INDICATIONS

Kidney transplantation is indicated in cats with decompensated chronic kidney disease or, less commonly, acute, irreversible renal failure. The critical first step for ensuring a successful outcome is appropriate patient selection. Cats whose renal function continues to decompensate despite aggressive medical management are candidates for kidney transplantation.

The most common pathologic conditions for which kidney transplantation is performed include chronic interstitial nephritis (48%), polycystic kidneys (10%), ethylene glycol toxicosis (9%), and renal fibrosis (6%).¹³ However, transplants have also been performed in cats with advanced kidney disease due to glomerulonephritis, pyelonephritis, amyloidosis, oxalate nephrosis, renal dysplasia, pyogranulomatous nephritis, or nephrosclerosis secondary to drug toxicosis.^14,16

Medically managing cats with chronic kidney disease begins by identifying the underlying cause of kidney dysfunction. In a study of kidney biopsy findings in cats with chronic kidney disease, tubulointerstitial nephritis was observed in 70% of cats, glomerulonephropathy in 15%, and lymphoma in 11%.¹⁷ But keep in mind that both tubulointerstitial nephritis and glomerulonephropathy are histologic rather than etiologic diagnoses. Serial assessment of any cat with chronic kidney disease is required to tailor therapy and provide prognostic information. Direct therapy at slowing the progression of disease through supportive and symptomatic therapy.

The cornerstone of patient management is a combination of dietary and drug therapy, which minimizes the clinical and physiologic consequences of reduced renal function.

Provide the right diet

Dietary recommendations vary based on the International Renal Interest Society (IRIS) stage of disease, but once azotemia is present, a diet formulated for kidney disease management is recommended.¹⁸ A delicate balance exists between reducing protein intake and maintaining appetite and body weight. It is important for cats with mild to moderate chronic kidney disease to maintain adequate caloric intake to avoid protein malnutrition. Protein, phosphorus, and sodium restriction should begin when azotemia persists in the well-hydrated state (IRIS stage 2 disease).¹⁸ Proteinuric cats may benefit from treatment with an angiotensin-converting enzyme inhibitor such as benazepril, although a definitive benefit is still lacking.^19,20

Ensure adequate hydration

Adequate hydration is equally important for maintaining renal function. Polyuric, uremic cats are prone to dehydration, which contributes to progressive renal dysfunction. Strategies to improve water consumption include providing fresh water, using drinking fountains, and feeding a canned food diet. Subcutaneous fluid administration may be indicated with progression of renal insufficiency or uremia since fluid administration may help maintain optimal hydration and improve the quality of life for many cats.

Treat anemia

Anemia develops in later stages of chronic kidney disease as a multifactorial consequence of decreased erythropoietin production by the failing kidneys, decreased erythrocyte survival due to uremic toxins, and gastrointestinal bleeding. Recombinant human erythropoietin administration is effective in correcting nonregenerative anemia in most cats with chronic kidney disease.²¹ Many treated cats demonstrate an improvement in appetite and quality of life, although the risks of anti-erythropoietin antibody formation, polycythemia, and hypertension require careful monitoring.

Address other consequences of renal damage

Ongoing causes and consequences of renal injury that should be addressed include hypertension, uremic gastritis, metabolic acidosis, and mineral and electrolyte abnormalities such as hypokalemia, hyperphosphatemia, and hypercalcemia.

Hypertension is a well-documented sequela of chronic kidney disease, with a recently reported prevalence of 20% in affected cats.²² Evaluate cats with consistently elevated systolic blood pressure readings for ocular manifestations of hypertensive retinopathy, including retinal hemorrhages, retinal detachment, and blindness. Amlodipine, a calcium channel blocker, is effective in managing hypertension and reducing the prevalence of ocular lesions in cats.^23-25

Uremic gastritis presumptively develops because of reduced clearance of plasma gastrin. The degree of hypergastrinemia may be an indicator of the severity of chronic kidney disease.²⁶ H₂-receptor blocking agents, such as famotidine, are commonly used to improve appetite and nutritional intake, presumptively through decreased severity of gastrointestinal ulceration.