Transplant Kidney Research Articles

Association of COVID-19 With Risk of Posttransplant Diabetes Mellitus.

Posttransplant diabetes mellitus (PTDM) is an important complication for solid organ transplant recipients (SOTRs). COVID-19 has been associated with an increased risk of incident diabetes in the general population. However, the association between COVID-19 and new-onset PTDM has not been explored. Using the National COVID Cohort Collaborative Enclave, we conducted a cohort study of adults without diabetes receiving a solid organ transplant (heart, lung, kidney, or liver) in the United States between April 1, 2020, and March 31, 2023, with and without a first diagnosis of COVID-19 (COVID+ versus COVID-) within 180 d of SOT. We propensity score matched a single COVID+ SOTR with a COVID- SOTR who was diabetes free at the same point posttransplant. Within this matched cohort, we used multivariable Cox proportional hazards models to examine the adjusted risk of PTDM associated with COVID+. Among 1342 COVID+ SOTRs matched to 1342 COVID- SOTRs, the crude rate of newly diagnosed PTDM in the 2 y post-COVID was 17% in those with versus 13% in those without COVID-19 (P = 0.007). COVID-19 was significantly associated with new PTDM (adjusted hazard ratio, 1.37; 95% confidence interval, 1.12-1.68 at 2 y). Similar to other viral infections, COVID-19 is associated with an increased risk of PTDM in SOTRs.

Subureteric injection for the treatment of vesicoureteral reflux in transplant kidneys.

Treatment of de novo vesicoureteral reflux (VUR) into the transplanted kidney constitutes a clinical challenge. Herein, we present our data on patients who underwent endoscopic subureteric injection for the treatment of VUR following renal transplantation (RT) in our center. The patients who underwent endoscopic subureteric injection for VUR into the transplanted kidney after RT in our department between 2008 and 2023 were reviewed retrospectively. Indication for subureteric injection, age, gender, laterality, number of injections, amount of material used, renal failure etiology, auxiliary procedures, and treatment success were noted. All interventions were performed by pediatric urologists who also perform RT. During a median followup of 27.5 (4-160) months, 22 patients (17 women, 77.2%) and 23 transplanted ureters (13 right, eight left, one bilateral) were treated with subureteric injections. In all patients, the indications for subureteric injection were recurrent febrile urinary tract infection (UTI), and the grades of VUR varied between I and IV. Patients received a median of 1.65 cc (0.7-2.7) dextranomer-hyaluronic acid copolymer. In total, 10 RTs (eight from living donors, two from cadaveric donors) were performed in another center, whereas 13 RTs were carried out in our center (eight from cadaveric donors and five from living donors). Among the patients who were transplanted in our center, the rate of subureteric injections due to de novo symptomatic VUR after RT was 2.2% (13/593 patients). After subureteric injections, five patients required a second injection due to the recurrence of VUR. Ureteroureterostomy (to the native ureter) was performed in two patients who had further UTIs after the second endoscopic treatment. Eventually, 19/21 patients (90.4%) benefited clinically from the endoscopic treatment and none of the patients underwent re-do ureteroneocystostomy. It is noteworthy that the etiology of renal failure was VUR nephropathy in seven (31.8%) patients. Subureteric injection provides a high clinical success for the treatment of de novo VUR after RT.

Treatment of Renal Capsule Lesion in a Transplanted Kidney: A Case Report and Literature Review

Expanded donor criteria have been established to reduce organ wastage, as various factors can lead the disposal of kidneys, such as anatomical abnormalities, traumatic injuries, and iatrogenic injuries during organ retrieval surgery. We report a case of kidney transplantation in which a capsular lesion was identi!ed and repaired during organ preparation (back table) and review of the literature regarding transplant kidney injuries. A diabetic and hypertensive 52-year-old patient with chronic kidney disease undergoing dialysis therapy for 2 years was admitted for a deceased donor kidney transplant. "e donor was a 35-year-old man with brain death secondary to traumatic brain injury in a car accident. During the kidney preparation on the back table, a capsular lesion was visualized on the upper pole of the right kidney. Continuous suture of the renal capsule was performed using a 3-0 CatGut suture to correct the defect and reconstruct the renal surface. After renal reperfusion, no active bleeding was observed from the sutured area. "e patient had a good postoperative course with no complications. "e main complications associated with capsular lesions and complete capsular denudation are bleeding and hematoma formation, as well as urinary and lymphatic extravasation through the exposed renal parenchyma. Treatment may involve direct cauterization using electrocautery or argon plasma, or the use of hemostatic agents. Successful repair of capsular lesions not only prevents complications such as bleeding during reperfusion and urinary !stulae but also plays a crucial role in expanding the pool of organs available for transplantation.

