Carcinoid Syndrome and Tumor in Dogs
Carcinoid tumors are small neuroendocrine tumors, typically of the gastrointestinal tract, that secrete serotonin, a naturally occurring neurochemical that is usually associated with sleep and memory functions. Carcinoid tumors are rare, slow growing tumors that are formed by the endocrine cells (secreting cells) of the mucosal lining of organs, such as the stomach and intestine.
Carcinoid tumors secrete the amines serotonin and histamine into the bloodstream, as well as a number of peptides, chemical compounds such as bradykinins and tachykinins, which are responsible for tissue contraction. Although carcinoid tumors are rare in animals, they occur primarily in dogs older than nine years.
The condition or disease described in this medical article can affect both dogs and cats. If you would like to learn more about how this disease affects cats, please visit this page in the PetMD health library.
Symptoms and Types
Primary carcinoid tumors in dogs are usually found in the stomach, small intestine, colon, lungs, gallbladder, and liver. The general clinical symptoms of carcinoid tumors in animals include anorexia, vomiting, dyschezia, weight loss due to liver failure, and heart disease.
Like with many types of cancer, the actual causes and risk factors for carcinoid tumors are unknown. Clinical signs in dogs vary greatly, and depend on the location of the tumor and how far the metastasis has advanced. The size of the tumor and how it may be impeding the functionality of the organ will also have a lot of influence on how ill your pet feels, and whether or not it will be fatal.
There are a variety of ways to diagnose carcinoid tumors. An intestinal tumor may cause some of the same symptoms as primary gastrointestinal diseases such as neoplasias (abnormal tissue growth), dietary indiscretion, parasites, and inflammation. Therefore, a differential diagnosis will be necessary. With carcinoid tumors, biochemical tests and urine analysis may yield normal results, with the exception of a mild non-regenerative anemia, electrolyte abnormalities, and elevated liver enzymes. An ultrasound image may lead to the identification of primary tumors and metastasis (spreading) in the abdomen and thorax (chest). However, a definitive diagnosis can only be made with a biopsy (sample) of the affected tissues. An electron microscopy, and immunohistochemical stains can help to confirm the diagnosis by identifying the substances that are typically secreted by carcinoid tumors.
Sometimes, complete surgical removal of the tumor can cure the condition. Reducing the size of the tumor through surgery may also help to eliminate the gastrointestinal symptoms that are caused by an obstruction of a large tumor. There are no standard therapies for treatment of carcinoid tumors, but your veterinarian may have some treatment options available that will help to keep metastasis to a minimum, or to help you to make your pet comfortable.
Living and Management
If a tumor can not be completely removed, routine blood tests will need to be conducted to determine whether destructive hepatic metastasis has occurred. A yearly ultrasound is also recommended for monitoring progress, so that if any metastasis has occurred in the liver, or in other organs, it can be treated promptly, before organ functionality is affected.