Renal resistive index correlates with peritubular capillary loss and arteriosclerosis in biopsy tissues from patients with chronic kidney disease.

BACKGROUND

The renal resistive index (RI) is a Doppler-derived measure that reportedly correlates with renal histological changes and renal disease severity and outcome. The aim of this study was to investigate the factors related to the RI elevation in chronic kidney disease (CKD).

METHODS

Using Doppler ultrasonography, RIs were determined in 30 patients with CKD, after which they were correlated with interstitial fibrosis, arteriosclerosis, arteriolosclerosis and peritubular capillary (PTC) density. PTC-positive areas were determined based on CD34 immunostaining. Interstitial fibrosis was detected with Masson trichrome staining. All histological markers were assessed using quantitative and semi-quantitative analyses and evaluated statistically using Pearson correlation tests, unpaired t tests and stepwise multiple regression analysis.

RESULTS

RI correlated positively with age (r = 0.603, p = 0.0004), systolic blood pressure (r = 0.775, p < 0.0001), diastolic blood pressure (r = 0.575, p = 0.001), interstitial fibrosis (r = 0.381, p = 0.038) and arteriosclerosis (r = 0.520, p = 0.003), and negatively with creatinine clearance (r = -0.471, p = 0.009) and CD34+ (PTC) areas (r = -0.437, p = 0.016). Patients with hypertension or diabetes mellitus showed higher RIs (p < 0.05) than those without the ailments. Multivariate analysis showed PTC and arteriosclerosis to be independent variables correlating with RI (r (2) = 0.321, p < 0.05).

CONCLUSIONS

To our knowledge, this is the first report of using RI measurements to evaluate peritubular capillary loss. Our findings indicate that increases in RI are associated with both arteriosclerosis and loss of PTCs.