five-minute Veterinary Consult: Canine & Feline (Fourth Edition) Blackwell Publishing

For further information on peritonitis see: [1] In Pra