Peritonitis in Dogs

There are many digestive disorders our dog can suffer from, and peritonitis is one of the most serious. It's inflammation of the peritoneum, the tissue lining the abdominal organs.

Fortunately, it's not usually the most common digestive condition seen in day-to-day veterinary practice. That said, when it occurs, the prognosis is guarded, so it's worth knowing about and knowing how to act. Let's take a detailed look at its symptoms and what we should do.

What is canine peritonitis?

To better understand this condition, we first need to know what the peritoneum is. The peritoneum is a very thin, sturdy connective membrane made up of two layers that can slide against one another. The outer layer, called the parietal layer, lines the entire wall of the abdominal cavity, while the one called the visceral layer covers the outer surface of all the organs located in the abdomen.

The peritoneum's main function is protecting the organs against possible infections, as well as letting them slide within the abdominal cavity normally. It also acts as thermal insulation, keeping the abdominal organs at a steady temperature. It supports these organs by helping supply blood to them.

As we can see, it has important, vital functions, and any imbalance in its physiology can have consequences, such as peritonitis. Peritonitis, then, is inflammation of this double membrane. It's a serious, often fatal condition in dogs, with a mortality rate ranging between 50% and 70%. It can be caused by many different factors and causes.

Causes of peritonitis in dogs

Some predisposing causes of peritonitis are more serious than others, and the prognosis will be worse accordingly. That said, this doesn't rule out the potential for peritonitis to develop from any of them.

Primary peritonitis (caused by infectious agents spreading through the bloodstream) is less common than secondary peritonitis (following some other event). Let's look at some examples of the latter type:

• Perforation of the abdominal cavity by an external foreign object.
• Trauma from car accidents (fragmenting an organ).
• Intestinal rupture due to an internal foreign object (splintered bones, metal...).
• Suture dehiscence after surgery. A possible surgical complication is stitches coming apart, letting contents leak out.
• Rupture of the bladder or uterus, exposing the abdominal cavity to fluid these organs may contain.
• Stomach perforation or intestinal ulcer.
• Abdominal tumors.
• Inflammation of various abdominal organs such as the liver or pancreas.
• Rupture or blockage of the gallbladder, with the possibility of bile leaking into the abdominal cavity, causing severe peritonitis.
• Gastric dilatation-volvulus over several hours. This causes stomach torsion and compromised blood flow to the spleen, releasing toxic substances such as free radicals, increasing the chances of peritonitis.

How is canine peritonitis diagnosed?

First, the vet will get a sense of the case by taking a history of our pet. Following this, they'll do a general physical exam of the animal to get an initial idea of how serious the situation is. Next, as with many conditions, additional tests will be needed. Vets can generally suspect peritonitis based on findings from X-rays, full bloodwork, and ultrasound.

As for bloodwork, results can vary. The vet may see findings typical of infection, such as elevated white blood cells, along with possibly elevated liver enzymes, lower hematocrit, etc.

X-rays can reveal the most significant, obvious findings, but ultrasound is the test that will best identify what's happening inside the abdominal cavity.

To confirm peritonitis, a sample of abdominal fluid can be drawn and analyzed, checking what type of cells and discharge are present in the abdomen. Diagnostic exploratory laparotomy (accessing the abdomen through surgical opening) can be considered to confirm peritonitis if there's doubt.

Peritonitis in dogs: common symptoms

The signs of peritonitis will vary depending on the underlying cause. Most include: fever, shock, low blood pressure, ascites or free fluid in the abdomen, abdominal pain (with a hunched or tucked-up posture), vomiting, and diarrhea.

Rupture of the gastrointestinal tract, with large volumes of intestinal contents leaking into the abdominal cavity, leads to acute peritonitis. Death from shock caused by large amounts of toxins and bacteria, along with acid-base and circulatory disturbances, can occur suddenly.

Treatment for canine peritonitis

The right therapy for peritonitis depends on the diagnosis and the results of the physical exam and lab tests. In severe cases of septic peritonitis, initial treatment needs to focus on saving the animal's life and stabilizing cardiovascular and other organ functions.

This treatment needs to include resolving the hypovolemic and toxic shock our pet may unfortunately be experiencing. To do this, fluid therapy, possible oxygen support, and strong antibiotic and anti-inflammatory therapy will be needed, along with treating any metabolic disturbances and accompanying symptoms the patient is experiencing (vomiting, abdominal pain, fever).

A recovery diet will also be needed as part of the patient's recovery. If they don't eat on their own after a day or so, a nasogastric tube will be needed to give semi-liquid food via syringe.

If peritonitis was caused by fluid leaking from inside abdominal organs into the abdominal cavity, surgery will be needed after stabilization to resolve it. Examples include reconstructing a ruptured bladder, gallbladder, intestines, etc.

Although the peritoneum can regenerate quickly, peritonitis should be considered a serious, life-threatening disease for our animal, with a guarded prognosis. This largely depends on the nature, cause, and severity of the disease, and therefore needs to be determined case by case.

Don't hesitate to see the vet if you suspect peritonitis based on any of the symptoms described. There are 24-hour clinics and hospitals that can treat your pet and try to resolve this condition, which puts our pets' lives so seriously at risk.