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 Table of Contents  
ORIGINAL ARTICLE
Year : 2017  |  Volume : 4  |  Issue : 2  |  Page : 47-50

Does graft kidney weight have any impact on renal allograft function?


Department of Urology and Renal Transplantation, Sir Ganga Ram Hospital, New Delhi, India

Date of Web Publication20-Jun-2017

Correspondence Address:
Mrinal Pahwa
78-C, Mianwali Colony, Gurgaon - 122 001, Haryana
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jina.jina_40_16

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  Abstract 

Introduction: Success of renal transplantation, besides other factors, depends on the total number of nephrons in the transplanted kidney. The aim of our study was to investigate the effect of ratio of donor kidney weight (DKW) to recipient body weight (RBW) on renal allograft function. Materials and Methods: We conducted a retrospective study at our hospital on 245 patients who underwent live-related kidney transplant. Patients were divided into three groups depending on the ratio of DKW in grams to RBW in kilograms. Results: Mean age of the recipients was 40.19 ± 11.86 years (15–68 years) and donor was 46.18 ± 10.98 years (22–75 years). Male:female ratio for recipients and donors was 205:40 and 163:82, respectively. The decrease in mean creatinine level was more rapid in Group 3 patients as compared with Group 2 and Group 1 patients at 7 days and the trend continued till 3 years. Conclusion: The higher DKW/RBW ratio is an important factor for early function and late function of grafts. Extreme mismatch between the DKW and RBW should be kept in mind, and the DKW/RBW ratio can help us prognosticate patients' renal allograft function.

Keywords: Donor weight, graft dysfunction, graft rejection, live related, renal allograft


How to cite this article:
Durrani AM, Pahwa M, Pahwa AR, Chadha S, Tyagi V, Jauhari H. Does graft kidney weight have any impact on renal allograft function?. J Integr Nephrol Androl 2017;4:47-50

How to cite this URL:
Durrani AM, Pahwa M, Pahwa AR, Chadha S, Tyagi V, Jauhari H. Does graft kidney weight have any impact on renal allograft function?. J Integr Nephrol Androl [serial online] 2017 [cited 2017 Sep 22];4:47-50. Available from: http://www.journal-ina.com/text.asp?2017/4/2/47/208579




  Introduction Top


Kidney transplantation is the method of choice for the treatment of end-stage renal disease (ESRD).[1] Long-term kidney graft function depends on multiple influences, among which the host versus graft immune response represents a major component. The Transplant Registry of the United States of America lists several antigen-independent risk factors for chronic graft dysfunction or rejection such as elderly donors or recipients; long preservation; African-American donors or recipients; high recipient body mass index (BMI); a child recipient; and recipient hypertension.[2] More pertinent to the transplantation situation is the seemingly moderate mass reduction that prevails after donor nephrectomy and also results in an adaptive response of the remaining kidney and hyperfiltration.[3],[4] Several studies have shown that the remaining kidney may present proteinuria after several decades.[5] Hence, reduced donor kidney mass due to any cause resulting in failure to meet the metabolic demands of the recipient could be an important determinant of chronic graft failure.[6],[7] Although donor kidney weight (DKW) seems to be the best surrogate index for nephron number, routine weighing of donor kidneys at the time of transplantation is not a normal practice. However, investigators have recorded DKW and measured kidney weight to body weight ratio. This ratio has proved to have a strong correlation with graft function in the first 3 years after transplantation in recipients without acute rejection.[7]

We conducted this study in an attempt to establish a relationship between the ratio of DKW and recipient body weight (RBW) in live donor kidney transplant patients.


  Materials and Methods Top


A retrospective study was carried out in 245 patients who underwent live-related donor renal transplantation from May 2008 to December 2012 at a tertiary center in New Delhi, India. Informed consent was obtained from all the patients, and ethical clearance was obtained from the Institutional Ethics Committee. Patients with acute graft rejection, acute tubular necrosis, sepsis, and drug toxicity were excluded from the study. Donor parameters which were recorded included age, gender, and recipient parameters included age, weight after dialysis, gender, and baseline serum creatinine level (mg/dL). During surgery, all the donors were operated by the same team, and the kidneys were weighed after defatting (preparing) the graft kidneys by an electronic weighing gadget kept in the dedicated operation theater. Patients were divided into three groups depending on the ratio of DKW in grams to RBW in kilograms.

