What’s the deal with bloodwork for healthy senior pets?
When an animal comes to the veterinary hospital for an illness, it’s a lot easier to understand why the doctor is recommending blood work, a urinalysis, a fecal sample, or x-rays. Basically, something is wrong and we are looking for confirmation of what that is and how to treat it. But what about the healthy animal that comes in – why should they have blood work? The reasons are many, particularly if they’re a senior cat or dog.
Let’s focus our thinking about senior pets.
If they’re healthy, cats and dogs can often live into their teen years, and many senior cats are old enough to get a drivers license! So what are we hoping to find on their blood work? Nothing. Nothing? Yes, nothing. We are hoping that we find nothing out of the ordinary, and that your senior pet is just as healthy on the inside as they are on the outside.
So the question really becomes what are we hoping not to find?
We’ll start by looking at cats. In particular, cats are good at hiding things from their owners so we don’t always have outward physical signs of disease until it’s relatively late in the process, making it a longer and more difficult job to treat them and get them back to being healthy.
- Hyperthyroidism – this is a very common disease in older cats where they develop a small growth on their thyroid gland that overproduces thyroid hormone, elevating their metabolism and causing a variety of problems. Sometimes that little nodule is palpable, sometimes it isn’t. Hyperthyroid cats are often eating very well but losing weight, being more active, vocalizing more, and many are having frequent episodes of vomiting and diarrhea. But early in the process, there may be no clinical signs whatsoever. And if we can catch it before your 12lb kitty has lost a dramatic amount of weight, developed high blood pressure, or a heart murmur because of thyroid problems, that’s the best time!
- Kidney disease – kitty kidneys work very, very well until they don’t. Relatively speaking, cats are desert animals with little access to water and their kidneys are therefore designed to be very efficient at saving any water they do drink and making very concentrated urine. It’s often a gradual process of losing kidney function, and while ultimately kidney failure isn’t something that can be reversed, it can be managed. And the earlier you catch it, the better it can be managed and the longer kitty can live a happy life.
- Diabetes mellitus – roly poly kitties are pretty cute, but being overweight makes them more prone to developing diabetes. In kitties, this disease has to do with the pancreas not making insulin, which controls glucose (sugar) metabolism. Too much glucose in the blood and not enough in the cells means that even though kitty is eating a lot and drinking a ton of water, their cells are actually starving and they’re losing weight. In the early stages, it can be very subtle so finding a high blood glucose on routine lab work means we can act quickly before severe weight loss, keto acidosis, or neuropathies happen.
- Anemia – red blood cells are produced in bone marrow and circulate in the blood, but their production is controlled by a hormone made by the kidney. And low red cells can have many causes, some of which include infection, cancer, or kidney disease. If things go on long or are severe, kitty needs a blood transfusion! So catching this early when it’s mild is key!
- Hypercalcemia – Calcium is one of many electrolytes in the body, and its level depends on a delicate balance of food, hormones, and kidney function.
But it’s not just kitties that are prone to senior maladies.
Their canine companions can have some of these same problems, but also different diseases that we can find on routine blood work.
- Hypothyroidism – dogs have the opposite problem as cats, whereby their thyroid gland stops producing thyroid hormone, thereby slowing down their metabolism. Common signs include weight gain and mild lethargy, which can easily look like “she’s just slowing down as she ages.” These dogs are also more prone to infections (skin, urinary, ear, etc) than their normal thyroid friends.
- Liver disease – the liver is quite the clearinghouse in the body, filtering blood and making a variety of digestive enzymes. Because it’s so active, it also can take a hit from many sides, and it isn’t until very late in liver disease that we can see outward symptoms like jaundice (yellowing of the skin), diarrhea and weight loss.
- Urinary infections – classically, a dog with a urinary tract infection gets brought in because they’re having accidents in the house, urinating every few minutes, or maybe straining or urinating blood. But it’s very possible to have subclinical disease that doesn’t have any symptoms, and if left undiagnosed can lead to a very serious kidney infection called pyelonephritis.
- Arthritis – this is a trick answer because aren’t really going to find arthritis on blood work. That would be too easy. But arthritic dogs are painful and uncomfortable and often placed on anti-inflammatory medications, which can have side effects. Blood work is used to monitor the liver and kidneys for these side effects, and if changes are noticed then medication doses need to be adjusted or the drug discontinued before serious problems occur.
While this isn’t an exhaustive list of the things that can be found on routine blood work in a healthy senior pet, it gives a little bit of an idea of the surprises that pop-up. We all hope for normal and “boring” blood work results, but that sometimes isn’t the case. To give a little perspective, a 1999 study from a major veterinary hospital in Los Angeles in conjunction with a diagnostic lab found that “clinically significant disease was found in 20% of dogs and 17% of cats” that were apparently normal at home and not being treated for any underlying medical problems at the time of their routine blood work.