Intrarenal Doppler indices in acute ureteric obstruction

Abstract

Context: Urolithiasis remains a major health problem despite advances in therapy. Obstruction results in an increase in pressure within the urinary tract, causing structural and physiologic changes. This study aimed to calculate the intra renal Resistivity Index (RI) of acutely obstructed kidney, to determine the significance of Resistivity Index Ratio (RIR) and difference in Resistivity Index of obstructed and contralateral non obstructed kidney.

Materials and methods: Prospective study with renal Doppler for patients presenting with acute unilateral ureteric obstruction. Seventy two patients between the age group 20-45 y presenting to the Department of Radiodiagnosis, between January - December 2006 with acute unilateral ureteric obstruction were included in the study. Gray scale and Doppler evaluation of the kidneys done; with assessment of the ureteric calculus. Renal Doppler indices calculated and follow up of the same done after relief of obstruction.

Statistical analysis: Statistical analysis was done using SPSS Software V13 and p-value <0.05 was considered as statistically significant.

Results: Forty two patients (58.33%) had mild, 28 (38.89%) moderate and 2 (2.78%) severe hydronephrosis. The mean RI of the obstructed kidney was 0.66±0.88 and that of contralateral non obstructed kidney was 0.569±0.05. Delta RI between the obstructed and contralateral non obstructed kidney was 0.08±0.03. The mean RIR between the obstructed and non obstructed kidney was 1.12±0.04 and the same after relief of obstruction was 1.03±0.06.

Conclusion: The intrarenal Resistivity indices are less sensitive indicators in predicting the diagnosis of acute ureteric obstruction, although Resistivity Index Ratio appears to be a better parameter. The indices within the normal range do not rule out the absence of obstruction. Hence these parameters should not be interpreted in isolation.

Keywords: Doppler indices; Ureteric obstruction.

[Table/Fig-4]:

Summary of distribution of RI, RIR and Delta RI values before and after intervention Abbreviations: RI- Resistivity Index, RIR-Resistivity Index Ratio, Delta RI-Delta Resistivity Index

[Table/Fig-6]:

a): Shows mild Hydroureteronephrosis (as denoted by →) b): Demonstrates distal ureteric calculus of size 0.6 cm (as denoted by →)

[Table/Fig-7]:

Intrarenal Doppler spectrum for the same case as in [Table/Fig-1], showing PSV: 24.5 cm/s, EDV: 8.65 cm/s ,RI: 0.64, Abbreviations: PSV- Peak Systolic Velocity, EDV-End Diastolic Velocity, RI-Resistivity Index