Association of Intrarenal Resistance Index and Systemic Atherosclerosis After Kidney Transplantation

Abstract

Background/Aim: Patients after kidney transplants are at risk of cardiovascular morbidity. An elevated resistance index (RI) is associated with renal graft failure, while a decreased RI can be due to a renal artery stenosis. The RI can also be measured in the carotid artery. Whether a correlation between intrarenal RI after kidney transplant in adult patients and the RI of the internal carotid artery exists is still unclear. Patients and Methods: In this prospective cross-sectional study, RI of kidney transplants and of the internal carotid artery were measured with duplex sonography. Carotid intima-media thickness as well as the Framingham risk score and the Augmentation index, all known markers of atherosclerosis, were assessed. Correlations between the RI in Carotid artery and the RI of the kidney transplant were based on Spearmen test with the level of significance set at p<0.05. Results: Ninety-eight consecutive patients [60% male, mean age of 48.7 (±15.6)] were included. The mean interval after transplantation was 27.5 (±8.5) months and mean serum creatinine was 308 (±220.3) mmol/ml The RI of the internal carotid artery and the renal transplant were significantly correlated (p<0.05). A correlation between the RIs and the Augmentation Index was found. Conclusion: The RI of the kidney transplant is correlated with the RI of the carotid artery and to markers of general atherosclerosis. This observation may be helpful to identify patients after kidney transplant with higher risk for cardiovascular events and gain indirect information on transplant renal artery stenosis.Kidney transplant is the most frequently performed organ transplant (1). Computed tomography (CT) and coronary Angio-CT are used for risk stratification in kidney transplant candidates for risk stratification before transplantation (2). It is the treatment of choice in end-stage renal disease (ESRD) and is ideally performed before initiation of hemodialysis (3). It is also more cost-effective than long-term dialysis (4). Color-coded Doppler sonography (CCDS) is part of the postoperative surveillance (5). The surveillance may start as early as during, but should be initiated immediately after transplant (6). Besides the diagnosis of arterial or venous obstruction, the intrarenal vascular resistance, called Resistance Index (RI) is measured (7). While the RI can be difficult to measure in orthotope kidneys it is often easier to assess in the more superficial transplant in the iliac fossa. Nonetheless, accessibility can be limited due to different factors such as pain, obesity, flatulence amongst others. The RI has been a proven to be sensitive marker of graft dysfunction, but is unspecific (8). The RI of the kidney transplant adapts rapidly to the host ( 9). An elevated RI of 0.80 (normal range=0.6-0.7) or higher indicates an unfavorable prognosis of renal function as well as increased mortality (10). A decreased RI can be a sign for a renal stenosis (11). RI measurement is observer dependent (12). There is a significant association between an incr...

Atherosclerosis and Intrarenal Resistance Index in Kidney Transplant Recipients

“…37 The association between RI and atherosclerosis has been studied before, showing that RI, in accordance with our study, is positively associated with atherosclerosis. 38,39 But next to these similarities‚ our study has also important differences. Our study provides a better understanding of the etiology of the RI buildup, with emphasis on atherosclerosis in the aortoiliac tract, with the aim of understanding how the intrarenal RI is constructed, whereas both Köger et al and Heine et al associated RI with traditional cardiovascular risk factors and subclinical atherosclerosis.…”