Polycystic Kidney Disease (PKD)
Dr. Arnold Plotnick
Radiographs with or without contrast. X-rays may or may not be helpful, depending on the age of the cat and the extent of the disease. As cats with PKD get older, the kidneys enlarge, and this can be detected on the x-rays. Early in the course of the disease, the contour of the kidneys is usually smooth. Later in the disease, the outer surface of the kidney becomes more irregular. Injection of an intravenous dye can highlight the urinary system on the x-rays. This test is not very helpful early in the disease; however, as the disease progresses, the dye may outline numerous cysts present throughout the entire kidney.
Physical examination findings and routine laboratory data are both insufficient for confirming or refuting a diagnosis of PKD early in the course of the disease, because the kidneys remain normal in size and maintain their normal contour. As the disease progresses, and the size and number of cysts increase, the kidneys enlarge; this may be detected on physical examination.
In severe, advanced cases, cysts may protrude beyond the normal kidney surface, causing an irregular contour which can be felt on physical examination. If chronic renal failure develops, blood tests will detect this, but blood tests alone cannot identify the cause of the kidney failure as being due to PKD.
Ultrasound. This is a sensitive, non-invasive technique for diagnosing cysts in the kidney. Small cysts are often detected as early as six to eight weeks of age, and occasionally as young as four weeks of age. After 10 months of age, the disease can be diagnosed with approximately 95 percent accuracy, using the proper equipment and experience.
There is no specific therapy for PKD at the moment. Treatment for cats with PKD in which the disorder has progressed to chronic renal failure is similar to that for chronic renal failure of any cause:
Restricted protein and phosphorus diet. These diets help reduce the levels of kidney toxins that contribute to the clinical signs of kidney failure, and may in fact slow the progression of renal failure.
Subcutaneous fluids. Some cats benefit from having their owners administer fluids under the skin. This helps encourage urination, maintain hydration and keep the levels of toxins in the bloodstream lowered.
Phosphorus binders. Cats with kidney failure have an impaired ability to excrete phosphorus. Elevated phosphorus levels contribute to the progression of kidney failure in cats. Phosphorus binders will bind up much of the phosphorus in the diet, making it unavailable to the cat and preventing elevated levels from developing.
Calcitriol (vitamin D). Cats with kidney failure cannot synthesize vitamin D properly. This may have deleterious effects on several body systems. Calcitriol is a synthetic form of Vitamin D. Administration of calcitriol must be monitored closely by your veterinarian
Erythropoietin. This hormone is made by the kidneys and it instructs the bone marrow to maintain the proper number of red blood cells in the circulation. As the kidneys fail, they produce less erythropoietin, and cats become anemic. Cats with severe anemia may benefit from having erythropoietin prescribed.
Antacids. Elevated levels of kidney toxins can cause stomach ulcers, nausea and vomiting. Antacids may help reduce these signs.