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Peritonitis in Dogs

Peritonitis is often associated with acute abdominal pain due to the sudden inflammation of the abdominal tissues, or peritoneum, hence the name for the condition. This causes fluid to shift into the peritoneal cavity, leading to severe dehydration and electrolyte imbalance. Peritonitis may be due to infectious causes such as the stomach flu or non-infectious causes such as a hernia.

While younger dogs tend to have acute abdomen due to infectious and traumatic causes, malignant cancers are more often the cause of acute abdomen in older dogs. It is crucial to determine the underlying cause of the acute abdomen as your veterinarian may have to perform emergency surgery to resolve it.

Symptoms and Types

• Lethargy
• Trembling
• Crying, Whimpering
• Abnormal posture (i.e., may be "guarding" the stomach by curling up, or leaning forward with back end higher in attempt to relieve pain)
• Heavy breathing
• Swollen abdomen (may be rigid to the touch
• Diarrhea, which may be black (also referred to as melena)
• May have vomiting if the stomach or intestines are involved

Causes

Infectious Causes

• Holes in the dog's stomach lining
• Viruses of the stomach or intestinal tract
• Feline infectious peritonitis virus
• Viral enteritis (stomach flu)
• Parasites of the stomach or intestines
• Bacterial infection of the uterus
• Abscesses of the liver, spleen, and/or pancreas

Non-infectious Causes 

• Tumors
• Cancers
• Poisoning
• Congenital Defects
• Trauma to the abdomen, possibly involving rupture of organs (hernia)
• Rupturing of the ureters (tubes which carry urine), bladder or of a pregnant uterus
• Congenital hernia causing entrapment of organs
• Obstruction of the urethra or ureters
• Kidney or gallbladder obstruction (e.g., calculi deposits)
• Gastric dilation and volvulus

Diagnosis

Your veterinarian will need a complete medical history to begin to identify what is causing the acute abdomen. The history you provide may give your veterinarian clues as to which organs are causing the sudden abdominal pain. He or she will also perform a complete physical examination to see if the pain is really in the abdomen and not the kidneys or back. If your dog has a swollen abdomen, your veterinarian will use a fine needle to withdraw some of the fluid from the abdomen to send to the laboratory for analysis.

A complete blood profile will be conducted, including a chemical blood profile, a complete blood count, an electrolyte panel and a urinalysis. Your veterinarian may also use a syringe to take urine from your dog to be sent to a lab for examination.

Your veterinarian will need to use visual diagnostics to examine the abdomen internally. X-rays and ultrasound will be used to locate the source of the disturbance in the abdomen. If your dog is young (still a puppy) a parvovirus blood test may also be given.