Comparison of Renal Transplant Scintigraphy With Renal Resistance Index for Prediction of Early Graft Dysfunction and Evaluation of Acute Tubular Necrosis and Acute Rejection

Evaluation of the Graft Kidney in the Early Postoperative Period: Performance of Contrast-Enhanced Ultrasound and Additional Ultrasound Parameters

OBJECTIVES

To evaluate the various quantitative parameters of Doppler ultrasound, contrast-enhanced ultrasound (CEUS), and shear wave elastography (SWE) of graft kidneys in the early postoperative period and to explore their utility in the diagnosis of parenchymal causes of graft dysfunction.

METHODS

In this ethically approved study, consecutive patients who underwent renal transplantation from March 2017 to August 2018 were recruited, and those with urologic or vascular complications and those who denied consent were excluded. All patients underwent ultrasound with Doppler, SWE, CEUS (using sulfur hexafluoride), and renal scintigraphic examinations 3 to 10 days after transplantation. A composite reference standard was used, including the clinical course, renal function test results, urine output, and histopathologic results for graft dysfunction. Cortical SWE values, quantitative CEUS parameters (generated from a time-intensity curve), and their ratios were analyzed to identify graft dysfunction and differentiate acute tubular necrosis (ATN) from acute rejection (AR).

RESULTS

Of the 105 patients included, 19 developed graft dysfunction (18.1%; 12 ATN, 5 AR, and 2 drug toxicity) in the early postoperative period. The peak systolic velocity in the interpolar artery showed a significant difference between control and graft dysfunction groups (P < .001) as well as between ATN and AR (P = .019). Resistive indices and SWE did not show significant differences. Ratios of the time to peak showed a significant difference between control and graft dysfunction groups (P < .05). The rise time and fall time of the large subcapsular region of interest and the rise time ratio were significantly different between ATN and AR (P = .03).

CONCLUSIONS

Contrast-enhanced ultrasound can be used to diagnose parenchymal causes of early graft dysfunction with reasonable diagnostic accuracy.

Prognostic value of dynamic renal scan with 99mTc-EC in patients with kidney transplantation: a prospective descriptive study

INTRODUCTION

Renal transplantation is the gold standard treatment for chronic kidney disease. Renal scintigraphy has been performed widely to evaluate postsurgical complications of transplantation, but there are little data regarding 99mTc-EC scintigraphy in kidney transplantation.

METHODS AND MATERIALS

This was a prospective descriptive study. All patients who underwent kidney transplantation and passed an uneventful postoperative period entered the study. Demographic characteristics, including age, gender, biochemical parameters before and after the transplantation and 99mTc-EC parameters including time to max, time to ½ max, slope from max to ½ max, upslope time interval and time to 2/3 max as well as episodes of rejection, were recorded. Patients were then followed up for 1 year at 3-, 6-, 9- and 12-month intervals.

RESULTS

Forty-one patients who underwent renal transplantation entered the study. Mean ± SD age of patients was 40.65 ± 12.84 years (min 17 and max 74 years). In total, 25% (10) of patients experienced one or two episodes of rejection and were hospitalized. Time of max, time of 1/2 max, time from max to 1/2 max, time of 2/3 max, time from max to 2/3 max and upslope time interval had a significant association with transplant rejection using a Cox regression model. With 1-min increase in time of max, the risk of rejection increased by 27% (hazard ratio = 1.27; CI, 1.03--1.56) and with 1-min increase in time of 1/2 max, the risk of rejection increased by 28% (hazard ratio = 1.28; CI, 1.14-1.45).

DISCUSSION

99mTc-EC renal scintigrahpy was able to predict kidney transplantation rejection in our patients. 99mTc-EC renal scintigrahpy is beneficial to evaluate transplant kidney function to prevent complications and helps close follow-up.

