Tuesday, August 26, 2008

an easy diagnosis

back a couple of weeks ago, i saw a case that taught me the value of selective medicine. i.e. medicine outside of the ivory tower of vet school.

my owners were an older couple in their 60s. they brought me their mixed breed, 7 year old pit-bullish dog for increased drinking. as they described her insatiable appetite for water, i was running through my head THE list for pu/pd (polyuria/polydipsia - increased urinating and drinking) which includes no less than 20 differentials. diabetes was a big concern of mine, as well as other considerations...until the owner stopped me by pointing out that the dog had a huge "knot" in her neck. a lightbulb lit up so bright it almost blinded my mind's eye as i stepped around the table and felt the dog's enormous lymph nodes. both mandibular (below the jaw) and one of the suprascapular (in front of the shoulder) lymph nodes were extremely large. the dog didn't have a fever and seemed to be feeling well otherwise. all very bad signs. they scream cancer! cancer! cancer! cancer!

what, you might wonder, about increased drinking and large lymph nodes made me think cancer right off the bat? when dogs have a type of cancer called lymphoma, the tumor cells produce a substance called PTH-rp. this is a mimic of parathyroid hormone (PTH), something the body already makes. it comes from the (surprise) parathyroid glands in the neck and is crucial in maintaining calcium balance in the body (it upregulates reabsorption of calcium from the intestines, bone, and kidney). when the cancer cells start making this mimic, the body cannot tell the difference between it and real PTH, so the body starts reabsorbing calcium in massive amounts. this hypercalcemia leads to dysfunction in the kidneys so that they can't do their job and properly reabsorb water. massive amounts of fluid are lost through the kidneys, and significant dehydration occurs. the animal will drink and drink and drink, but it cannot keep up with the needs of the body. if high enough, the hypercalcemia can be a life-threatening condition in itself. other diseases can cause hypercalcemia, including fungal infection (which we see a TON of here in the south). fungal can also cause enlarged lymph nodes. however, a recent study in JAVMA showed that the occurrence of elevated calcium with fungal disease is incredibly rare (much rarer than originally supposed). further, the dog was feeling good, had no fever, and no other signs besides lymphadenopathy and polydipsia.

i discussed with the owners my suspicion that their dog had lymphoma, a very common cancer of dogs. they were naturally taken aback by the news this seemingly benign problem (more drinking) could indicate such a potentially life-threatening disease. and money was a problem. i recommended complete staging - bloodwork, xrays, etc to see if the cancer had spread beyond the lymph nodes. they declined.

the treatment for lymphoma in dogs is chemotherapy (systemic treatment for systemic disease). this runs between $3000-4000 for the first course. unlike chemo in people, dogs don't usually get sick. the reason is that our treatment goals are different. in veterinary medicine we strive for quality of life, not quantity. dogs do not have a sense of the length of life (at least, not to our understanding). to prolong their lives through horrible suffering (vomiting, diarrhea, hair loss) to gain a few years is meaningless. instead of trying to give them more time, we try to give them remission time: life as a happy healthy dog. the doses used for chemotherapy are much smaller when compared with human doses. with chemotherapy, we can usually achieve remission and good quality of life for up to a year and a half post-diagnosis. some dogs don't respond, of course. this has to do with a variety of factors, including which kind of lymphoma they have (t-cell versus b-cell). but generally, dogs do well with chemo. several of my friends have dogs that have been through the gold standard chemo (UW-Madison protocol) and several rescue protocols (what are used once the dog stops responding to UW-Madison). as a sidenote: hypercalcemia is usually associated with t-cell lymphoma, which has a worse prognosis and a poorer response to chemotherapy.

i discussed this with the owners, and they were very frank with me. they didn't have health insurance for themselves and their myriad health problems, let alone four grand lying around to treat their dog. they wanted a diagnosis - and they wanted it cheap. then they wanted palliative care (steroids) that would carry their dog for perhaps another 3 months.

i had limited money and needed both a diagnosis and some steroids (which are cheap, thankfully). instead of getting to do my super-duper vet school ivory tower diagnostics, i had to pick very carefully what i wanted to spend my clients' money on. i suspected the calcium was high based on my physical exam, but i needed to be sure. thus, i elected to run an ionized calcium (which indicates the amount of free "usable" calcium in the body and is a better indicator of blood calcium than just a plain calcium on a chemistry panel) and do a fine needle aspirate of the lymph nodes (stick a needle in them and make slides for cytology).

i ran my iCa. it was 1.9. vet people who read this will be going HOLY HYPERCALCEMIA BATMAN! that's really high. my FNA revealed what i suspected. big fat abnormal lymphocytes (called lymphoblasts). and my diagnosis was complete.

i relayed the news to my owners, who elected to proceed with palliative (make them feel better till they die) care. steroids are great for beating lymphoma back into remission - but they are very temporary. eventually the cancer cells become resistant to steroids (thanks to the MDR gene) and the cancer comes roaring back. i explained this to them, and they understood. they took their dog home for her remaining days.

last i talked to them (about 5 days ago), my patient was doing well and her drinking had decreased somewhat (not totally but this is due to the steroids, which also cause increased drinking but for different reasons). i know that in some weeks time, i will be seeing her again - to perform the part of my job that i both appreciate and hate. until then...i hope she has quality time with her owners. i'm glad that i could give them peace of mind in knowing what they were dealing with and what their treatment options were.

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