Tips for percutaneous nephrolithotomy for transplant kidney stone

IntroductionThe management of urinary tract stones, particularly de novo kidney allograft stones, presents unique challenges for kidney transplant recipients because of their prevalence and specific clinical considerations. Here, we describe a case in which percutaneous nephrolithotomy was successfully used to fragment a large kidney allograft stone ≥20 mm in size.Case presentationA 57‐year‐old woman who underwent ureteroureterostomy post simultaneous pancreas–kidney transplantation presented with gross hematuria after 15 years. Computed tomography revealed a 23‐mm stone in the transplanted kidney. Initial attempts at endoscopic combined intrarenal surgery were changed to percutaneous nephrolithotomy because of poor ureter mobility and tortuosity. Stone fragmentation was achieved using pneumatic and ultrasonic lithotripsy. A second procedure using Swiss LithoClast® Trilogy enabled complete stone clearance and ureteral stent placement.ConclusionBy understanding the peculiarities of the percutaneous approach, we demonstrated the safe and effective use of a pneumatic and ultrasonic lithotripter for kidney allograft stone fragmentation.

Evaluating different methods for kidney recellularization

This study explores a potential solution to the shortage of kidneys for transplantation in end-stage renal disease (ESRD). Currently, kidney transplantation stands as the optimal option, yet the scarcity of organs persists. Employing tissue engineering, researchers sought to assess the feasibility of generating kidneys for transplantation. Pig kidneys were utilized since they possess higher similarities to human kidneys. Cells were removed via decellularization, which maintains the organ’s microarchitecture. Subsequently, pig kidney cells and human red blood cells were perfused into the vacant kidney structure to reconstitute it. The methodologies employed showed promising results, suggesting a viable approach to increase the recellularization rate in whole pig kidneys. This proof-of-concept establishes a groundwork for potentially extending this technology to human kidneys, tackling the organ shortage, thus positively enhancing outcomes for ESRD patients by increasing the availability of transplantable organs.

BK Virus Nephropathy After Kidney Transplantation and Its Diagnosis Using Urinary Micro RNA

BK virus-associated nephritis (BKVAN) is an important cause of graft loss in renal transplant recipients B K viremia occurs in up to 30% of renal transplant recipients. Since the discovery of BKV in 1971, effective prophylaxis and treatment have not been established, and it is not uncommon for a transplant kidney to be lost without cure of BKVAN. BK virus infection is reactivated when cellular immunity is suppressed, which is often during the first year after kidney transplantation when cellular immunity is most suppressed. Clinically, it is caused by reactivation of latent infection or new infection from the donor kidney, leading to viremia, viremia, and transplant nephropathy. BK virus nephropathy is currently diagnosed definitively by measuring the amount of BK virus DNA in the blood and proving SV40-positive cells in transplant kidney tissue obtained by transplant kidney biopsy, but the time required for diagnosis and the low sensitivity of immunohistochemistry using antibodies are problematic. Therefore, we investigated whether the diagnosis of BK virus nephropathy could be made earlier by searching for miRNAs in the urine of renal transplant recipients.

Application of Mixed Reality Technology in the Planning of PCNL for Special Types of Complex Upper Urinary Stones: A Pilot Study

ObjectiveTo evaluate the application of Mixed Reality technology in the planning of ultrasound-guided PCNL for special types of complex upper urinary stones. MethodsClinical data of 15 patients with complex upper urinary stones undergoing ultrasound-guided PCNL were analysed which included pelvic ectopic kidney, horseshoe kidney, spinal deformity, and transplant kidney. Based on preoperative CTU data, digital three-dimensional reconstruction is performed, and AI mixed reality is used to project three-dimensional images in real space. This facilitates preoperative design and planning. The consistency rate of target calyx and channel numbers, stone free rate, total operative time, percutaneous renal access establish time, decrease in hemoglobin level, surgical complications, and postoperative hospital stay are analyzed. ResultsAll patients underwent preoperative planning using mixed reality and successfully completed PCNL. Based on the preoperative planning, we utilized S-PCNL alone or combined with Needle-perc or antegrade/retrograde FURS. The consistency rate between preoperative planning and intraoperative completion was 87.6%. The stone free rate was 80%. The average time for establishing the main tract was 2.3±0.3 minutes, and the average total operative time was 61.5±12.2 minutes. The mean decrease in hemoglobin level was 9.6±1.2 g/L, and the average postoperative hospital stay was 4.6±0.5 days. There were no occurrences of Clavien-Dindo grade≥II complications. ConclusionPreoperative quantification and analysis of imaging data through mixed reality enable three-dimensional visualization and facilitate surgical plans, and effectively avoid the risks of surrounding organ injury in these special urinary stones cases, make complex surgeries smoother and more controllable.

