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6.3.2 Anaesthesia

The improvement of ureteroscopes and stone retrieval instruments allows ureteroscopic procedures to be carried out under sedation analgesia with a similar success rate (88-97%) to general anaesthesia. This is particularly true for distal ureteral stones in women (2,6,7).

6.3.3 Assessment of different devices

6.3.3.1 Ureteroscopes

Semi-rigid and thin ureteroscopes are available. Miniaturization avoids dilatation of the intramural ureter (with associated complications) in more than 50% of cases (8-10). The small diameter (6.0-7.5 F) allows easier progression of the ureteroscope up to the proximal ureter.

The use of flexible ureteroscopes (7-7.5 F) has been evaluated (1,2,11-15). They are suitable for access to the upper part of the ureter and renal collecting system, without dilatation of the intramural ureter in more than 75% of cases. In the lower ureter, a flexible ureteroscope is not suitable because of its tendency to fall back into the bladder (1,3).

6.3.3.2 Disintegration devices

Laser lithotripsy is a reliable method for the treatment of ureteral stones regardless of the hardness of the stone (16). It is the only applicable method when performing flexible URS (12,17,18). A 365 urn holmium:yttrium aluminium garnet (Ho:YAG) laser fibre is the best choice for ureteral stones, as minimal deflection is required to access the stone. The 200 urn fibre is more expensive and should be reserved for fragmentation of intrarenal calculi (12,19). The ideal energy and frequency settings are less than 1.0 J and 5-10 Hz. If manipulated with

care, the laser does not damage the ureteral mucosa (16,18,20). An operating time for laser lithotripsy between 7 min and 45 min is acceptable (18).

Laser lithotripsy using pulsed dye laser has similar results to that using the Ho:YAG laser (21). Ho:YAG lithotripsy seems to give better stone-free results at 3 months than electrohydraulic lithotripsy (97% versus 87%) for distal ureteral stones (5). However, for ureteral calculi less than 15 mm in diameter, laser lithotripsy will require a longer time than the electrohydraulic technique (5).

Ballistic lithotriptors (pneumatic or electropneumatic) using a 2.4 F probe in a semi-rigid ureteroscope provide excellent fragmentation rates (90-96%). Low capital cost and simple and safe handling are major advantages of this type of device. Its cost-effectiveness is three times that of laser lithotripsy (9,14,22-24). Nevertheless, migration of stones towards the renal pelvis from the mid- or proximal ureter might be a limiting factor of ballistic lithotripsy (25).

6.3.3.3 Baskets

Ureteroscopic removal of small ureteral stones with a basket is a relatively quick procedure with a lower morbidity rate than lithotripsy (3,4). The basket technique should be attempted first for small distal ureteral calculi. Several new designs of endoscopic stone retrieval baskets are available. The nitinol tipless basket is more effective than a flat wire basket (4,13,23), because laser or electrohydraulic lithotripsy might break the wires of the basket (16).

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