Saudi Journal of Kidney Diseases and Transplantation

: 2020  |  Volume : 31  |  Issue : 2  |  Page : 448--453

Changes in body mass index after pediatric renal transplantation

Seyed Seifollah Beladi Mousavi1, Ehsan Valavi2, Majid Aminzadeh3, Heshmatollah Shahbazian1, Hasan Otukesh4, Rozita Hoseini4, Bahman Cheraghian5,  
1 Department of Internal Medicine, Chronic Renal Failure Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
2 Department of Pediatric Nephrology, Chronic Renal Failure Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
3 Division of Pediatric Endocrinology and Metabolism, Hyperlipidemia Research Center, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
4 Department of Pediatric Nephrology, Ali Asghar Children's Hospital, Iran University of Medical Sciences, Tehran, Iran
5 Department of Epidemiology, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran

Correspondence Address:
Ehsan Valavi
Department of Pediatric Nephrology, Chronic Renal Failure Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz


Significant weight gain following renal transplantation is common in adult and pediatric recipients and mostly depends on receiving higher doses of steroids, changes in mood and feelings, as well as their level of physical activities. This study was performed to evaluate body weight and body mass index (BMI) before and after kidney transplantation in children and adolescents. In this cross-sectional study, 71 pediatric renal transplant recipients (42 boys and 29 girls) were included. World Health Organization criteria were used for comparing Z-score BMI for age in our cases. Overweight was defined as Z-score BMI >+1 SD (standard deviation) and obesity as >+2 SD. At the time of transplantation, the mean age was 10.8 ± 3 years (5-16 years) and based on BMIZ-score, the patients were found to be thin (BMIZs <-2 SD) in 16.9%, normal (BMIZs = -2 to +1 SD) in 67.6%, overweight (>+1 SD to +2 SD) in 9.9%, and obese (BMIZs >+2 SD) in 5.6%.The mean follow-up duration after transplantation was 3.57 ± 1.68 years (1-7 years) and at the time of reevaluation after transplant, their mean age was 14.4 years (6-18 years). The mean BMI was 22 ± 5.3 kg/m2, and for BMI grouping, the patients were thin in 7%, normal in 54.9%, overweight in 21.1%, and obese in 17%. Pretransplant thinness (BMIZs <-2 SD) was found in 12 patients (16.9%), equally in boys and girls, and in most of them (83.3%), BMIZs changed to normal or even >+1 SD after transplant. Chronic continuous decrease of glomerular filtration rate (CCD/GFR) was found in 27 cases (38%); 74.1% were male (P = 0.045), hypertriglyceridemia was found in 74.1% (P = 0.023%), hypercholesterolemia in 63% (P = 0.032),and obesity in 18.5% (p = 0.5). The incidence of obesity has tripled after kidney transplantation. It was not a risk factor for graft or patient survival in our experience, whereas pretransplant obesity had some effects on long-term graft outcome.

How to cite this article:
Beladi Mousavi SS, Valavi E, Aminzadeh M, Shahbazian H, Otukesh H, Hoseini R, Cheraghian B. Changes in body mass index after pediatric renal transplantation.Saudi J Kidney Dis Transpl 2020;31:448-453

How to cite this URL:
Beladi Mousavi SS, Valavi E, Aminzadeh M, Shahbazian H, Otukesh H, Hoseini R, Cheraghian B. Changes in body mass index after pediatric renal transplantation. Saudi J Kidney Dis Transpl [serial online] 2020 [cited 2021 Apr 20 ];31:448-453
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Full Text


Growth retardation is common in the early phases of chronic kidney disease in pediatric patients. Advances in renal replacement therapy and use of supplemental therapy to improve renal osteodystrophy, metabolic acidosis, anemia, and, eventually, linear growth retardation have allowed newborns and young children to grow and survive long enough to receive renal transplants.[1]

Significant weight gain following transplantation, especially during the 1st year of transplantation, is frequent in adult and pediatric renal transplantation and mostly depends on receiving higher doses of steroids.[2]

Overweight and obesity are frequently seen in adult solid organ transplantation, and both are risk factors for a few general morbidities and cardiovascular disease.[3] Hypertension, impaired glucose tolerance, hyperlipidemia, chronic inflammation within fatty tissues, and atherosclerosis in these patients may be effective in progression to chronic allograft failure and reducing kidney and patient survival.[4] Hyperlipidemia is also a frequent phenomenon after renal transplantation. It is due to increased nutrient intake related to steroid consumption and a side effect of calcineurin inhibitors.[5]

The prevalence of overweight and high body mass index (BMI) has been studied in many studies in adults, but very little is known about obesity in pediatric renal transplantation. This study was conducted as a cross-sectional evaluation of body weight and BMI following kidney transplantation in children and adolescents.

