Insights into Feline Kidney Transplants

Lillian R. Aronson, VMD, Diplomate ACVS

Renal transplantation continues to remain a viable treatment option for cats with early decompensated chronic kidney disease or irreversible acute renal failure.

Renal transplantation continues to remain a viable treatment option for cats with early decompensated chronic kidney disease or irreversible acute renal failure.^1,2

The ability to perform renal transplantation as a treatment in cats has been attributed to a number of factors including the:

• Development of microsurgical techniques in veterinary practice
• Ability to use an allograft from an unrelated donor
• Application of the drug cyclosporine for immunosuppressive therapy.^3-5

It is estimated that between 400 to 500 cases of feline renal transplantation have been performed at a few limited centers around the country (Table). In a study comparing survival time of cats that had undergone a renal transplant to a control population of cats treated medically, renal transplantation appeared to prolong survival time and quality of life compared with the medical management of the disease.⁶

Although there is not a retrospective study encompassing all of the cases that have been performed to date, both published and unpublished information from different centers suggests that survival to discharge and long-term survival are improving.^6,7 This is likely related to:

• More stringent case selection
• Surgical experience
• The clinician’s ability to better recognize early, and treat successfully, both peri-operative as well as long-term complications.

INDICATIONS

The most common histopathologic diagnosis (identified from native kidney biopsy samples) of cats needing a renal transplant is chronic interstitial nephritis. Other conditions that have resulted in renal transplants in the cat include:

• Polycystic kidney disease
• Oxalate nephrosis
• Membranous glomerulonephropathy
• Ethylene glycol & lily toxicity
• Renal fibrosis
• Amyloidosis
• Pyelonephritis
•  Renal dysplasia.

Because of the potential long-term effect on the allograft, it is unclear whether patients with pyelonephritis or amyloidosis are appropriate candidates for the procedure.

RECIPIENT SELECTION

The best time to intervene with surgery is not completely known in this patient population. Surgical intervention has been recommended in cats with early decompensated chronic kidney disease or irreversible acute renal failure.^8,9 Indications of decompensation include continued weight loss, worsening of the anemia, and azotemia in the face of medical therapy. It is important to note that some clinically stable candidates can rapidly deteriorate and die without prior evidence of decompensation.

Evaluating Potential Candidates

Both physical and biochemical parameters need to be carefully evaluated when determining a cat’s candidacy for renal transplantation. Current evaluation at our facility involves:

• Laboratory tests: Complete blood count, serum biochemistry profile, blood type and crossmatch, and thyroid evaluation
• Urinary tract evaluation: Urinalysis, urine culture, and urine protein:creatinine ratio
• Abdominal evaluation: Abdominal radiographs and ultrasound
• Cardiovascular disease evaluation: Thoracic radiography, electrocardiography, echocardiography, and blood pressure measurement
• Screening for infectious disease: FeLV, FIV, Toxoplasma titer (IgG, and IgM).

Based on historical experience, cats that are FeLV positive or have an active FIV infection, patients with recurrent urinary tract infections that have failed a cyclosporine challenge (see Why a Cyclosporine Challenge?), and those with underlying neoplasia are declined as candidates for the procedure.

Risk & Survival Factors

Limited information exists regarding risk factors associated with morbidity and mortality in these patients.

• The degree of anemia, azotemia, urine specific gravity, and age do not determine a suitable patient for transplantation, although azotemia has been identified with complications.
• The degree of azotemia prior to surgery was found to be a risk factor in one study.⁶ In a second study, the level of azotemia significantly increased the risk of neurologic complications in the perioperative period, but was not related to long-term survival.¹¹
• In 3 separate studies, age was identified as a factor associated with survival following discharge.^6,11,12 Preoperative blood pressure, duration of anesthesia, and weight have also been shown to influence overall survival.^6,12

Objective information is still needed for a number of gray areas, including cats with echocardiographic abnormalities, hyperthyroidism, diabetes, inflammatory bowel disease, and upper respiratory infections. Additionally, questions regarding the appropriate nutritional status for these patients comes up repeatedly.

POTENTIAL DONOR EVALUATION

Kidney donors are young (1–3 years of age) and in excellent health. Standard screening includes:

• Complete blood count and serum biochemistry profile
• Urinalysis and culture
• FeLV and FIV testing and Toxoplasma titer (IgG and IgM).

