Ultrasound Screening for Transplant Renal Artery Stenosis Risk Stratification Using Standardized Criteria in Structured Reporting: A Validation Study.

OBJECTIVES: To evaluate the effectiveness of templated ultrasound reports using transplant renal artery stenosis (TRAS) risk stratification (RS), particularly with regard to utilization of downstream angiographic studies and angiographic presence of TRAS. METHODS: Ultrasounds with TRAS-RS templated reports from August 2017 to May 2020 were included. Studies were excluded if performed <28 days posttransplant and where TRAS was not clinically considered. A total of 530 ultrasounds met inclusion/exclusion criteria. TRAS-RS criteria were recorded (renal artery velocity ≥300 cm/s, spectral broadening in the renal artery, and intraparenchymal acceleration time ≥0.1 second). Depending on the number of criteria present, recipients were stratified into low (0/3), intermediate (1/3), high (2/3), and very high (3/3) risk for TRAS. Student's t-test was performed to identify whether the TRAS-RS category was associated with 1) performance of angiography to assess for TRAS and 2) angiographic presence of TRAS. RESULTS: Of the 530 ultrasounds, 74 (14%) underwent angiography. Of these, 41 (55%) were positive for TRAS (overall positive rate, 8%). Number of ultrasounds, angiograms, and angiograms positive for TRAS, respectively, in each of the TRAS-RS categories for the 530 cases were: low probability: n = 370 (70% of all studied reports), 7 angiograms (2%), and 0 (0%) positive for TRAS; intermediate: n = 87 (16%), 24 angiograms (28%), and 8 (33%) positive; high: n = 46 (9%), 23 angiograms (50%), and 14 (61%) positive; and very high: n = 27 (5%), 20 angiograms (74%), and 19 (95%) positive. TRAS-RS score was associated with subsequent performance of angiography and positive rate for TRAS (P < .01). CONCLUSION: Implementing a defined ultrasound screening tool with templated reporting for TRAS allowed for effective selection of those requiring an angiogram.

Short- and Long-term Outcomes of Kidney Transplants From Very Small (≤15 kg) Pediatric Donors With Acute Kidney Injury.

BACKGROUND: Kidneys from small deceased pediatric donors with acute kidney injury (AKI) are commonly discarded owing to transplant centers' concerns regarding potentially inferior short- and long-term posttransplant outcomes. METHODS: We retrospectively analyzed our center's en bloc kidney transplants performed from November 2007 to January 2015 from donors ≤15 kg into adult recipients (≥18 y). We pair-matched grafts from 27 consecutive donors with AKI versus 27 without AKI for donor weight, donation after circulatory death status, and preservation time. RESULTS: For AKI versus non-AKI donors, median weight was 7.5 versus 7.1 kg; terminal creatinine was 1.7 (range, 1.1-3.3) versus 0.3 mg/dL (0.1-0.9). Early graft loss rate from thrombosis or primary nonfunction was 11% for both groups. Delayed graft function rate was higher for AKI (52%) versus non-AKI (15%) grafts (P = 0.004). Median estimated glomerular filtration rate was lower for AKI recipients only at 1 and 3 months (P < 0.03). Graft survival (death-censored) at 8 years was 78% for AKI versus 77% for non-AKI grafts. Late proteinuria rates for AKI versus non-AKI recipients with >4 years follow-up were not significantly different. CONCLUSIONS: Small pediatric donor AKI impacted early posttransplant kidney graft function, but did not increase risk for early graft loss and decreased long-term function. The presently high nonutilization rates for en bloc kidney grafts from very small pediatric donors with AKI appear therefore unjustified. Based on the outcomes of the present study, we infer that the reluctance to transplant single kidneys from larger pediatric donors with AKI lacks a rational basis as well. Our findings warrant further prospective study and confirmation in larger study cohorts.

Sonographically Diagnosed Urothelial Thickening in Kidney Allografts: A Noninvasive and Clinically Highly Relevant Marker for the Detection of Acute Rejection.

