Screening and medical management of feline kidney transplant candidates - Veterinary Medicine
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Screening and medical management of feline kidney transplant candidates
Hundreds of cats with failing kidneys have successfully recovered after undergoing this life-saving procedure. Find out how to determine whether some of your feline patients would make good candidates and how to monitor transplant recipients long-term.


VETERINARY MEDICINE


A standard premedication and anesthetic protocol including an anticholinergic, an opioid, and an inhalant anesthetic agent is used based on the preoperative evaluation and an individual anesthesiologist's preference. Perioperative broad-spectrum antibiotics are administered for the duration of the procedure. Atracurium besylate is used as needed to maintain muscular relaxation during microvascular anastomosis. Dopamine may be administered as a continuous-rate infusion to ensure adequate systolic blood pressure. Mannitol may be given to induce osmotic diuresis in all donor cats before nephrectomy, as well as in recipient cats after vascular anastomosis.38 Administering mannitol may minimize acute tubular necrosis associated with temporary ischemia that occurs during transplantation. A recent report demonstrated that preserving nephrectomized kidneys in cold sodium gluconate or phosphate-buffered sucrose solutions for up to seven hours had no negative impact on patient survival.41

Intraoperatively, standard physiologic parameters are measured continuously, and drug adjustments are made if needed. Arterial or venous blood gas and electrolytes are assessed periodically, and imbalances are corrected as necessary.

Surgery

Donor cats. The donor kidney is removed through a ventral midline celiotomy. Vascular dissection is assisted by using magnifying loupes or a dissecting microscope. Assessment of both donor kidneys is performed, although the left kidney is preferred because of the increased length of the vascular pedicle.42 The donor kidney must be supplied by a single artery (some cats have two arteries supplying a single kidney), and a minimum length of 0.5 cm is generally required to complete the arterial anastomosis.42 The accompanying renal vein is measured to create a sterile template to guide the creation of the donor phlebotomy site. The entire length of the ureter is isolated from the kidney to the urinary bladder before nephrectomy.

Several techniques for vascular anastomosis and ureteral implantation in cats have been described in the literature. Recent reports detail anastomosis of the donor kidney vessels to the postrenal aorta and vena cava.43 Cats in previous studies suffered rear limb complications when the external iliac vessels were used for anastomosis.43

Recipient cats. The surgical approach in the recipient cat is similar to that in the donor cat. The area between the left renal artery and caudal mesenteric artery is isolated and exposed in preparation for the graft. The donor kidney is harvested only after the recipient vessels are prepared for graft implantation. The donor renal artery is anastomosed end-to-side to the aorta by using 8-0 to 10-0 nylon in a simple interrupted pattern.42 The renal vein is anastomosed to the caudal vena cava with two rows of simple continuous sutures with 7-0 silk.43

Several techniques for implanting the ureter into the urinary bladder have been described. Using an extravesicular ureteroneocystostomy is associated with the quickest resolution of renal pelvic dilation after transplantation, and mucosal apposition of the ureter to the bladder significantly reduces the incidence of postoperative obstruction.44,45 To prevent torsion of the transplanted kidney on its pedicle, the renal capsule is attached to the abdominal body wall after creating a peritoneal-transverse abdominis muscle flap.42 One of the recipient's diseased kidneys is biopsied for diagnostic and prognostic purposes, but the native organs are left in place and only removed at a later date if necessary. For postoperative nutritional support, a gastric or esophageal feeding tube is placed before recovery (if not already placed).

Postoperative recovery

Transplant patients are kept free of stress, and handling is minimized. Balanced electrolyte solutions are continued and supplemented as needed to correct acid-base or electrolyte abnormalities. Blood pressure must be monitored frequently during the first 12 to 24 hours, as postoperative hypertension may be severe.46 Supplemental nutrition is provided through gastrostomy or esophagostomy tubes until oral food and water are accepted. PCV, total plasma protein concentrations, serum creatinine concentrations, serum electrolyte concentrations, and trough whole blood cyclosporine concentrations are assessed daily. Voided urine is collected to assess urine specific gravity and determine 24-hour urine output. Renal function and hemodynamic parameters usually return to normal within three to five days after surgery.13 If the transplant recipient remains anorectic or depressed or the serum creatinine concentration continues to rise with production of isosthenuric urine, then graft rejection should be suspected.37 An ultrasonographic examination of the urinary tract should be performed to assess renal graft perfusion, as well as to identify any hydronephrosis or hydroureter. These latter conditions usually suggest stricture at the site of ureter implantation rather than transplant rejection, and surgical intervention may be required rather than changes in medication regimen.


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Source: VETERINARY MEDICINE,
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