Imaging in Renal Transplants: An Update

Renal transplantation has become the best treatment for the patients with chronic renal insufficiency. The surgical procedures, immunosuppressive regiments and patient follow-up have evolved especially in the last 10 years. However, the diagnosis for renal transplantation dysfunction remained the same in these years. Serum creatinine levels and estimated glomerular filtration rate calculated by serum creatinine based equations are used in routine patient follow-up. Pelvic ultrasonography and color Doppler ultrasonography are used as a first-line imaging method. Assessment of allograft functions both qualitatively and quantitatively are possible using nuclear medicine procedures. Surgical complications, acute tubular necrosis, subacute and/or acute rejection, infections, toxicity due to immunosuppressive medications, complications relating the collecting system, chronic rejection are the main causes for renal function impairment. The imaging procedures can diagnose the worsening of renal transplant function; however, they still lack the ability to differentiate types of rejection as histopathology or differentiate rejection from other causes of allograft dysfunction. The transplant biopsy gives detailed diagnosis for allograft dysfunction, guide the treatment and therefore it is the preferred diagnostic choice in recent years. On recent years, literature on radionuclide imaging is focused on perfusion analysis for the early diagnosis of renal transplant dysfunction and prognostic use of perfusion parameters, and then this article will focus on these studies and their outcome.

Deceased vs. living donor kidney transplantation in prediction of acute renal allograft rejection using Tc-99m DTPA renal scan

OBJECTIVES

No data are available regarding different prognostic values of Tc-99m diethylenetriaminepentaacetic acid (DTPA) renal scan in kidney transplantation (KT) recipients according to two distinct donor types: deceased donor KT (DDKT) and living donor KT (LDKT). We evaluated whether the interpretation of Tc-99m DTPA renal scan should be different by the donor type in predicting acute renal allograft rejection (AR).

METHODS

One hundred and seven KT recipients (61 DDKT and 46 LDKT) were included in this study. Tc-99m DTPA renal scan was performed 1 week after KT. AR was defined as pathological evidence of renal allograft rejection during the first 6 months of KT. Clinical factors and Tc-99m DTPA renal scan findings were compared between patients with and without AR. To further analyze the effect of the donor type, they were again compared within DDKT and LDKT recipients, respectively.

RESULTS

AR occurred in 15 patients (7 DDKT and 8 LDKT recipients). Among all patients, time to peak uptake (TTP) of the cortex (TTP_CX) measured by Tc-99m DTPA renal scan was independently predictive of AR. Moreover, TTP_KD (TTP of the whole transplanted kidney) and TTP_CX were the only predictors of AR among DDKT recipients. The most accurate predictors were TTP_CX and kidney area on renal scan for DDKT and LDKT, respectively. However, these parameters could not predict AR for the opposite donor type.

CONCLUSIONS

AR could be effectively predicted by Tc-99m DTPA renal scan obtained at 1 week post-KT. Different parameters should be applied according to the donor type in the prediction of AR.

99mTc-mercaptoacetyltriglycine Cortical Renography Predicts Outcomes in Adult Living Donor Renal Transplant Recipients

BACKGROUND

The clinical utility of ^99mTc-mercaptoacetyltriglycine cortical renography for the prediction of graft function in kidney transplant recipients has been unknown.

METHODS

We retrospectively reviewed post-transplant cortical renograms in 40 kidney transplant recipients. We analyzed the correlation between T_1/2 (elimination half-life) and graft function (measured-to-expected glomerular filtration rate [GFR]) 1 week, and 1, 3, and 6 months post operation compared with whole-kidney renograms.

RESULTS

Delayed drainage (T_1/2 > 11 minutes) was observed in 22 recipients (55%). T_1/2 and postoperative GFR ratio were inversely correlated (1 week: R² = 0.317, P = .0002; 1 month: R² = 0.206, P = .003; 3 months: R² = 0.117, P = .031; 6 months: R² = 0.161, P = .010). Recipients with delayed drainage had a significantly lower GFR ratio than those with normal drainage 1 week (median, 0.93 vs 1.32; P = .001), 1 month (median, 1.65 vs 2.23; P = .0010), 3 months (median, 1.55 vs 2.17; P = .041), and 6 months (median, 1.67 vs 2.34; P = .018) post operation, respectively. Whole-kidney renograms failed to discriminate recipients with lower GFR ratio at 1, 3, and 6 months.

CONCLUSIONS

T_1/2 in post-transplant cortical renography was inversely correlated with early graft function and may predict early post-transplant graft function.

