It is never too late to learn, or be surprised by something new


Although I don’t take many new clients these days, when a dear former client asked if I would look at a cat belonging to a friend of hers, I was happy to oblige. Tuxedo was a middle-aged black and white wisp, not even six pounds. Previously diagnosed with the common feline endocrine disorder hyperthyroidism, she had not been getting any treatment for six months.

“I think the vet said it was because of kidney problems,” her owner replied when asked why he had stopped medication. “She seemed okay at first, ” he continued. “But the last three weeks, she’s barely eating.” Tuxedo was thin, dehydrated, and exceedingly frail.

We’ve discussed hyperthyroidism before, but here’s a quick refresher. Usually the result of a benign but hormone-producing tumor of the thyroid gland, typical symptoms are excessive appetite combined with weight loss. Other signs may include excessive drinking and urination, hyperactivity or bizarre behavior, vomiting, coughing, elevated heart rate, heart murmurs, and a palpable thyroid nodule. Occasionally a cat will present differently, looking depressed with a poor appetite.

“First things first,” I said. “Let me review her past lab work, then draw blood and see where things stand now.”

Soon I was able to tell Tuxedo’s dad that there was no evidence of kidney problems, past or present. “It was her liver enzymes that were abnormal last year,” I said, ” but everything looks pretty good now.” Everything except her thyroid hormone levels, which were quite high.

First things first. We needed to treat the hyperthyroidism and see if that made her feel better. But there was a problem. When she was eating, her owner had hidden the pills in her food, but now he had no way to give the tablets. I offered all my tricks for how to pill a cat, but Tux’s dad had tried everything. Everything, that is, except transdermal medication.”

Transdermal. Trans – meaning across. Dermal – meaning skin. You’re probably familiar with the concept in human medicine. Nicotine patches to quit smoking, hormone patches for birth control, narcotic patches for pain. The idea is to formulate medication into a gel that is applied to the skin from where it will theoretically be absorbed into the blood. Since Mother Nature has designed skin to keep stuff out, not let stuff in, this method doesn’t always work. Efficacy varies depending on the drug, and the individual patient, but I have had success using transdermal medication for hyperthyroidism before. It was worth a try.

I hoped correcting the hyperthyroidism would solve the problem, but she looked so poorly, there might be other issues lurking. We gave fluids and an appetite stimulant, ordered the transdermal medication from a compounding pharmacy, and sent her home with instructions to wear gloves and rub a measured amount of the gel on the inside of her ear twice daily, alternating ears. Then we crossed our fingers and hoped for the best,

Three weeks later Tuxedo was eating and had gained three quarters of a pound. That may not sound like much but it’s ten percent of her body weight. That’s like ten pounds on a hundred-pound person. Over the next few visits, we adjusted her dosage and monitored liver enzymes. She seemed all better. “We should recheck in six months or any time she isn’t doing well,” I said. “But remember, she needs this medication for the rest of her life.” I hesitated.

When Tuxedo had first arrived, she had looked so fragile I hadn’t even considered her as a candidate for other options – like the actual cure – radioactive iodine treatment called I-131. (You can read all about it at Tuxedo’s dad was enthusiastic about the idea.

“This transdermal medication works well,” he agreed, “but I travel a lot and it’s difficult to have to medicate her twice a day.” First things first. Before I-131 treatment, additional diagnostics, including chest X-rays, are required. I offered to take radiographs right then.

Tux was very cooperative having her picture taken but my heart sank when I saw a large circular density in the front part of her chest where there should have just been clear lung field. It’s called an anterior mediastinal mass and is often very bad news. “There are two major possibilities,” I said, pointing out the area on the film. “Lymphoma or thymoma.”

Lymphoma is a malignant cancer with a poor prognosis. If Tuxedo had lymphoma, then hyperthyroidism was the least of her worries. We’d be talking chemotherapy. A thymoma is a tumor of the thymus gland, usually benign, but with potential negative effects, some quite serious. If Tuxedo had a thymoma, it might warrant surgery, radiation, or other intervention. First things first. Since as many as half of all cats with lymphoma test positive for Feline Leukemia Virus or Feline Immunodeficiency Virus, we did a quick screening and ruled those out. After that, well, it was up to her Dad. “It doesn’t make sense to go for I-131 until we know what that mass is,” I said. Based on her age and history, thymoma was most likely but without a biopsy, we couldn’t know for sure.”

Tuxedo went to an internal medicine specialist for ultrasound and apiration of the mass. The doctor called with interesting news. “It was a cyst, full of fluid. She should be fine for hyperthyroid treatment.”

A cyst? In 30 years of practice I have never knowingly seen an anterior mediastinal cyst. The specialist sent me an article about similar cases. It seems these cysts can develop from a variety of sources and are often benign, incidental findings with no clinical significance, and not requiring any treatment. I thought back to all the chest masses I have seen in cats over the years. Since many owners do not pursue definitive diagnosis, I wondered how many might have been benign cysts like this?

We will monitor Tuxedo’s cyst, but having ruled out more serious problems, she can go to Radiocat with the specialist’s blessing. And I have learned something new.