Modified scope reduces luminal pressure by 40%

May 20, 2008

Use of dead space within a ureteroscope can enhance its performance and reduce intrarenal pressure without compromising the efficiency and structural integrity of the instrument, Joseph V. DiTrolio, MD, of the University of Medicine and Dentistry of New Jersey in Roseland, reported at the AUA annual meeting.

Use of dead space within a ureteroscope can enhance its performance and reduce intrarenal pressure without compromising the efficiency and structural integrity of the instrument, Joseph V. DiTrolio, MD, of the University of Medicine and Dentistry of New Jersey in Roseland, reported at the AUA annual meeting.

By placing grooves at the 3 o'clock and 9 o'clock positions down part of the length of a semi-rigid ureteroscope, they were able to decrease luminal pressures by nearly 40% in an in vitro model.

"With the standard ureteroscope, the fluid is trapped in the ureter and renal pelvis, and much of it is reabsorbed by the patient," Dr. DiTrolio explained. "It's also difficult for the clinician to see because the water has no easy path out. Our thought was that with grooves, the fluid would drain alongside the scope and back into the bladder, which is easily drained itself."

Working with representatives from the New Jersey Institute of Technology, Dr. DiTrolio's group made two 10F artificial ureters from silicone. A standard 6.9F semi-rigid scope served as the control; the modified scope featured the bilateral backflow grooves, which began at the dilated 13F section of the scope's shaft from 10 to 25 cm.

Both scopes had 50 cc syringes attached to them, as well as a perfusion pump, which was set to 20 cc/hour and connected to the bridge of each scope. One scope was placed into each artificial ureter at distances of 12.3 and 16 cm, and the ureter was obstructed 5.3 cm distal to the tip of the scope. Leak point was identified when the fluid from the infusion pump was seen backflowing at the interface of the ureteroscope and ureter.

At the 12.3-cm mark, the modified ureteroscope required 33% less fluid than the regular scope to reach the leak point on three consecutive readings. At 16 cm, the difference was 38%. Over the length of the groove, Dr. DiTrolio noted, up to 50% less pressure was required.