Simultaneous Liver-Kidney Transplant vs. Safety Net Kidney after Liver Transplant: How Has the Policy Change Impacted Graft and Patient Outcomes?

Simultaneous Liver-Kidney Transplant vs. Safety Net Kidney after Liver Transplant: How Has the Policy Change Impacted Graft and Patient Outcomes?

Incidence of Glomerulonephritis and Clinical Outcomes of Kidney Biopsy Patients at the National and Transplant Kidney Institute, 2016-2022

Incidence of Glomerulonephritis and Clinical Outcomes of Kidney Biopsy Patients at the National and Transplant Kidney Institute, 2016-2022

Early and Late Microvascular Inflammation Have Differing Etiological Causes and Clinical Expression.

Microvascular inflammation (MVI) is an important pathological feature of antibody-mediated rejection (AMR). How posttransplant time affects its clinicopathological expression is little understood. This retrospective, single-center study screened 3398 kidney transplant biopsies and dichotomized 202 MVI ≥ 2 (Banff glomerulitis + peritubular capillaritis ≥ 2) samples by 9-mo median incidence time for comparison. The prevalence of MVI ≥ 2 was 12.4% in transplant kidneys, which failed more frequently than propensity-matched normal controls (n = 202; P < 0.001). Epidemiological risk factors for early MVI ≥ 2 were delayed graft function, prior AMR, and circulating donor-specific antibodies (DSAs+). Prior recipient sensitization occurred in 72.3%. Early MVI ≥ 2 was classified AMR in 65.3% and cellular rejection in 34.7%, and demonstrated excellent functional recovery and graft survival comparable to normal control kidneys. Late MVI ≥ 2 was predicted by younger (18 = 29 y) age, female recipient, living-donation, prior methylprednisolone, cyclosporine (versus tacrolimus, levels <5 ng/mL), absent antiproliferative therapy, and DSA+ using multivariable epidemiological modeling. Nonadherence caused 49.5%, with iatrogenic minimization responsible for 47.5%, usually for recipient infection. Late MVI ≥ 2 was because of AMR in 93.1%, and characterized by greater interstitial fibrosis, tubular atrophy, complement degradation split-product 4d (C4d) staining of peritubular capillaries+, endothelial C4d staining of glomerular capillaries+, transplant glomerulopathy and vasculopathy scores, DSA strength, and graft failure than early MVI ≥ 2 or normal transplant kidneys. Death-censored graft survival in 149 unique MVI ≥ 2 kidneys was independently determined by nonadherence, serum creatinine, proteinuria, DSA+, Banff C4d staining of peritubular capillaries+, and chronic interstitial fibrosis scores. MVI score and time lost significance using multivariable Cox regression. The changing expression of MVI ≥ 2 over time is best explained by differences in underimmunosuppression and microvascular injury from AMR impacting allograft function and survival.

Association between pre-heart transplant kidney function and post-transplant outcomes in Black and White adults.

It remains unknown whether estimated glomerular filtration rate (eGFR) using the refit Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation without a term for race is associated with mortality and the need for kidney replacement therapy (KRT) differentially between Black and White heart transplant recipients. We studied 25,900 adults included in the Scientific Registry of Transplant Recipients. We classified recipients into six categories of eGFR (< 30, 30 to < 45, 45 to < 60, 60 to < 90, 90 to < 120, ≥ 120ml/min/1.73 m2) using the race-neutral CKD-EPI refit equation, and assessed survival with multivariable adjusted Cox proportional hazards regression. The association between pre-transplant race-neutral eGFR and mortality varied by race (Pinteraction = 0.006). Compared to White patients with an eGFR of 90-120ml/min/1.73 m2, the mortality rates were 57% (95% CI 1.25, 1.98), 29% (95% CI 1.11, 1.51), 34% (95% CI 1.19, 1.52), and 19% (95% CI 1.06, 1.33) higher in Black patients with an eGFR less than 30, 30-45, 45-60, and 60-90ml/min/1.73m2, respectively; and 53% (95% CI 1.28, 1.82), 49% (95% CI 1.33, 1.66), and 23% (95% CI 1.11, 1.35) higher among White patients with an eGFR less than 30, 30-45, and 45-60ml/min/1.73 m2, respectively. The association between pre-transplant eGFR and the need for KRT during follow-up was similar between Black and White patients (Pinteraction = 0.57). Worsening pre-transplant eGFR using the new race-neutral CKD-EPI refit equation was associated with a higher rate of post-heart transplant mortality and KRT in Black and White recipients. The racial disparity in post-heart transplant mortality was narrower in the setting of severe kidney dysfunction.

