Section: Diagnosis In-depth
Veterinary care should include diagnostic tests and subsequent treatment recommendations.
Diagnosis In-depth
Medical tests are needed to establish the diagnosis of osteosarcoma, exclude other diseases that may cause similar symptoms, and determine the impact of osteosarcoma on your dog. Tests that your veterinarian may wish to perform include:
Complete physical exam. A thorough exam is necessary to localize the site of the cancer and also to assess your pet's general health. Your pet's general condition may drastically influence the treatment that is recommended.
Radiographs (X-rays) of the affected bone. Although the appearance of the bone on an X-ray may be suggestive of cancer, X-rays are not diagnostic of this condition. There is no risk to your pet in performing an X-ray; however, if your pet is unwilling to lie still long enough to have the radiographs taken, due to pain from the bone cancer or their personality, your veterinarian may recommend that a mild tranquilizer or even anesthesia be administered.
Radiographs of the chest/lungs. The lungs are the most common location to which bone tumors spread. Therefore, X-rays of the chest should always be taken prior to surgery. Dogs that already have evidence of cancer in the lungs are not good candidates for amputation because their disease is advanced; however, they may be considered for other treatments such as palliative radiation therapy and possibly chemotherapy.
Complete blood cell count (CBC). This is a test run on blood that counts the number of red blood cells that carry oxygen in the body and white blood cells that fight infection that are circulating in the blood stream. This is a standard test to screen your pet's general heath and to ensure that it is safe to perform other procedures, such as surgery. However, it does not reveal cancer in the blood.
Biochemical blood profile. This is a test run on blood to assess the general health of your pet's organs. It assesses the health of the liver, which filters toxins, creates bile and metabolizes nutrients taken into the body in the food, and function of the kidney, which filters the blood to preserve body water and make urine, and measures levels of electrolytes in the blood. When the measured values differ from values obtained from a pool of healthy animals, or normal values, dysfunction of the organ(s) is suspected. Dysfunction may or may not be associated with the spread of cancer to an organ.
Urinalysis. These are tests run on a sample of urine. Like the blood tests, it gives your veterinarian information about your pet's general health. Most importantly, it assesses the health of the kidneys, but it also indicates the presence or absence of a urinary tract infection. The urine may be collected by catching some in a cup or by performing a cystocentesis that removes urine from the bladder by means of a needle passed through the belly into the urinary bladder.
Biopsy of the tumor. This is an essential procedure for definitive diagnosis of bone cancer. Because it is painful to biopsy bone, this procedure is done under anesthesia. Your veterinarian or a veterinary specialist will insert a large needle into the affected area of bone to remove a core of tissue. The tissue sample is then submitted to a pathologist to determine the form/type of cancer. There is a minimal risk of fracturing the bone with this procedure, but because it is essential for the diagnosis, the risk is worth taking. Your pet is likely to be in pain after this procedure and pain medications are often administered. A narcotic patch placed on the skin to allow absorption of a constant level of pain reliever may also be used.
Your veterinarian may recommend additional diagnostic tests to ensure optimal medical care. These are selected on a case-by-case basis. An example includes:
Bone scan. This is a specialized type of X-ray that is done to look for spread of the cancer to other bones. These scans are available only in limited veterinary referral centers, because they require specialized machines. To perform this type of scan, your pet is given an injection of a radioactive substance that localizes to sites of bone damage. A special camera is then used to take X-rays of all the bones in the body. It is a non-specific test that requires interpretation by a radiologist, but it can help determine if there are multiple bones that are affected by bone cancer. This is a very uncommon finding but one that would drastically influence the treatment recommendations. There is no risk to your pet from this type of radiation, but he/she will usually be required to stay at least one night in a special holding cage in the hospital. This allows the radioactive substance to be expelled from your pet's body via urine and feces.
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