  • Group 1: DKW/RBW - (<2)
  • Group 2: DKW/RBW - (2–3), and
  • Group 3: DKW/RBW - (>3).


Serum creatinine in milligrams per deciliter on the day of surgery, 7th day, 6 months, 1 year, and 3 years after the surgery was recorded and their means were compared. The follow-up period ranged between 18 and 68 months with a mean follow-up of 26 months.

Statistical testing was conducted with the Statistical Package for the Social Science system version SPSS 17.0 (SPSS Inc., Chicago, USA).


  Results Top


This retrospective cohort study reviewed the medical records of 368 consecutive kidney transplant recipients from May 2008 to December 2012. Of the 368 cases, 123 cases comprising 8 deceased donor kidney transplantations, 23 rejection episode cases, 42 cases who were lost to follow-up, and 50 cases with inappropriate data were excluded from the study. A total of 245 consecutive patients who underwent live donor kidney transplants regardless of age and sex were included in the study after applying the exclusion criteria.

Mean age of the recipients was 40.19 ± 11.86 years with a range of 15–68 years, and the mean age of the donors was 46.18 ± 10.98 years with a range of 22–75 years. The gender distribution analysis revealed that 205 recipients were males whereas only forty patients were females. The sex ratio was reverse for donors as 163 were females and 82 were males. The average weight of the donor kidney was 141.92 g (minimum - 75 g, maximum - 210 g). There was statistically significant correlation between donor body weight and donor BMI with DKW (r = 0.355, P= 0.005 for body weight; r = 0.279, P= 0.03 for BMI). Patients were divided into three groups depending on the ratio of DKW in grams to RBW in kilograms.

  • Group 1: DKW/RBW - <2 had 64 (26.25%) patients
  • Group 2: DKW/RBW - 2–3 had 150 (61.2%) patients
  • Group 3: DKW/RBW - >3 had 31 (12.7%) patients.


The mean serum creatinine value in mg/dL at 7 days, 6 months, 1 year, and 3 years was recorded in the three groups as shown in [Table 1]. The comparison showed that the decrease in mean creatinine level was more rapid in Group 3 patients as compared with Group 2 and Group 1 patients at 7 days (0.93, 1.14, and 1.46 in Groups 3, 2, and 1, respectively). At 6 months, all the groups had statistically significant difference in the decrease (P < 0.05); at 1 year, it was significant between Groups 1 and 3 (P = 0.010); and again at 3 years, it was significant between Groups 1 and 3 (P = 0.006).
Table 1: Mean serum creatinine values of recipients in the postoperative and follow-up period

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  Discussion Top


Renal transplantation is considered the treatment of choice for ESRD because of better survival and improved quality of life compared with dialysis treatment.[8] Short-term allograft outcomes have been significantly improved during the past decade due to advances in the use of immunosuppressants.[9] Long-term allograft outcomes have also improved as a result of efforts to identify donor–recipient factors that affect graft function, although many questions remain unanswered.[8]

Nyengaard showed that both glomerular number and size showed significant negative correlation to age and significant positive correlation to kidney weight whereas body surface area (BSA) correlated positively to kidney weight and total glomerular volume but not to number of glomeruli.[10] Kidney weight correlated well with BSA at all ages (r = 0.76, P< 0.001) in another study.[11] We also observed that donor body weight and BMI can be treated as a surrogate marker of kidney weight.

