Renal Transplant Imaging and Intervention:
Practical Aspects - 1
Charles V. Zwirewich, MD
Transplantation has revolutionized treatment of endstage renal disease by proving more cost effective than hemodialysis [1], with a lower morbidity and improved quality of life [2]. Since the first successful renal transplant in 1954, advancements in immunology have led to steadily improving patient and graft survival rates. Introduction of cyclosporine-A (Cs-A) in the 1980s revolutionized organ transplantation by producing a 20% improvement in graft survival. Registries now report 2-year patient survival exceeding 90% for HLA identical matches, and 85-90% for cadaveric and living-related non-HLA identical transplants [3,4,5].
Despite high graft and patient survival figures, a variety of parenchymal, vascular and urologic complications can threaten the transplant in the postoperative period. This presentation will review:
- The pertinent surgical anatomy of the transplanted kidney
- Normal postoperative sonographic and Doppler findings
- A practical approach to the investigation and treatment of renal allograft dysfunction in the immediate (under 7 days), early (under 1 month), and late (over 1 month) postoperative periods.
The differential diagnosis of graft dysfunction will be reviewed, stressing the importance of the clinical history, sonographic and doppler findings, and pathologic material obtained by ultrasound-guided biopsy in establishing diagnosis and guiding therapy.
To be eligible for a graft, the patient must have evidence of endstage renal failure defined as current or impending (less than 6 months) dialysis dependency. Glomerulonephritis (55%), diabetic nephropathy (20-30%), chronic pyelonephritis (8%), and polycystic kidney disease (5%) account for the majority of transplant indications [6]. Potential recipients are investigated to determine whether any absolute contraindications to transplantation are present (Table 1).
Table 1: Contraindications to Renal Transplantation
| Systemic malignancy |
|
|---|
| Active infection |
|
|---|
| Seropositivity for: |
HIV
Hep B Surface Antigen |
|---|
| Noncompliant patient |
|
|---|
A chest radiograph and abdominal ultrasound (US) or computed tomography (CT) are used to screen for sites of occult infection or malignancy. Voiding cystourethrography (VCU) may identify correctable ureteral reflux in patients with a history of recurrent urinary infection. A static cystogram is useful to evaluate preoperative bladder volume in long-term dialysis patients or diabetics. Living related donors undergo excretory urography or US to ensure that two structurally normal and functioning kidneys are present, and abdominal aortography to determine the anatomic site and number of renal arteries prior to harvesting [7].
Immunologic testing is performed to select compatible donor/recipient matches and to reduce the incidence of antibody-mediated graft rejection and donor-related disease transmission. The recipient and donor must have matching ABO blood groups and cytomegalovirus (CMV) serostatus. The degree of matching for HLA loci A, B, and DR is assessed. A panel reactive antibody (PRA) crossmatch between the serum of the recipient and cells of the donor should be negative [2], although this is not essential [3]. Grafts are allocated on a point system taking into account, in order of priority:
- Quality of the HLA match
- Degree of antibody sensitization based on the PRA crossmatch
- Waiting time accrued by the recipient
- Medical urgency [3]
While advanced age is not a contraindication per se, older patients are most likely to have significant cardiopulmonary disease, making them poor candidates. Fewer than 5% of transplant recipients are over the age of 65. Seventy five to 85% of grafts are cadaveric in origin in North American registries [8].
Surgical implantation of the graft is performed through an extraperitoneal incision in the right or left iliac fossa. The external iliac artery and vein are skeletonized and the surrounding lymphatics ligated. Care is taken to minimize the amount of dissection in the renal hilum and periureteral fat so as to reduce the risk of compromising renal and ureteral arterial blood supply. Under normal circumstances, right renal grafts are placed in the left iliac fossa and left grafts in the right fossa in order to facilitate the vascular anastomosis and ensure correct orientation of the ureter. This involves reversing the anterior-posterior orientation of the kidney; hence, a left donor kidney is flipped anteroposteriorly before it is placed in the right iliac fossa (Figure 1a).
Figure 1a.
An end renal artery-to-side external iliac artery anastomosis is preferred over the end-to-end renal-to-internal iliac artery technique because it carries a lower incidence of renal artery stenosis [6,9]. An end-to-side anastomosis is made between the renal and external iliac veins (Figure 1b).
Figure 1b.
The ureteral length is kept as short as possible to reduce the risk of ischemia and subsequent necrosis or fibrosis of the distal segment. An antirefluxing extravesical ureteroneocystostomy is created by placing a small incision anterolaterally in the bladder and anastomosing the ureter to bladder, mucosa to mucosa [6]. The muscular layers of the bladder wall are then closed over the ureter, forming an intramural tunnel to prevent reflux (Figure 1c). Stenting of the transplanted ureter is generally not required except in cases where the anastomosis is technically difficult and postoperative edema and hydronephrosis are likely.
Figure 1c.
Native kidneys are left in situ unless the patient has chronic vesicoureteral reflux or renal parenchymal infection, infected stones, or renovascular hypertension refractory to medical therapy. In patients with massively enlarged polycystic kidneys, one may be removed to make room for the transplant [10].
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Dr C V Zwirewich
Vancouver Hospital & Health Sciences Centre
Vancouver, B.C.
zwirecv@unixg.ubc.ca
Last updated 11th August 1998