High-tech testing: needed or not?
This past week I went to a continuing education seminar... while having lunch at my desk. It was great. No ferry. No hotel. No missing my kids. I got a cup of tea, went online to the "meeting" where I could view the graphics, and dialed an 800 number on my speaker phone for the audio. The web site allowed participants to give feedback to the presenters, and to type in questions. The meeting was attended by veterinarians from all over the world. These types of seminars are becoming more commonplace as the veterinary industry uses telecommunication options to educate veterinarians and promote their products. This lecture, sponsored by IDEXX Laboratories, was about a test called the Urine Protein Creatinine Ratio, or UPC. Until recently, veterinarians had to send samples out to commercial labs to get a UPC but IDEXX now has a product that allows those with the right equipment to run UPCs economically right in their practices.
So what is a Urine Protein Creatinine Ratio and why would we want to do one on your pet, Puddles? A UPC test measures the amount of protein in Puddles's pee. Why would we want to know that? Because proteinuria, i.e., protein in the urine, may be a sign of kidney disease.
The kidneys are one of the most important organs in the body. They control fluid and electrolyte balance, remove waste from the blood, maintain proper hemoglobin levels, regulate blood pressure and acid/base status, and help with calcium absorption. Ah, you say, no worries. Your vet just ran blood work and said that Puddles's kidney function was fine. Well, here's the rub. Puddles could lose more than 75 percent of her kidney function and still have normal blood tests. That's right. You could surgically remove one kidney and half of the other and not be able to tell on blood work. That's where the UPC comes in.
Each kidney is made up of thousands of little units called nephrons. Kidney failure (technically called renal failure) is classified into 4 stages. In Stage 4, 95 percent of the nephrons are kaput. Metabolic waste products build up in the body. This is called azotemia and is readily noted on blood work. The urine is dilute and contains protein. Clinical signs include excessive drinking and urination, loss of appetite, and vomiting. Veterinarians are great at diagnosing Stage 4 renal failure. We just don 't have much luck treating it. The lecturer compared it to having your car broken down by the side of the road with the engine on fire. Easy to see the problem, too late for an easy fix.
Stage 3 renal failure isn't much better, with 90 percent nephron function loss and mild to moderate azotemia. Symptoms may be subtle, including insidious changes in urination habits, slight increase in water consumption, and slight decrease in appetite and body condition. In Stage 2, symptoms may be even more vague, or nonexistent. Blood tests may be normal, though if you tested repeatedly you might see numbers slowly creep from the lower end of the normal range to the upper end. In Stage 1 Puddles will have no clinical signs and no abnormalities on blood tests. The only way we may be able to diagnose these early stages is by checking for proteinuria. The car is still running, but the "Engine" light is on. The UPC is the kidneys' early detection system.
For the most accurate UPC, your veterinarian may advise collecting a specimen sterilely by passing a needle through Puddles's belly wall into the bladder and drawing out urine with a syringe. It's not as bad as it sounds. But in many cases you can collect urine at home and bring in the pee, without the pet. If the UPC is normal, you're done. If the UPC is elevated, it's not necessarily cause for concern. Transient proteinuria can occur with fever, stress, exercise, or infection. All these things need to be ruled out first. Then, if Puddles has repeatedly elevated UPCs, that is confirmation of early renal disease.
Diet and meds
What do we do if we find Stage 1 or 2 renal disease? Put Puddles on a protein-restricted, low phosphorus renal diet. It is much easier to get a pet to switch over to these foods when he is still feeling well. By the time Puddles hits Stage 3 or 4, it's hard enough to get him to eat, let alone change him to a diet that is, let's face it, a little bland. Other early interventions that may slow the progression of kidney disease may include the use of supplements such as fish oil, B vitamins, and fiber. By monitoring the UPC, your veterinarian can track whether these changes are helping. If Puddles won't accept the special diet, or if the diet does not lessen the proteinuria, many specialists are now advising treatment with a class of drugs called ACE-inhibitors, especially in pets with hypertension, a common sequella to renal failure. These medications may reduce the proteinuria, as well as lower blood pressure.
Who should get tested? IDEXX has a long list. Pets who are old or sick. Those on medications that may potentially damage the kidneys. Breeds prone to kidney disease such as soft-coated Wheaton terriers. Any dog with abnormal lab test results such as low albumin blood levels, proteinuria, or excessively dilute urine. Lyme-positive dogs. Now, in my dotage I have become increasingly more cynical. IDEXX has something to gain by encouraging veterinarians to run a lot of UPCs. Does it really make sense to follow these recommendations? Isn't it enough to just run a routine urinalysis? After all, there's a little square on that dipstick that measures protein and it's a cheap and easy test.
The answer is both technical and philosophical. Technically, the UPC is ten times more sensitive than a standard dipstick. In other words, Puddles's routine urinalysis could be negative for protein and he could still actually have proteinuria - he just needs a better test to detect it. Philosophically, it depends on what you would do with the information and how much you want to spend. The UPC is fairly modest in price, but if the initial screen elevated, you can expect additional tests to follow. Then you have to decide about treatment and monitoring.
One in three cats and one in five dogs will develop kidney disease in their lifetimes. It seems reasonable to me to screen at-risk individuals and institute a few nutritional changes. It could be particularly useful here on the Vineyard with our large numbers of Lyme-positive dogs, who may have a greater chance of developing kidney disease than the general population. Maybe it was the comfort of sitting with my feet up in my own office, or the skill of the lecturers. Maybe it was the fact that I have the equipment or that the in-house UPCs will cost less than the send-out version. Whatever it was, they overcame my skepticism and I ordered a box today. If you think your Puddles could benefit from screening for early renal disease, talk it over with your veterinarian, and bring a urine specimen.