Low donor body weight as compared with recipient weight has been associated with decreased graft function. The number of nephrons transplanted (directly related to the kidney weight) has an impact on the outcome of the graft following transplant, and it is quite logical to state that more the number of nephrons transplanted, better will be the outcome of graft function.[12] The impact of matching the kidney weight (which correlates with both glomerular volume and nephron number) to the RBW has been studied only in relatively small cohort of patients and only in living donors, where the graft does not have the same accumulating injuries as those from deceased donors.[10],[13],[14]

Song et al. showed that the graft kidney weight measured before implantation was 182.9 g with a standard deviation of 31.6 g (range: 117–280 g) and the mean RBW was 59.1 kg with a standard deviation of 11.0 kg.[15] Hwang et al. showed that the mean kidney weight was 203 g with a standard deviation of 39 g and average RBW was 59.5 kg with a standard deviation of 10.5 kg.[9] Both studies showed concordance with our results.

Song et al. also investigated the effect of DKW/RBW ratio on long-term graft function.[15] Their retrospective data from 213 kidney transplant recipients at least 5 years posttransplantation showed a positive correlation with the DKW/RBW ratio, which was seen in our study till 1 year (at 60 months after transplantation, r = 0.158, P= 0.023). In a study by Hwang et al. which included a consecutive series of 123 adult-to-adult living kidney transplants with a follow-up of >10 years,[9] patients were divided into three groups; “low” (DKW/RBW <2.85; n = 29), “medium” (2.85 >DKW/RBW <4.04; n = 63), and “high” (DKW/RBW >4.04; n = 31). Among the three groups, the mean serum creatinine levels at 1 and 6 months as well as 1 year after transplantation were significantly lower among patients with a high DKW/RBW ratio than in those with a medium or low ratio, which was seen in our study also. Graft survival rates at 5 and 10 years after transplantation were significantly lower in the “low” group. They observed a statistically significant association between DKW/RBW ratio and graft survival (P = 0.018).

In a study on 82 living donor kidney transplant patients, Kim et al. concluded that recipients with a low renal mass or mismatching kidney size have higher chances of chronic graft nephropathy and those with higher DKW/RBW ratio have better graft function which was seen in our study also.[14] Kim et al. showed that donor–recipient size match, using DKW/RBW ratio, affected graft function at 1 year after living donor kidney transplantation, with statistical significance.[16] If the serum creatinine level at 1-year posttransplantation is the major determinant of long-term graft outcome, the DKW/RBW ratio could be considered as an important guideline for the selection of potential living donor which was seen in our study also. Giral et al. in a multicenter cohort of 1189 patients observed that the graft glomerular filtration rate increased by a mean of 5.74 mL/min between the third and sixth posttransplantation months among patients with a low DKW/RBW ratio (2.3 g/kg) which remained stable between 6 months and 7 years but then decreased at a mean rate of 3.17 mL/min per year (P = 0.0001).[17] In addition, low DKW/RBW ratios conferred greater risk for proteinuria, need of more antihypertensive drugs, and segmental or global glomerulosclerosis. Moreover, a DKW/RBW of ≤2.3 g/kg was associated with a 55% increased risk for transplant failure by 2 years of follow-up. The conclusion of this study further strengthens our results.

The above studies and our results are in concordance and achieved the aim in showing that there is a relationship in the ratio of DKW to RBW on renal allograft function with higher DKW/RBW ratio having more better function till 1 year. Therefore, a larger kidney weight from a donor would be more suitable to a recipient whose body weight is less for better allograft function rather than a smaller weighing kidney to an obese and a large recipient. This will help us in predicting and prognosticating which kidneys will have better function keeping in mind the DKW/RBW ratio.


