A SIMPLE METHOD TO ESTIMATE THE INTRAVESICAL VOLUME FROM OUTSIDE OF THE BODY

Abstract

If continuous recording of the intravesical volume from outside of the body using a simple apparatus becomes possible, it will surely be helpful in the physiological and pathophysiological study of the urinary bladder.
Principle and method.
A certain amount (30μ Curie) of isotope (¹³¹I-hippuran) was put into the bladder and suprapubic radioactivity during the process of bladder expansion was continuously recorded with a special collimeter (2cm in diameter) and correlated with the intravesical volume.
a) Study with ballon.
After 30μ Curie of the isotope was instilled into the balloon, water was poured in steps. Tip of collimeter was fixed at the height of 5cm from the center of the empty balloon. Recorded radioactivity decreased stepweise and it was well correlated with the instilled water volume.
b) Study with dog's bladder.
Isotopic solution was instilled into the dog's empty bladder and the lower abdominal midline radioactivity was recorded at the point of 0, 5, 10 and 15cm cephalad to the pubic symphysis, at the skin surface. The radioactivity was heighest at 10cm cephalad to the symphysis in middle sized dogs, and at 5cm in small dogs.
Next, the collimeter was placed at the point of the heighest radioactivity and recording was made during the stepwise retrograde instillation of water into the bladder. The result was the same as in the case of balloons, showing a stepseise decrease of radioactivity in accordance with increasing water volume.
c) Study in clinical cases.
At first 30μ Curie of ¹³¹I-hippuran was instilled into the empty bladder of a male adult and radioactivity at the skin level of the low abdominal midline was recorded during retrograde water instillation. This was repeated by shifting the collimeter on the skin. The curve shows the mount-shaped pattern, and its peak point was dependent upon the distance of collimater from the pubic symphysis. The water volume at the peak of the curve in this case was respectively 10cc, 50cc, 250cc and 400cc when the distance from the symphysis was 0cm, 2cm, 4cm and 6cm. The peak was higher when the recording place is nearer to the pubic symphysis. Therafter we recorded the radioactivity in the following manner: At first 20ml of isotope solution was instilled into the empty bladder and the point of maximum count was found out in the midline. (Usually, it was at the upper edge of the pubic symphysis, but in some cases 1 or 2cm cephalad to it.). The collimeter was fixed at this point and then radioactivity was recorded during the stepwise dilution of radioisotope.
Thirteen adult patients (11 men, 2 women) were examined in the above manner. In some cases, the highest point of the curve was at the start in which the intravesical volume was 20ml, but in others the peak was found at the volume over 20ml. The reproducibility of the curve was verified by repeated examination in each case including a case who had marked bladder deformity. Therefore, if the curve of suprapubic radioactivity during retrograde water instillation was recorded in. advance it could be used as a control to estimate the irtravesical volume during the expanding process of the bladder with urine from the kidney. Application of this method to the excretory cystometory was satisfactory. Furthermore, this method was valuable to estimate the urine-time ratio in diagnosis of intermittent hydronephrosis induced by alchoholic beverage.