Limited clinical value of two consecutive post-transplant renal scintigraphy procedures

Objectives

Duration of delayed graft function (DGF) and length of hospital stay (LOS) are outcomes of interest in an era that warrants increased efficacy of transplant care whereas renal allografts originate increasingly from marginal donors. While earlier studies investigate the predictive capability of a single renal scintigraphy, this study focuses on the value for both DGF duration and LOS of consecutively performed scintigraphies.

Methods

From 2011 to 2014, renal transplant recipients referred for a Tc-99m MAG3 renal scintigraphy were included in a single-center retrospective study. Primary endpoints were DGF duration and LOS. Both the first (≤ 3 days) and second scintigraphies (3–7 days after transplantation) were analyzed using a 4-grade qualitative scale and quantitative indices (TFS, cTER, MUC10, average upslope).

Results

We evaluated 200 first and 108 (54%) consecutively performed scintigraphies. The Kaplan-Meier curves for DGF duration and qualitative grading of the first and second scintigraphy showed significant differences between the grades (p < 0.01). The Kaplan-Meier curve for the delta grades between these procedures (lower, equal, or higher grade) did not show significant differences (p = 0.18). Multivariate analysis showed a significant association between the qualitative grades, from the first and second scintigraphy, and DGF duration, HR 1.8 (1.4–2.2, p < 0.01) and 2.8 (1.8–4.3, p < 0.01), respectively.

Conclusions

Qualitative grades of single renal scintigraphies, performed within 7 days after transplantation, can be used to make a reliable image-guided decision on the need for dialysis and to predict LOS. A consecutive renal scintigraphy, however, did not show an additional value in the assessment of DGF.

Key Points

• Post-transplant renal scintigraphy procedures provide information to predict delayed graft function duration and length of hospital stay.

• Performing two consecutive renal scintigraphy procedures within 1 week after transplantation does not strengthen the prediction of delayed graft function duration and length of hospital stay.

• Single renal scintigraphy procedures can be used to provide clinicians and patients with a reliable indication of the need for dialysis after transplantation and the expected duration of hospitalization.

Electronic supplementary material

The online version of this article (10.1007/s00330-019-06334-1) contains supplementary material, which is available to authorized users.

Practical Method for Calculation of Graft Index in Renal Transplant Scintigraphy: A Technical Note

Some quantitative indices have been described for renal transplant scintigraphy in evaluating graft dysfunction, some medical complications, and in predicting early and delayed graft function and long-term graft prognosis. Graft index is very useful and more accurate than many other indices in the prediction of delayed graft function and long-term prognosis. In this technical note, the method of calculation of graft index is shown in detail for the authors who want to use this index in further studies or in clinical practice.

ACR Appropriateness Criteria® Renal Transplant Dysfunction

Renal transplantation is the treatment of choice in patients with end-stage renal disease because the 5-year survival rates range from 72% to 99%. Although graft survival has improved secondary to the introduction of newer immunosuppression drugs and the advancements in surgical technique, various complications still occur. Ultrasound is the first-line imaging modality for the evaluation of renal transplants in the immediate postoperative period and for long-term follow-up. In addition to depicting many of the potential complications of renal transplantation, ultrasound can also guide therapeutic interventions. Nuclear medicine studies, CT, and MRI are often helpful as complementary examinations for specific indications. Angiography remains the reference standard for vascular complications and is utilized to guide nonsurgical intervention. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer-reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Can transplant renal scintigraphy predict the duration of delayed graft function? A dual center retrospective study

Introduction

This study focused on the value of quantitatively analyzed and qualitatively graded renal scintigraphy in relation to the expected duration of delayed graft function after kidney transplantation. A more reliable prediction of delayed graft function duration may result in a more tailored and patient-specific treatment regimen post-transplantation.

Methods

From 2000 to 2014, patients with early transplant dysfunction and a Tc-99m MAG3 renal scintigraphy, within 3 days post-transplantation, were included in a dual center retrospective study. Time-activity curves of renal scintigraphy procedures were qualitatively graded and various quantitative indices (R20/3, TFS, cTER, MUC10) were combined with a new index (Average upslope). The delayed graft function duration was defined as the number of days of dialysis-based/functional delayed graft function.