OBJECTIVE. The objective of our study was to investigate the significance of sonographic features in assessing for acute kidney allograft rejection in the modern era. MATERIALS AND METHODS. In this retrospective study, 107 adult patients with a kidney allograft biopsy performed between 2015 and 2018 and diagnostic ultrasound performed within 2 weeks of the biopsy were included. Acute rejection was diagnosed on the basis of biopsy tissue sample results using the Banff criteria. The following ultrasound features were assessed: perfusion, cortical echogenicity, corticomedullary differentiation, urothelial thickening, change in renal length, renal artery velocity, and intraparenchymal arterial resistive index. Subjective measures of perfusion, echogenicity, corticomedullary differentiation, and urothelial thickening were assessed independently and in consensus by three abdominal radiologists; multirater kappa values were calculated for interobserver variability. The Wilcoxon rank sum test and chi-square test were used to evaluate the differences between two groups (rejection vs no rejection) and the sonographic features. Sensitivity, specificity, positive predictive value, and negative predictive value (NPV) were calculated for sonographic features that are associated with acute rejection. RESULTS. Of the sonographic features, only the presence of urothelial thickening was significantly associated with acute rejection (p < 0.001) and had substantial agreement (κ = 0.61) among readers. Urothelial thickening was highly sensitive (96%; 95% CI, 79-100%) with a high NPV (98%; 95% CI, 86-100%). CONCLUSION. Urothelial thickening on ultrasound is a highly sensitive finding for acute kidney rejection with a high NPV and thus may play a role in sonographic prebiopsy screening. Other historically associated sonographic features seem to play little, if any, role in the screening and assessment for kidney allograft rejection in the modern era.

Urologic complications after transplantation of 225 en bloc kidneys from small pediatric donors ≤20 kg: Incidence, management, and impact on graft survival.

Pediatric en bloc kidney transplants (EBKs) from small deceased pediatric donors are associated with increased early graft loss and morbidity. Yet, urologic complications post-EBK and their potential impact on graft survival have not been systematically studied. We retrospectively studied urological complications requiring intervention for 225 EBKs performed at our center January 2005 to September 2017 from donors ≤20 kg into recipients ≥18 years. Overall ureteral complication incidence after EBK was 9.8% (n = 22) (12% vs 2% for EBK donors < 10 vs ≥ 10 kg, respectively [P = .031]). The most common post-EBK urologic complication was a stricture (55%), followed by urine leak (41%). In all, 95% of all urologic complications occurred early within 5 months posttransplant (median, 138 days). Urologic complications could be successfully managed nonoperatively in 50% of all cases and had no impact on graft or patient survival. In summary, urologic complications after EBK were common, associated with lower donor weights, occurred early posttransplant, and were often amenable to nonoperative treatment, without adversely affecting survival. We conclude that the higher urologic complication rate after EBK (1) should not prevent increased utilization of small pediatric donor en bloc kidneys for properly selected recipients, and (2) warrants specific discussion with EBK recipients during the preoperative consent process.

Combined Ex Vivo Hypothermic and Normothermic Perfusion for Assessment of High-risk Deceased Donor Human Kidneys for Transplantation.

BACKGROUND: Despite careful clinical examination, procurement biopsy and assessment on hypothermic machine perfusion, a significant number of potentially useable deceased donor kidneys will be discarded because they are deemed unsuitable for transplantation. Ex vivo normothermic perfusion (EVNP) may be useful as a means to further assess high-risk kidneys to determine suitability for transplantation. METHODS: From June 2014 to October 2015, 7 kidneys (mean donor age, 54.3 years and Kidney Donor Profile Index, 79%) that were initially procured with the intention to transplant were discarded based on a combination of clinical findings, suboptimal biopsies, long cold ischemia time (CIT) and/or poor hypothermic perfusion parameters. They were subsequently placed on EVNP using oxygenated packed red blood cells and supplemental nutrition for a period of 3 hours. Continuous hemodynamic and functional parameters were assessed. RESULTS: After a mean CIT of 43.7 hours, all 7 kidneys appeared viable on EVNP with progressively increasing renal blood flow over the 3-hour period of perfusion. Five of the 7 kidneys had excellent macroscopic appearance, rapid increase in blood flow to 200 to 250 mL/min, urine output of 40 to 260 mL/h and increasing creatinine clearance. CONCLUSIONS: Favorable perfusion characteristics and immediate function after a 3-hour course of EVNP suggests that high-risk kidneys subjected to long CIT may have been considered for transplantation. The combined use of ex vivo hypothermic and normothermic perfusion may be a useful strategy to more adequately assess and preserve high-risk kidneys deemed unsuitable for transplantation. A clinical trial will be necessary to validate the usefulness of this approach.

