The kidneys are two bean-shaped organs located just beneath the ribcage in dogs and cats. Their function is to filter the blood and eliminate the harmful chemicals your body does not need through urine. When there is disease present, either acute or chronic, the kidney function is decreased, and these chemicals are not eliminated properly.
Certain lab values give us an indication of whether or not disease is present. The most common values we check in the blood are the BUN (blood urea nitrogen) and creatinine. The BUN will be elevated if the kidneys are not able to remove urea from the blood normally. The creatinine will be elevated if the kidney function is impaired or the kidneys have some level of disease. We also check the urine concentration. In a healthy animal, the urine will be concentrated. In an animal with kidney disease, the urine is dilute. This is because the kidneys lose their concentrating ability when disease is present. We will often see protein in the urine as well as diseased kidneys do not process protein normally.
There is a new test that screens for early renal disease, known as the SDMA (symmetric dimethylarginine). SDMA is a more reliable and early indicator of kidney function. This is because it is a renal biomarker specific to kidney function. Often this value will be elevated before the BUN and creatinine are elevated, or before we see any changes in the urine.
Other values are also affected in renal disease. Often, the potassium will be low and need to be supplemented. Phosphorus is often high, and oral phosphate binders are used to bring this value down. Also, we often use a medication called Calcitriol to help keep the calcium and phosphorus in balance so that patients do not develop secondary hyperparathyroidism, a big word for overactive parathyroid gland.
Hypertension, or high blood pressure, is commonly seen with kidney disease. Once we have made a diagnosis of kidney disease, we will check your pet’s blood pressure and if elevated, start them on a medication to help lower the blood pressure.
Pets in renal failure commonly show signs of drinking more water than normal and urinating more than they normally do. Often, these pets feel ill and will vomit or have a decreased appetite. We often see weight loss as a result of this disease as well.
Acute renal failure can be caused by toxins such as antifreeze, lilies, and NSAIDs. Chronic renal failure means the kidney disease has been taking place over a longer period of time. If treated aggressively, with several days of hospitalization and IV fluids, acute renal failure may be reversed. Chronic renal failure needs long-term management, such as a diet change to a prescription kidney diet, long-term medications to help manage hypertension(high blood pressure), calcium, and phosphorus levels, and giving subcutaneous fluids at home or in the hospital.
It is so important to monitor kidney values every year with routine bloodwork in young pets. Once your pet becomes a senior (7-8 years of age depending on breed), we need to check those values every six months. Keeping your pet on a good quality diet and keeping clean water readily available as well as supplementing with fish oil can help keep the kidneys nice and healthy.