 Materials and Methods

In this retrospective, analytical, cross- sectional study, 71 pediatric renal allograft recipients who were followed up at Abuzar Children’s Hospital and Golestan Hospital in Ahvaz, and Labbafinejad Hospital and Ali- Asghar Children’s Hospital in Tehran, Iran, were enrolled. The Ethical Committee of Ahvaz Jundishapur University of Medical Sciences approved the study protocol. The inclusion criteria were as follows: <16 years of age at transplantation; first renal transplantation; treatment with prednisolone, cyclosporine or tacrolimus, and mycophenolate mofetil since transplantation; and an allograft functioning for at least one year.

Demographic and clinical data and laboratory results were obtained. Biochemical parameters including serum urea, creatinine, total cholesterol, and triglyceride were measured by conventional methods and assayed on all patients before and after transplantation.

BMI was calculated based on the following formula: BMI (kg/m2) = weight ÷ height[2]. World Health Organization criteria were used for comparing BMIZ-score (BMIZs) for age in our cases; overweight was defined as BMIZs >+1 SD to +2 SD (standard deviation), obesity as >+2 SD, thinness as <-2SD, and other cases were placed between -2 SD and +1 SD of BMIZs. Hyperlipidemia was defined as total cholesterol and triglyceride levels > the 95th percentile.

All the variables were compared by Student’s /-test, Mann-Whitney U-test, and Chi-square test (for quantitative and qualitative variables). McNemar test was used to compare the frequency of overweight before and after follow- up. Quantitative variables were provided as mean and SD. In addition, the risk was expressed as odds ratio (OR) with 95% confidence interval (CI). However, P <0.05 was regarded as being statistically significant.


At the time of transplantation, among 71 enrolled cases (42 boys and 29 girls), the mean age was 10.8 ± 3 years (5-16 years) and the median weight was 27 kg (13-48 kg). At this time, the mean BMI was 16.7 ± 2.9 kg/m2, and based on BMIZs, they were as follows: 16.9% thinness (BMIZs <-2 SD), 67.6% normal (-2 to +1 SD), 9.9% overweight (>+1 SD to +2 SD), and 5.6% obese (>+2 SD) [Table 1]. The most frequent causes of end-stage renal disease in our patients were obstructive uropathy (26%), hypoplastic dysplastic kidney (19%), and chronic glomerulonephritis (18%). Hyper- triglyceridemia and hypercholesterolemia were frequent at the time of transplantation (38.2% and 54.3%, respectively). All but one patient received kidney transplant from a living donor.{Table 1}

The mean follow-up duration of patients after transplantation was 3.57 ± 1.68 years (1-7 years) and at the study time, their mean age was 14.4 years (6-18 years). The mean BMI was 22 ± 5.3 kg/m2 and BMIZs grouping was as follows: 7% thinness, 54.9% normal, 21.1% overweight, and 17% obesity. Hypertriglyce- ridemia and hypercholesterolemia were also frequent at the study time (57.1% and 47.1%, respectively). Hypertension was found in 21% and proteinuria in 22.5% of patients [Table 2].{Table 2}

Pretransplant growth retardation (BMIZs <-2SD) was found in 12 patients, equally in boys and girls and in most of them (83.3%), BMIZs changed to normal or overweight (>+1 SD) during follow-up. In three cases of normal weight group before transplantation, the BMI changed to thinness after transplantation. Post- transplant thinness was more frequent in boys (threefold), older cases (mean: 17.7 years ± 0.44, P = 0.009), and those with high graft duration (mean: 4.5 years ± 1.3, P = 0.026), but overweight and obesity were more frequent in girls, younger aged cases, and those with less transplant duration [Table 2].

Among our 12 posttransplant obese patients (BMIZs >+2 SD), two were obese, two were overweight, and eight (66.6%) had BMIZs <-1 SD (six normal weight and two thinness) before transplantation. Their mean age was 14 ± 2.3 years, 50% were male (P = 0.47), 83.3% had hypertriglyceridemia (P = 0.042), and 75% hypercholesterolemia (P = 0.035). There was no statistically significant association between obesity and hypertension, proteinuria, and chronic decrease of renal function P <0.05).

CCD/GFR was found in 27 cases (38%); 74.1% of them were male (P = 0.045); hyper- triglyceridemia was found in 74.1% P = 0.023%), hypercholesterolemia in 63% P = 0.032), and obesity in 18.5% (P = 0.5). The CCD/GFR was statistically significantly associated with pretransplant overweight and obesity (P = 0.01), but after transplantation, there was no correlation.

Posttransplant overweight and obesity were more frequent in one-year follow-up P = 0.01), but they were not statistically correlated with patients’ age, the causes of ESRD, pre- transplant overweight, hypertension, and chronic continuous decrease of GFR (P >0.05).

