Aorto-Iliac Artery Calcification and Graft Outcomes in Kidney Transplant Recipients

Impact of Pelvic Calcification Severity on Renal Transplant Outcomes: A Prospective Single-Center Study

Background: Vascular calcifications (VC) are increasingly prevalent in patients with chronic kidney disease. This study aimed to assess the incidence of iliac artery calcifications in kidney transplant (KT) patients and explore the relationship between iliac VC burden measured by pelvic calcification score (PCS) and renal transplant outcomes. Methods: This prospective study involved 79 KT recipients. VC quantification, using a pre-transplant computed tomography (CT) scan, was performed by assessing calcifications in the common and external iliac arteries bilaterally, resulting in an overall PCS ranging from 0 (no calcifications) to 44 (extensive calcifications). Based on PCS values, patients were divided into three equal-sized groups: PCS Group 1 (PCS 0-4), PCS Group 2 (PCS 5-19), and PCS Group 3 (PCS > 19). Post-transplant outcomes tracked for at least 1 year were patient and graft survival, graft function (urea, creatinine, MAG-3 clearance), and incidence of MACE during the first post-transplant year. Results: Calcifications were present in at least one arterial segment in 61 patients (77.2%). One-year patient survival was 95%, and one-year graft survival was 92.4%. Patients in PCS Group 3 had significantly lower one-year patient and graft survival compared to those in PCS Group 1 and 2 (p = 0.006 and p = 0.008, respectively). MACE and renal function indicators 1-year post-transplant were similar across all PCS groups. Conclusions: Our study demonstrated that a significant majority of KT recipients exhibited iliac VC during pre-transplant CT assessments. Patients in PCS Group 3 exhibited significantly lower one-year patient and graft survival rates compared to those in PCS Groups 1 and 2, indicating that this subgroup may require more intensive post-transplant monitoring and management.

Association of the Calcification Score of the Abdominal Aorta, Common Iliac, and Renal Arteries with Outcomes in Living Kidney Donors

BACKGROUND

Vascular calcification is an ever-more-common finding in protocoled pre-transplant imaging in living kidney donors. We intended to explore whether a connection could be found between the Agatston calcification score, prior to kidney donation, and post-donation renal function.

METHODS

This is a retrospective analysis of 156 living kidney donors who underwent living donor nephrectomy between January 2010 and December 2016. We quantified the total calcification score (TCaScore) by calculating the Agatston score for each vessel, abdominal aorta, common iliac, and renal arteries. Donors were placed into two different groups based on their TCaScore: <100 TCaScore group and ≥100 TCaScore group. The relationship between TCaScore, 1-year eGFR, proteinuria, and risk of 1 measurement of decreased renal function (eGFR < 60 mL/min/1.73 m²) over 5 years of follow-up was investigated.

RESULTS

The ≥100 TCaScore group consisted of 29 (19%) donors, with a median (interquartile range) calcification score of 164 (117-358). This group was significantly older, 56.7 ± 6.9 vs. 45.5 ± 10.6 (p < 0.001), had a higher average BMI (p < 0.019), and had a lower preoperative eGFR (p < 0.014). The 1-year eGFR was similarly diminished, 69.9 ± 15.7 vs. 76.3 ± 15.5 (p < 0.048), while also having an increased risk of decreased renal function during the follow-up, 22% vs. 48% (p < 0.007).

CONCLUSIONS

Our study, through univariate analyses, found a relationship between a TCaScore > 100, lower 1-year eGFR, and decreased renal function in 5 years. However, a higher-than-expected vascular calcification should not be an excluding factor in donors, although they may require closer monitoring during follow-up.

Ipsilateral Aorto-Iliac Calcification is Not Directly Associated With eGFR After Kidney Transplantation: A Prospective Cohort Study Analyzed Using a Linear Mixed Model

Aorto-iliac calcification (AIC) is a well-studied risk factor for post-transplant cardiovascular events and mortality. Its effect on graft function remains unknown. The primary aim of this prospective cohort study was to assess the association between AIC and estimated glomerular filtration rate (eGFR) in the first year post-transplant. Eligibility criteria were: ≥50 years of age or ≥30 years with at least one risk factor for vascular disease. A non-contrast-enhanced CT-scan was performed with quantification of AIC using the modified Agatston score. The association between AIC and eGFR was investigated with a linear mixed model adjusted for predefined variables. One-hundred-and-forty patients were included with a median of 31 (interquartile range 26-39) eGFR measurements per patient. No direct association between AIC and eGFR was found. We observed a significant interaction between follow-up time and ipsilateral AIC, indicating that patients with higher AIC scores had lower eGFR trajectory over time starting 100 days after transplant (p = 0.014). To conclude, severe AIC is not directly associated with lower post-transplant eGFR. The significant interaction indicates that patients with more severe AIC have a lower eGFR trajectory after 100 days in the first year post-transplant.

