Investigation of Different Methods of Intraoperative Graft Perfusion Assessment during Kidney Transplantation for the Prediction of Delayed Graft Function: A Prospective Pilot Trial

Delayed graft function (DGF) after renal transplantation is a relevant clinical problem affecting long-term organ function. The early detection of patients at risk is crucial for postoperative monitoring and treatment algorithms. In this prospective cohort study, allograft perfusion was evaluated intraoperatively in 26 kidney recipients by visual and formal perfusion assessment, duplex sonography, and quantitative microperfusion assessment using O2C spectrometry and ICG fluorescence angiography. The O2C tissue spectrometry device provides a quantitative method of microperfusion assessment that can be employed during kidney transplantation as an easy-to-use and highly sensitive alternative to ICG fluorescence angiography. Intraoperative microvascular flow and velocity in the allograft cortex after reperfusion predicted DGF with a sensitivity of 100% and a specificity of 82%. Threshold values of 57 A.U. for microvascular flow and 13 A.U. for microvascular velocity were identified by an ROC analysis. This study, therefore, confirmed that impairment of microperfusion of the allograft cortex directly after reperfusion was a key indicator for the occurrence of DGF after kidney transplantation. Our results support the combined use of intraoperative duplex sonography, for macrovascular quality control, and quantitative microperfusion assessment, such as O2C spectrometry, for individual risk stratification to guide subsequent postoperative management.

Influence of Immunosuppressive Regimen on Diffusivity and Oxygenation of Kidney Transplants-Analysis of Functional MRI Data from the Randomized ZEUS Trial

The ZEUS study was a multi-center randomized controlled trial investigating the effect of early conversion from a ciclosporin-based to an everolimus-based regimen on graft function twelve months post-transplantation. In this investigator-initiated sub-study, functional magnetic resonance imaging (fMRI) of kidney grafts was prospectively performed to non-invasively assess differences in graft oxygenation, diffusion and perfusion between groups and time-points using diffusion-weighted imaging (DWI) and blood oxygen level-dependent (BOLD)-MRI. Sixteen patients underwent DWI and BOLD-MRI at months 4.5 and 12 post-transplantation on a 3 Tesla and 1.5 Tesla (n = 3) MR scanner. After exclusion due to image quality, outlier values or missing data, DWI was analyzed for ten subjects; BOLD for eight subjects. The diffusion coefficient ADC_D decreased in the CsA-treated group over time, whereas it increased in the EVE group (p = 0.046, medulla). The change in ADC_D from months 4.5 to 12 significantly differed between groups in the cortex (p = 0.033) and medulla (p = 0.019). In BOLD, cortico-medullary transverse relaxation rate R2* increased (decreased tissue oxygen) in the CsA-treated and decreased in EVE-treated groups over time. Similarly, R2* values at month 12 were higher in the CsA-treated group compared to the EVE-treated group. There was no significant difference for the perfusion fraction F_P. In conclusion, this prospective sub-study of the ZEUS trial suggests an impact of immunosuppressive regimen on fMRI parameters of the kidney graft.

Role of high resolution contrast-enhanced magnetic resonance angiography (HR CeMRA) in management of arterial complications of the renal transplant

INTRODUCTION

Transplant renal artery (RA) stenosis (TRAS) is the most frequent posttransplantation vascular complication. Contrast enhanced magnetic resonance (CeMRA) angiography has been established as the preferred imaging technique for the evaluation of TRAS because it does not require the use of iodinated contrast material and does not expose the patient to ionizing radiation. Digital subtraction angiography (DSA) is the gold standard in the evaluation of arterial tree of the renal allograft.

AIM OF THE WORK

This study was carried out to assess the accuracy of CeMRA in the detection of arterial complications after renal transplantation.

PATIENTS AND METHODS

Thirty renal transplant patients with suspected arterial complications in which both CeMRA and DSA were performed were included in the study. The HR CeMRA shows 93.7% sensitivity, 80% specificity, 88.2% positive predictive value, 88.9% negative predictive value and 88.5% accuracy.

CONCLUSION

HR CeMRA is an accurate reliable tool in the assessment of arterial complications after renal transplantation. It may replace DSA as a diagnostic modality with reservation of interventional techniques for endovascular treatment of suitable cases.

Prediction of renal allograft function with early Doppler ultrasonography

INTRODUCTION

Doppler ultrasonography (USG) is an useful, noninvasive diagnostic tool for the management and follow-up of the transplanted kidney. However, it is believed that the value of Doppler USG is limited to discrimination of acute rejection episodes. We tested whether early Doppler USG findings were predictive of 1-month and 1-year allograft functions in noncomplicated renal transplant recipients (RTRs).

PATIENTS AND METHODS

Resistive index (RI) and pulsatile index (PI) values obtained by doppler USG within the first week of transplantation were correlated with allograft function at 1 month and 1 year in 45 (10 women, 35 men, mean age: 27 years) noncomplicated cases. Patients with complications during the first posttransplant year were not included.

RESULTS

There was a negative correlation between both RI and PI with creatinine clearance values at 1 month and at 1 year posttransplant. There was a significant decline in allograft function among cases with either RI > or = 0.7 or PI > or = 1.1. Patients with impaired allograft function have higher RI and PI values.

CONCLUSION

Renal allograft survival is influenced by many factors. However, no reliable simple parameter has been identified to predict long-term outcome. Doppler USG performed during the early transplantation period with calculation of RI and PI may have a predictive value to forecast early and long-term outcomes of noncomplicated kidney transplants.