Prediction of the severity and outcome of acute tubular necrosis based on continuity of Doppler spectrum in the early period after kidney transplantation

Use of Intraoperative Duplex Ultrasound and Resistance Index Reduces Complications in Living Renal Donor Transplantation

BACKGROUND

The treatment of choice in end-stage renal disease is transplantation. Hemodynamic disturbances can evoke graft loss, while early ultrasound identification of vascular problems improves outcome. The aim of this study was to identify differences in postoperative complications with and without systematic intraoperative Doppler ultrasound use.

METHODS

The primary outcome was the postoperative rate of complications and the secondary aim was to find a predictive resistance index cut-off value, which would show where surgical reintervention was necessary. Over a 10-year period, 108 renal transplants were performed from living donors at our institution. In group 1 (n = 67), intraoperative duplex ultrasound and intraparenchymatous resistance index measurements assessed patients, while in group 2 (n = 41), no ultrasound was performed.

RESULTS

There were no intergroup differences in the overall postoperative complication rate or in benefit to graft or patient survival with Doppler use. However, significantly more vascular complications (10% vs 0%, P = .02) and more acute rejections (37% vs 10%) occurred in group 2 than in group 1. Therefore, an intraoperative cut-off value of the resistance index 0.5 was proposed to justify immediate surgical revision.

CONCLUSIONS

This is the first report demonstrating benefits of systematic intraoperative Doppler ultrasound on postoperative complications in renal transplantation from living donors. Our results support surgical revision with a resistance index <0.5.

Effect of Donor- and Recipient-Related Factors on Arterial Resistance Index After Kidney Transplant

BACKGROUND

The assessment of color Doppler resistance index (RI) of the intra-renal arteries has been shown to be a good predictor of short-term and long-term graft survival after kidney transplant. In this study, we investigated the influence of donor- and recipient-related factors on RI evaluated early after kidney transplant.

METHODS

We prospectively analyzed 90 kidney transplant patients who underwent RI assessment within the first month after the transplant, subdivided into 2 groups according their RI values lower (group A) or higher (group B) than 0.646 (median value).

RESULTS

Patients in group A had a lower human leukocyte antigen (HLA) mismatch number (3.3 ± 1 versus 3.9 ± 0.9, P = .007) and were significantly younger (42.8 ± 11 years versus 47.8 ± 11 years, P = .03) than patients in group B. All the others variables examined were not significantly different between the 2 groups. Multivariate logistic regression analysis confirmed that HLA mismatch number (P = .03) and recipient age (P = .03) are independent predictors of RI.

CONCLUSIONS

Our data suggest that HLA mismatches and donor age can influence recipient kidney vascular resistance in the early period after transplantation.

Disturbances of kidney graft perfusion as indicators of acute renal vein thrombosis in contrast-enhanced ultrasonography

INTRODUCTION

The aim of this study was to evaluate the usefulness of contrast-enhanced ultrasound (US-CE) to diagnose acute renal vein thrombosis (ARVT), acute rejection episodes (ARE), or acute tubular necrosis (ATN) in kidney grafts.

MATERIALS AND METHODS

We analyzed 171 US-CE among kidney transplantation patients in the early postoperative period. Patients underwent US-CE following a standard diagnostic protocol including real-time ultrasound (B-mode) and color Doppler ultrasound with spectral flow analysis. Tissue perfusion was analyzed based upon time-intensity curves for two regions: the renal cortex and the renal pyramids.

RESULTS

Of 14 patients, in whom standard ultrasound showed high resistance parameters in the renal artery, three showed ARVT and 11 had ATN or ARE, which were confirmed by biopsy. Among patients with ARVT, the US-CE showed a lack of contrast perfusion into the cortex and renal pyramids. Patients with ARE/ATN showed slower contrast inflow into the parenchyma with reduced but still present perfusion. The differences in mean signal intensity values were significant for both the cortex and the renal pyramids: cortex: -53.8±5.4 dB versus -35.0±3.5 dB (P<.05) and pyramids: -54.8±5.4 dB versus -37.0±3.5 dB (P<.05).

CONCLUSION

US-CE is a noninvasive method that provides easy, reliable differentiation of ARVT from ARE/ATN.

Early kidney graft size and Doppler parameters are associated with kidney graft function 1 year after transplantation

BACKGROUND

The aim of this study was to assess the association of various ultrasonography (US) and Doppler parameters of kidney graft as measured at 1 month posttransplant with 1-year graft function.

MATERIALS AND METHODS

The study cohort included 125 adult recipients of deceased donor kidney transplantations between January 2006 and February 2009. All patients underwent an US-Doppler examination performed by a trained nephrologist at 1 month posttransplant using an Acuson-Siemens Sequoia 512. Graft length and intrarenal Doppler indices were measured at the midsegmental artery level. Relative graft size was calculated by dividing graft length with body mass index. Graft function was assessed at 1 year by estimated glomerular filtration rate (eGFR) using the 4-variable Modification of Diet in Real Disease study equation. Linear and logistic regression analyses were used to assess the relationship between US-Doppler parameters and eGFR.

RESULTS

Univariate linear regression showed a significant correlation between eGFR at 1 year and graft length at 1 month (P = .009), relative graft length <0.50 cm per kg/m(2) (P = .004), resistance index >0.75 (P = .031), and end-diastolic velocity <9 cm/sec (P = .006). Logistic regression analyses showed that eGFR <60 mL/min/1.73 m(2) at 1 year was significantly associated with graft length <12 cm at 1 month (odds ratio [OR], 2.4; 95% confidence interval [CI], 1.16-4.92; P = .017), relative graft length <0.5 cm per kg/m(2) (OR, 2.54; 95% CI, 1.20-5.35; P = .014), resistance index >0.75 (OR, 2.86; 95% CI, 1.30-6.29; P = .009), and end-diastolic velocity <9 cm/sec (OR, 2.37; 95% CI, 1.01-5.56; P = .047).

CONCLUSION

In this retrospective analysis, kidney transplant recipients with greater graft length at 1 month, specifically when standardized to body size, showed better graft function at 1 year posttransplantation. Higher intrarenal diastolic blood flow and lower resistance index at 1 month were also predictive of better graft function at 1 year.

Biological modulation of renal ischemia-reperfusion injury

PURPOSE OF REVIEW

Biological modulation of renal ischemia-reperfusion injury holds the potential to reduce the incidence of early graft dysfunction and to safely expand the donor pool with kidneys that have suffered prolonged ischemic injury before organ recovery.

RECENT FINDINGS

In the current review, we will discuss clinical studies that compare kidney transplant recipients with and without early graft dysfunction in order to elucidate the pathophysiology of ischemic acute allograft injury. We will specifically review the mechanisms leading to depression of the glomerular filtration rate and activation of the innate immune system in response to tissue injury.

SUMMARY

We conclude that the pathophysiology of delayed graft function after kidney transplantation is complex and shares broad similarity with rodent models of ischemic acute kidney injury. Given the lack of specific therapies to prevent delayed graft function in transplant recipients, comprehensive efforts should be initiated to translate the promising findings obtained in small animal models into clinical interventions that attenuate ischemic acute kidney injury after transplantation.