Ahmed Shafik

Department of Surgery and Experimental Research, Faculty of Medicine, Cairo University, Cairo, Egypt

Received 3/20/98 Accepted 4/30/98

3. MATERIAL AND METHODS

3.1 Subjects

12 healthy volunteers (9 men and 3 women) signed an informed consent before entering into the study. The study was approved by the Internal Review Board at our institution. Mean age was 38.6 ± 11.3 SD years (range 26-44). They had no history of urinary troubles. Urinalysis and sonography of the urinary tract were normal. Physical examination, including neurologic assessment, was also normal.

3.2 Methods

With the subject lying in a supine position, a 3F balloon-tipped ureteric catheter with a metallic clip at its end for fluoroscopic control was introduced into the renal pelvis. The balloon measured 0.5 cm in diameter and was made of latex (London Rubber Industries Ltd, London, UK). The catheter was connected to a strain gauge pressure transducer (Statham, 230B, Oxnard, California, USA). Pressure measurements started with the gauge at zero level. The filling of the balloon when it was not in the renal pelvis (i.e. in air) showed no transient pressure rise.

The pressures in the anal canal and rectum were simultaneously measured by means of a two-channel microtip catheter (Wiest Urocompact, California, USA). The catheter was placed 8-10 cm from the anal orifice so that the distal transducer resided in the rectum. The proximal transducer was adjusted to lie in the anal canal 2-3 cm from the anal orifice. The basal pressures in the renal pelvis as well as in the rectum and anal canal were recorded. The balloon in the renal pelvis was filled with saline in increments of 2 ml up to 12 ml and the pressure response of the renal pelvis, rectum and anal canal to renal pelvic distension by the balloon was recorded. The catheter was then withdrawn from the renal pelvis to the ureter using a mechanical device for automatic catheter withdrawal (902, Disa, Copenhagen, Denmark).

The position of the catheter was fluoroscopically controlled. The balloon in the ureter was filled with saline in increments of 0.25 ml up to 1 ml and the pressure response of the ureter, anal canal and rectum was recorded while the balloon was situated in the upper, middle and lower third of the ureter.

Renal pelvic and ureteric distension was done twice: once rapidly with a balloon filling at a rate of 1 ml/s and another time slowly at a rate of 1 ml/min.

3.2.1 External anal sphincter electromyography

The electromyographic (EMG) activity of the external anal sphincter to balloon distension of the renal pelvis and ureter was evaluated.

A concenteric needle EMG electrode was introduced into the external anal sphincter using the technique previously described (16). The normality of the sphincter had been ascertained by EMG testing before starting the experiment.

3.2.2 Anesthetisation of the renal pelvis, ureter and external anal sphincter

The renal pelvis and ureter were anesthetised by administration of 5 ml of 2% xylocaine (Astra, S_dert@lje, Sweden) diluted with 15 ml of saline using a 3 F ureteric catheter which was introduced through the ureteric orifice into the renal pelvis.

The pressure response of the anal canal, rectum and external anal sphincter to separate distension of the renal pelvis and ureter in its upper, middle and lower third was registered after 20 minutes of local anesthesia and 2 hours later when the effect of the anesthetic had waned. On another day, the test was repeated using saline instead of xylocaine.

The external anal sphincter was anesthetised by injecting 1 ml of 2% xylocaine diluted with 2 ml normal saline. A 23 gauge needle was introduced into the perianal skin, 0.5-1 cm lateral to the anal verge and 0.5 cm deep, and 1.5 ml of the anesthetic solution was injected on each side of the anal orifice. The EMG activity of the external anal sphincter as well as the rectal and anal canal pressure response to renal pelvic and ureteric distension was determined after 20 minutes of anesthetisation and 2 hours later when the anesthetic effect had disappeared.

To assure reproducibility of the results, the pressure measurements were done at least twice in each individual and the mean value was calculated.

3.2.3 Statistical analysis

The results were analysed statistically using the Student’s t test. Differences assumed significance at p < 0.05 and values were given as mean ± standard deviation.