What is Kidney Disease?
Kidney disease happens when one or both kidneys aren’t working properly, which means they can’t filter the blood as they should. This disease affects both dogs and cats. Since kidney function is vital, its impairment can lead to severe health consequences.
What are Kidneys?
The kidneys play an important role in the body by controlling the amount and makeup of blood and urine. In cats and dogs, they are located on either side of the spine, towards the middle of their back, just under the ribs. They reabsorb useful substances into the blood and filter harmful ones, like waste products and excess water, which are excreted as urine. Although cats and dogs have two kidneys just like humans, one kidney can often be enough to sufficiently filter body waste.
Types of Kidney Disease: Acute vs. Chronic
About one in three cats and one in ten dogs will develop kidney disease at some point in their lives. It can appear in any pet but is more prevalent in older animals. It can be classified as acute, also called Acute Kidney Injury (AKI), or chronic, called Chronic Kidney Disease (CKD). With AKI, the kidneys suddenly stop working due to a sudden injury, while CKD involves a gradual loss of renal function over three months or more.
This blog post will focus on AKI, but stay tuned for a future post about CKD!
Causes of AKI in cats and dogs
There are many potential causes of renal injuries in cats and dogs. Nephrotoxins are substances that can cause kidney toxicity in large quantities. Examples include lilies in cats, grapes/raisins in dogs, and certain drugs like penicillin and ibuprofen.
Pets with existing risk factors like pancreatitis, liver disease, diabetes mellitus, cardiovascular issues, or severe burns are more prone to AKI. If you’re concerned, consult your vet for detailed information and risks specific to your pet.
Recognizing AKI in your pet
Clinical signs of AKI include a decreased appetite or energy, vomiting, diarrhea, or strange breath odour. Noticeable changes in thirst and urination—either a sudden increase or decrease—are key indicators of a renal injury. Symptoms usually appear suddenly and last for a short period of time, ranging from hours to days.
Diagnosing AKI
At presentation to the hospital, your veterinarian will use your pet’s medical history, clinical signs, and a series of diagnostic tests to determine if your pet has AKI. Dehydration and abdominal pain during a complete physical exam may suggest renal issues. Blood tests can evaluate blood pressure, cell counts, and levels of blood urea nitrogen (BUN) and creatinine. Azotemia is a condition when a patient has high levels of BUN and creatinine in their blood and is a sign of renal failure. Creatinine is a waste product from the normal breakdown of muscle tissue in the body, and BUN is a waste product resulting from protein metabolism. As the kidneys’ filtration rate is decreased, the excretion of these substances is impaired, causing their levels to rise in the blood.
A urine test can be performed to evaluate Urine Specific Gravity (USG) to determine if the kidneys can effectively concentrate or dilute urine in the body. This test can also help to rule out bacterial infections that could possibly cause renal injury.
Diagnostic imaging may be performed to visually assess renal status. Radiographs may help to assess the size and shape of the kidneys, but an ultrasound could be more helpful as it allows for precise measurements of renal size and identification of cysts or masses.
AKI is often diagnosed using the International Renal Interest Society (IRIS) AKI staging system for dogs and cats. This system uses blood creatinine levels and urinating flow rate to determine the disease’s severity. It is on a five-grade scale, with Grade I/V being the most acute, and Grade V/V the most severe. Ask your veterinarian for more information on IRIS grading.
Treating AKI
Treatment focuses on addressing the injury’s cause and removing toxins to restore the pet’s water-electrolyte balance. Your veterinarian will create a personalized treatment plan tailored to what they determine is best for your pet’s needs.
Water is key! Keeping your pet hydrated will help their kidneys properly filter toxins from their blood. With this disease, kidney function is compromised, so providing enough fluids supports their filtering capacity. Typically, dogs and cats need 50-70 mL of water per kg of body weight daily. Please consult your vet if you have concerns about your pet’s water intake.
The processes involved with injury recovery require lots of energy! It is important that your pet receives the necessary nutrients that their body needs to heal. You can support your cat or dog’s nutrition by providing easily digestible food, stimulating appetite, and following your veterinarian’s feeding recommendations. If your pet isn’t eating their daily calorie requirements, your veterinarian may also recommend placing a feeding tube to help your pet get the food they need.
Prognosis for AKI
The prognosis for AKI varies based on medical history, injury cause, and severity. Some patients may recover fully, but about half of the patients that survive will develop a chronic form of the disease. Between 40 and 65% of dogs and 60 to 75% of cats do not survive from this disease.
In conclusion, while AKI in cats and dogs is a serious condition, advances in veterinary medicine have greatly improved our ability to diagnose and treat this ailment effectively. By working together with your veterinarian and providing the necessary care and attention, you can help ensure your beloved pets continue to enjoy their days with vitality and joy.
Written by: Brianna Chan, Clinical Studies Summer Research Student
Reviewed by:
Dr. Sarah K. Abood, DVM, PhD, Associate Professor, Nestlé Purina Professorship in Companion Animal Nutrition
Dr. Ashley Spencer, MHSc, DVM, DACVIM
References:
Lee, Y.J., Chan W., Hsu W.L., Lin K.W., Chang C.C. (2012). Prognostic factors and a prognostic index for cats with acute kidney injury. Journal of Veterinary Internal Medicine, 26: 500-505. https://doi.org/10.1111/j.1939-1676.2012.00920.x
Mugford, A., Li R., Humm K. (2013). Acute kidney injury in dogs and cats 1. Pathogenesis and diagnosis. In Practice, 32:253-264 https://doi.org/10.1136/inp.f2868
Ross, L. (2011). Acute kidney injury in dogs and cats. Veterinary Clinics of North America: Small Animal Practice, 41: 1-14. https://doi.org/10.1016/j.cvsm.2010.09.003
Thoen, M.E., Kerl, M.E. (2010). Characterization of acute kidney injury in hospitalized dogs and evaluation of a veterinary acute kidney injury staging system. Journal of Veterinary Emergency and Critical Care. 21(6): 648-657. https://doi.org/10.1111/j.1476-4431.2011.00689.x
(2016). Grading of acute kidney injury. International Renal Interest Society, http://www.iris-kidney.com/pdf/4_ldc-revised-grading-of-acute-kidney-injury.pdf