Redistribution of Renal Blood Flow after SWL Evaluated by Gd-DTPA-Enhanced Magnetic Resonance Imaging

Abstract

Extracorporeal shockwave lithotripsy (SWL) is currently accepted as an effective noninvasive treatment for a wide variety of urinary tract calculi. However, the bioeffects of high-energy shockwaves on renal parenchyma have yet to be fully elucidated. The objective of this study was to measure the acute changes in regional renal hemodynamics associated with SWL utilizing dynamic gadolinium-DTPA-enhanced magnetic resonance imaging (MRI). Seven patients who underwent SWL for renal calculi had an MRI study within 4 hours after the treatment. To assess renal hemodynamics, a bolus of Gd DTPA (0.03 mmol/kg) was administered, and dynamic contrast enhanced images was obtained. Regions of interest (ROI) were defined over the cortex and medulla to obtain signal intensity-v-time curves. The contralateral kidney in each patient was used as the control. The initial slope of the contrast-enhanced signal intensity-v-time curve was used as a measure of the perfusion index (PI). In six patients, perfusion imaging showed a consistent trend of decreased cortical flow (29+/-8%) and a concomitant increase in medullary flow (34+/-14%) in the region of the kidney that was targeted with SWL in six patients (86%). This study shows that renal hemodynamics are modified by SWL. We hypothesize that this change represents a shunting of flow from cortex to medulla in an attempt to prevent ischemia of the medulla.

Inhibition of inducible nitric oxide synthase prevents shock wave therapy induced renal injury

“…4,25,26 Several clinical studies, measuring renal resistive index or followed renal blood velocity in the kidney subjected to SWT, showed that an increase in resistive index or a reduction in blood velocity indicative of vasoconstriction occurred. 4,5,27 It has also been reported that there is a decrease in renal perfusion in kidney following SWT procedure by using dynamic gadolinium-DTPA enhanced magnetic resonance imaging. 27 Studies focused on two possible explanations for the impairment of renal flow; renal sympathetic nerves may be activated by shock waves and vasoconstriction may be occurred by vasoconstrictors released from kidneys in response to the shock waves.…”

“…4,5,27 It has also been reported that there is a decrease in renal perfusion in kidney following SWT procedure by using dynamic gadolinium-DTPA enhanced magnetic resonance imaging. 27 Studies focused on two possible explanations for the impairment of renal flow; renal sympathetic nerves may be activated by shock waves and vasoconstriction may be occurred by vasoconstrictors released from kidneys in response to the shock waves. As a result of this transient ischemic insult, it is thought that free oxygen radical Figure 2.…”

Efficacy of poly(adenosine diphosphate-ribose) polymerase inhibition in extracorporeal shock wave-induced renal injury

“…Several clinical studies, measuring renal resistive index or followed renal blood velocity in the kidney subjected to SWT, showed that an increase in resistive index or a reduction in blood velocity indicative of vasoconstriction occurred. 4,27,28 It has also been reported that there is a decrease in renal perfusion in kidney following ESW procedure by using dynamic gadolinium-DTPA enhanced magnetic resonance imaging. 27 Studies focused on two possible explanations for the impairment of renal flow; either renal sympathetic nerves may be activated by shock waves or, alternatively, the vasoconstriction may be secondary to vasoconstrictors released from kidneys in response to the shock waves.…”

“…4,27,28 It has also been reported that there is a decrease in renal perfusion in kidney following ESW procedure by using dynamic gadolinium-DTPA enhanced magnetic resonance imaging. 27 Studies focused on two possible explanations for the impairment of renal flow; either renal sympathetic nerves may be activated by shock waves or, alternatively, the vasoconstriction may be secondary to vasoconstrictors released from kidneys in response to the shock waves. As a result of this transient ischemic insult, it is thought that oxygen free radical generation due to ischemia/reperfusion injury may take place, which further contribute to parenchymal damage by lipid peroxidation and disruption of cellular membranes.…”

Functional MRI of the kidney: tools for translational studies of pathophysiology of renal disease

“…Preliminary data were obtained in a small number of subjects (n ϭ 6) undergoing extracorporeal shock wave lithotripsy (ESWL), which results in a physical shock to the renal parenchyma in the vicinity of the focal point (92). Figure 2 illustrates the signal intensity vs. time changes observed in the renal parenchyma following the bolus injection of Gd-DTPA.…”