|Year : 2019 | Volume
| Issue : 2 | Page : 94-97
Role of renal doppler spectral study in detecting allograft dysfunction in early post-transplant period
Ramya Vedula1, Farha Furruqh2, Arpana Iyengar1
1 Department of Pediatric Nephrology, St. John's National Academy of Health Sciences, Bengaluru, Karnataka, India
2 Department of Radiology, St. John's National Academy of Health Sciences, Bengaluru, Karnataka, India
|Date of Web Publication||4-Dec-2019|
50-1-40/14/2, F202, Sridevi Residency, Apseb Colony, Seethammadhara, Visakhapatnam - 530 013, Andhra Pradesh
Source of Support: None, Conflict of Interest: None
Doppler sonography is routinely used to assess global and segmental perfusion abnormalities in renal allograft. However, its utility in distinguishing between the causes of allograft dysfunction is unclear, and information is lacking on the outcomes of allografts with abnormal findings. In this single center study, we retrospectively reviewed the records of pediatric allograft recipients who underwent Doppler spectral study within 3 weeks of transplantation. Resistive index (RI) of >0.7 was considered abnormal. Serum creatinine at the time of Doppler and at 3-month follow-up was documented. Among 34 children transplanted over 5 years, delayed graft function (DGF) was observed in 36% of allografts. RI was significantly higher for allografts with DGF than those without DGF (0.85 ± 0.17 vs. 0.69 ± 0.10; P = 0.004). Serum creatinine was significantly higher for allografts with abnormal than normal Doppler. However, there was no significant association between RI and the underlying histopathology. RI at the level of segmental (r = 0.62) and arcuate arteries (r = 0.55) correlated well with serum creatinine. Allografts with high and normal RI had comparable serum creatinine at 3-month follow-up (median [interquartile range] 0.65 [0.6, 0.9] vs. 0.7 [0.65, 0.8]; P = 0.98).
Keywords: Kidney transplant, pediatric, resistive index
|How to cite this article:|
Vedula R, Furruqh F, Iyengar A. Role of renal doppler spectral study in detecting allograft dysfunction in early post-transplant period. Asian J Pediatr Nephrol 2019;2:94-7
|How to cite this URL:|
Vedula R, Furruqh F, Iyengar A. Role of renal doppler spectral study in detecting allograft dysfunction in early post-transplant period. Asian J Pediatr Nephrol [serial online] 2019 [cited 2020 Apr 3];2:94-7. Available from: http://www.ajpn-online.org/text.asp?2019/2/2/94/272305
| Introduction|| |
Renal Doppler is used routinely as a noninvasive bedside tool for the assessment of renal allograft perfusion. The role of resistive index (RI) in predicting allograft dysfunction has been inconsistent in reports including adult and pediatric patients.,,, We undertook this study to examine the role of RI in identifying allograft dysfunction and the impact of abnormal Doppler spectral analysis in immediate posttransplantation period, on renal allograft function at the time of Doppler and at 3 months after transplantation.
| Methods|| |
Following approval of the Institutional Ethics Committee, we undertook a retrospective study of case records of all children who underwent renal transplantation during June 2011–October 2016 at our center. The demographic and clinical details of the recipient and donor were recorded with particular attention to immunosuppression. Doppler sonography and renal ultrasonography were done at clinical suspicion of allograft dysfunction and before discharge from hospital, in all patients. Transplanted kidneys were evaluated with gray-scale ultrasound and Doppler (Toshiba-Nemio XG, Tokyo, Japan) using linear (6–11 MHz) and convex (3–6 MHz) probes by a single radiologist. The same radiologist, who was blinded to the allograft outcome and serum creatinine values retrospectively analyzed these reports and the images. The size and echotexture of the allograft kidney was evaluated, and peritransplant collection or hydronephrosis was looked for. Color Doppler included evaluation of renal vascularity and perfusion. Spectral analysis was used to calculate RI for renal arteries at the anastomosis, hilum, poles and mid-region, and arcuate arteries. Standardized presets were used for gray-scale and Doppler imaging. Color Doppler was conducted with the highest possible signal gain setting that lacked background noise; low-pulse repetition frequencies (0.2–0.4 Hz) were used to increase sensitivity to low velocities. The presence or absence of vascularity in the renal vessels was noted. As shown in [Figure 1], spectral analysis of arterial flow should demonstrate sharp systolic upstroke with a low-resistance waveform and continuous antegrade diastolic flow. The RI at arcuate artery, calculated as (peak systolic velocity − end diastolic velocity)/peak systolic velocity, is normally between 0.5 and 0.7, and a value >0.7 is considered abnormal [Figure 2].
|Figure 1: Color Doppler image of a transplant kidney with cursor placed on the arcuate artery (yellow arrow). Spectral image of the flow within the arcuate artery (red arrow)|
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|Figure 2: High resistive index in the arcuate artery of a patient with delayed graft function|
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Based on the rate of recovery of allograft function, patients were classified as delayed graft function (DGF), if there was a need for dialysis; slow graft function, if there was no need for dialysis but the serum creatinine fell by ≤30% from baseline; and immediate graft function (IGF), if there was >30% decrease in creatinine level from baseline, in the first week after renal transplantation., Where available, findings on allograft histopathology in the immediate posttransplantation period ( first 2–3 weeks) were documented. In children who underwent renal transplant for focal segmental glomerulosclerosis (FSGS), disease recurrence was defined as significant proteinuria (≥3+ on dipstick) and light or electron microscopy suggestive of FSGS and diffuse foot process effacement, respectively.
