Oblique Pyelography
Oblique Pyelography For Focusing Of Extracorporeal Shock Wave Lithotripsy
Akira Kimura,Eiji Higashihara,and Yoshio Aso.
Department of Urology, Fuculty of Medicine, The University of Tokyo.
running head
In ESWL by Dornier HM-3, preoperative oblique pyelograms facilitate the adjustment of the renal stone to the focus.
Key words : ESWL, Excretory pyelogram.
Abstract
In ESWL, the adjustment of the renal stone to the focal point of the shock wave is essential. In Dornier HM-3, the original lithotriptor, the adjustment is monitored by two x-ray images. Since the monitors give oblique views of stones,the preoperative oblique views of the excretory pyelogram facilitate not only the initial positioning of the patient but also the re-adjustment of partially destroyed stones during the treatment.
Though ESWL presented an innovative non-invasive treatmentof urolithiasis‚Pj, this modality is not without any side effect. Complications such as perirenal, or subcapsular hematoma are reported, and the complications occur frequently when too many shot are required‚Qj.
@ A thorough effort to adjust stone to the focal point of shock wave cautiously during the treatment will decrease the number of shot required for stone disintegration, thereby decreasing the frequency of complications and increasing the cost-effectiveness. @
In Dornier HM-3, the original and widely distributed lithotriptor, the adjustment is monitored by two x-ray images. Since the monitors give oblique views of stones, thepreoperative oblique views of the excretory pyelogram facilitate the adjustment of the renal stone to the focal point of the shock wave. We recommend to take two oblique views 15 minutes after the contrast injection(fig.1).
Since the excretory pyelograms are necessary irrespectiveof the methods of treatment, it gives only minimum burden to the patients to take oblique view films.
This simple procedure yields two advantages in ESWL. First, it facilitates the initial positioning of the patient. Since vision of the monitor is small, approximately10 cm in diameter, it is not rare that stone is out of sightin the monitor. Only two or three vertebrae and/or ribs may be visualized in it.By comparing this view with preoperativeoblique pyelogram, the operator can easily recognize direction and distance from the focus to stone.
The second advantage is that stone can be refocused easilyduring the treatment by looking at the oblique view films. Depending on the size of stone, roughly 500 to 1500 shock waves are required for complete stone disintegration. Whenever 100 to 200 shock waves are released, the degree of disintegration is monitored by x-ray and re-focusing is madedepending on the stone movement. When a renal pelvic stone is disintegrated into two particles of the same size, the operator cannot correctly pair stone images of two monitors,unless he knows three dimensional structure of the collecting system(fig.2). Without the preoperative oblique pyelograms, the operator is forced to focus sequentially to the four points consisting of two by two pairing. This mightlead to ineffective shot. From the preoperative oblique pyelograms, the operator can recognize three dimensional structure of the collecting system. This facilitates proper correspondence of two monitor images and leads to the properadjustment of stone to the focus(fig.3).
Reference
1.Chaussy,Ch., Brendel,W., and Schmiedt,E.: Extracorporeally induced destruction of kidney stones by shock waves. Lancet,2: 1265-1268,1980.
2.Rubin,J.I., Arger,P.H., Pollack,H.M. et al: Kidney Changes after Extracorporeal Shock Wave Lithotripsy:CT Evaluation. Radiology,162:21-24,1987.
