Histopathologic findings and classification of feline renal transplants.

Seventy-seven feline transplant kidney specimens, obtained from 1 to 3,183 days (9 years) after transplantation, were reevaluated histologically and classified on the basis of the Banff '97 guidelines for human renal transplant kidneys. Overall, this classification system appeared useful in detecting rejection reactions and confirmed the finding in humans that biopsies can diagnose subclinical rejection and therefore are an important diagnostic tool for the follow up of renal transplants. However, on the basis of serum creatinine values, the severity of the acute or active and chronic lesions was not accurately reflected by this scoring system. This is thought to be due to the significant differences in histologic rejection patterns, especially in acute or active rejection, in cats when compared with humans. Tubulitis, lymphocytic glomerulitis, and vasculitis, which are the main pillars of the Banff '97 acute or active rejection scoring system, are either rare or not found in cats. The presence of significant necrotizing glomerulitis and vasculitis in feline renal transplants might imply that the rejection is complicated by acute antibody-mediated rejection. Alternatively, cyclosporine toxicity also should be considered because some of these kidneys show other signs of cyclosporine toxicity. Finally, the significance of subcapsular and interlobular phlebitis, rarely described in human rejection reactions but a distinct entity in cats, is unknown. From this study, it is clear that there are significant differences in the histology of acute or active rejection between humans and cats and that a better understanding of the histologic appearance of renal allografts will be especially beneficial for treatment and prognostic purposes.

Renal transplantation in cats.

Feline renal transplantation can offer long-term survival with a normal quality of life for cats with renal failure. However, it is important to remember that renal transplantation is a treatment option and not a cure. Renal transplantation is never performed on an emergency basis or prophylactically. Feline renal transplantation requires special microvascular instruments and an operating microscope. Careful patient selection and perioperative monitoring have improved the success rate. The new microemulsified form of cyclosporine is recommended for immunosuppression. As survival times have steadily improved, long-term complications, such as diabetes and neoplasia, are now being recognized.

Management of hypertension controls postoperative neurologic disorders after renal transplantation in cats.

OBJECTIVES: To determine the prevalence and describe the management of hypertension and central nervous system (CNS) complications after renal transplantation in cats. We also compared the prevalence of CNS complications between cats monitored and treated for postoperative hypertension and a previously described, historical control group of cats not monitored or treated for postoperative hypertension. STUDY DESIGN: Retrospective clinical study. ANIMALS OR SAMPLE POPULATION: A total of 34 client-owned cats that received renal allografts for the treatment of end-stage renal failure. METHODS: Medical records were reviewed. Data obtained included preoperative and postoperative systolic blood pressures, antihypertensive therapy, response to treatment, neurologic signs, and clinical outcome. The results were compared with a historical control group of feline renal allograft recipients that were neither monitored nor treated for postoperative hypertension. RESULTS: Severe postoperative hypertension occurred in 21 of 34 of cats. Hypertension was treated in all 21 cats with subcutaneously administered hydralazine which reduced systolic blood pressure to less than 170 mm Hg in 15 minutes in 20 of 21 cats; hydralazine produced hypotension in one cat and failed to control hypertension in 1 cat. After transplantation, seizures were observed in one cat and other neurologic complications (stupor, ataxia, and central blindness) were observed in three cats. The prevalence of seizures and neurologic complication-related deaths after transplantation was significantly reduced with treatment of postoperative hypertension. CONCLUSIONS AND CLINICAL RELEVANCE: Hypertension is a major contributing factor to postoperative seizure activity after renal transplantation in cats; treatment of hypertension reduces the frequency of neurologic complications.

Comparison of two surgical techniques for renal transplantation in cats.

OBJECTIVE: To compare two surgical techniques for renal transplantation in cats with respect to graft warm ischemia time, total surgical time, operative and postoperative complications, and return to normal renal function based on measurement of plasma creatinine concentrations. STUDY DESIGN: Research study using normal cats. ANIMALS OR SAMPLE POPULATION: Fourteen adult, feline leukemia virus and feline immunodeficiency virus (FELV/FIV) negative, neutered male and spayed female cats. MATERIALS AND METHODS: Fourteen cats underwent heterotopic renal isograft transplantation with nephrectomy of the contralateral kidney. Renal arterial end-to-end anastomosis to the external iliac artery was performed in eight cats and renal arterial end-to-side anastomosis to the aorta was performed in six cats. Cats were monitored for 14 days after surgery. Renal function was evaluated by daily measurement of plasma creatinine concentrations. The cats' health was assessed by the daily recording of body weight, rectal temperature, postoperative complications, urine production, appetite, packed red blood cell volume, and total serum protein. Ultrasonographic assessment of the isograft was performed every third day. Animals were euthanatized or adopted 14 days after surgery and histopathologic analysis of biopsies or whole isograft tissues was performed. RESULTS: Nine of fourteen cats survived the 14-day study period. Although not statistically significant, mean total surgical time and graft warm ischemia time was shorter for the arterial end-to-side anastomosis. Mean daily plasma creatinine concentrations were not significantly different between the two groups. Five of eight cats (62%) undergoing the arterial end-to-end technique developed neuropraxia and lameness of the ipsilateral pelvic limb. Five cats died or were euthanatized because of other complications. CONCLUSIONS AND CLINICAL RELEVANCE: The arterial end-to-side technique appears to be the better method for renal transplantation in cats. Shorter graft warm ischemia and total surgical times, absence of pelvic limb complications, and an adequate return to normal renal function were associated with this technique.

Acute toxoplasmosis following renal transplantation in three cats and a dog.

Three cats and 1 dog that had undergone renal transplantation because of end-stage renal disease were examined because of complications 3 to 6 weeks after surgery. One cat died prior to treatment of the complications; Toxoplasma cysts were found in sections of the renal allograft, and Toxoplasma tachyzoites were found in other organs. The other 2 cats and the dog died despite treatment, and protozoal cysts, as well as tachyzoites, were identified in other organs but not within the allografts, suggesting that reactivation of latent infection following immunosuppression was the most likely cause of disseminated toxoplasmosis. These cases illustrate that toxoplasmosis can be a fatal complication in renal transplant recipients. We currently recommend that feline and canine donors and recipients undergo serologic testing for toxoplasmosis prior to surgery. In addition, we suggest that seropositive donors not be used for seronegative recipients and that seropositive recipients and that seropositive recipients be monitored closely after surgery for clinical signs of toxoplasmosis.

Ultrasonographic evaluation of renal autografts in normal cats.

The purpose of this study was to determine changes in resistive index (RI) and renal size that occur in normal feline kidney autografts in the immediate post-transplant period. Qualitative changes in renal parenchymal echogenicity and pelvic dilation were also noted, although this was not a major focus of the study. Fourteen domestic short-haired cats underwent bilateral nephrectomies followed by an autograft of the right kidney to either the aorta or external iliac artery. Due to post-operative complications, only nine of these cats completed the study. Ultrasonographic determination of the RI and renal size was made before transplantation and on days 1, 4, 7, 10, and 13 following transplantation. No significant changes in renal RI were identified during the study. Renal size increased significantly, peaking at 63% above baseline on day 7, and stayed elevated at 50% above baseline on day 13. There was no evidence of rejection or other abnormalities found on histologic evaluation of the transplanted kidneys. It was concluded that the RI of normal feline renal autografts does not significantly change in the immediate post-operative period. However, significant renal enlargement, likely due to a combination of post-operative edema and hypertrophy, does occur. This study provides baseline information for comparison with feline allografts in the immediate post-transplant period.