Continuous variables are described as mean ± standard deviation or median (interquartile range) based on normality of data distribution, and groups were compared using parametric or nonparametric tests (two-tailed t- test; Wilcoxon rank-sum test, one-way analysis of variance, or Kruskal–Wallis test, as applicable). Categorical variables were reported as counts and percentages and compared using the Chi-square or Fisher's exact test. P < 0.05 was considered statistically significant. Data were analyzed using Stata software, version 13.1, for Windows (Stata Corp, College Station, Texas, USA).
| Results|| |
[Table 1] summarizes the baseline characteristics of 34 children (44.1% boys) who underwent renal transplantation at the age of 10.8 ± 3.3 years, chiefly from live related donors (88.2%). Congenital anomalies of kidney and urinary tract were the leading (44%) cause of native kidney disease. DGF and IGF were observed in 12 (36%) and 20 (60%) allografts, respectively. Risk factors or etiology of DGF included deceased donor transplantation, recurrence of FSGS, and prolonged cold ischemia time in four cases each. Eleven of the 12 cases with DGF had histopathological diagnosis. Allograft nephrectomy was performed in one child due complete renal vascular thrombosis, as suggested by absent flow in renal vein and reversal of diastolic arterial flow.
Multiple renal arteries and segmental perfusion defects were not observed in any cases. RI was statistically significantly higher for allografts with DGF than those without DGF (0.85 ± 0.17 vs. 0.69 ± 0.10; P = 0.004) [Figure 3]. RI was better correlated with serum creatinine at segmental (r = 0.62) and arcuate arteries (r = 0.55) compared to the indices at hilum (r = 0.49) and anastomotic site (r = 0.44). Serum creatinine was significantly higher in children with RI >0.7 than those with normal RI (median [interquartile range] 2.5 [1.5–4.0] mg/dl vs. 0.8 [0.7–1.0] mg/dl; P = 0.009). RI was similar for allografts with a histopathological diagnosis of acute tubular necrosis, acute rejection, and recurrent FSGS, at 0.89 ± 0.2, 0.82 ± 0.02, and 0.95 ± 0.07, respectively (P = 0.6). Hence, RI did not correlate with histopathological diagnosis.
|Figure 3: Comparison of resistive indices (RI) in children with and without delayed graft function (DGF)|
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The mean time to recovery from DGF was 32 ± 10.8 days. At discharge from the hospital, serum creatinine did not differ statistically significantly between patients with normal and abnormal peritransplant Doppler (RI 0.8 [0.6–0.8] vs. 1.0 [0.7–1.4]; P = 0.12) [Figure 4]. On follow up at three months [Figure 4], the median creatinine in children with normal and abnormal peri-transplant Doppler study was comparable [0.65,(IQR 0.6,0.9); 0.7(IQR 0.65,0.8), P=0.98].
|Figure 4: Comparison of serum creatinine at the time of Doppler and at 3-month follow-up in patients with arcuate artery resistive index (RI) ≤ 0.7 and > 0.7|
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| Discussion|| |
Doppler ultrasound is an important diagnostic tool in cases with impaired kidney function. RI is used as an indicator of hemodynamic health of transplanted kidney and is reported to be a significant predictive parameter for allograft failure. While some studies,, have used RI in pediatric transplantation, the role of RI in predicting allograft dysfunction remains unclear. An RI over 0.8 is suggested to indicate allograft rejection, whereas an RI below 0.7 makes rejection unlikely. Similarly, in our study, patients with DGF had significantly higher RI than those with IGF, and there was a good correlation between serum creatinine and RI in the immediate peritransplant period. While early studies suggested that duplex Doppler sonography is both sensitive and specific in diagnosing allograft rejection,,, more recent studies in adult allograft recipients have contested that view.,, Similarly, there was a lack of correlation of RI with allograft histology in our study.
The role of early posttransplant Doppler RI in predicting long-term allograft survival is controversial. While some studies support a role for RI, other researchers have found no correlation between early transplant Doppler RI and long-term outcomes.,,,, The present study found no relationship between early peritransplant Doppler RI and early and short-term allograft function. Ali Ghorbani et al in their prospective study on young renal allograft recipients observed a strong positive correlation between RI and pulsatility index 6 days after transplantation and day 6 serum creatinine, supporting our observations.
The present study is limited by its retrospective design and lack of repeated measurements of RI. Adding sequential Doppler ultrasound at the time of discharge and at 3-month follow-up might have demonstrated improvement in RI as DGF resolved.
| Conclusion|| |
Renal Doppler is a useful bedside tool to detect allograft vascular thrombosis and allograft dysfunction in the peritransplant period. While arcuate and segmental artery RI have good correlation with serum creatinine, allografts with high and normal RI in the peritransplant period have comparable renal function at 3-month follow-up.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]