Uterine Tumors in Dogs

Overview of Canine Uterine Tumors

Uterine tumors are cancers that arise from the uterus. They are rare in dogs and are most commonly benign, but may also be malignant. Uterine tumors, by definition, only occur in intact female dogs. They are usually seen in middle aged to older dogs.

What to Watch For

Signs of uterine tumors in dogs may include:

• Vaginal discharge
• Abdominal distension
• Anorexia (lack of appetite)
• Constipation
• Vomiting
• Weight loss
• Lethargy
• Straining to urinate
• Frequent urination

Diagnosis of Uterine Tumors in Dogs

• Complete history and physical exam
• Complete blood count (CBC)
• Biochemical profile
• Urine analysis
• Chest radiographs (x-rays)
• Abdominal radiographs or ultrasound exam
• Mass biopsy

Treatment of Uterine Tumors in Dogs

Ovariohysterectomy or spay is the treatment of choice. Chemotherapy may be recommended in selected cases.

Home Care and Prevention

Monitor for recurrence of original clinical signs and spay your female dogs.

In-depth Information on Uterine Tumors in Dogs

Many dogs with uterine tumors have no clinical signs of illness. This is because most tumors are benign and therefore do not spread to other organs. The most common tumor types are leiomyomas (fibroids) and fibromas. Malignant tumors are often adenocarcinomas or leiomyosarcomas. Large tumors may cause compression of other abdominal organs and may result in constipation, vomiting, or frequent urination. Abdominal distension is sometimes noted due to large tumor size or development of fluid in the abdomen secondary to the tumor.

In many cases, the tumor may be present concurrently with an infection in the uterus, called pyometra. Dogs with pyometra are commonly lethargic, excessively thirsty, anorexic, vomiting and often have vaginal discharge. Licking of the vulva is common in animals with vaginal discharge, which may prevent observation of the discharge itself. Other conditions may cause similar clinical signs to those seen in animals with uterine tumors. These include:

• Vaginitis or vaginal tumors. Infection or tumors of the lower reproductive tract may cause discharge and licking as well.
• Tumors of other abdominal organs. Masses associated with the liver, spleen, or gastrointestinal tract may also cause abdominal distension and possible fluid accumulation in the abdomen.
• Liver/kidney/gastrointestinal/metabolic diseases. Many diseases can cause general lethargy, anorexia and vomiting. These are not signs specific to one organ system, but should prompt a visit to the veterinarian for appropriate evaluation.

In-depth information on Diagnosis

A complete history and physical exam are crucial. A thorough history is always important in establishing a list of possible diagnoses. A physical exam may reveal an enlarged uterus, or vaginal discharge that had gone unnoticed previously in some dogs. Additional tests may include:

• Complete blood count. A CBC evaluates the red and white blood cells as well as the platelets. The results may be normal in a pet with a uterine tumor, but an elevated white blood cell count may be seen with both tumors and infections of the uterus.
• A biochemical profile evaluates blood sugar, blood proteins and electrolytes, as well as providing information about liver and kidney function. This is useful to get an overall idea of systemic health and may guide further diagnostic testing.
• Urine analysis. Evaluation of the urine is part of a complete laboratory assessment and gives a better indication of kidney function than the biochemical profile alone.
• Abdominal x-rays or abdominal ultrasound exam. Imaging studies of the abdomen will allow visualization of the uterus. A normal uterus is hard to see on x-rays, so a prominent uterus is often a sign of uterine pathology. An abdominal ultrasound is useful to differentiate a fluid filled uterus from a uterine tumor.
• Chest radiographs. X-rays of the chest are a good idea to look for evidence of spread of cancer to the lungs. Although most uterine tumors are benign, the malignant types are aggressive tumors and may quickly spread to other organs, including the lungs. It is important to know if there is evidence of metastatic disease (spread of cancer from the primary site) prior to treating the pet.
• Mass biopsy. Biopsy of a uterine tumor involves obtaining tissue for microscopic analysis. This enables the veterinarian to determine if the tumor is benign or malignant. The best way to obtain a tissue sample for biopsy is generally to remove the entire uterus and the ovaries.

In-depth Information on Therapy

Surgery is the treatment of choice for dogs with uterine tumors. It is not clear how hormones may influence growth of uterine tumors, so it is advisable to remove not only the uterus, but the ovaries as well. Surgery therefore serves not only as a diagnostic modality, but as a therapeutic one as well.

• If the tumor is benign, surgery should be curative.
• If the tumor is malignant, chemotherapy may be recommended in addition to surgery. The purpose of chemotherapy is to prevent spread of malignant cells to other organs. Unfortunately, the efficacy of chemotherapy for malignant uterine tumors is not well known.
• In cases of pyometra in addition to the presence of a tumor, antibiotics are indicated to treat the infection.

Follow-up Care for Dogs with Uterine Tumors

Optimal treatment for your dog requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your dog does not improve over the expected time frame.

If your dog has a benign uterine tumor, the prognosis is excellent following surgery. Routine follow-up two weeks after surgery is recommended for a recheck exam and suture removal.

If a malignant tumor is diagnosed, your pet should be seen regularly by your veterinarian. This generally entails a follow-up visit at two weeks, six weeks, and then every three months. Follow-up x-rays of the chest and an abdominal ultrasound exam should be performed every few months to monitor for evidence of metastasis of the primary tumor to other organs.

Dogs receiving chemotherapy drugs are often seen every one to three weeks.

If your dog is having any problems at home, this should be brought to the attention of your veterinarian. Signs to watch for include lack of appetite, vomiting, continued vaginal discharge, apparent pain, weight loss, or any other abnormal behavior.