Resistive Index of Renal Grafts: Its Relation to Systemic and Renal Vascular Factors
Gabriel Chanta1, Mauricio Pattin1, Raul Bozzo2, Norberto Souto1, Fernando Margulis1, Roberto Sabbatiello1, Daniel Di Tullio1, Miguel Raño1, Ruben Schiavelli1.
1División de Nefrología y Trasplante Renal , Argerich Hospital, Buenos Aires , Argentina; 2Epidemiologia y Prevención Cardiovascular , Instuto Cardiovascular Buenos Aires , Buenos Aires , Argentina
The resistive index (RI) reflects the resistance to blood flow caused by the distal vascular bed.
Objective: To determine the relation of intrarenal RI to systemic cardiovascular and nephropathy risk factors in renal transplant recipients (RTRs).
To establish whether RI varies according to the measurement site (interlobar or cortical arteries) to assess the influence of the vessel diameter.
Material and Methods: Vascular Doppler ultrasound of both the renal graft and carotid arteries was performed in 84 stable renal transplant patients more than 3 months post-transplant. Definition of RI: (Peak Systolic Velocity (PSV)-End Diastolic Velocity (EDV))⁄PSV. RI < 0.75 was determined as normal and ≥ 0.75 as increased.
Carotid findings were described as intima-media thickness, as follows: normal < 1 mm, increased 1 1.4 mm, and plaque > 1.5 mm.
Results: Distribution by sex: 34 men (40, 5%), and age: 47.8 +/-13.8. Sixty-six RTRs were transplanted from cadaveric donors (CD) (78.5%), out of whom 17 were transplanted from expanded criteria donors, according to UNOS. The other 18 were transplanted from living donors (LD) (21.5%).
The variables analyzed that were statistically associated with increased RI were: age 51.1 vs. 43.9, p=0.002; post-transplant time (months) 104.5 vs. 62.5, p=0.029; MDRD (ml/min) 47.5 vs. 59.3, p=0.014; previous cardiovascular events 10 vs. 2, p=0.028; and carotid plaque (≥1.5 mm) 26/44 vs. 14/40, p=0.027.
When performing a multivariate analysis, the age and post-transplant time (months) variables were statistically significant , with p=0.004 and p=0.044 respectively.
Diabetes and delayed graft function showed an associative trend with the highest resistive index, without reaching significant values.
Conclusion: The RI measurement site is not determining as values were similar in cortical and interlobar arteries, thus inferring that the vascular area of more distal arteries does not determine RI.
An increased RI would reflect the ageing of both the patient and organ, associated with cardiovascular risk factors . Further studies are needed to verify these data.