320.4: Are we ready to use neonatal kidneys for transplantation?

320.4: Are we ready to use neonatal kidneys for transplantation?

P.030: Evaluation of relationship between CD68-positive macrophages and clinical and laboratory parameters in kidney transplant recipients who experienced transplant kidney biopsy.

P.030: Evaluation of relationship between CD68-positive macrophages and clinical and laboratory parameters in kidney transplant recipients who experienced transplant kidney biopsy.

Knowledge and willingness to donate kidney for transplantation among general population in Saudi Arabia

IntroductionKidney transplantation is the preferred treatment for end-stage renal disease (ESRD), offering a superior quality of life and extended survival compared to other renal replacement therapies. As the number of ESRD patients grows, so does the demand for organ transplants. The prevalence of ESRD is anticipated to escalate further due to the rising rates of diabetes mellitus (DM), hypertension (HTN), and obesity. Organ donation, particularly from living donors, remains the main source of transplants in the region, despite the notable underutilization of potential deceased donors’ organs. The objective of this research is to assess the level of knowledge, attitudes, and willingness to donate kidneys among the general population, a pivotal step in addressing the organ shortage crisis.MethodsThis cross-sectional study was conducted in the Aseer region of Saudi Arabia using a previously validated questionnaire. The questionnaire collected demographic data and insights into general attitudes, knowledge, and beliefs about organ donation. Logistic regression was used to identify predictors of knowledge and willingness to donate.ResultsThe study involved 705 participants, predominantly young adults with a high level of education. Awareness of kidney donation was high, and knowledge about donation was broad, especially regarding religious permissibility and awareness of the donor registry. However, only 25% expressed willingness to donate their kidneys, and a 4% were already registered as donors. Furthermore, higher educational level was not associated with higher odds of knowledge or willingness to donate.ConclusionDespite the considerable awareness, actual donor registration rates were low, highlighting the necessity for targeted educational interventions and a deeper understanding of the cultural and socioeconomic barriers that exist.

Assessment of hemodynamic and blood parameters that may reflect macroscopic quality of porcine kidneys during normothermic machine perfusion using whole blood

PurposeUsing ex vivo normothermic machine perfusion (NMP) with whole blood we assessed marginal porcine kidneys under reperfusion. The aim was to link measureable machine and clinical blood parameters with the currently used visual assessment. This could serve as a baseline for a standardized evaluation score to identify potentially transplantable kidneys in the future.MethodsKidneys and autologous whole blood were procured from slaughterhouse pigs (n = 33) and were perfused for 4 h using NMP. The hemodynamic parameters arterial pressure (AP), renal blood flow (RBF) and intrarenal resistance (IRR) were measured. Activity of aspartate transaminase (AST), gamma-glutamyltransferase (GGT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH) and lactate were assessed in blood at 0/1/2/4 h. Kidneys were grouped into “potentially transplantable” (PT) or “not transplantable” (NT) based on their overall macroscopic appearance after NMP by an experienced physician.ResultsPT-kidneys (n = 20) had a significantly lower IRR and higher RBF than NT-kidneys (n = 13). GGT, ALP and LDH did not differ significantly, but at 4 h, AST was significantly higher in PT-kidneys compared to NT-kidneys. Lactate levels kept increasing during NMP in NT-kidneys and were significantly higher at 1/2/4 h than in PT-kidneys.ConclusionThe immediately assessed macroscopic aspects of examined kidneys correlated with hemodynamic parameters, increased lactate and lower AST in this study. In the future, NMP with whole blood could be a useful tool to extend the donor pool by allowing the assessment of otherwise unknown characteristics of marginal kidneys before transplantation.

Impact of intra-patient variability of tacrolimus on allograft function and CD4 + /CD8 + ratio in kidney transplant recipients: a retrospective single-center study.

