ABSTRACT
PURPOSE: The purpose of this study was to evaluate regional renal hemodynamics in a noninvasive manner using gadolinium-DPTA magnetic resonance imaging (MRI) before and after extracorporeal shockwave lithotripsy (SWL). In addition, the renoprotective effect of intravenous aminophylline was evaluated on the perfusion on kidneys undergoing SWL. PATIENTS AND METHODS: Ten randomly selected patients were evaluated for regional renal blood flow in the cortex and medulla with Gd-DTPA MRI studies within 2 weeks before and 4 hours after SWL. Five of these patients were treated with 500 mg of intravenous aminophylline 45 minutes prior to SWL. Renal hemodynamics were assessed utilizing relative perfusion indices (PI) calculated from signal intensity-v-time curves obtained from regions of interest (ROI). The ROI choice was based on the contrast-enhanced MRI images. Relative PIs of pre-SWL and post-SWL studies were compared in the first group of patients. Relative PIs of the treated kidney were compared with those of the contralateral kidney in the second group of patients, who received aminophylline. RESULTS: In the group not treated with aminophylline, there was no significant difference in cortical perfusion before SWL (average PI -7+/-3%). However, after lithotripsy, there was a reduction of cortical flow (average PI 31+/-12%) in the treated kidney. In the group treated with aminophylline, renal hemodynamics study after SWL revealed no significant difference in relative perfusion (average PI -8+/-6%). Relative PIs of the medulla were small for all patients, but standard errors were large, indicating a wide range of values. CONCLUSIONS: This study helps to establish reduced cortical flow after SWL and demonstrates that aminophylline attenuated this response in the kidneys subjected to lithotripsy. It appears that aminophylline administration causes no alteration in medullary blood flow.
