Intestinal Tumors in Cats and Dogs
What are intestinal tumors?
The intestine is the portion of the digestive tract between the stomach and the anus. It is divided into two major sections:
small intestine and large intestine. Most food products are absorbed in the small intestine while the large intestine is
responsible for absorption of water and excretion of solid waste material. The average age at which intestinal tumors are
diagnosedranges between 10-12 years for cats and 6 to 9 years for dogs. There are many different types of intestinal
tumors, including
lymphoma, adenocarcinoma, mast cell tumor, and leiomyosarcoma.


How common are intestine tumors in cats and dogs?
Intestinal tumors account for less than 10% of all tumors in dogs and cats and their incidence increases with age in both
dogs and cats.

What are the symptoms of intestine tumors in cats and dogs?
The symptoms indicative of intestinal tumors include weight loss, diarrhea, vomiting, anorexia, and less frequently black
colored stool and anemia. The clinical symptoms often relate to the location of the tumor along the gastrointestinal (GI)
tract. For example, vomiting is associated with lesions in the upper region of the GI tract whereas weight loss is associated
with lesions in the small intestine.

How is the diagnosis made?
Upon the presentation of the above symptoms, the veterinarian will typically perform a series of tests, including physical
exam to look for any masses that may be felt, blood tests, chemistry profile and
imaging studies. Imaging studies can
include plain X-rays, contrast radiography, and/or abdominal ultrasound. The ultrasound studies can localize the tumor,
evaluate whether the cancer has spread to other nearby organs, and guide biopsy. Ultrasound may also be helpful in
distinguishing between malignant and non-malignant intestinal disease based on the thickness of th intestinal wall. The
most definitive way to confirm/rule out intestinal tumors is to perform a medical procedure called endoscopy. It is a
minimally invasive diagnostic procedure that assesses the interior surfaces of an organ like intestine by inserting a tube
into the body. The instrument may have a rigid or flexible tube and not only provide an image for visual inspection and
photography, but also enable taking
biopsies which can then be sent to the lab for analysis. When non- and minimally
invasive diagnostic tests fail to confirm a diagnosis, an exploratory surgery may be performed on pets with persistent
symptoms. The advantages of this procedure are that the entire area can be directly visualized and full thickness biopsy
samples can be taken but the disadvantages include the risks associated with any surgical procedure.

Does cancer cause pain in pets?
Pain is common in pets with cancer, with some tumors causing more pain than others. In addition to pain caused by the
actual tumors, pets will also experience pain associated with cancer treatments such as surgery, radiation therapy or
chemotherapy. Untreated pain decreases the pet's quality of life, and prolongs recovery from the illness, treatment or
injury. It is, therefore, essential that veterinary teams that are taking care of pets with cancer should also play a vital role in
educating pet owners about recognizing and managing pain in their pets. The best way to manage cancer pain in pets is to
prevent it, a term referred to as preemptive pain management. This strategy anticipates pain ahead of time and
administers pain medication before the pet actually experiences pain, thus ensuring the pet's maximum comfort.

To learn more about which tumors are likely to cause a lot of pain, how to recognize pain in pets with cancer and what
cancer pain management options are available for your pet, please visit the
Cancer Pain Management section.

How important is nutritional support for pets with cancer?
Cancer cachexia (a term referring to progressive severe weight loss) is frequently observed in pets with cancer. Pets with
cancer lose weight partly because of lack of appetite and partly because of cancer-induced altered metabolism. Some of
the causes for decreased appetite are related to the cancer itself (for example, tumors may physically interfere with food
chewing, swallowing, and digestion process) and some may be related to the side effects of cancer treatment (for example,
some chemotherapy drugs cause nausea and vomiting, and radiation therapy can cause mouth inflammation).

Proper nutrition while undergoing cancer treatment is essential to maintain your pet's strength, improve survival times,
quality of life and maximize response to therapy. Adequate nutritional support was shown to decrease the duration of
hospitalization, reduce post-surgery complications and enhance the healing process. Additionally, pets with cancer need to
be fed diets specifically designed to provide maximum benefit and nutritional support for the patient. To learn more, please
visit the
Cancer Nutrition section.

What are the treatment options for intestine tumors in cats and dogs?
With the exception of lymphoma, surgery is the primary treatment for intestinal tumors. There have not been enough
clinical studies to determine whether
chemotherapy following surgical treatment provides any benefit to the pets. One
retrospective study suggested that cats receiving doxorubicin (a chemotherapeutic drug) did better compared to cats that
did not, but more studies are needed to determine what drugs and what combinations are the most effective for each
particular tumor type.
Radiation therapy is not generally used for this particular disease due to concerns regarding
possible damage to surrounding normal tissues in the abdominal cavity.

What are the surgery-associated risks for intestine tumors in cats and dogs?
The risks associated with surgery include life-threatening sepsis (a serious medical condition characterized by a whole-
body inflammatory state caused by infection) and peritonitis (inflammation of the abdominal lining).

How do I find a qualified veterinary oncologist?
To locate a qualified veterinary oncologist worldwide who can discuss with you appropriate cancer treatment plan for your
pet's cancer condition, please visit the "
Locate a veterinary oncologist" section.  

Are there any clinical trials investigating new treatments for intestinal cancer in cats or dogs?
Although there are no clinical trials specifically designed to test new treatments for intestinal tumors in dogs, there are
several clinical trials available for cats and dogs with any tumor type for which your pet may qualify. To learn more these
trials (which are partially or fully funded by the institutions), please visit the
Dog Clinical Trials (any tumor type) or Cat
Clinical Trials (any tumor type) section.  

To learn more about veterinary clinical trials in general, please visit the
Pet Clinical Trials section.

What is the prognosis for intestinal tumors in cats and dogs?
The prognosis for pets diagnosed with intestinal tumors will depend on a variety of factors, including the specific tumor
type, the stage of the disease and whether the cancer has spread to other organs. For pets whose cancer has not spread
to other organs, long-term survival is possible. It is estimated that approximately 40% of dogs with small intestinal tumors
remain alive 1 year after diagnosis. Dogs diagnosed with adenocarcinoma and leiomyosarcoma have frequent metastases
to lymph nodes and the liver. Dogs with small intestinal adenocarcinoma have shorter average survivals of 12 days without
treatment and between 4-10 months with surgery. Dogs with leiomyosarcoma who survive surgery survive 1-2 years. For
cats with adenocarcinoma, approximately 50% will metastasize to the local lymph nodes, 30% to the peritoneal cavity, and
20% or less to the lungs. Cats with small intestinal adenocarcinoma have a significant risk associated with surgical
treatment but those who live 2 weeks after the surgery may experience long term control of the cancer. Cats with cancer in
the large intestines have survival approximately 3.5 months for
lymphoma, 4.5 months for adenocarcinoma, and 6.5
months for
mast cell tumor.

  • Withrow Stephen J, and David M. Vail. Small Animal Clinical Oncology. St Louis: Saunders Elsevier, 2007.
  • Morrison Wallace B. Cancer in Dogs and Cats: Medical and Surgical Management. Baltimore: Williams&Wilkins, 1998.
Comprehensive guide to cancer diagnosis and treatment in cats and dogs
© 2007 Pet Cancer Center. ALL RIGHTS RESERVED.
Last updated 2/19/2017