Kidney failure in dogs: clinical signs
Kidney failure in dogs is a common disease in veterinary practice. It is estimated to affect 5.8% of dogs, according to a review of medical histories conducted at Michigan State University(1).
It can develop at any time in the animal’s life, but it is more common in older dogs, particularly over 7 years, which is why it is considered a geriatric disease. In fact, 15% of dogs aged 10 older present structural and functional changes to the kidneys. Kidney failure in dogs follows a progressive and irreversible clinical course, with a tendency to uraemia and azotaemia.
Early detection is key to slowing disease progression
Early detection of kidney failure in dogs and the correct treatment can really help delay disease progression. Studies conducted at Kansas State University(2) and the University of Minnesota(3) showed that the survival rate of affected animals increases if treatment and a renal diet are initiated in the early stages of the disease as they help stabilise kidney function. Advance Veterinary Diets Renal is a special diet developed by Advance for these specific medical needs.
However, early diagnosis is not always possible because the disease manifests itself slowly. Many of the signs of kidney failure are not subtle and go unnoticed by animal owners. When they are detected, it is often too late to treat the disease effectively. In many cases, dogs only have 30% kidney function when the disease is diagnosed. As the kidneys can lose their function over the years, it is important to establish early proactive monitoring.
Kidney failure in dogs: clinical signs
- Loss of appetite Kidney failure usually causes a loss of appetite, which is exacerbated by an impaired ability to taste and smell, which means that the animal lacks the stimulation to eat.
- Unexplained weight loss. A study published in the journal Veterinary Medicine International(4) found a significant association between weight loss and the risk of kidney failure in dogs. It is estimated that a loss of 10 kilograms increases the probability of developing kidney failure by 50%.
- Vomiting. The accumulation of waste in the blood because the kidneys no longer filter it properly is usually the cause of the nausea and vomiting seen in kidney failure.
- Changes in urination. Patients often have polyuria (abundant excretion of urine exceeding 50 mL/kg/day). They may also have oliguria, which means they urinate more frequently, and nocturia (frequent urination at night). In these cases, the urine is usually paler in colour because it is diluted. However, anuria, i.e., practically no urination at all, is common in the final stages of the disease or during a renal crisis.
- Anaemia. Typical signs are excessive sleep, fatigue and low energy. This problem is due to a decrease in the hormone erythropoietin as a result of kidney failure. Erythropoietin regulates the body’s production of oxygen-carrying red blood cells, so low levels result in fatigue.
- Polydipsia. Patients are anxious and drink more water than usual, which in dogs means more than 100 mL/kg/day, according to a study carried out at the University of Barcelona(5). The increased thirst is due to the fluid imbalance following a decline in plasma levels of antidiuretic hormone (ADH).
Kidney failure in dogs: diagnosis
In the physical examination, the vet will notice that the animal is much thinner than expected for its breed and level of physical activity. They will probably also observe periodontal disease, pale mucous membranes, a sparse coat, palpable thyroid gland and small kidneys. In advanced stages, vets may detect a heart murmur and high blood pressure.
The diagnosis of kidney failure requires a complete blood profile, including blood chemistry and blood count. A urinalysis, blood pressure tests and, if possible, a kidney ultrasound are also recommended. Dogs with chronic kidney failure usually have abnormal electrolyte levels and high blood pressure. Certain enzymes, proteins and parameters such as blood urea nitrogen and creatinine will also be high.