R. John D'A. Honey

Background and Purpose: Electrodes used by the Dornier MFL 500 lithotripter have a specified lifespan, after which, the manufacturer recommends replacing the electrode before continuing the treatment. The aim of this study was to investigate whether electrodes continue to function effectively beyond 100% consumption by measuring the pressure output of electrodes up to 300% consumption or until electrode failure. Materials and Methods: We assessed new, refurbished, and twice-refurbished electrodes to compare their respective performances. Results: Rather than a decrease, there was a trend toward increased pressure output beyond 100% electrode consumption, with no drop in pressure prior to 300% consumption or electrode failure. All three types of electrodes functioned adequately above 100% consumption. Conclusion: These observations suggest that discarding the electrode before the completion of the treatment or electrode failure is not warranted. Using a single electrode rather than multiple electrodes to complete a treatment has the potential to save both time and cost.

Flexible nephroscopes and ureteroscopes make it possible to see calculi in remote calices, but it is often impossible to remove these with existing technology. Flat-wire baskets impede deflection and can traumatize the papilla. This study compares the performance of a new 3.2F tipless nickel-titanium (Nitinol) basket with that of an existing 3.0F flat-wire basket. Specifications were compared using a 15F nephroscope and a 7.5F flexible ureteroscope in a pig kidney model. A calculus was placed in a calix, and the author and two residents were timed while using both baskets to retrieve the stone. To open fully, the flat-wire basket needed to protrude 1.2 cm further than the tipless basket. The tipless basket did not restrict deflection of the nephroscope, whereas the flat-wire basket limited flexion by 24° and extension by 28°. The tipless basket did not restrict extension of the 7.5F ureteroscope but limited flexion by 10°. The flat-wire basket limited flexion by 79° and extension by 72°. Using the pig kidney model, the three operators took a mean of 5.3, 11.8, and 6.4 seconds to catch the stone with the tipless basket. Using the flat-wire basket, the mean times were 15.3, 34.5, and 28.9 seconds (combined data: 8.2 seconds for the tipless basket and 27.8 seconds with the flat-wire basket; P = 0.0001). Only the flat-wire basket was seen to traumatize the papilla. The Nitinol tipless basket has significant advantages over the flat-wire basket.