The diagnostic evaluation of a donor cat is similar to that described for the recipient. Specific investigation of urinary
tract anatomy and function is performed by using abdominal ultrasonography, excretory urography, or computed tomography angiography.34 Cats positive for anti-Toxoplasma gondii antibodies are no longer used as donors. Ethical concerns have arisen regarding the use of living feline donors for kidney
transplantation. In people, the risk of mortality associated with kidney donation is about 0.03%.35 Similar nominal risks have been observed in donor cats undergoing unilateral nephrectomy. In one study, no perioperative
deaths were reported, and serum creatinine and urea nitrogen concentrations remained within reference ranges.36 Most transplant programs also require adoption of the donor cat, regardless of the outcome of the recipient.
The crucial advance that made clinical organ transplantation feasible between unrelated individuals was the development of
immunosuppressive drugs to prevent or control rejection. Foreign tissue rejection is determined by T cell-mediated recognition
of cell surface major histocompatibility complex proteins and the peptides they display. Transplanting kidney allografts from
unrelated, histoincompatible feline donors results in an acute rejection within five to eight days.37
Table 3 General Immunosuppression Protocol for Feline Kidney Transplant Recipients*
Organ transplant recipients are maintained on lifelong immunosuppressive therapy to prevent rejection of the foreign allograft
(Table 3). The most current protocols include combination therapy using microemulsified cyclosporine and prednisone.16 Some transplant institutions recommend administering cyclosporine for two weeks before surgery to ensure adequate serum
trough levels at the time of surgery, thus preventing initiation of a host vs. graft immune response. Cyclosporine is usually
administered at 3 to 5 mg/kg given orally every 12 to 24 hours to obtain whole blood trough concentrations of 500 ng/ml for
the first month, then 150 to 250 ng/ml for life.16,38 Immunosuppressive prednisolone therapy is also initiated just before surgery at 0.25 mg/kg given orally every 12 hours,
adjusting to once daily after 30 days.16,38
Multiple agents have been known to alter cyclosporine metabolism by increasing the blood cyclosporine concentration and reducing
cyclosporine elimination. A regimen using ketoconazole with cyclosporine allows a significant reduction in the cyclosporine
dose in people after kidney transplantation.39 The same drug interaction has been demonstrated in cats.40 The benefit is the possibility of once-daily dosing and a lower cost. The disadvantages are the additional pilling requirements
and ketoconazole-associated hepatotoxicosis. Comparison studies are still lacking to provide a substantial advantage over
the current protocols used.
TRANSPLANT PROCEDURE OVERVIEW
Anesthesia and preoperative management
Anesthesia of patients with end-stage kidney disease is challenging because of altered renal physiology and pharmacokinetics.
Chronic kidney disease affects the hematopoietic, cardiovascular, neurologic, metabolic, endocrine, gastrointestinal, pulmonary,
and immunologic systems in individual and interrelated ways. Many characteristic metabolic derangements are present in transplant
patients including anemia, acidemia, hyperphosphatemia, hypocalcemia, and uremia. Identification of any dysfunction within
these body systems should be performed preoperatively so that correction may be attempted if possible.
Preoperative management of the transplant patient includes parenteral fluid diuresis with balanced electrolyte solutions.
If treatment with recombinant human erythropoietin and subsequent transplant delay is inappropriate, anemic patients are given
blood transfusions to achieve a PCV of > 30% before surgery. Immunosuppressive therapy is continued the day of surgery, as
described earlier. Placing a jugular catheter is ideal to monitor hemodynamic parameters before, during, and after surgery.