Barriers to live and deceased kidney donation by patients with chronic neurological diseases: Implications for donor selection, donation timing, logistics, and regulatory compliance.

Live and deceased kidney donation by the numerous patients with advanced, progressive systemic neurological diseases, and other chronic neurological conditions (eg, high C-spine injury) remains largely unexplored. In a review of our current clinical practice, we identified multiple regulatory and clinical barriers. For live donation, mandatory reporting of postdonation donor deaths within 2 years constitutes a strong programmatic disincentive. We propose that the United Network for Organ Sharing should provide explicit regulatory guidance and reassurance for programs wishing to offer live donation to patients at higher risk of death during the reporting period. Under the proposal, live donor deaths within 30 days would still be regarded as donation-related, but later deaths would be related to the underlying disease. For deceased donation, donation after circulatory death (DCD) immediately following self-directed withdrawal of life-sustaining treatment ("conscious DCD") is not universally covered by existing DCD agreements with donor hospitals. Organ procurement organizations should thus systematically strive to revise these agreements. Obtaining adequate first-person consent from these communicatively severely impaired patients may be challenging. Optimized preservation and allocation protocols may maximize utilization of these DCD kidneys. Robust public debate and action by all stakeholders is necessary to lower existing barriers and maximize donation opportunities for patients with chronic neurological conditions.

Impact of Willingness to Accept Hepatitis C Seropositive Kidneys Among Hepatitis C RNA-Positive Waitlisted Patients.

BACKGROUND: Kidney transplantation from hepatitis C seropositive (HCV+) donors may benefit hepatitis C RNA-positive (RNA+) candidates, but it is unclear how the willingness to be listed for and accept such kidneys affects waitlist and transplant outcomes. METHODS: In a single-center retrospective analysis, HCV+ transplant candidates (N = 169) listed from March 2004 to February 2015 were evaluated. All RNA+ candidates were offered the option to be listed for HCV+ donors. RNA- candidates were listed only for HCV- donors. RESULTS: Fifty-seven patients (51% of all RNA+ transplant candidates) willing to accept HCV+ donors were listed for both HCV+ and HCV- donor kidneys. During 6-year follow up, 43 (75%) of 57 patients accepting HCV+ versus 19 (35%) of 55 patients not accepting HCV+ received a deceased donor kidney transplant (P < 0.0001). Multivariable analysis demonstrated that willingness to be listed for and accept HCV+ kidneys was associated with receiving deceased donor kidney transplant (P = 0.0016). Fewer patients accepting HCV+ donors (7 [12%] vs 16 [29%]) were removed from the list due to death or deteriorated medical condition (P = 0.0117). Posttransplant patient and graft survival rates were not significantly different. Overall patient survival since the listing (combined waitlist and posttransplant survival) was similar among the groups. CONCLUSIONS: HCV RNA+ candidates had better access to transplantation and similar overall survival before the era of widespread use of direct-acting anti-HCV agents.

Pediatric en bloc kidney transplantation from very small (≤10 kg) donation after circulatory death (versus brain death) donors: Single-center matched-pair analysis of 130 transplants.