Atherosclerosis and Intrarenal Resistance Index in Kidney Transplant Recipients

Atherosclerosis of the aortoiliac vessels can adversely affect kidney perfusion after kidney transplantation. Atherosclerosis severity can be determined using the calcium score (CaScore). Potential problems with posttransplantation kidney perfusion can be determined using the intrarenal resistance index (RI). This study investigated the association between aortoiliac CaScore and RI in kidney transplant recipients.

Methods

Kidney transplant recipients (2004-2019), for whom the CaScore and RI were determined, were included in this dual-center cohort study. CaScore was measured in 3 aortoiliac segments using noncontrast CT imaging. RI was determined using Doppler ultrasound. Multivariable linear regression analyses were performed between the CaScore and RI, adjusted for confounding variables.

Results

The mean age of the 389 included patients was 59 (±13) y. The mean RI (unitless) was 0.71 (±0.09)' and the median CaScore (unitless) was 3340 (399-7833). In univariable linear regression analyses with RI as the dependent variable, CaScore (β = 0.011; P < 0.001) was positively associated with RI. Moreover, recipient age (β = 0.014; P < 0.001), history of diabetes (β = 0.029; P = 0.003), recipient history of vascular interventions (β = 0.032; P = 0.002), prior dialysis (β = 0.029; P = 0.003), deceased donor transplantation (β = 0.042; P < 0.001), donation after cardiac death (β = 0.036; P = 0.001), an increase in cold ischemia time (β = 0.011; P < 0.001), and the Comprehensive Complication Index (β = 0.006; P = 0.002) were also positively associated with RI, whereas preoperative recipient diastolic blood pressure (β = -0.007; P = 0.030) was inversely associated. In multivariable analyses, CaScore and RI remained significantly (P = 0.010) associated, independent of adjustment for potential confounders. Furthermore, in univariable linear regression analyses, multiple graft function characteristics were associated with RI.

Conclusions

A significant association was found between CaScore and RI, independent of adjustment for multiple potential confounding factors, leading to a better insight into the development and interpretation of RI. Aortoiliac atherosclerosis should be considered when interpreting the RI and determining the possible cause of malperfusion and graft failure after kidney transplantation.

A CT-based pelvic calcification score in kidney transplant patients is a possible predictor of graft and overall survival

OBJECTIVES

Computerized tomography (CT) is the most accurate method for evaluating pelvic calcifications, which are of utmost importance for planning kidney transplantation (KT). The aim of our study was to evaluate the incidence and distribution of iliac artery calcifications and correlate the novel pelvic calcification score (PCS) with cardiovascular risk factors and graft and overall survival in KT patients.

METHODS

We retrospectively included 118 KT patients operated at our institution with pretransplant pelvic CT. Calcification morphology, circumference and length of both common and external iliac arteries were independently scored by two uroradiologists. PCS was calculated as the total score sum of all three calcification features in all vessels. PCS correlation with graft and patient survival was performed.

RESULTS

Calcification in at least one vascular segment was found in 79% of patients. PCS was significantly higher in male patients (p = 0.006), patients over 55 years (p < 0.001), and patients on haemodialysis (p = 0.016). Patients with a PCS >3 had significantly shorter graft and overall survival rates (p = 0.041 and p = 0.039, respectively).

CONCLUSIONS

The extent of iliac artery calcification in KT recipients quantified by PCS on pretransplant CT correlates with graft and overall patient survival. A PCS over three was associated with worse clinical outcomes and could become a possible prognostic factor.

ADVANCES IN KNOWLEDGE

Our novel PCS is a robust method for quantifying iliac artery calcification burden. Since higher a PCS correlates with worse patient and graft survival, PCS has the potential to become a prognostic factor in kidney transplant patients.

Association of Abdominal Arterial Calcification Score with Patients' Survival and Kidney Allograft Function after Kidney Transplant

BACKGROUND

Abdominal arterial calcification (AAC) is common among candidates for kidney transplant. The aim of this study is to correlate AAC score value with post-kidney transplant outcomes.

METHODS

We modified the coronary calcium score by changing the intake data points and used it to quantitate the AAC. We conducted a retrospective clinical study of all adult patients who were transplanted at our center, between 2010 and 2013, and had abdominal computed tomography scan done before transplantation. Outcomes included mortality, pulse pressure (PP) measured by 24 h ambulatory blood pressure monitoring system, and kidney allograft function measured by iothalamate clearance.

RESULTS

For each 1000 increase of AAC score value, there is an associated 1.05 increase in the risk of death (95% CI 1.02, 1.08) (p < 0.001). Overall median AAC value for all patients was 1784; Kaplan-Meier curve showed reduced survival of all-cause mortality for patients with AAC score value above median and reduced survival among patients with cardiac related mortality. The iothalamate clearance was lower among patients with total AAC score value above the median. Patients with abnormal PP (< 40 or > 60 mmHg) had an elevated median AAC score value at 4319.3 (IQR 1210.4, 11097.1) compared to patients with normal PP with AAC score value at 595.9 (IQR 9.9, 2959.9) (p < 0.001).

CONCLUSION

We showed an association of AAC with patients' survival and kidney allograft function after kidney transplant. The AAC score value could be used as a risk stratification when patients are considered for kidney transplant.