Peritoneal Cancer in Cats

picture of a striped cat

Although peritoneal neoplasms are somewhat uncommon in cats compared to those that affect other organs, they can still happen on occasion. More often than not, they are metastases of a tumor that has first developed in another location.

Primary tumors of the peritoneum in both cats and dogs are not frequently diagnosed in these species. In today’s article, we are looking at how this type of cancer is diagnosed, if it can be treated, and what its potential causes might be.

What Causes Peritoneal Cancer in Cats?

Whether discussing cancer affecting other organs or the abdominal lining, it is always important to know whether the tumor is a primary one or has in fact spread from another organ.

In terms of the causes, cancer is one of the most puzzling conditions affecting our pets even these days, despite the many studies performed on all species. There are a number of factors, from genetic ones (cats that have a history of cancer in their parents and grandparents are more likely to develop it) to environmental ones such as continuous exposure to toxic substances.

Another potential factor for the development of peritoneal cancer would be peritonitis. Defined as the inflammation of the peritoneum, this condition can appear as a result of trauma, surgery, or an event affecting other organs, such as the rupture of the urinary bladder or the gallbladder.

Sometimes, the peritoneum might develop local inflammation due to any of these causes, but it might not turn into generalized peritonitis. The latter is life-threatening and requires immediate medical assistance as cats can lose their life in a matter of less than 24 hours after they’ve developed peritonitis.

The inflammation of the abdominal lining can also result from the cat becoming infected with the Feline Infectious Peritonitis Virus (caused by specific strains of the feline coronavirus).


The symptoms of peritoneal cancer in cats can be quite confusing and might not immediately convince pet owners to take their cats to the veterinary clinic as soon as possible.

Depending on the development of the disease, some cats might show clinical signs such as lethargy and weakness, with the absence of an appetite for both food and water. Others might prefer sitting in cold spots in an attempt to decrease local inflammation or just soothe themselves.

Several additional noticeable symptoms are listed below:

Another aspect we have to note with regard to the peritoneum is that there are, in fact two types — one is the abdominal lining, meaning the membrane that covers the entirety of the abdominal cavity, but the other is actually the membrane that covers many of the organs inside the abdominal cavity. In both of these cases, the symptoms are similar, and neoplasms often exist both on the surface of some organs and on the surface of the abdominal lining.


As previously mentioned, cats rarely develop primary tumors of the peritoneum, so the chances that the animal is first diagnosed with a neoplasm in another organ only to then reveal the presence of another in the abdominal lining is quite high.

The vet will use a number of tests for diagnosing peritoneal cancer in cats. The first and most basic ones will be a complete blood count, biochemistry, as well as urine or fecal samples.

An ultrasound can be used to determine the presence of formations on the organs or on the parietal peritoneum. CT is sometimes utilized to reveal the exact size of the tumors.

Besides these imaging techniques, the veterinarian will employ a fine needle aspirate or a biopsy to determine exactly what type of tumor the cat has developed. This is important as it can influence the therapy that the oncologist, pet owner, and clinician can then select.

Treatment of Peritoneal Cancer in Cats

There are three major therapy options when it comes to treating cancer in cats – surgery, chemotherapy, and radiation therapy. Sometimes, a combination of two of these treatments might be attempted.

Unfortunately, peritoneal cancer is extremely difficult to treat. In theory, if the tumor is perfectly localized, the diagnosis has established that it is in its incipient stages, or if it is benign, it can be removed surgically.

However, many cats that have peritoneal cancer have not only parietal peritoneal masses (meaning tumors in their abdominal wall) but also visceral peritoneal masses, which makes surgical removal practically impossible.

In these cases, the vet will recommend a number of medications that can at least decrease the local inflammation and improve the cat’s general quality of life. Chemotherapy might be attempted, as well, only to determine if the tumors can be operated on later on.

Final thoughts

Unfortunately, peritoneal cancer is often lethal as there aren’t many options when it comes to treating it. As is the case with other types of neoplasia, peritoneal cancer tends to affect cats that are typically older than the age of 7 or 8.

However, those that have a history of peritoneal lesions or those that are genetically predisposed to cancer, in general, have a higher likelihood of developing cancer of the peritoneum.



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