En bloc kidney transplants (EBK) from very small pediatric donation after circulatory death (DCD) donors are infrequent because of the perception that DCD adversely impacts outcomes. We retrospectively studied 130 EBKs from donors ≤10 kg (65 consecutive DCD vs 65 donation after brain death [DBD] transplants; pair-matched for donor weight and terminal creatinine, and for preservation time). For DCD vs DBD, median donor weight was 5.0 vs 5.0 kg; median recipient age was 57 vs 48 years (P = .006). Graft losses from thrombosis (DCD, 5%; DBD, 7%) or primary nonfunction (DCD, 3%; DBD, 0%) were similar in both groups (P = .7). Delayed graft function rate was higher for DCD (25%) vs DBD (14%) (P = .2). Graft survival (death-censored) for DCD vs DBD at 5 years was 87% vs 91% (P = .3). Median estimated GFR (mL/min per 1.73 m2 ) was significantly lower for DCD recipients at 1 and 3 months; at 6 years it remained stable at 100 (DCD) and 99 (DBD). DCD impacted early posttransplant graft function, but did not appear to impart added risk for graft loss and long-term function. Very small (≤10 kg) DCD EBK donors should be considered as an option to augment the deceased kidney donor pool; larger studies with longer follow-up must confirm these findings.

Predonation Volume of Future Remnant Cortical Kidney Helps Predict Postdonation Renal Function in Live Kidney Donors.

Purpose To determine whether the predonation computed tomography (CT)-based volume of the future remnant kidney is predictive of postdonation renal function in living kidney donors. Materials and Methods This institutional review board-approved, retrospective, HIPAA-compliant study included 126 live kidney donors who had undergone predonation renal CT between January 2007 and December 2014 as well as 2-year postdonation measurement of estimated glomerular filtration rate (eGFR). The whole kidney volume and cortical volume of the future remnant kidney were measured and standardized for body surface area (BSA). Bivariate linear associations between the ratios of whole kidney volume to BSA and cortical volume to BSA were obtained. A linear regression model for 2-year postdonation eGFR that incorporated donor age, sex, and either whole kidney volume-to-BSA ratio or cortical volume-to-BSA ratio was created, and the coefficient of determination (R2) for the model was calculated. Factors not statistically additive in assessing 2-year eGFR were removed by using backward elimination, and the coefficient of determination for this parsimonious model was calculated. Results Correlation was slightly better for cortical volume-to-BSA ratio than for whole kidney volume-to-BSA ratio (r = 0.48 vs r = 0.44, respectively). The linear regression model incorporating all donor factors had an R2 of 0.66. The only factors that were significantly additive to the equation were cortical volume-to-BSA ratio and predonation eGFR (P = .01 and P < .01, respectively), and the final parsimonious linear regression model incorporating these two variables explained almost the same amount of variance (R2 = 0.65) as did the full model. Conclusion The cortical volume of the future remnant kidney helped predict postdonation eGFR at 2 years. The cortical volume-to-BSA ratio should thus be considered for addition as an important variable to living kidney donor evaluation and selection guidelines. © RSNA, 2018.

Vascular complications in kidney transplant recipients.

Vascular complications are a significant source of morbidity and mortality among renal transplant recipients. Imaging using ultrasound, CT, and MRI plays a key role in diagnosing such complications. This review focuses on the major vascular complications of renal grafts, which include transplant renal arterial and venous stenoses, arterial and venous thromboses, arteriovenous fistulas, and pseudoaneurysms. Etiology, diagnostic modalities useful for diagnosis, and imaging appearance will be presented.

Screening for Transplant Renal Artery Stenosis: Ultrasound-Based Stenosis Probability Stratification.

OBJECTIVE: The objective of our study was to evaluate which spectral Doppler ultrasound parameters are useful in patients with clinical concern for transplant renal artery stenosis (TRAS) and create mathematically derived prediction models that are based on these parameters. MATERIALS AND METHODS: The study subjects included 120 patients with clinical signs of renal dysfunction who had undergone ultrasound followed by angiography (either digital subtraction angiography or MR angiography) between January 2005 and December 2015. Five ultrasound variables were evaluated: ratio of highest renal artery velocity to iliac artery velocity, highest renal artery velocity, spectral broadening, resistive indexes, and acceleration time. Angiographic studies were categorized as either showing no stenosis or showing stenosis. Reviewers assessed the ultrasound examinations for TRAS using all five variables, which we refer to as the full model, and using a reduced number of variables, which we refer to as the reduced-variable model; sensitivities and specificities were generated. RESULTS: Ninety-seven patients had stenosis and 23 had no stenosis. The full model had a sensitivity and specificity of 97% and 91%, respectively. The reduced-variable model excluded the ratio and resistive index variables without affecting sensitivity and specificity. We applied cutoff values to the variables in the reduced-variable model, which we refer to as the simple model. Using these cutoff values, the simple model showed a sensitivity and specificity of 96% and 83%. The simple model was able to categorize patients into four risk categories for TRAS: low, intermediate, high, and very high risk. CONCLUSION: We propose a simple model that is based on highest renal artery velocity, distal spectral broadening, and acceleration time to classify patients into risk categories for TRAS.

