Alteration in Resistive Index of Renal Vasculature Following Extracorporeal Shock Wave Lithotripsy for Renal Stones

Introduction: Extracorporeal Shockwave lithotripsy (ESWL) may be associated with both anatomic and functional injuries to the kidney when used in the management of uncomplicated kidney stones. Assessment of the resistive index (RI) is a non invasive diagnostic modality for studying changes in the arterial system. RI, which is measured by color doppler ultrasonography, reflects resistance of intrarenal arteries that indirectly shows the renal blood flow.

Aim: To assess changes in intrarenal RI following ESWL in the ipsilateral and contralateral kidneys & to study correlation of alteration in resistive index with age of the patient.

Methodology: A total of 38 patients with solitary renal calculus, who underwent extracorporeal shockwave lithotripsy were included in the study. The patients were evaluated for the RI in ipsilateral (diseased) and contralateral kidneys; before, 3 hrs after and 1week after ESWL. Serum creatinine levels & creatinine clearence were measured pre ESWL and 4 weeks after ESWL.

Results: RI in ipsilateral kidney pre ESWL was 0.590 and post ESWL (3 hrs after ESWL) was 0.646, it showed a statistical significant increase with a p value of <0.001. 1week post ESWL resistive index values were comparable to pre ESWL value with no significant difference. ESWL had no effect on serum creatinine & creatinine clearance measured pre ESWL & 4 weeks post ESWL.

Conclusion: Doppler studies of the kidneys treated with ESWL have shown a transient rise of RI in our study, the long term effect of rise in RI after ESWL still remains to be evaluated.