Tacrolimus is a critical component of immunosuppressive therapy for kidney transplant recipients. Intra-patient variation (IPV) of tacrolimus levels affects the function of transplanted kidney. This study aimed to investigate the impact of tacrolimus IPV on kidney function, examine its association with post-transplant duration, and assess its effect on the immune status of transplant recipients. This retrospective study was conducted from January 2016 to February 2022. IPV was evaluated using the coefficient of variation (CV) of tacrolimus trough levels from 6 to 48months after transplantation. Patients were divided into low- and high-IPV groups based on the median CV. Significant differences in kidney function, CD4 + /CD8 + ratio, and post-transplant duration between these groups were analyzed. Among 189 patients, tacrolimus IPV showed a strong correlation with serum creatinine clearance rate (Ccr) and estimated glomerular filtration rate (eGFR) (p < 0.05). Tacrolimus IPV was significantly correlated with post-transplant duration in only two patients (p < 0.05). Using a median CV of 15.4% to categorize patients, the high IPV group, compared to the low IPV group, exhibited significantly higher eGFR at 6-9months (p < 0.05), lower Ccr at 9-12months (p < 0.05), and reduced Ccr and eGFR at 15-18months (p < 0.05). Six months after transplantation, the high IPV group had a significantly lower CD4 + /CD8 + ratio than the low IPV group (p < 0.05). This study highlights the significant impact of tacrolimus IPV on transplant kidney function and immune status in transplant patients at various post-transplantation intervals.

Cognitive Impairment in Liver Tranplant Recipients: A Cross-Sectional Study.

The proportion of older transplant recipients has increased. Cognitive impairment is not rare after kidney transplant, but data on this issue in liver transplant recipients are scarse. In this cross-sectional study, we evaluated all liver transplant recipients from a single center in Brazil from July 2018 to June 2020 in terms of cognitive performance to determine the prevalence of neurocognitive disorder. We compared liver transplant recipients with neurocognitive disorder with liver transplant recipients without neurocognitive disorder. We also compared those with an alcoholic cause of liver transplant with other patients. The presence of depressive symptoms was assessed. We performed correlations of clinical data with cognitive scores. In a sample of 100 recipients with median age of 62 years (interquartile range, 56.2-69 y), neurocognitive disorder was present in 21% of the group. Patients with cognitive impairment were older (68 y [61-72] vs 61 y [52-68]; P = .019) and had a trend to higher proportion of persistent kidney injury (33.3% vs 13.9%; P = .055) versus patients without cognitive impairment. Recipients with alcoholic cause of liver transplant exhibited worse cognitive performance in the Mini-Mental State Examination (score of 26 [23.7-28.2] vs 28 [26-29]; P = .024) and the Alzheimer Disease Assessment Scale-cognitive (score of 10.4 [8.6-14.2] vs 8 [6.3-10]; P = .008) than other patients. Weak negative correlations were shown in cognitive performance scores versus recipient age (Semantic Verbal Fluency test, r = -0.334 [P = .001]; Clock Drawing test, r = -0.209 [P = .037]; Alzheimer Disease Assessment Scale-cognitive, r = -0.323 [P = .001]). Neurocognitive disorder was common in liver transplant recipients, in part due to increased age. This study also suggested a role for alcoholic cause of liver transplant and persistent kidney injury in the development of cognitive impairment.

Potential kidney donors among patients with out-of-hospital cardiac arrest and a termination of resuscitation rule

ImportanceUncontrolled donation after circulatory determination of death (uDCD) has been developed and can serve as a source of kidneys for transplantation, especially when considering patients that meet extended criteria donation (ECD). ObjectiveThis study assessed the theorical size and characteristics of the potential pool of kidney transplants from uDCD with standard criteria donation (SCD) and ECD among patients who meet Termination of Resuscitation (TOR) criteria following Out of Hospital Cardiac Arrest (OHCA). Methods and participantsThis study focused on adult patients experiencing unexpected OHCA, who were prospectively enrolled in the Parisian registry from May 16th, 2011, to December 31st, 2020. ResultsDuring the study period, EMS attempted resuscitation for 19,976 OHCA patients, of which 64.5% (12,890) had no return of spontaneous circulation. Among them, 47.4% (9,461) had TOR criteria, representing no chance of survival, and from them, 8.8% (1,764) met SCD criteria and could be potential organ donors and 33.6% (6,720) met ECD for kidney donors. The mean potential number per year of uDCD candidates with SCD and ECD remain stable respectively around 98 (±10.8) and 672 (±103.8) cases per year. Elderly patients (≥65 y.o.) represented 61.2% (n = 5,763/9,461) of patients who met TOR and 100% (5763/5763) of patients who could have matched both ECD criteria and TOR. Conclusion and relevanceImplementing uDCD program including SCD and ECD for kidney transplantation among OHCA cases quickly identified by the TOR, holds significant potential to substantially broaden the pool of organ donors. These programs could offer a viable solution to address the pressing burden of kidney shortage, particularly benefiting elderly recipients who may otherwise face prolonged waiting times and limited access to suitable organs.