  Conclusion Top


Based on our results, we conclude that the higher DKW/RBW ratio is an important factor for early function and late function of grafts. Extreme mismatch between the DKW and RBW should be kept in mind, and the DKW/RBW ratio can help us prognosticate patient's renal allograft function. If more than two donors are available, preference should be given to the donor expected to have a bigger kidney.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Hariharan S, Johnson CP, Bresnahan BA, Taranto SE, McIntosh MJ, Stablein D. Improved graft survival after renal transplantation in the United States, 1988 to 1996. N Engl J Med 2000;342:605-12.  Back to cited text no. 1
    
2.
Chertow GM, Brenner BM, Mackenzie HS, Milford EL. Non-immunologic predictors of chronic renal allograft failure: Data from the United Network of Organ Sharing. Kidney Int Suppl 1995;52:S48-51.  Back to cited text no. 2
    
3.
Fotino S. The solitary kidney: A model of chronic hyperfiltration in humans. Am J Kidney Dis 1989;13:88-98.  Back to cited text no. 3
    
4.
Ramcharan T, Matas AJ. Long-term (20-37 years) follow-up of living kidney donors. Am J Transplant 2002;2:959-64.  Back to cited text no. 4
    
5.
Hakim RM, Goldszer RC, Brenner BM. Hypertension and proteinuria: Long-term sequelae of uninephrectomy in humans. Kidney Int 1984;25:930-6.  Back to cited text no. 5
    
6.
Brenner BM, Milford EL. Nephron underdosing: A programmed cause of chronic renal allograft failure. Am J Kidney Dis 1993;21 5 Suppl 2:66-72.  Back to cited text no. 6
    
7.
Taal MW, Tilney NL, Brenner BM, Makenzie HS. Renal mass: An important determinant of late allograft outcome. Transplant Rev 1998;12:74-84.  Back to cited text no. 7
    
8.
Saxena AB, Busque S, Arjane P, Myers BD, Tan JC. Preoperative renal volumes as a predictor of graft function in living donor transplantation. Am J Kidney Dis 2004;44:877-85.  Back to cited text no. 8
    
9.
Hwang JK, Kim YK, Kim SD, Park SC, Choi BS, Kim JI, et al. Does donor kidney to recipient body weight ratio influence long-term outcomes of living-donor kidney transplantation? Transplant Proc 2012;44:276-80.  Back to cited text no. 9
    
10.
Nyengaard JR, Bendtsen TF. Glomerular number and size in relation to age, kidney weight, and body surface in normal man. Anat Rec 1992;232:194-201.  Back to cited text no. 10
    
11.
Hoy WE, Douglas-Denton RN, Hughson MD, Cass A, Johnson K, Bertram JF. A stereological study of glomerular number and volume: Preliminary findings in a multiracial study of kidneys at autopsy. Kidney Int Suppl 2003;(83):S31-7.  Back to cited text no. 11
    
12.
Andrés A, Mazuecos A, García García-Doncel A. A disproportionately greater body weight of the recipient in regards to the donor causes chronic graft nephropathy. A study of paired kidneys. Nephrol Dial Transplant 2004;19 Suppl 3:iii21-5.  Back to cited text no. 12
    
13.
Douverny JB, Baptista-Silva JC, Pestana JO, Sesso R. Importance of renal mass on graft function outcome after 12 months of living donor kidney transplantation. Nephrol Dial Transplant 2007;22:3646-51.  Back to cited text no. 13
    
14.
Kim YS, Moon JI, Kim DK, Kim SI, Park K. Ratio of donor kidney weight to recipient bodyweight as an index of graft function. Lancet 2001;357:1180-1.  Back to cited text no. 14
    
15.
Song S, Huh W, Kwon CH, Park JB, Shin M, Kim TS, et al. Can the kidney weight and recipient body weight ratio predict long-term graft outcome in living donor kidney transplantation? Transplant Proc 2013;45:2914-8.  Back to cited text no. 15
    
16.
Kim SI, Kim YS, Kim MS, Moon JI, Park K. True living donor kidney weight-to-recipient body weight ratio influences posttransplant 1-year renal allograft function. Transplant Proc 1998;30:3120.  Back to cited text no. 16
    
17.
Giral M, Foucher Y, Karam G, Labrune Y, Kessler M, Hurault de Ligny B, et al. Kidney and recipient weight incompatibility reduces long-term graft survival. J Am Soc Nephrol 2010;21:1022-9.  Back to cited text no. 17
    



 
 
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