Vascular Calcifications in Kidney Transplant Recipient

Overview

Kidney transplant candidates undergo extensive diagnostic evaluation aimed at assessing their cardiovascular (CV) risk, which remains the leading cause of disability and death in this patient population. This includes among others an assessment of the iliac arterial calcification. Chronic kidney disease (CKD) patients have an increased incidence of arterial calcifications due to many factors, such as increased age, hyperparathyroidism, diabetes mellitus and hypercholesterolemia. Furthermore, the severity of pelvic arterial calcifications may impact the surgical planning of kidney transplantation (KT), choice of anastomosis site, complexity of the surgery, and patient and graft survival. Vascular calcifications are recognized as a good biomarker of overall cardiovascular burden. Although computerized tomography (CT) is the imaging modality of choice for calcification evaluation, compared to pelvic X-ray and Doppler ultrasound, it is not officially included in the guidelines of different international associations, which offer general recommendations for the assessment of iliac vessels. Nevertheless, centers are increasingly using CT in their pretransplant workup, either routinely or only in patients with increased CV risk. Also, impaired bone metabolism and its consequences have an important role in the development of vascular calcification. The investigators will determine the relationship between calcification burden of iliac arteries which will be assessed on CT and the serum level of bone remodeling biomarkers, including parathyroid hormone, (PTH), calcium, phosphates, OPG/RANK/RANKL (engl. osteoprotegerin/receptor activator of nuclear factor (NF)-κΒ/RANK ligand) and Gla-Rich protein (GLP). According to investigator knowledge, this will be the first prospective study that will correlate the degree of iliac arteries calcification based on CT analyses with the serum level of various bone remodeling markers, and their impact on clinical outcome in kidney transplant recipients. The investigators expect this research to improve insights into incidence and distribution of iliac artery calcifications in patients following kidney transplantation, their correlation with clinical data and bone remodeling markers and confirm the appropriateness of using computerized tomography in a routine pretransplantation work-up.

The hypothesis of this study is that incidence and severity of arterial calcification raise with age of the patient and time spent on hemodialysis. Additionally, poorer graft and patient survival and overall risk for future cardiovascular events correlate with the severity of arterial calcifications following successful kidney transplantation. Study will include 50 patients who will undergo kidney transplantation. Non-contrast CT scan of abdomen and pelvis will be performed, and blood level of bone remodeling markers will be determined in all patients. Two radiologists will independently assess the severity of iliac artery calcifications, by using quantitative scoring system developed by Davis et al. and newly developed pelvic calcification score. Pelvic calcification score (PCS) will be determined by assessing common iliac artery (CIA) and external iliac artery (EIA) calcifications bilaterally, based on their morphology (no calcification, thin linear calcification, 1mm in thickness and bulky calcification\>2mm in thickness and convex luminal margins, scores 0-3), circumference and length (no calcification, 1-25%, 26-50%, 51-75%, \> 76%, scores 0-4, respectively). PCS could vary from 0-44. Serum level of bone remodeling biomarkers will be determined on hospital admission. Demographic and clinical data (body mass index - BMI, principal disease and additional conditions, type and duration of renal replacement therapy, KT side-and arterial segment used, hospitalization time, and graft and overall survival) will be recorded. Patients will be followed at least one year after KT, the function of kidney transplant will be assessed by measurement of serum creatine and renal scintigraphy