The McNemar statistic test showed that overweight and obesity statistically significantly increased after renal transplantation P = 0.043), and they were more frequent in those with <3-year graft duration (P = 0.013) and hypertriglyceridemia (P = 0.005), but it was not associated with pretransplant hyperlipide- mia, CCD/GFR, proteinuria, and hypertension.


Advances in pediatric renal transplantation and improvement of patient and graft survival have increased weight gaining in recipient children. Overweight and obesity are also significantly increased in children and adolescents after renal transplantation.[6] Catch up of weight gain and BMI in the 1st year after renal transplantation is always seen to be related to the use of steroids; resolving of uremia; changes in mood, feelings, and appetite; as well as the level of physical activities.[7]

In this study, thinness (BMIZs <-2 SD) was frequent (16.9%) before transplantation, but in most of them, weight gaining improved after transplantation. The BMIZs >+1 SD (overweight and obesity) changed from 15.4% to more than 38% after renal transplantation. Hyperlipidemia was also frequent, and most of the obese patients had hypertriglyceridemia (83.3%) and hypercholesterolemia (75%).

Posttransplant obesity in our study (17%) was slightly more frequent in comparison with some other studies; 11% in Vester et al,[8] 13% in Omolojal et al,[1] and 12.5% in Bonthuis et al.[9] Reduction of short-term graft function; increased cardiac, pulmonary, and surgical complications; and increased patient mortality are some of the well-known complications of renal transplantation in obese adult patients.[10] Surprisingly, Meier-Kriesche et al demonstrated that even mild obesity (BMI >25) was an independent risk factor for both decreased graft survival and patient survival.[11] However, these findings were not supported in some other studies.[12] In our study as some other studies,[13] the posttransplant obesity and overweight were not associated with decrease in renal function, and also proteinuria and hypertension did not significantly increase in our obese cases. However, CCD/GFR was associated with hyperlipidemia and male gender in our study.

Steroid therapy is a known risk factor for weight gain in the 1st year after transplantation, and it can be sustaining in the long-term follow-up.[14],[15] This finding is supported by the NAPRTCS data,[16] and corticosteroid avoidance or withdrawal can decrease the adiposity and increase in height gain.[9],[15] Degi et al found a close correlation between BMI SDS and the percentage of body fat and body fat mass in their pediatric cases after renal transplantation. The prevalence of overweight (BMI >85th percentile) in their study increased from 3.2% to 24.4%, at 49-month median follow-up.[17] It seems that simultaneous effects of appetite improvement and reduced physical activity are the main causes of weight gain shortly after transplantation.

Pretransplant obesity is also associated with increased surgical complications and diminished short-term and long-term graft survival. BMI >30 kg/m2 was associated with increased patient mortality in Modlin et al’s adult study.[18] They found that cardiac diseases were the main cause of patient mortality, especially in obese recipients. Mitsnefes et al showed that pretransplant obesity was associated with worse short-term (one-year) renal allograft function in pediatric patients.[19] Obesity and overweight are not frequent before transplantation in children, and two of our four obese cases had Bardet-Biedl syndrome. Similar to some of the abovementioned adult studies, our pretransplant children with more than +1 SD Z-score BMI (overweight and obesity) had a statistically significant association with chronic decrease of renal function (P = 0.01). Although the cause of the worse outcome in obese patients is not clear, hyperlipidemia, hyperfiltration, renal venous hypertension, and glomerular hypertrophy have been proposed as the predisposing factors for kidney failure and chronic allograft nephropathy.[20]

The majority of our obese cases (66.6%) occurred in patients who had a BMIZ <+1 SD before renal transplantation, and it was significantly more in those <3 years posttrans- plantation. It seems that compatibility of transplant recipients with their new condition and decrease of steroids could improve diet and weight control as well as height gain.

In our study, posttransplant thinness was found only in five cases and 60% of them had CCD/GFR when compared with overweight (20%) and obese cases (41.7%); on the other hand, the follow-up duration was significantly more in thinness group. Hence, it seems that posttransplant thinness should be further studied in a multicentric large sample size survey.

This study had a small sample size and short duration of follow-up (mean: 3.5 years) as some of its limitations. The short duration of this study also prevented it from finding the exact correlation of obesity/overweight with long-term graft survival. In addition, we could not evaluate the exact socioeconomic status of the families and the calorie intake and physical activity of the children. Regardless, our data showed that increase in BMI, obesity, and hyperlipidemia is common in children after renal transplantation. Hyperlipidemia was more frequent in obese patients and was significantly correlated with chronic continuous decreased of GFR, so appropriate control of diet, weight gain, and serum lipids after transplantation should be beneficial.


This study was supported by the vice- chancellor for Research of Ahvaz Jundishapur University of Medical Sciences (No. u-88244). We would like to thank Dr. Sharhani for helping us with the statistical analysis.

Conflict of interest: None declared.


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