Tony Johnson, DVM, DACVECC
Anyone treating cats in a clinical setting will have to deal with the common specter of feline kidney disease at some point in their professional life. I recall, early in my career, letting an owner know that her cat had the unfortunate triad of elevated BUN, creatinine, and isosthenuria. “I’m sorry, ma’am, your cat has kidney disease,” I said on the phone.
“She has kitty disease?” she responded. It’s so common in cats that kitty disease is an apt moniker.
As an ER vet, I don’t often handle the chronic aspects of care – I usually encounter either acute kidney injury (what was, until recently, known as Acute Renal Failure, or ARF) or end-stage chronic renal failure. I thought it might be prudent to brush up on how long-term management of chronic renal disease in cats is handled and see if anything new popped up. I hope some of things I found will be helpful to you.
One thing I found is that it’s no longer just about diet. The days of Sorry, she has kidney disease, we need to switch to a new diet (only) are in the rearview mirror now. Managing secondary complications (such as hypertension and hypokalemia), keeping a healthy weight, and staging degree of remaining renal function (among others) are what it’s all about these days. So, let’s run through those.
Hydration
I am torn on sub-Q fluids (SQF), to be honest. I realize the importance of supporting the kidneys’ role in filtering toxins, but the adverse consequences that SQF may have on the patient-owner bond have to be considered. It’s super-easy for us to recommend it – and it can be a helpful intervention. We do it nearly every day in practice, so why should it be any different at home? Well, for one, just as cats are not small dogs when it comes to medicine, homes are not veterinary clinics, and pet owners are not technicians. When my own eldercat had CKD years ago, I thought I could help him out by giving some SQF a few times a week.
Boy, was I wrong.
Philo hated the living hell out of it (he was a horrid patient) and, after a time, hated the hell out of me. He’d go hide when he saw the bag of LRS come out, and, after a time, he’d hide from me no matter what. I abandoned the practice before our relationship was totally kaput. I may have denied him a few extra weeks of life, but I wasn’t about to destroy what time we had left.
So, talk to your owners and feel them out for what they think the cat’s level of tolerance is. They really do know their pets. Some cats will sit pretty and get tanked up, and for those owners who can handle needles, it works out great. For other cats, like Philo, it might be too stressful to make it worthwhile. And some owners are so needle-phobic that asking them to do it is like asking them to drink a cupful of spiders.
When it all lines up and you have a willing patient and owner team, 100 to 150ml of LRS (which the techs tell me stings less than saline or Normosol) done every few days can be helpful; just keep the potential for fear, anxiety, and stress – of both the human and feline kind – topmost in your mind.
Staging
CKD used to be just an on-off sort of thing – you either had it or you didn’t. Not so much anymore! In this shiny new era of CKD management, staging of the condition (and changing therapies based on advancing stage) is the new normal.
For more info on IRIS staging of renal disease, visit http://www.iris-kidney.com/.
Electrolytes/PO4
Chronic hypokalemia is a problem in cats with compromised kidney function, and hypokalemia itself can contribute to worsening of the disease. Luckily, many renal diets have increased levels of potassium to help offset this. But for cats who are found to be hypokalemic on serial lab work, oral K supplements (like potassium gluconate 2 to 6 mEq/cat PO q24h or potassium citrate 20 to 30 mg/kg PO q24h) can help. And don’t forget – since potassium is a primarily intracellular ion, normal or low-normal K on a panel can actually mean depleted whole-body K. Try to keep K levels around 4, and remember that K is necessary for proper GI function, so that anorexic cat might be not eating because his guts are not moving – which sets him up for a vicious cycle.
Hyperphosphatemia is another common problem in “kitty disease” and chronically elevated PO4 can contribute to declining renal function. Most renal diets have decreased levels of phosphorus, but sometimes the need arises for oral phosphate binders. If the level hasn’t dropped after 4 to 6 months on a kidney-friendly diet, time to add in a phosphate binder. One thing to remember, though, is that most PO phosphate binders (like aluminum hydroxide [30–100 mg/kg/day], calcium carbonate [90 to 150 mg/kg/day], and lanthanum carbonate [30 mg/kg/day]) will only bind phosphorus in food, so forcing them on an anorexic cat will do nothing but make the cat angry with you – and hate the medication. So, mix with food and monitor the PO4 levels every 4 to 6 months.
Diet
Every pet-food company, and every pet-food company’s brother, now has a kidney-friendly diet for cats. I won’t go into great detail here, because you probably stock one and recommend one already. I will offer up one nugget to think on, though: cats who won’t eat a kidney-friendly diet (at home, or in the hospital) are eating themselves – quite literally. Their bodies are digesting muscle for nutrition, and not much is higher in protein than muscle. So, if they won’t eat what you prescribe and are losing weight, let them eat what they want. Just try a few go-rounds of renal diets first (which may mean a special order if they don’t like what you routinely stock).
Hypertension
I was a veterinary technician in the ER before I became a veterinarian, and I recall one night when a renal transplant patient came in. He was a beautiful Siamese cat and must have been one of the first transplant recipients in the U. S.; the year was 1991.
He came in for acute onset blindness and his normally beautiful blue eyes were now dilated black circles of doom. He had blown his retinas due to unchecked hypertension. I will never forget his howls of confusion and fear as he tried to navigate his newly black world of blindness.
$20k in transplant costs and he lost the battle to a then-unrecognized complication.
Nowadays, hypertension is a commonly known side-effect of CKD and therapy is ever-evolving. Monitoring blood pressure is far more commonplace than it was 30 years ago, and just about every clinic has the ability to check a cat’s BP. Blood pressure >200 mmHg can represent an emergency, and consultation with a criticalist or internist is recommended.
Don’t forget the contribution of fear and anxiety to BP (“white-coat” hypertension): any elevated reading must be viewed in light of the cat’s mental state and level of arousal. Checking BP after the cat has acclimated to the hospital, but before any procedures such as a blood draw, will ensure more accurate readings.
Cats with CKD and a blood pressure persistently over 160 mmHg would probably benefit from antihypertensive treatment. Amlodipine, a calcium-channel blocker, is currently my drug of choice (0.625–1.25 mg/cat q24h) but several other options exist and data indicating that angiotensin-receptor blockers such as telmisartan may be superior to amlodipine mean that the regimen may be changing in the future. (More info here: https://onlinelibrary.wiley.com/doi/full/10.1111/jvim.15331)
I learned quite a bit as I mosied through this new world of chronic kidney management, and I hope you did, too. There’s quite a bit I didn’t include here that may help some of your kitty disease patients – acid-base, anemia, GI ulceration, and a host of others. You may want to do a little exploration of your own through CE classes or online resources such as VIN. And don’t forget – kidney transplantation is a thing now, so for that special owner who might consider it, remember to discuss it as an option. Ditto hemodialysis. You might get some funny looks along the way, but one day someone will go for it.
Keep up with what’s new in CKD management and your patients, their happy kidneys, and their happy owners will thank you.
This article was reviewed/edited by board-certified veterinary behaviorist Dr. Kenneth Martin and/or veterinary technician specialist in behavior Debbie Martin, LVT.
