Veterinary Medicine - February 2008 - (Page 94) Managing feline kidney transplant patients PEER-REVIEWED 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 TABLE 1 Initial Diagnostic Evaluation of Feline Kidney Transplant Candidates • Complete blood count with differential cell count • Serum chemistry profile • Urinalysis with aerobic urine culture and sensitivity testing • FIV and FeLV testing • Total serum thyroxine concentration • Toxoplasma gondii IgG and IgM titers 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. Metabolic acidosis in people can exacerbate azotemia and promote further protein catabolism, muscle wasting, and hypokalemia.27 Alkalization therapy (usually oral potassium citrate or sodium bicarbonate) is indicated if acidosis is severe; commercial renal diets are formulated with alkalizers. Hypokalemia (reported in 20% to 30% of cats with chronic kidney disease) may exacerbate kidney disease and can cause weakness and muscle wasting.28 Provide supplementation with oral potassium gluconate or potassium citrate in these cats. Hyperphosphatemia develops secondary to a decreased glomerular ltration rate. Oral phosphate-binding agents are indicated in cats that cannot maintain normal serum phosphorus concentrations with dietary phosphorus restriction alone. Calcitriol production may also be impaired in chronic kidney disease, disrupting calcium homeostasis and contributing to the development of renal secondary hyperparathyroidism.29 Calcitriol supplementation is now advocated in dogs with normal phosphorus and increased serum parathyroid hormone (PTH) concentrations.30 Monitor serum phosphorus and PTH concentrations to document control and prevent adverse effects of toxicosis. TABLE 2 Conditions That May Preclude Kidney Transplantation in Cats • Cardiac disease* • FeLV or FIV infection • Urinary tract infection • Uncontrolled hyperthyroidism • Neoplasia • Diabetes mellitus • Poor body condition or cachexia • Fractious temperament or noncompliant owners • Other uncontrolled or poorly controlled disease conditions such as inflammatory bowel disease or feline asthma complex *Mild or well-controlled disease may not automatically exclude a patient from kidney transplantation; consultation with a kidney transplant surgeon before referral is recommended. • Blood type • Thoracic radiography • Abdominal ultrasonography • Electrocardiography and echocardiography • Cyclosporine challenge and repeat urine culture (if indicated) DIAGNOSTIC EVALUATION Recipient cats Perform a thorough screening of a potential transplant recipient to identify abnormalities and concurrent diseases before transplant referral. A typical required preoperative diagnostic protocol as well as conditions that preclude transplantation are listed in Table 1 and Table 2, respectively. Obtain a minimum database including a complete blood count, serum chemistry pro le, urinalysis, urine culture, and serum total thyroxine concentration. Any cat with a negative urine culture result but with a history of urinary tract infection should undergo a two- to three-week cyclosporine challenge followed by a second urine culture. If a positive culture result is obtained, institute treatment for presumptive chronic pyelonephritis and obtain a second culture after treatment. A second positive culture result eliminates the cat as a potential transplant recipient. Feline leukemia virus (FeLV) and feline immunode ciency virus (FIV) infections are contraindications to transplantation because of the theoretically increased risk of secondary infections once immunosuppression is initiated. A serum titer against Toxoplasma gondii antibodies does not signify active infection, but candidates should be considered 94 February 2008 VETERINARY MEDICINE
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