To determine compatibility, a blood type and red cell crossmatch are performed between the feline kidney donor and recipient. Although rare, incompatible crossmatch tests between AB compatible donor and recipient pairs have been identified.¹³ Additionally, we currently perform computed tomography (CT) angiography to evaluate the renal vasculature and parenchyma for abnormalities (Figure 1).¹⁴ This technique has allowed us to identify patients unsuitable for donation prior to surgery, including patients with renal infarcts as well as those with multiple renal arteries.

Figure 1. Arterial phase of CT angiography; this technique allows accurate evaluation of the renal vasculature of the donor cat prior to nephrectomy

Although, in my experience, renal donation does not appear to affect normal life expectancy, long-term monitoring is recommended.

TRANSPLANT SURGERY

Preoperative Care

Preoperative care will vary depending on the stability of the patient.

• Hemodialysis may be necessary in some cases in order to stabilize the patient prior to surgery.
• Intravenous fluid therapy of a balanced electrolyte solution (1.5–2× daily maintenance requirements) is administered to most patients. However, underlying cardiac disease may preclude this rate of fluid therapy due to development of pulmonary edema and pleural effusion.
• Whole blood transfusions or packed red cells may be used to correct anemia (depending on the stability of the cat) prior to or at the time of surgery. The first unit that is administered is a unit that had been previously collected from the crossmatch compatible donor cat. It has been suggested that the administration of a unit of blood from the donor cat may decrease the incidence of allograft rejection.
• Hormonal therapy, including darbopoietin or erythropoietin, can be administered if a delay in the transplant procedure is expected. This therapy can greatly reduce the need for blood products at time of surgery. Although uncommon, antibodies to erythropoietin have been identified in cats and owners should be cautioned that this could result in significant morbidity and increase in cost during the postoperative period. The current risk with darbopoietin is unknown at this time, but thought to be less than with erythropoietin.
• Calcium channel blocker amlodipine (Norvasc, Pfizer.com) may be indicated (0.625 mg/cat PO Q 24 H) if the cat is hypertensive.
• Gastrointestinal protectants and phosphate binders are given if deemed necessary; a nasogastric or esophagostomy tube may be placed prior to surgery if the cat is anorectic.
• Immunosuppression is begun in our facility 24 to 96 H prior to transplantation. See An Imperative Inclusion: Immunosuppression  for a complete discussion on this critical aspect of transplantation.

Surgery

Currently, at our facility, 3 surgeons are involved with each transplant procedure: 2 surgeons to perform the procedure on the donor and recipient and a third surgeon to close the donor following nephrectomy (Figure 2).

Figure 2. Image of the surgical set up for the transplant procedure; in our facility, the donor and recipient surgeries are performed simultaneously

Donor Surgery

The donor is brought into the surgical suite approximately 45 min prior to the recipient to allow preparation of the donor kidney for the nephrectomy.

1. The left and right kidneys are examined for a vascular pedicle that consists of a single artery. The left kidney is preferred because it provides a longer vein than the right kidney (Figure 3). The renal artery and vein are cleared of as much fat and adventitia as possible.

2. The ureter is dissected free to the point where it joins the bladder. The nephrectomy will be performed when the recipient is prepared to receive the kidney.

3. At the time of the original incision, the donor is given a dose of mannitol (0.25 g/kg IV). Fifteen min prior to nephrectomy, an additional dose (1 g/kg IV) is given to the donor cat.

4. Mannitol is used to reduce the incidence and duration of acute tubular necrosis that can occur during warm ischemia.

Figure 3. Isolation of the donor renal artery (A) and vein (B) for nephrectomy

Recipient Surgery

The majority of the recipient surgery is performed using an operating microscope.

1. In the current surgical procedure, the renal artery is anastomosed end-to-side to the caudal aorta (proximal to the caudal mesenteric artery), and the renal vein is anastomosed end-to-side to the caudal vena cava (Figure 4).

2. Partial occlusion clamps are used to obstruct blood flow in both vessels. Using templates made from the donor vessels, windows are created that match the size of the renal artery and vein, respectively. Nylon suture (8-0) is used for the arterial anastomosis and silk (7-0) for the venous anastomosis. Suture size and type may vary depending on the facility performing the procedure.

