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Rhett Butler is a 10 year old black lab who presented to us last week with a history of chronic cough with a 3 month duration. He had been losing weight over the past 3 months as well. The owners reported that he lives only in their yard and had not been to any other places where he could have been exposed to infectious dogs.
On presentation, Rhett looked thin and a bit depressed. He was slow to respond to stimuli in the exam room. On physical examination, Rhett was pale and breathing rapidly, though shallowly throughout the exam. He had a deep honking cough when his trachea (windpipe) was manipulated. The lungs themselves sounded clear. Listening to the heart, we could hear a murmur which had not been there 4 months ago when he was examined. Murmurs occur when the blood in the heart is not flowing smoothly, usually due to leaky valves.
Rhett is an 80 pound dog, but the bones of his spine were sticking out. We noted an enlarged lymph node in the shoulder area (prescapular) on the left side and increased lymph nodes behind the knees as well (popliteal nodes).
At this point, our problem list included:
Our diagnostic plan included radiographs (x-rays) of the chest, echocardiogram (ultrasound of the heart, and a blood panel. The radiographs indicated an enlarged heart and a suspicious mass in front of the heart in between the lungs in an area called the mediastinum. Our suspicion at this point was that the mass was probably the enlarged mediastinal lymph node. This enlargement could be due to infection or cancer.
notice the white mass to the left of the heart
Ultrasound of the heart revealed a leaky mitral valve (the valve between the left ventricle and the left atrium along with an enlarged left atrium caused by the backward flow of blood into the atrium due to the valve leak. The left ventricle was enlarged and the thickness of the left ventricular walls were thinner than normal. Fortunately, the heart was contracting well as measured by the fractional shortening which was normal. Our diagnosis was of an enlarged heart due to a failing heart muscle know as dilated cardiomyopathy. This is a syndrome common to large breed dogs in which the heart muscle gets weaker and weaker over time until it can't pump efficiently.
Normal Heart anatomy Dilated Cardiomyopathy (double click on images to enlarge)
Because we were concerned about the possibility of the mass in the chest being cancer of the lymph node (lymphoma), we took a biopsy of the enlarged pre-scapular lymph node in hopes of diagnosing the problem. Biopsy of the lymph node in the chest posed too much of a risk because of all the blood vessels and nerves located around it.
Since the blood was sent to an outside lab, we had to wait until the next day to find out the results. In the meantime, we started Rhett on drugs to help his heart, in hopes of improving cardiac output and reducing the size of the left atrium which could possibly help with the coughing. It turns out that the left atrium lives right in between the left and right main bronchi which feed air to the lungs. When it is enlarged, it can bump the bronchi and cause coughing.
The next morning, we received the blood work back from the lab. The major organs, liver and kidneys were normal, however the white blood cell count was extremely high (150000, when 15000 is normal). The pathologist reviewed the cells under the microscope and pronounced that Rhett had an aggressive form of leukemia called lympyhoblastic leukemia. This is a disease in which the lymphocytes (white blood cells involved in the immune system) in the bone marrow become cancerous and reproduce unchecked. They make so many cells that they can crowd out the bone marrow so that other cells can not be formed properly. In addition, this high number of cells in the blood vessels can cause poor blood perfusion as the blood is more viscous than normal. This type of leukemia has a very guarded to grave prognosis. Chemotherapy can help prolong life a few months, but ultimately, it is usually fatal.
We notified the owner of this, and he was shocked because Rhett was doing better at home on the heart medications. He was more active and coughing significantly less. We decided to wait for the lymph node biopsy results before deciding our next step. A few days later the lymph node biopsy returned and it was described as non cancerous. At this point we had to base our diagnosis on the original blood count, but Rhett just didn't seem as sick as he should be if this were the right diagnosis.
We then sent Rhett to a cancer specialist for a second opinion. He agreed that this was an unusual case, in which the the lab data didn't appear to match the pet's condition. Therefore, he did a bone marrow aspiration to see exactly what type of cells were being produced. The pathologist felt that the cells in the bone marrow were a less aggressive type of cancer called lymphocytic leukemia. In this disease, there are large numbers of lymphocytes, but they are almost normal looking in appearance. Fortunately, this disease responds much better to drug therapy and there is a much better chance of surviving up to 3 years statistically. Rhett has both his heart problem and this leukemia to deal with, but for now, he appears to be making a good recovery.