Bodie, a middle-aged cocker spaniel, recently went with his family on a road trip down to Florida for a few weeks. When they returned home to the Vineyard, they noticed Bodie was a little mopey. He was drinking more water than usual, and urinating frequently. “Traveling can be fun,” I said, “but also stressful.” Maybe Bodie was simply tired from all the excitement? I know I sometimes feel in need of a vacation after being away on vacation. Maybe he hadn’t had access to water as often as he would have at home, and now was drinking extra to compensate? Another possibility was a stress-induced urinary tract infection. We see this fairly often in pets coming to visit the Vineyard. Why not in an Island dog traveling to Florida and back?
Bodie’s owners had come prepared by bringing along a urine specimen. Analysis showed his urine was excessively dilute, and contained a trace of blood. Now, when we see an animal drinking and peeing excessively, with unusually dilute urine, we have a chicken-or-egg situation. Which came first, the excessive drinking or the excessive urination? Are Bodie’s kidneys not working properly, resulting in abnormal water loss in his urine, thus causing him to drink more to compensate? Or is something making Bodie unusually thirsty, resulting in excessive drinking that then causes production of large quantities of watery urine, hence the need to pee more often?
“It could just be a urinary tract infection,” I told his owners, “but this urinalysis isn’t completely consistent with that diagnosis.” I suggested blood tests to rule out things like diabetes, kidney or liver dysfunction, adrenal gland disorders, even Lyme disease. When the results were in, I scratched my head. Normal blood sugar. Kidneys fine. Slight changes in liver enzymes, but nothing dramatic. No tick-borne diseases. The only thing clearly abnormal was an elevated blood calcium level.
I hate elevated calcium levels. Why? Because most of the time, these are spurious results. Spurious is a great word. Merriam-Webster defines it as “outwardly similar or corresponding to something without having its genuine qualities.” In other words, the test result could just be wrong. Get a new sample and test again, or send the sample out to the big reference lab for confirmation, and much of the time the second test will show normal calcium levels. So when I see hypercalcemia (the technical term for elevated blood calcium), I often ask owners to come back for me to draw a new sample to send to an outside laboratory. Except in this case, Bodie really doesn’t like needles and blood draws … I mean he really, really doesn’t like them … and I hate upsetting either patients or their people. “It’s perfectly possible this is just lab error,” I told his family. “But if it’s real, it could indicate serious problems.”
Calcium is an essential mineral that plays many roles in the body. It’s not just in bones. Calcium helps muscles contract, activates enzymes, and regulates all kinds of things, so the body works hard to make sure there is enough calcium, but not too much. If Bodie’s retest confirmed an elevated total calcium, the next step would be to collect yet another blood sample to measure “ionized calcium” levels. This requires a special drawing technique, preventing the blood from contacting air. It differentiates calcium circulating free in the bloodstream from calcium bound to carrier molecules, like albumin. Unless you want an hour-long lecture on biochemistry and pathophysiology, you just have to trust me that this is important. I usually run these tests sequentially, because of the cost, but for Bodie we jumped right to testing ionized calcium to minimize how many times we might need to draw blood. It was a good call. His ionized calcium was elevated.
So now we have to talk about the parathyroid glands. Bear with me. These tiny organs in the neck secrete parathyroid hormone (PTH), which is a player in regulating calcium levels. A tumor in these glands can cause excessive PTH secretion, which then causes hypercalcemia. This is called “primary hyperparathyroidism.” Symptoms may include excessive drinking, urination, muscle weakness, weight loss, trembling, poor appetite, and urinary tract infections. Bodie certainly fit the bill. Rechecking his earlier blood work, I noticed his phosphorus levels were low-normal, another clue consistent with this possible diagnosis. Luckily the lab had enough blood left to order a PTH level. While waiting the week it would take to get PTH results, I pondered other possibilities. Anal gland cancer and mammary cancer can cause hypercalcemia. I checked Bodie carefully for suspicious masses. Nope. Renal failure can cause hypercalcemia, but our initial blood tests had ruled this out. Addison’s disease, an adrenal gland disorder, was unlikely, as his electrolytes were normal, but atypical Addison’s was still possible. Diagnosis would require further blood tests. Multiple myeloma? Unlikely, as his globulin levels were normal.
Bodie’s PTH levels come back in the “gray zone,” neither confirming nor ruling out any specific diagnosis. I discussed his case with veterinarians at the reference laboratory. They confirmed that the ionized calcium level was too high to ignore, despite the fact that Bodie’s owners say he has been feeling better and is no longer drinking and peeing excessively. His family agreed that they don’t want to take any chances, so we are taking the advice of specialists and pursuing the next diagnostic step, referring him to specialists off-Island for an ultrasound of his neck and abdomen, looking for tumors. If they do find a parathyroid tumor, they can remove it surgically, followed by careful monitoring of his calcium levels. Happily, the prognosis for primary hyperparathyroidism is good. If they find some other kind of cancer, which we fervently hope doesn’t happen, then we will cross that bridge when we come to it. And if they don’t find any explanation at all, then we will rely on their expertise to give us suggestions as to what we should do next, if anything, about that annoying, problematic elevated calcium.