The author's Labrador, M, was diagnosed with Cushing's disease in its latter stages. Dr. Holcomb encourages owners to have their dogs checked annually to increase the chances of catching a problem before it gets too far along.

Departing from his usual Q&A format, Dr. Tom expands on last issue's tribute to a favorite duck dog€¦and offers some valuable insights, as well.

A black Labrador puppy, who became known as "M," came into my life in December of 1998.

She was a gift from Bob Mann, a client of mine. Over time she became a very good duck dog. Throughout her growing years and into her final year she continued to perfect her skills as a retriever, working with a tenacity of purpose that occasionally got her in trouble.

I remember one day, teal hunting on a favorite pond, when one of us dropped a bird that swam to the opposite shore. By the time I realized things were not going as expected I could only see M's rear sticking out of the bank. I took off around the pond and found her, by then with just her tail sticking out of a hole in the bank. I had to actually pull her out backwards. No duck but at least I got my dog back.

Last fall we had three great mallard hunts just as the ponds and marshes were freezing up.

The pond we hunted on is large, deep and surrounded by timber down to the water's edge. It was the only one in the area that had not frozen over, and needless to say, the ducks were using it like mad.

In one of our heated battles with incoming mallards someone wounded one that, unknown to us, coasted over the silt dam at the upper end of the pond and fell on the partly frozen water. Only M knew it was there and before I could get her stopped she was out on the thin ice making the retrieve. Fortunately, all went well and she got back without complications.

As I worried about the dangers of the thin ice I had no way of knowing that another much more serious problem was beginning inside her. Over the next several weeks I noted an increase in her water consumption. She had always been a big water drinker but she was now drinking four to six quarts of water per day, and normal for a dog her size would be about four to six cups daily.

I also started to note a thinning of her hair coat, loss of muscle mass and a pot-bellied appearance to her abdomen. M had always been a chow hound so I was slow to pick up on how ravenous her appetite had become.

It was at this point that I realized there was something seriously wrong with my dog. It was in her best interest for me to step aside as her veterinarian and let someone with more objectivity handle the diagnosis and treatment plan. I called in my young associate, Dr. Jennifer Hoffelmeyer, and told her what M's history and clinical signs were.

We agreed that I would become a client and she would take over diagnosis and treatment options. I would make the final decisions. I had never put myself in the position of being the client before. I had always tried to combine the two in caring for my pets. I later realized how conflicting that dual role can be.

After doing a complete physical exam, Dr. Hoffelmeyer obtained samples of blood and urine from M for a base profile. Fortunately we had the results of a blood profile that I had run in April 2008 as part of her annual physical. All values were well within normal range at that time.

Following completion of the in-house lab work Dr. Hoffelmeyer informed me that M had a high white blood count and that the differential white count showed a stress response or response to high levels of steroids. The serum chemistries showed high liver enzymes with especially high alkaline phosphatase. Her BUN was mildly elevated, indicating possible low grade kidney issues. Urinalysis confirmed mild urinary tract problems.

Dr. Hoffelmeyer came to me with this information and her thoughts on the differential diagnosis list€¦and the question, "How do you want me to proceed?" Top on her list of possible disease processes was Cushing's disease.

Cushing's is a disease in which the adrenal gland secretes high levels of cortisol continuously. It causes all the clinical signs I had observed gradually expressing themselves over the prior few weeks. Other less obvious pathology occurs, namely reduced immune response, poor wound healing and GI upsets.

Dr. Hoffelmeyer and I went over possible further testing that could be performed to arrive at an exact diagnosis and I agreed to additional blood work with ultrasound and radiograph of the anterior abdomen and lungs. I was watching my dog become more unsteady on her feet as each day went by and was anxious for more information but did not want to put her through an invasive surgical procedure. On we went.

Base cortisol levels were high and remained high eight hours after the administration of a low dose of dexamethasone. This confirmed the diagnosis of Cushing's disease. Next an endogenous ACTH test was run and the results indicated that the source of the cortical was from an adrenal cortical tumor.

What now? Dr. Hoffelmeyer informed me that 50 percent of these tumors are malignant and that surgery is risky. I asked her to do ultrasound and radiographs -- again, nothing invasive -- to see what they might tell us.

Unfortunately, the news was not good. M had a large diffuse mass in the area of the left adrenal gland. There were many small tumor nodules in the lungs. Obviously this was a very aggressive tumor that had metastasized to the lungs and probably other organs of the body.

At this point, as M's owner I talked with the rest of my family and other staff members so everyone was on board. That evening I euthanized her and set her free from her pain. She just lay there and let me give her the IV injection.

She seemed so accepting. Just as she knew putting her in the kennel of the truck or in the johnboat or beside me at the farm pond was the right thing for me to do, so she seemed to know that I had chosen the right time for her to go. And there I was again conflicted by being both her veterinarian and her owner.

I did not share this episode in my life as a plea for sympathy or compassion but rather to help each of you better understand your relationship with your veterinarian and how he or she can help you work your way through a problem. Complex diseases such as Cushing's disease develop in a slow insidious manner that makes them especially hard to diagnose in their early stages.

As I related, the

steps to a diagnosis include history taking, physical exam, appropriate laboratory tests and the development of a workable treatment plan. Your place in this process is very important in the history component. Obviously a dog cannot talk. A physical exam on an annual basis with some basic blood work may also catch a problem before it gets too far along.

As the owner of the dog, you should make decisions as to what tests are the most cost effective and are the least invasive. Your veterinarian should give you good information to help you make these decisions. Once a diagnosis is made then a treatment plan will in fact arrest the disease process and alleviate the suffering. If not, then you must consider at what point in the progression of the disease you will elect euthanasia.

The next morning Dr. Hoffelmeyer did a post-mortem exam of M's body and found a large tumor mass surrounding her kidney with multiple tumors in her lungs. The pathologist found on microscopic examination that the largest mass was an adrenocortical carcinoma and the others were metastatic tumors from it.

M was cremated and her ashes now sit next to those of several other dogs on a shelf in my office.

I remain at htholcombdvm@qwest.net for your questions or comments.