3. Once the vascular anastomosis is finished, a ureteroneocystotomy is performed using a technique to appose ureteral and bladder mucosa. Three techniques have been described and are currently being performed at different centers around the country. At our facility, an intravesicular mucosal apposition technique is used.¹⁵ Two extravesicular techniques have also been described, including a technique in which the entire ureter and ureteral papilla from the donor is harvested.^16,17

4. Prior to closure, 1 of the native kidneys is biopsied and the allograft is pexied to the abdominal wall using 6 interrupted sutures of 5-0 prolene to prevent torsion and avulsion. The native kidneys are not removed at this time since they can act as a reserve if graft function is delayed. If warranted, the native kidneys can be removed at a later date.

Figure 4. Image of the native and allograft kidney. The native kidney can be seen on the left adjacent to the gloved finger. The suture in the native kidney marks the location of a renal biopsy. The allograft is on the right. The native kidneys are usually left in situ to act as a reserve if graft function is delayed.

Postoperative Care

• The recipient is administered a balanced electrolyte solution until water and food are accepted.
• Blood analysis, including a packed cell volume, total protein, renal panel, and blood cyclosporine level are checked every 2 to 4 days.
• Broad spectrum antibiotics are administered.
• Voided urine is collected and assessed daily.
• Central venous pressure is measured continuously until fluid balance stabilizes and the patient can be weaned from fluid therapy.
• During the first 48 hours, blood pressure is monitored every 1 to 2 hours for the development of hypertension.

If the systolic blood pressure is > than 180 mm Hg, hydralazine (2.5 mg SC for an approximately 4-kg cat) is administered.

If the cat is refractory to hydralazine, acepromazine (0.005 mg/kg IV) has been used.

COMPLICATIONS

Peri-Operative Complications

Typically, azotemia resolves within the first 24 to 72 H following surgery. If improvement in renal function does not occur or improvement is initially identified but then worsens, an ultrasonographic examination of the allograft is recommended:

• The allograft should be evaluated for adequate blood flow as well as any signs of a ureteral obstruction including hydronephrosis and/or hydroureter. If repeat ultrasonographic evaluations reveal worsening hydronephrosis, then a ureteral obstruction should be suspected and the cat taken back to surgery.
• If graft perfusion has ceased, torsion of the allograft or thrombosis of the renal artery with vascular obstruction may have occurred. If no sign of urine flow obstruction is present and graft perfusion is adequate then delayed graft function should be considered.

Following discharge, the cat should be examined weekly until cyclosporine levels have stabilized (typically 6–8 weeks). During each examination, renal function and urine should also be evaluated. The intervals between veterinary visits are increased once the cat stabilizes (4×/year in stable patients).

Long-Term Complications

Long-term complications that still challenge us include those associated with the allograft and complications secondary to chronic immunosuppressive therapy.

Renal Complications

Renal complications following transplantation include:

• Acute and chronic rejection
• Calcium oxalate nephrosis
• Allograft rupture
• Delayed graft function
• Hemolytic uremic syndrome
• Ureteral complications, including retroperitoneal fibrosis.

Suspected acute rejection episodes are treated with intravenous administration of cyclosporine, 6.6 mg/kg Q 24 H over 4 to 6 H, and prednisolone, 10 mg/kg IV Q 12 H. This treatment can be repeated if necessary.

Immunosuppressive Complications

Complications secondary to chronic immunosuppressive therapy include:

• Development of infections (including opportunistic infections)
• Diabetes mellitus
• Neoplasia.

Toxoplasma gondii seropositive cats remain acceptable candidates for transplantation, but should receive lifelong prophylactic chemotherapeutics to prevent fatal infections. The prevalence of malignant neoplasia in cats following renal transplantation has been reported from 9.5% to 24%, with lymphoma being the most common type reported (Figure 5).^18,19

Figure 5. Gastrointestinal lymphosarcoma in a cat (A) 4 years following renal transplantation with metastasis to the renal allograft (B); note the 2 native polycystic kidneys in B

CONCLUSION

Renal transplantation has become a life-saving measure for cats with renal failure.

Based on published and unpublished reports of cats having undergone renal transplantation, 70% to 92% were discharged from the hospital and median survival times ranged from 360 to 613 days.^6,7,20 Current information suggests that survival times following discharge are improving.^3,6,7,20

Continued clinical experience in the management of both short- and long-term complications, as well as the ability to identify specific risk factors both pre- and postoperatively will hopefully continue to improve long-term outcome in these patients.

