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Effects of High Energy Shock Wave Exposure on Renal Function during Extracorporeal Shock Wave Lithotripsy for Kidney Stones T. Kishimoto, M. Senju, T. Sugimoto, K. Yamamoto, W. Sakamoto, M. Umori, T. Kanasawa, S. Wada, M. Maekawa Department of Urology, Osaka City University Medical School, Osaka, Japan
Key Words. Extracorporeal shock wave lithotripsy • Kidney function • Renal contusion • Renoscintigraphy ■ Urinary enzymes • Urinary low molecular proteins Abstract. In order to study the effects of high energy shock wave exposure on the kidney in extracorporeal shock wave lithotripsy (ESWL) using Domier HM3, renal hemodynamics and renal function before and after ESWL were analyzed by "mTc-DTPA renoscintigraphy. Various urinary enzyme activities (LDH, GOT, GPT, NAG, y-GTP) and low molecular protein concentrations (ai-microglobulin, ß2-microglobulin) before and after ESWL were also com pared. In the early phase of the renoscintigram obtained in the 1st min after injection of 99mTc-DTPA, the time required to reach maximum radioactivity was significantly prolonged after ESWL in both the affected and contra lateral kidney. This indicated that renal blood flow decreased in both the affected and contralateral kidney imme diately after ESWL. An analysis of the 30-min renoscintigram showed that urinary clearance was delayed in the affected kidney in spite of no overt obstruction due to stone fragments. As for urinary enzyme activities and low molecular protein concentrations, they were standardized by urinary creatinine concentration measured at the same time. Urinary LDH, GOT, GPT and NAG activities remarkably increased on the day of ESWL followed by a decrease close to pretreatment levels on the 4th day, though these levels were still significantly higher than pretreat ment levels. Urinary y-GPT activity was significantly higher than the pretreatment level only on the day of ESWL. Urinary a i-microglobulin and ß2-microglobulin concentrations significantly increased on the day of ESWL and were still high on the 4th day. These results suggested that renal tissue may be damaged by ESWL using the high energy shock wave lithotriptor though temporarily, and that the impairment in proximal renal tubular function may con tinue over a comparatively long period of time.
Extracorporeal shock wave lithotripsy (ESWL) is known to be the least invasive treatment for upper uri nary tract stones, but recent studies have shown that it is not without effects on the body especially using the high energy shock wave lithotriptor. For example, side effects such as damage to the skeletal muscle and hemolysis , changes in hemodynamics during ESWL , gastric and duodenal mucosal erosion  and pancreatitis  have been reported. As for side effects on the kidney, which is most affected by the shock waves, subcapsular hemato-
ma, perirenal hematoma and hemorrhage into renal cysts have been reported [5-7], It has also been reported that morphological changes of the kidney such as subcapsular hematoma and loss of corticomedullary differ entiation are observed at a high rate of 63% by magnetic resonance imaging , and that urinary N-acetyl-ß-ZJglucosaminidase (NAG) activity increases after ESWL . However, it is not clear as to the degree of the effects of high energy shock wave exposure on the kidney and whether these effects are reversible. Furthermore, there have been few reports on the side effects of ESWL on the kidney in regard to renal hemodynamics and renal funcDownloaded by: University of Exeter 184.108.40.206 - 6/7/2020 6:12:31 AM
Shock Wave Exposure on Renal Function
affected whole kidney
contralateral whole kidney
Fig. 1. Setting method of the whole kidney and ROI (left) and examples of time-activity curves of both kidneys and ROI in first pass after 99mTc-DTPA injection (right).
Materials and Methods Materials Patients with kidney stones treated by ESWL using the Domier kidney lithotriptor HM3, who had no evidence of urinary tract obstruction by excretory pyelography and who had no other compli cations such as liver function disorders or hypertension, were stud ied. When staghorn stones and large stones of over 3 cm in diameter are treated by ESWL, large amounts of residual stone fragments often form a stone street in the ureter, resulting in urinary tract obstruction. Therefore, patients with stones of less than 3 cm were studied. All cases were treated under epidural anesthesia, because high energy shock waves were used and the voltage to generate the shock waves was set at 18 kV for all cases.
Analysis of Renal Hemodynamics and Renal Function by 99mTc-DTPA Renoscintigraphy Renoscintigraphy was done in 21 patients with kidney stones (19 males, 2 females; average age 49.0). The patients were given a bolus injection of 370 MBq of 99mTc-DTPA through a forearm vein before and 2-3 h after ESWL. Radioactivity was measured at every second for the 1 st min after injection and at every 20 s for 30 min thereafter at a matrix of 64 X 64. A scintillation camera (X410S) was used, and Simis 4 was used for data processing. The data were collected for the left and right whole kidney (Ri, R2), the region of interest (ROI) in the kidney affected by the shock waves (R3) and the corre sponding ROI in the contralateral kidney (R4) from each patient. The region in the lower contralateral kidney excluding the bladder was regarded as the background (fig. 1 left). Renal hemodynamics were determined by calculating TFmax (time required to reach max imum radioactivity) and UpFmax (maximum radioactivity) of the first pass until 1 min after injection of 99mTc-DTPA (fig. 1 right). To obtain TFmax, the time-activity curve was differentiated (f'