Results

A total of 377 patients were included, with a mean age (± SD) of 52 ± 14 years, and 58% were male. A total of 274 (73%) patients experienced delayed graft function≥ 7 days. Qualitative grading for the prediction of delayed graft function≥ 7 days had a sensitivity and specificity of respectively 87% and 65%. The quantitative indices with the most optimal results were cTER (76% sensitivity, 72% specificity), and Average upslope (75% sensitivity, 73% specificity).

Conclusions

Qualitative renal scintigraphy grading and the quantitative indices cTER and Average upslope predict delayed graft function ≥ 7 days with a high sensitivity. This finding may help to support both clinicians and patients in managing early post-operative expectations. However, the specificity is limited and thus renal scintigraphy does not reliably help to identify patients in whom the course of delayed graft function is longer than anticipated.

Scintigraphic texture analysis for assessment of renal allograft function

Purpose

Early detection and monitoring of kidney function during the post-transplantation period is one of the most important issues for improving the accuracy of an initial diagnosis. The aim of this study was to evaluate texture analysis (TA) in scintigraphic imaging to detect changes in kidney status after transplantation.

Material and methods

Scintigraphic images were used for TA from a total of 94 kidney allografts (39 rejected and 55 non-rejected). Images corresponding to the frames at the 2^nd, 5^th, and 20^th minute of the study were used to determine the optimum time point for analysis of differences in texture features between the rejected and non-rejected allografts.

Results

Linear discriminant analysis indicated the best performance at the fifth minute frame for classification of the rejected and non-rejected allografts with receiver operating characteristic curve (A_z) of 0.982, corresponding to 91.89% sensitivity, 96.49% specificity, and 94.68% accuracy. Also, TA can differentiate acute tubular necrosis from acute rejection with A_z of 0.953 corresponding to 88% sensitivity, 92.31% specificity, and 90.62% accuracy at the 5^th minute frame. The best correlation between texture feature and kidney function was achieved at the 20^th minute frame (r = -0.396) for glomerular filtration rate.

Conclusions

TA has good potential for the characterisation of kidney failure after transplantation and can improve clinical diagnosis.

Peri- and Postsurgical Evaluations of Renal Transplant

Renal transplantation is the best treatment of choice for patient with chronic renal insufficiency because it provides better quality of life and longer survival. Survival rates for grafts and patients have improved over the recent decades because of significant evolution of surgical techniques and immunosuppressive treatment. However, renal transplantation is still associated with several complications, which may result in poor outcome. Cause of allograft dysfunction, which occurs in the early or late post-transplantation period, should be recognized immediately, so that it can be managed correctly. Surgical complications are rare and include renal artery stenosis, vascular thrombosis, hematoma, ureteral obstruction, urinary leak, hematoma, lymphocele, and perinephric fluid collections. Parenchymal complications, which are histopathologically categorized according to Banff classification, include antibody-mediated rejection, T-cell mediated rejection, interstitial fibrosis and tubular atrophy, calcineurin inhibitors, acute tubular injury, and others. Detection of changes in the allograft function is an important task in the appropriate management of complications. Although first-line imaging tool in the recognition of complications is ultrasonography, radionuclide imaging is a modality capable of assessing graft function qualitatively and quantitatively. Sequential renal scintigraphy is of particular importance in the differential diagnosis of complications, which need prompt and accurate management. Renal scintigraphy within 24-48 hours of transplantation surgery is recommended to serve as a baseline for comparison when functional impairment develops. In addition, studies have shown that early renal scintigraphy has a predictive value for the short-term and long-term graft outcomes. This article focuses in the main complications after renal transplantation, their imaging findings, and the role of renal scintigraphy.

Role of nuclear medicine imaging in evaluation of complications following renal transplant

Evaluation of a failing renal allograft is a complex and challenging diagnostic problem. While ultrasonography with colour Doppler is usually the first approach for evaluation of graft dysfunction, radionuclide imaging is an excellent modality which provides complementary information regarding the perfusion and function of the allograft without any deleterious effect on the precious allograft. In this article, we review the imaging techniques of the nuclear medicine studies most commonly performed after renal transplant, discuss their roles and limitations in different clinical settings and illustrate with cases from our institution. Lastly, we will explore future development in the arena of nuclear imaging for renal transplant related complications.