Duplex Sonographic Measurements in Allografted Kidneys: A Cross-Sectional Study

The role of renal resistive index as a prognostic tool in kidney transplantation: a systematic review

Background

In kidney transplant recipients (KTRs), observational data have reported conflicting findings about the utility of renal resistive index (RRI) in determining outcomes. We aimed to synthesize the current literature and determine the prognostic role of RRI in KTRs.

Methods

We conducted a systematic review to assess the role of RRI in predicting death, graft failure, graft function, and proteinuria. Of the 934 titles/abstracts reviewed, 26 studies were included. There was significant heterogeneity in RRI measurements and thresholds as well as in analytic methods and a meta-analysis could not be performed.

Results

All included studies were observational and included 7049 KTRs. Eight studies analyzed death, of which five reported a significant association with higher RRI. In the remaining three, small sample sizes and lower/multiple RRI thresholds may have limited detection of a statistically significant difference. Three studies investigated all-cause graft failure and an association with RRI was reported but varied by time of RRI measurement. Three out of five studies that analyzed a composite of patient and graft outcomes reported an association with RRI. Evidence analyzing death-censored graft failure, graft failure (unclear if death-censored or all-cause), measures of graft function, and proteinuria were conflicting. Most studies had a moderate to high risk of bias.

Conclusions

RRI likely has a prognostic role in predicting patient outcomes, reflecting patient systemic vascular disease burden rather than graft hemodynamics. Since cardiovascular diseases are a major cause of death and graft loss, RRI may be explored as a non-invasive tool to risk stratify KTRs.

Three-dimensional imaging of living transplanted kidney vasculature by 3D color Doppler ultrasonography

Background: It is of clinical importance to display the vasculature of transplanted kidney in three-dimensional (3D) and in non-invasive way. 3D color Doppler ultrasonographic imaging (3D-CDUI) is a non-invasive technique to display the 3D vasculature of living organs. Objective: Probe into characteristics of 3D vasculature of living transplanted kidney by 3D-CDUI, and evaluate the clinical value of 3D-CDUI on monitoring complications after operation of renal transplant. Methods: Nine patients who received allogeneic transplantation of kidney were monitored with 3D-CDUI. The instruments used included ACUSON Sequoia 512 and TomTec computer station of 3D-CDUI. Using magnetic positioning free-hand scanning, the 3D reconstruction and display of renal tissue structure and blood flow were performed off-line. Results: All patients underwent 3D-CDUI examinations without any side effect or complication. When acute rejection occurred, the 3D distribution change of renal blood flow signal could be observed clearly. During treatment of acute necrosis of renal tubules, changes of renal blood flow signal in 3D color Doppler images could be detected earlier compared with 2D color Doppler images. The position of embolized vassels could be diagnosed accurately by 3D-CDUI. Conclusion: The 3D-CDUI was helpful to improve diagnosis level of ultrasonography by monitoring complications after renal transplantation.

The predictive value of resistive index obtained by Doppler ultrasonography early after renal transplantation on long-term allograft function

DUSG is a useful diagnostic tool for the follow-up of renal transplant recipients. The measurement of intrarenal arterial RI by DUSG has been proven to predict short-term AF. The aim of the study was to evaluate the predictive value of DUSG performed during the early after RTx on long-term AF. Seventy patients were enrolled into study. DUSG was performed at third and seventh days after RTx. Patients were divided into two groups according to rate of recovery of graft function as patients with normal graft function and abnormal graft function. Although the RI values were correlated with the AF early after transplantation, they were not correlated with long-term AF. However, the rate of recovery of graft function at early period after RTx was correlated with creatinine level at first year and with glomerular filtration rate at first year and last visit. Although the RI has no predictive value for long-term AF, the rate of recovery of graft function at early post-transplantation period has predictive value for long-term AF; patients with higher RI values early after RTx should be followed carefully for the development of chronic allograft injury.

Relation of resistive and pulsatility indices with graft function after renal transplant

OBJECTIVES

There are conflicting data regarding the use of some measured indices by Doppler ultrasound such as the resistive index and the pulsatility index in predicting renal allograft dysfunction. This study sought to evaluate the association of early postoperative Doppler indices and 3-month serum creatinine levels in renal transplant recipients.