Predictive assessment of kidney functional recovery following ischemic injury using optical spectroscopy.

Functional changes in rat kidneys during the induced ischemic injury and recovery phases were explored using multimodal autofluorescence and light scattering imaging. The aim is to evaluate the use of noncontact optical signatures for rapid assessment of tissue function and viability. Specifically, autofluorescence images were acquired in vivo under 355, 325, and 266 nm illumination while light scattering images were collected at the excitation wavelengths as well as using relatively narrowband light centered at 500 nm. The images were simultaneously recorded using a multimodal optical imaging system. The signals were analyzed to obtain time constants, which were correlated to kidney dysfunction as determined by a subsequent survival study and histopathological analysis. Analysis of both the light scattering and autofluorescence images suggests that changes in tissue microstructure, fluorophore emission, and blood absorption spectral characteristics, coupled with vascular response, contribute to the behavior of the observed signal, which may be used to obtain tissue functional information and offer the ability to predict posttransplant kidney function.

Learning Curve for Laparoendoscopic Single-Incision Live Donor Nephrectomy: Implications for Laparoendoscopic Practice and Training.

BACKGROUND: The learning curve for laparoendoscopic single-incision live donor nephrectomy, which is technically more complex than the multiport, conventional laparoendoscopic approach, is unknown. PATIENTS AND METHODS: In a retrospective cohort study, we analyzed the learning curve of the initial 114 consecutive single-incision laparoendoscopic nephrectomies performed in nonselected live kidney donors. RESULTS: Median donor body mass index was 26 kg/m2 (range 20-34). In all, 92% of the nephrectomies were performed on the left side; 18% of the recovered kidneys had multiple renal arteries. Cumulative sum (CUSUM) analysis of operating time (OT) demonstrated that the learning curve was achieved after case 61. For the learning curve phase (Group 1 [cases 1-61]) vs the postlearning phase (Group 2 [cases 62-114]), the difference of the mean OT was 20 minutes (p = 0.05). Mean warm ischemic time in the donors was significantly longer during the learning phase (Group 1, 6 minutes; Group 2, 5 minutes; p = 0.04). Rates of conversions to multiport procedures and of donor complications were not significantly different between Groups 1 and 2. For the recipients, we observed delayed graft function in 2 (2%) cases, no technical graft losses; and 1-year death-censored graft survival was 100% (p = n.s. for all comparisons of Group 1 vs 2). CONCLUSIONS: Single-incision laparoendoscopic donor nephrectomy had a long learning curve (>60 cases), but resulted in excellent donor and recipient outcomes. The long learning curve has significant implications for the programs and surgeons who contemplate transitioning from multiport to single-incision nephrectomy. Furthermore, our observations are highly relevant for informing the development of training requirements for fellows to be trained in single-incision laparoendoscopic nephrectomy.

Comparison of ferumoxytol-enhanced MRA with conventional angiography for assessment of severity of transplant renal artery stenosis.

