What are the common causes of peritonitis?

Peritonitis is often caused by rupture of an abdominal organ, infection, or trauma, and may also arise as a post-surgical complication. The specific cause requires examination by a vet — seek professional advice for an accurate diagnosis.

How does the vet confirm a diagnosis of peritonitis?

The vet combines the clinical history, physical examination, blood tests, abdominocentesis, and imaging (ultrasound or X-ray) to look for free abdominal fluid or signs of infection. Culture of fluid or tissue samples may also be performed if needed.

Does peritonitis always require surgery?

Not always. Mild or controllable infections may be managed with conservative supportive care first. However, abdominal contamination or organ rupture usually requires surgical debridement and repair — the decision depends on the vet's assessment.

What follow-up is needed after treatment?

Regular follow-up appointments are usually needed to monitor blood tests, abdominal imaging, and clinical symptoms. Supportive treatment or anti-infective therapy may be adjusted accordingly — follow your vet's instructions for scheduling.

How much do the tests and treatment usually cost?

Costs vary by clinic and region — ask your vet for an estimate before proceeding.

Disease Guide

Peritonitis in Dogs & Cats: Symptoms, Diagnosis & Treatment Guide [2025]

Inflammation of the peritoneum — a serious emergency requiring urgent veterinary treatment

Take 1 minute to check the symptoms first

Last updated: 2026/01/06

Pethealthmap Editorial Team

Sources: WSAVA, AVMA, National Taiwan University Veterinary Hospital

When to See a Vet

Seek Emergency Care Immediately

•Sudden, obvious abdominal distension with tightness and discomfort
•Rapid or labored breathing with visible respiratory effort
•Sudden drop in alertness or noticeable confusion

Schedule a Clinic Visit Soon (within 24–72 hours)

•Significant decrease in appetite or complete refusal to eat
•Repeated vomiting or persistent diarrhea occurring multiple times
•Pain response when the abdomen is touched, or obvious abdominal rigidity

01What symptoms indicate something is wrong?

Peritonitis typically causes systemic discomfort and obvious abdominal symptoms. In some cases, the condition progresses rapidly and carries acute life-threatening risk.

Lethargy, excessive sleepiness, or noticeably reduced activity
Reduced appetite or complete refusal to eat
Repeated vomiting or persistent diarrhoea
Rapid weight loss over a short period
Persistent or recurring fever and abnormal body temperature
Pain or abdominal rigidity on palpation of the abdomen

Seek emergency care immediately if you notice the following symptoms:

⚠️ Sudden, marked abdominal distension and rigidity
⚠️ Rapid breathing or noticeably laboured, distressed respiration
⚠️ Sudden collapse in alertness or obvious confusion

02How to assess your pet at home? Key observations and when to seek emergency care

Observing and recording key changes at home helps your vet quickly assess the situation and arrange the necessary tests.

Note when changes in alertness and activity level began and how they have progressed
Measure and record body temperature daily if possible
Document the frequency, content, and timing of vomiting episodes
Record stool consistency, frequency, colour, and any presence of mucus or blood
Weigh your pet at the same time each day and track any weight changes
Take photos or videos of abdominal appearance or abnormal behaviour to share with your vet

03How does the vet make a diagnosis? Common examination and tests

After your pet arrives at the clinic, the vet will combine the clinical history, imaging, and laboratory results to determine whether peritoneal infection or another abdominal condition is present.

Physical examination

thorough assessment of vital signs and abdominal palpation to confirm pain and rigidity

Complete blood count (CBC)

evaluates white and red blood cells for signs of infection or anaemia

Blood biochemistry

assesses liver and kidney function and electrolyte balance

Abdominocentesis and cytology

collection of abdominal fluid to examine its cellular composition

Bacterial culture

performed when infection is suspected to identify the causative organism

Imaging

abdominal ultrasound, X-ray, or CT scan for further evaluation if needed

Referral to a specialist or referral hospital for advanced care or surgical assessment if required

04How is peritonitis treated and managed? Medications, dietary adjustments, and care guide

Management of peritonitis centres on supportive care and infection control. Severe or contaminated cases require surgical intervention followed by close post-operative monitoring.

Intravenous fluid support and electrolyte monitoring and correction are typically required during the acute phase
Anti-infective and anti-inflammatory treatment as appropriate to the clinical situation
Abdominal contamination or perforation may require surgical debridement and repair
Continuous monitoring of vital signs and abdominal status during hospitalisation or the post-operative period
Blood transfusion, oxygen supplementation, or other supportive therapies may be arranged as needed
Schedule regular follow-up appointments as directed to monitor blood tests, abdominal imaging, and clinical progress

05What to prepare before your vet visit? Key information to help your vet assess quickly

Note when symptoms started, how they have progressed, and whether there was any sudden worsening

Record recent diet, any food changes, or whether your pet may have ingested a foreign object

List the number and timing of vomiting episodes, diarrhoea, or bloody stools

List all current medications, supplements, and recent vaccinations

Bring videos, photos, or written records to help the vet understand the course of illness

Call ahead to book an appointment or choose a clinic or referral hospital equipped for abdominal examination

This content is for reference only and cannot replace a professional veterinary diagnosis. If your pet shows signs of illness, please seek veterinary care promptly.