The introduction of flexible ureteroscopes and smaller semirigid ureteroscopes along with the continued miniaturization of both has revolutionized the endoscopic management of ureteral calculi. The addition of new technology to the armamentarium of the endoscopist such as newer baskets, stone entrapment devices, an array of different wires, access sheaths, and the holmium:yttrium-aluminum-garnet (Ho:YAG) laser have advanced the field of endourology to yield excellent outcomes in the ureteroscopic management of ureteral stones.
Ureteroscopy for Lower Ureteral Stones (Below Iliac Vessels)
When approaching a lower ureteral calculus, rigid cystoscopy is the first step performed to identify the ureteral orifice. A wire is then cannulated into the ureteral orifice, and a 5-Fr open-ended catheter is placed over the wire through the cystoscope to perform a retrograde pyelogram. A retrograde pyelogram via a rigid cystoscope provides a map of stone location as well as collecting system anatomy and potential pitfalls that may be encountered during ureteroscopy. A safety wire is then placed through the 5-Fr open-ended catheter and passed up to the kidney under fluoroscopic guidance. Ureteroscopy should not proceed without a safety wire, which provides access to the collecting system when a case is terminated early and a stent is placed. Hydrophilic wires with different tips (curved, straight, or polytetrafluoroethylene [PTFE]/hydrophilic) can be used for impacted stones that do not permit passage of routine PTFE wires. These wires may also be helpful with J-hooking ureters or other anatomic variations as well. If additional difficulty is encountered advancing the wire past an impacted calculus, then the 5-Fr open-ended catheter can be passed over the wire to the level of the stone, and the additional backing can sometimes enable a wire to pass. A wire should never be forced because it can perforate the ureter or travel through the submucosa. If a glidewire is required to pass the stone, it should be replaced with a stiffer wire after access is achieved. If purulence is encountered at the time of wire placement, a stent should be placed, a culture sent, and ureteroscopy should not be attempted until the patient has completed a course of culture-specific antibiotics. The bladder should always be drained before initiating ureteroscopy.
Ureteral calculi below the iliac vessels are best treated with semirigid ureteroscopy, which affords maximum irrigation and visualization, as well as larger working channels to accommodate the largest lithotripsy devices. The semirigid ureteroscope should be placed down the urethra and alongside the safety wire. The ureteroscope is then placed into the ureteral orifice again alongside the safety wire. At times, the ureteral orifice may be narrow, making passage of the ureteroscope challenging. In these instances, a second wire can be placed through the semirigid ureteroscope and into the ureteral orifice to tent it open with a train-tracking technique, facilitating access into the ureter ( Fig. 41.1 ). Even with the train-tracking technique, the distal ureter does not always accommodate the ureteroscope and at times must be dilated. A balloon dilating device, a ureteral dilating sheath, or serial ureteral dilators can be used in these circumstances under fluoroscopic guidance. Caution must be taken to not dilate over the stone because this can cause significant ureteral trauma or complete extrusion of the stone through the ureter. A small percentage of ureters cannot be accessed with primary ureteroscopy. In these instances, a ureteral stent is placed to allow for passive ureteral dilation, and ureteroscopy can be reattempted with high success after a minimum of 1 week.
Several devices provide stone entrapment to minimize retropulsion of the calculus. Retropulsion of calculi can convert a relatively uncomplicated distal ureteroscopy into a more complicated proximal ureteroscopy and even leave residual fragments in the kidney, hence decreasing stone removal outcomes. The device is deployed through the ureteroscope just above the stone under direct visualization, and the ureteroscope is then repassed to the calculus alongside both the safety wire and entrapment device. Lithotripsy then commences. The bladder should be intermittently drained to avoid overdistension of the bladder and keep intraureteral pressures lower.
Types of intracorporeal lithotripsy include a variety of technologies, although Ho:YAG laser is clearly the current most efficacious and safe laser available. Other technologies include pneumatic or ballistic, ultrasonic, and electrohydraulic (EHL). These other forms of lithotripsy can be equally effective but have limitations, and we therefore recommend Ho:YAG as the first-line option.
Several techniques can increase visualization during ureteroscopy. Continuous controlled high-pressure irrigation (<200 mm H 2 O) with automatic irrigation devices or hand pump irrigation facilitate maximal visualization. Warm fluid is preferred, and normal saline should be used exclusively. Using the smallest instruments available through the scope also preserves flow. Laser settings are chosen based on the appearance of the stone and the laser available. If the stone appears soft and a high-power laser is available, then starting at a setting of 0.2 joules (J) and 50 Hertz (Hz) is an option and allows for “painting” and “dusting” of the stone while minimizing stone movement ( Fig. 41.2 ). If the stone appears harder, then the laser should initially be set at the lowest settings (0.6 J and 6 Hz) and gradually increased if necessary, thus ensuring the gradual fragmentation of the stone and minimizing retropulsion.