How Kidneys Work
The kidneys are a pair of organs inside the abdomen or belly that are part of the urinary tract, also known as the urogenital system. Their job is to filter toxins, waste, and extra water from the blood. They do this by making urine, which gets transported to the bladder via tubes called ureters. Kidneys also help maintain the electrolyte balance within the body, make red blood cells, and control blood pressure. When the kidneys don’t work properly, numerous body systems can be affected, including the heart and brain.
Kidney disease is classified in a few ways. Treatment, outcome, and causes will differ a bit between each category. Most commonly, you will see kidney disease referred to as either acute kidney failure (AKA acute kidney injury/AKI, acute renal failure/ARF) or chronic kidney failure (AKA chronic kidney disease/CKD, chronic renal disease, chronic renal failure/CRF).
Acute kidney failure is caused by sudden injury to the kidneys that results in failure of the kidneys to function properly. This malfunction leads to a rapid decline of the health of the kidneys themselves as well as the other body systems that the kidneys normally help maintain. While acute kidney failure is very serious, and a pet can become extremely ill, some pets can survive with proper treatment.
The most common causes of acute injury include decreased blood supply (i.e. ischemia), toxins, heart failure, burns, liver failure, cancer, kidney infections, venom, urinary tract obstruction, and sepsis (i.e. blood infection). The most common toxins in dogs are grapes/raisins, ethylene glycol/antifreeze, certain antibiotics (e.g. gentamycin), and nonsteroidal anti-inflammatory drugs/NSAIDs (e.g. ibuprofen).
With acute kidney failure, kidney cells are damaged to the point that they don’t receive oxygen from red blood cells. They lose their ability to filter the blood properly, leading to loss of some electrolytes (e.g. potassium) and retention of others (e.g. phosphorus) which damages the cells further. The filter portion of the kidneys gets clogged with damaged cells and proteins that normally wouldn’t be filtered into the urine. Inflammation of the kidneys further damages the cells and the dysfunction and damage compounds on itself quickly. Severe dehydration can occur. At some point, this process is irreversible, although if the kidneys recover, they may be able to still function a little. In some cases, acute kidney failure patients recover, only to develop chronic renal failure because of the permanent damage. Unfortunately, about half of dogs that develop acute kidney failure do not survive.
Symptoms and Identification
Dogs in acute kidney failure develop severe symptoms, very quickly- usually in less than a week of the kidney injury, although it can occur within minutes to hours of the injury for toxins like antifreeze. Fever or low temperature can occur. Tummy pain, weakness, bad breath, throwing up and loose stool, drooling, and/or seizures can be seen. Many dogs will drink and urinate a lot at first. If acute renal failure worsens, the kidneys may stop working altogether and the dogs will not urinate at all.
Bloodwork and urinalysis are commonly performed to diagnose kidney failure. In cases of acute kidney failure, blood work can show changes in the white blood cells, which fight infection and cause inflammation. Bloodwork laboratory values that show how the kidneys are functioning (e.g. BUN, creatinine, and SDMA) may be extremely elevated. Other lab values may indicate how the body is handling the disease and what may have caused it. Other abnormal lab values may suggest what caused the kidney disease (e.g. toxin, infection). Urinalysis will show if the kidneys can concentrate the urine correctly, if protein is being lost in the urine, and if other problems are occurring in the urinary tract such as infection or kidney/bladder stones. Blood pressure, x-rays, and abdominal ultrasound may also be performed to assess the severity of disease, get an idea of how the kidneys look, and to check for potential causes.
International Renal Interest Society (IRIS) offers grading methods to help monitor and treat patients in acute and chronic kidney failure. Grades 1-4 are based on how well the kidneys can concentrate urine and filter toxins out of the blood. Laboratory values (e.g. SDMA, creatine) and urinalysis are used as criteria to move from one grade to the next, with grade 1 indicating mild kidney failure (i.e. minimal laboratory value changes) and 4 being severe (i.e. major changes). Subgrading also helps determine severity and treatment needs. Subgrading in acute failure is mostly based on the kidneys ability to produce urine.
Kidney failure can happen at any age. No breeds or gender are specifically prone to the disease.
If treated early, dogs in acute kidney failure may improve. Much treatment and intensive care is needed. Hospitalization with intravenous (IV) fluids and electrolytes, medications to help increase urine production (e.g. furosemide), antibiotics to combat infection, and other treatments to manage what caused the kidney failure are often needed. Hospitalization and intensive care usually take several days before starting to see improvement. Urinalysis and bloodwork rechecks will likely be performed numerous times to monitor the pet. Some veterinarians will refer dogs to a specialty hospital that provides 24-hour care in order to best provide for the pet’s needs.
Veterinary cost varies quite a bit depending on the underlying cause and how the pet responds. Initial identification tests for diagnosis usually range from $200-750. Hospitalization and intensive care for acute kidney failure can range from $750-3,000.
Unfortunately, little can be done to prevent kidney failure. Avoid exposing your pet to toxic substances. Take him or her in for yearly check ups. Monitor for changes in drinking and urinating habits to ensure treatment can be started as soon as your pet becomes sick. Always call your vet with questions/concerns.
Langston C, Ettinger J: Acute Uremia. Textbook of Veterinary Internal Medicine, 7th ed. St. Louis, Saunders Elsevier 2010 pp. 1969-1985.
Liss D; When Good Kidneys Go Bad: Toxins causing AKI. IVECCS, 2019.
Vaden SL, Levine J, Breitschwerdt EB: A retrospective case-control of acute renal failure in 99 dogs. J Vet Intern Med 1997 Vol 11 (2) pp. 58-64.
Cowgill L: IRIS Grading of Acute Kidney Injury. 2016. Accessed August 24, 2020.
De Loor J, Daminet S, Smets P, et al: Urinary biomarkers for acute kidney injury in dogs. J Vet Intern Med 2013 Vol 27 (5) pp. 998-1010.
Mitani S, Yabuki A, Taniguchi K, et al: Association between the intrarenal renin
Eatroff AE, Langston CE, Chalhoub S, et al: Long-term outcome of cats and dogs with acute kidney injury treated with intermittent hemodialysis: 135 cases (1997-2010). J Am Vet Med Assoc 2012 Vol 241 (11) pp. 1471-8.