Extrarenal factors influencing resistance index in stable kidney transplant recipients

Increased intrarenal resistance index (RI) has been associated with decreased long-term allograft and patient survival in kidney transplant recipients. Taking into account the potential role of endothelial dysfunction, systemic inflammation, arteriosclerotic lesions, and left ventricle remodeling, we performed a cross-sectional study that aimed to evaluate extrarenal factors that may have influence on kidney graft RI in a large cohort of stable kidney transplant recipients.

One hundred seventy-four kidney transplant recipients were enrolled into the study. Mean time after transplantation was 8.4±1.8 years. Echocardiography, carotid ultrasound (intima-media thickness), pulse wave velocity, and Doppler examination of kidney graft were performed. The inflammatory markers, adhesion molecules, and plasma N-terminal prohormone of brain natriuretic peptide concentrations were also measured. Patients were divided into quartile subgroups based on RI value (Q1: RI≤0.68, Q2: RI=0.69-0.72, Q3: RI=0.73-0.76, and Q4: RI≥0.77).

The analyzed subgroups were comparable with respect to demographics (except age) and anthropometric parameters as well as comorbidities. The values of age, serum phosphate, pulse wave velocity, left ventricular mass (LVM), and LVM index (LVMI) increased in subsequent RI quartile subgroups. The strongest correlation was found between RI and age, LVM, LVMI, and plasma parathormone concentration and was negative with estimated glomerular filtration rate. In backward stepwise multivariate regression analysis, the RI variability was explained by age, LVMI, and serum phosphate concentration.

Arterial stiffness and left ventricular hypertrophy may significantly influence the intrarenal vascular resistance measured using Doppler sonography in stable kidney transplant recipients.