PURPOSE: To determine the accuracy of ferumoxytol-enhanced magnetic resonance angiography (MRA) in assessing the severity of transplant renal artery stenosis (TRAS), using digital subtraction angiography (DSA) as the reference standard. MATERIALS AND METHODS: Our Institutional Review Board approved this retrospective, Health Insurance Portability and Accountability Act-compliant study. Thirty-three patients with documented clinical suspicion for TRAS (elevated serum creatinine, refractory hypertension, edema, and/or audible bruit) and/or concerning sonographic findings (elevated renal artery velocity and/or intraparenchymal parvus tardus waveforms) underwent a 1.5T MRA with ferumoxytol prior to DSA. All DSAs were independently reviewed by an interventional radiologist and served as the reference standard. The MRAs were reviewed by three readers who were blinded to the ultrasound and DSA findings for the presence and severity of TRAS. Sensitivity, specificity, and accuracy for identifying substantial stenoses (>50%) were determined. Intraclass correlation coefficients (ICCs) were calculated among readers. Mean differences between the percent stenosis from each MRA reader and DSA were calculated. RESULTS: On DSA, a total of 42 stenoses were identified in the 33 patients. The sensitivity, specificity, and accuracy of MRA in detecting substantial stenoses were 100%, 75-87.5%, and 95.2-97.6%, respectively, among the readers. There was excellent agreement among readers as to the percent stenosis (ICC = 0.82). MRA overestimated the degree of stenosis by 3.9-9.6% compared to DSA. CONCLUSION: Ferumoxytol-enhanced MRA provides high sensitivity, specificity, and accuracy for determining the severity of TRAS. Our results suggest that it can potentially be used as a noninvasive examination following ultrasound to reduce the number of unnecessary conventional angiograms. LEVEL OF EVIDENCE: 3 J. Magn. Reson. Imaging 2017;45:779-785.

Diagnosis and Management of Transplanted Kidney Extrarenal Pseudoaneurysms: A Series of Four Cases and a Review of the Literature.

Extrarenal pseudoaneurysms of transplanted kidneys are very rare but can have devastating consequences. In the past, these extrarenal pseudoaneurysms have often led to graft loss as well as significant morbidity and mortality. The role of advanced diagnostic imaging studies and of modern radiologic interventional management has not been studied. In this case series, we present four cases of extrarenal pseudoaneurysms of transplanted kidneys, describe the clinical scenarios and imaging that led to the angiographic diagnosis, and discuss the various endovascular and surgical approaches to management.

Incidences of acute kidney injury, dialysis, and graft loss following intravenous administration of low-osmolality iodinated contrast in patients with kidney transplants.

PURPOSE: To determine the incidence of acute kidney injury (AKI), need for emergent dialysis, and renal graft loss in patients with kidney transplants, who underwent CT examinations with low-osmolality iodine-based contrast material (IBCM). MATERIALS AND METHODS: Our institutional review board approved this retrospective Health Insurance Portability and Accountability Act compliant study. From January 2005 to April 2015, a total of 224 CT examinations were performed using low-osmolality IBCM in patients with kidney transplants. Six patients who had septic or cardiogenic shock and 30 patients with documented, failed transplants were excluded from our analysis, yielding a total of 188 examinations. Of these, pre- and post-CT serum creatinine (SCr) values were available for 104 examinations, to allow evaluation of AKI. The mean baseline SCr and estimated glomerular filtration rate (eGFR) in this subgroup were 1.37 mg/dL (median 1.18, range 0.5-6.05) and 65.8 mL/min/1.73 m2, respectively (median 65, range 9-114). AKI was defined as a rise in SCr of either (a) ≥0.3 mg/dL or (b) ≥0.5 mg/dL in the 24- to 72-h period following IBCM administration. For all patients undergoing the 188 examinations, need for dialysis and graft loss 30 days after contrast administration were evaluated. RESULTS: In patients with pre- and post-CT SCr values, the incidence of AKI was 7% (7/104) based on a rise of ≥0.3 mg/dL and 3% (3/104) based on a rise of ≥0.5 mg/dL. All three patients with the more strict definition (≥0.5 mg/dL) had a pre-CT eGFR <60 mL/min/1.73 m2. No patient required dialysis or had renal graft loss 30 days after contrast administration. CONCLUSION: The incidence of AKI after administration of low-osmolality IBCM administration in renal transplant recipients is low, with no instances of emergent dialysis or graft loss at 30 days post contrast.