Utility of the Doppler ultrasound parameter, resistive index, in renal transplant histopathology.

BACKGROUND: Doppler ultrasonography is routinely used by many clinicians during long-term follow-up to identify high-risk patients without diagnosing the exact cause of graft dysfunction. Despite a number of studies showing a correlation between intrarenal resistive index (RI) and renal function in patients with kidney diseases, correlations between RI and renal histopathologic characteristics have not been sufficiently evaluated in renal transplant recipients. The aim of this study was to examine this relationship in grafted kidneys. PATIENTS AND METHODS: The intrarenal RI was retrospectively compared with biopsy findings in 28 kidney recipients. All renal biopsy specimens were reviewed by light microscopy and immunofluorescence staining. For glomerulosclerosis, we considered the percentage of glomeruli showing this change; for interstitial fibrosis/tubular atrophy and interstitial infiltration, we graded abnormalities according to the methods of Kliem et al (Kidney Int 49:666, 1996). RESULTS: The percentage of globally sclerosed glomeruli was significantly greater among patients with RI values higher than 0.75 than below this level (23% vs 47%; P = .022). Patients with grade 1 interstitial fibrosis and tubular atrophy (n = 14) showed lower RI values (0.68 +/- 0.03 vs 0.74 +/- 0.06; P = .047) than those with grade 3 fibrosis (n = 12). Similarly, lower RI values (0.66 +/- 0.02 vs 0.73 +/- 0.05; P = .014) were observed among patients with grade 1 (n = 13) compared with grade 3 interstitial infiltration (n = 13). CONCLUSION: RI seemed to provide a prognostic marker for the graft rather than yielding an exact diagnosis of renal graft dysfunction.