1 Department of Surgery and Transplantation and 2 Department of Anesthesiology, University Hospital, Catania, Italy
Keywords: hypertension; kidney cysts; kidney transplantation; living related donors; living related kidney transplantation; renovascular hypertension
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Introduction |
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Cystic lesions of the kidney are relatively common, especially in adults over the age of 50 years, where the incidence ranges up to 50% [1]. Because most cystic lesions of the kidney are morphologically simple and histologically benign, kidneys containing such cysts should not be refused for transplantation, even in living kidney transplantation and when the cysts are relatively large in size [2].
Simple renal cysts may cause hypertension and loss of kidney function [3] and hypertension is generally regarded as an exclusion criterion for living kidney donors [4]. We report a case in whom the potential family donor had a 6-cm cyst in her left kidney and mild hypertension. The kidney was successfully transplanted and continues to provide the recipient with satisfactory renal function 1 year after transplantation; the donor has regained normal blood pressure.
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Case |
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The patient's 66-year-old mother, who was identical in ABO blood type and in good health, volunteered to be his donor. The donor had not previously suffered from hypertension, but during evaluation for living donation we discovered she had a mild hypertension (AP 160/90 mmHg), and we started treatment with a ß-blocker; her creatinine clearance was 106 ml/min, but the renogram using 99mTc-DTPA demonstrated a cystic lesion on the left kidney, with a comparable function of both left and right kidneys. A contrast-enhanced computed tomography (CT) scan clearly showed the presence of a 6-cm simple cyst on the superior surface of the left kidney, with distortion of the renal artery (Figure 1). The morphological findings on CT scan seemed to be benign, showing a clean, round border, thin wall and homogeneous content.
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At the operation, which was performed through a flank incision, the left kidney appeared normal except for a 6-cm cyst on the anterior surface near the hilum. The donor's kidney was removed and the unroofing of the cyst was performed. Frozen-section histological examination of the cystic wall showed the lesion to be benign, and the kidney was transplanted into the recipient's right iliac fossa, using a standard technique.
Immunosuppression consisted of a combination of induction basiliximab and maintenance tacrolimus, mycophenolate mofetil and prednisone therapy. The patient's post-operative recovery was uneventful and serum creatinine rapidly decreased to 1.8 mg/dl on the fourth post-transplant day. The donor's blood pressure returned to normal values (AP 130/70 mmHg) on the third post-operative day; she refused antihypertensive therapy and was discharged on the fourth post-operative day without complications.
To date, 15 months after transplantation, the left kidney has continued to provide the recipient with satisfactory renal function; his blood pressure is normal (AP 140/90) with only one antihypertensive medication (ß-blocker). An ultrasound performed 1 year post-transplant did not show abnormal findings in the transplanted kidney. The mother enjoys normal renal function (serum creatinine 0.90 mg/dl) and blood pressure (AP 120/70 mmHg).
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Discussion |
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Cystic lesions of the kidney are relatively common, occurring with a reported incidence of 2450% in adults over the age of 50 years, and their incidence increases with age [1,3].
Most simple cysts are epithelial lined, fluid-filled cavities that have very thin, transparent exterior walls [2]. The finding of renal cell carcinoma in multi-loculated cysts and the occasional demonstration of this malignancy in mural plaques of solitary cysts [5] make accurate diagnosis extremely important before transplantation of cystic kidneys.
Hypertension is generally accepted as a relative contraindication for living kidney transplantation [4]. The shortage of cadaver donor kidneys has led to increased utilization of expanded criteria donors, including hypertensive donors. With regard to the evaluation of donors with hypertension, only 64% of US transplant centres exclude a donor taking an antihypertensive agent; these results indicate that many centres currently use living donors with borderline or mild hypertension [4].
Smith et al. [6] found that the functional transplant survival does not differ significantly between the non-hypertensive and hypertensive cadaveric donors. Conversely, Fleishhacker [7] demonstrated that the use of kidneys procured for transplantation from hypertensive donors resulted in significant decreased short- and long-term graft survival.
In older cadaveric donor (>55 years) with hypertension, only long-standing hypertension (>10 years) with diabetes and/or low creatinine clearance are risk factors for decreased graft survival [8,9]. Moreover, transplantation of a marginal kidney, especially in living donation, is associated with a significant survival benefit when compared with maintenance dialysis.
The coexistence of hypertension and a renal cyst is described in the literature [3]. Pedersen et al. [3] showed that there is a significant association between simple renal cysts and higher arterial blood pressure; however, this association was more evident in patients with underlying renal disease. It is suggested that occasionally renal cysts may be responsible for the elevation of blood pressure.
It is suggested that in patients with large renal cysts, the lesion may, through renal parenchymal compression and/or renal arterial compression or distortion, cause ischaemia and in turn activate the reninangiotensin system [3,10]. Luscher et al. [10] collected 22 case reports in which percutaneous aspiration or surgical removal of simple cysts caused a significant fall in arterial blood pressure in most patients.
In our potential donor, the radiological findings on CT scan were clearly benign, despite the cyst's large size. Angiography demonstrated that the vascular distortion caused by the cyst was probably responsible for the donor's hypertension. Because the kidneys exhibited normal function by creatinine clearance and 99mTc-DTPA renogram, we considered the cyst responsible for the donor's hypertension, so the cystic kidney was thought to be a suitable organ for living kidney transplantation. By choosing the left cystic kidney, we accomplished three important goals. First, removal of the cystic lesion permitted a careful and accurate histological examination of the cyst wall, while being a curative procedure if the lesion proved to be malignant. Secondly, according to the policy of other transplant centres when an anatomical disparity between kidneys is found in a potential living donor [2], we transplanted the kidney that was in some way abnormal, in order to preserve the donor's post-operative renal function. Thirdly, in removing the left cystic kidney we treated the donor's hypertension, and provided a satisfactory renal function in the recipient.
The post-operative normalization of blood pressure values in both the donor and the recipient confirmed our hypothesis that the donor's hypertension was caused by the cyst.
According to Schulak et al. [2], all cystic lesions should have their walls excised and biopsied, and their contents cultured at the time of transplantation. Follow-up imaging studies should be performed periodically after transplantation, as the occurrence of carcinoma in simple cysts has been reported [5].
In conclusion, we have described a living kidney transplantation in which the donor had a simple renal cyst with arterial hypertension. The kidney has functioned very well and has provided the recipient with excellent renal replacement, and the donor has regained a normal blood pressure value. Because of the shortage of kidneys for transplantation, we believe that kidneys with large benign cysts should not be refused for use arbitrarily. A thorough histological evaluation before transplantation should be carried out; the coexistence of hypertension does not contra-indicate the transplantation, as hypertension may be caused by the cyst itself.
We conclude that, with careful examination of potential living donors, existing donor selection criteria can be expanded to include certain donors who were previously excluded.
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Notes |
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References |
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