CT = computed tomography; FeLV = feline leukemia virus; FIV = feline immunodeficiency virus;
IgG = immunoglobulin G; IgM = immunoglobulin M

References

1. 1. Gregory CR, Bernsteen L. Organ transplantation in clinical veterinary practice. In Slatter DH (ed): Textbook of Small Animal Surgery. Philadelphia: WB Saunders, 2000, p 122.
2. Mathews KG. Renal transplantation in the management of chronic renal failure. In August J (ed): Consultation in Feline Internal Medicine, 4th ed. Philadelphia: WB Saunders, 2001, p 319.
3. Gregory CR, Gourley IM, Taylor NJ, et al. Preliminary results of clinical renal allograft transplantation in the dog and cat. J Vet Intern Med 1987; 1:53.
4. Gregory CR, Gourley IM. Organ transplantation in clinical veterinary practice. In Slatter DH (ed): Textbook of Small Animal Surgery. Philadelphia: WB Saunders, 1993, p 95.
5. Gregory CR. Renal transplantation. In Bojrab MJ (ed): Current Techniques in Small Animal Surgery. 4th ed. Philadelphia: Lippincott, Williams and Wilkins, 1998, p 434.
6. Schmeidt CW, Holzman G, Schwarz T, et al. Survival, complications and analysis of risk factors after renal transplantation in cats. Vet Surg 2008; 37:683.
7. Mathews KG, Gregory CR. Renal transplants in cats: 66 cases (1987-1996). JAVMA 1997; 211:1432.
8. Gregory CR, Bernsteen L. Organ transplantation in clinical veterinary practice. In Slatter DH (ed): Textbook of Small Animal Surgery. Philadelphia: WB Saunders, 2000, p 122.
9. Mathews KG. Renal transplantation in the management of chronic renal failure. In August J (ed): Consultation in Feline Internal Medicine, 4th ed. Philadelphia: WB Saunders, 2001, p 319.
10. Katayama M, McAnulty JF. Renal transplantation in cats: Patient selection and preoperative management. Compend 24:868, 2002.
11. Adin CA, Gregory CR, Kyles AE, et al. Diagnostic predictors and survival after renal transplantation in cats. i 2001; 30:515.
12. Snell W, Aronson LR, Beale L, et al. Retrospective descriptive evaluation of the anesthetic records of 100 cats undergoing renal transplantation surgery: Preliminary results. Unpublished manuscript.
13. Weinstein NM, Blais MC, Harris K, et al. A newly recognized blood group in domestic shorthair cats: The Mik red cell antigen. J Vet Intern Med 21:287, 2007.
14. Bouma JL, Aronson LR, Keith DM, et al. Use of computed tomography renal angiography for screening feline renal transplant donors. Vet Radiol Ultrasound 2003; 44:636.
15. Gregory CG, Lirtzman R, Kochin EJ, et al. A mucosal apposition technique for ureteroneocystostomy after renal transplantation in cats. Vet Surg 1996; 25:13.
16. Hardie RJ, Schmiedt C, Phillips L, et al. Ureteral papilla implantation as a technique for neoureterocystotomy in cats. Vet Surg 34:393, 2005.
17. Mehl ML, Kyles AE, Pollard R, et al. Comparison of 3 techniques for ureteroneocystostomy in cats. Vet Surg 34:114, 2005.
18. Schmeidt CW, Grimes JA, Holzman G. Incidence and risk factors for development of malignant neoplasia after feline renal transplantation and cyclosporine-based immunosuppression. Vet Comp Oncol 2009; 7:45.
19. Wooldridge J, Gregory CR, Mathews KG, et al. The prevalence of malignant neoplasia in feline renal transplant recipients. Vet Surg 2002; 31:94.
20. Aronson LR. Renal transplantation. Unpublished manuscript, 2009.

Lillian R. Aronson, VMD, Diplomate ACVS, is an associate professor of surgery and the coordinator and founder of the Feline Renal Transplant Program in the Soft Tissue Surgery Service at University of Pennsylvania’s Matthew J. Ryan Veterinary Hospital. Dr. Aronson successfully initiated the Feline Renal Transplant Program in 1998, after serving as the coordinator of the renal transplant program for animals at University of California–Davis. In addition to feline renal transplantation, her research expertise includes canine renal transplantation, feline lymphocyte proliferation and cytokine gene expression, and microvascular surgery. Dr. Aronson received her veterinary degree and completed an internship at UPenn and completed a small animal surgical residency at UCDavis.