MATERIALS AND METHODS

During a 1-year period, all patients who underwent renal transplant at our hospital were recruited into a prospective study. Doppler ultrasound was performed on all patients 6 days and 3 months after the transplant and the resistive index and the pulsatility index were calculated for each patient. Then, the association between these indices and 3-month outcomes of patients were investigated.

RESULTS

Thirty-eight patients including 21 men (mean age, 36.6 ± 13.1 y) were evaluated. There was a positive correlation between the resistive index and the pulsatility index at 6 days after transplant and the serum creatinine measured at the same day (P < .001 and r=0.570 for resistive index; P < .001 and r=0.547 for pulsatility index). There was also a positive correlation between the pulsatility index and the resistive index at 6 days after transplant and 3-month serum creatinine level (P = .009 and r=0.420 for resistive index; P = .009 and r=0.417 for pulsatility index). There were negative correlations between the resistive index and the pulsatility index on the sixth day after surgery and creatinine clearance measured at 6 days and 3 months after transplant.

CONCLUSIONS

This study reveals a strong-to-medium correlation between the resistive index and the pulsatility index, serum creatinine level, measured 6 days after transplant.

Color Doppler indexes in early phase after kidney transplantation and their association with kidney function on six month follow up

BACKGROUND

Doppler ultrasonography (DU) and measurement of its indexes, resistive index (RI) and pulsatility index (PI), is used to investigate transplanted kidney hemodynamic status and function. The aim of this study was to determine the correlation between Doppler indexes in the early phase after transplantation with long-term transplanted kidney function.

MATERIALS AND METHODS

In this cross-sectional study on 38 newly kidney transplant patients, we performed DU with assessment of its indexes within 48 hours, 1 week, and 6 months after kidney transplantation. Serum creatinine after stability and 6 months after kidney transplantation were assessed. Cyclosporine level was measured 1 week after kidney transplantation and compared with DU indexes.

RESULTS

About 71% of kidney transplanted patients reached their normal initial creatinine level(cr<1.5 mg/ dl) and 28% of all patients were involved in kidney dysfunction after 6 months (increase in basic creatinine level more than 25%).There was no significant difference between mean RI and PI in patients with normal and disturbed kidney function based on creatinine level in early posttransplantation period but there was linear correlation between mean RI and PI within 48 hours and 1 week with kidney function after 6 months. Also no association between cyclosporine level and RI and PI was shown. There was a direct association between age and the levels of RI and PI 6 months after transplantation.

CONCLUSION

This study suggests assessment of RI and PI in early period after transplantation and can be used as predictive parameters for long-term function of transplanted kidney and RI more than 0.80 in early phase after transplantation has an acceptable sensitivity and specificity to predict long-term kidney dysfunction.

Role of resistive index measurement in diagnosis of acute rejection episodes following successful kidney transplantation

OBJECTIVE

This study was performed to evaluate the role of resistive index (RI) in the diagnosis of rejection episodes following successful kidney transplantation.

MATERIALS AND METHODS

One hundred and one unrelated living first kidney allograft adult recipients (75 males and 26 females) of overall mean age of 39 years were enrolled and prospectively followed for 6 months. The measurement of RI by Doppler ultrasonography was performed in all patients on days 3 and 7 as well as at months 1, 3, and 6 in addition to when there was graft dysfunction. We determined serum creatinine and cyclosporine levels.

RESULTS

Twenty-seven patients (26.7%) experienced 33 acute rejection episodes during the follow-up. There were significant differences between mean RI among patients with normal function vs rejection: 0.606 +/- 0.065 vs 0.866 +/- 0.083 (P < .05), respectively. Overall, elevated levels of cyclosporine, ischemic acute tubular necrosis (ATN), and renal artery thrombosis were observed in 8, 5, and 3 patients, respectively. No association was observed between these factors and RI.

CONCLUSIONS

RI was significantly higher in patients with acute rejection episodes. It had no association with ATN or cyclosporine toxicity. Hence, RI may be useful to diagnose acute renal allograft rejection following renal transplantation.