Sonological predictors of complications of percutaneous renal biopsy—a prospective observational study

Percutaneous renal biopsy, although essential for renal disease diagnosis, is associated with a number of post-biopsy complications ranging from gross haematuria to AV fistula to death. In this study, we carried out an active haematoma surveillance and attempted to correlate renal sonological parameters—kidney length, renal parenchymal changes, renal cortical and parenchymal thickness for their potential use in prediction of post-renal biopsy complications.MethodsThis was a prospective study done from April 2022 to April 2023 on all adult patients undergoing native or transplant kidney biopsy. Baseline clinical, laboratory and renal sonological parameters were noted prior to biopsy. USG-guided renal biopsy was done and any haematoma at 0 h, 12 h and 24 h post-biopsy noted. Biopsy complications including need for any interventions were noted.ResultsOut of the 240 patients enrolled in the study, 58.3% experienced post-biopsy complications. Among these, 5% of patients encountered major complications, with 3.33% necessitating medical intervention following renal biopsy procedures. A high percentage, 98.89%, exhibited hematoma formation within 12 h post-biopsy. Furthermore, our analysis revealed that a hematoma size exceeding 1.2 cm at the 12-h mark exhibited a sensitivity of 100% and specificity of 71% in predicting the need for blood transfusion. Renal parenchymal changes were the most reliable sonological parameters for predicting post-biopsy complication on multivariate analysis.ConclusionThe incidence of major complications requiring interventions following renal biopsy is notably low. Our study highlights the significance of renal sonological characteristics, including parenchymal thickness, cortical thickness and parenchymal changes, in predicting these complications. Furthermore, we emphasize the utility of hematoma surveillance immediately post-biopsy and at the 12 h, as a valuable tool for predicting the necessity of post-biopsy interventions. This approach can aid in efficiently triaging patients and determining the need for further observation post-renal biopsy.

Age- and Sex-Specific Myocardial Blood Flow Values in Patients Without Coronary Atherosclerosis on Rb-82 PET Myocardial Perfusion Imaging.

Quantitative myocardial blood flow (MBF) on positron-emission tomography myocardial perfusion imaging is a measure of the overall health of the coronary circulation. The ability to adequately augment blood flow, measured by myocardial blood flow reserve (MBFR), is associated with lower major adverse cardiovascular events and all-cause mortality. The age-specific ranges of MBFR in patients without demonstrable coronary artery disease have not been well established. We aimed to determine the effect of age and sex on MBF in a cohort of patients without demonstrable coronary artery disease. Patients who underwent positron-emission tomography myocardial perfusion imaging studies from 2012 to 2022 on positron-emission tomography/computed tomography cameras were included if the summed stress score was 0, the coronary calcium score was 0, and the left ventricular ejection fraction was ≥50%. Those with known coronary artery disease, prior history of coronary intervention, diabetes, heart/kidney/liver transplant, cirrhosis, or chronic kidney disease stage IV+ were excluded. MBF was calculated using a net retention model (ImagenQ, Cardiovascular Imaging Technologies, Kansas City), and quantile regression models were developed to predict MBF. Among 2789 patients (age 59.9±13.0 years, 76.4% females), median rest MBF was 0.73 (0.60-0.91) mL/min·g, stress MBF was 1.72 (1.41-2.10) mL/min·g, and MBFR was 2.31 (1.96-2.74). Across all ages, males augmented MBF in response to vasodilator stress to a greater degree than females but achieved lower absolute stress MBF. Younger males in particular achieved a higher MBFR than their female counterparts, and this gap narrowed with increasing age. Predicted MBFR for a 20-year-old male was 3.18 and female was 2.50, while predicted MBFR for an 80-year-old male was 2.17 and female was 2.02. In patients without demonstrable coronary artery disease, MBFR is higher in younger males than younger females and decreases with age in both sexes. Age- and sex-specific MBFR may be important in risk prediction and guidance for revascularization and warrant further study.