Preoperative Considerations

Prior to surgical intervention for calculi, the patient should undergo preoperative anatomic imaging with CT noncontrast scan, ultrasound, KUB, or IVP. This will provide important details concerning the stone, including the location and size, which will aid in deciding on the treatment modality. Our standard remains to obtain CT imaging because in addition to the above information, the Hounsfield unit density and skin-to-stone distance may be calculated in order to predict success with alternative treatment options [17, 27, 28]. A detailed history and physical examination should be completed, and the patient should be medically optimized prior to surgery. Preoperative laboratory evaluation should include a urine culture, or urine dipstick in uncomplicated cases, 1–2 weeks prior to the surgery date and treated with culture-specific antibiotics, if necessary. Based on the AUA Best Practice Policy Statement, the antimicrobial prophylaxis of choice to be given prior to ureteroscopy is a fluoroquinolone or TMP-SMX with a duration of less than or equal to 24 h [33]. Alternative choices include aminoglycoside (aztreonam) ± ampicillin, first- or second- generation cephalosporin, or amoxicillin/clavulanate [33].

Technique

Table 13.2 lists an example of the instrument list required for ureteroscopic stone management, though the surgeon’s preference may favor alternatives. Figure 13.2 illustrates a step-by-step approach to ureterscopy. The patient is placed in the dorsal lithotomy position. A 19–22 F rigid cystoscope is inserted through the urethra into the bladder. The ureteral orifice is cannulated with a guidewire and advanced to the level of the renal pelvis. It may be useful to perform a retrograde pyelogram (RPG) using a 5 F open-ended ureteral catheter to delineate the anatomy of the collecting system prior to the placement of the guidewire.

Table 13.2

An example of a list of instruments required to perform ureteroscopy for the treatment of calculi

Rigid cystoscope (19–22 F) with 30° lens

Open-ended ureteral catheter (5 F)

Guidewire (Boston Scientific Sensor, following should be available: straight and angled Boston Scientific Glidewire and Boston Scientific Amplatz Super Stiff)

Flexible ureteroscope (Olympus P5/P6 fiberoptic ureteroscope, Storz Flex Xc digital ureteroscope)

Semi-rigid ureteroscope (ACMI Micro-6)

Camera and light source

Irrigation setup and endoscopic irrigator (Pathfinder, Boston Scientific Single Action Pumping System)

Adaptor (Applied Medical Sureseal, US Urology UroSeal)

Holmium laser fiber (200 or 270 μm) with setup

Radiopaque contrast (omnipaque)

Basket (1.5 F or 2.2 F N-circle, Cook 2.4 F N-compass)

Double J ureteral stent (6 F, 22–28 cm)

Optional – Cook ureteral access sheath (9.5/11.5 F, 10.7/12.7 F, 12/14 F or 14/16 F, 35–45 cm)

Optional – Cook ascend AQ dilation balloon

Optional – Cook dual lumen catheter or 8/10 F ureteral dilator Optional – Boston Scientific 8/10 F coaxial dilator

For distal or mid-ureteral stones, the semi-rigid ureteroscope is used to enter the ureter alongside the guidewire up to the level of the stone (Fig. 13.3). The semirigid ureteroscope has a larger working channel and is preferred over flexible ureteroscopes for distal ureteral stones. Depending on the size of the stone, it may be extracted with a basket or fragmented with holmium laser lithotripsy with subsequent extraction or evacuation of the fragments with irrigation. Generally, stones that are less than 4 mm may be successfully removed with a basket or graspers (Fig. 13.4). When removing stones or stone fragments, however, extreme care must be taken to make sure that the stone is withdrawn without resistance because ureteral avulsion is a risk if this is not done properly [34]. In addition, no blind basketing should be done for this reason.

For proximal ureteral or renal calculi, a flexible ureteroscope should be used. The flexible ureteroscope may either be inserted over a guidewire or inserted through a ureteral access sheath based on the surgeon’s preference. Free-handed technique alongside a guidewire may also be done in certain circumstances if preferred. If the ureteroscope does not pass the orifice, it may be necessary to sequentially dilate the distal ureter, which is the authors’ preference, or a balloon dilator may be used. Ureteral sheaths are available in a variety of diameters—from 9.5/11.5 to 14/16 F with lengths of 20–55 cm. Ureteral access sheaths facilitate repetitive access into the upper tract for basket stone extraction while decreasing operative time, improving stone-free rate, and decreasing intrarenal pressure [35–37]. However, they can be associated with ureteral injuries [38]. Therefore, it is recommended to insert these over a stiff wire, and excessive force should be avoided when inserting the access sheath. If the ureteral sheath does not insert easily, the inner obturator may be passed initially and then placement of the entire device should be attempted subsequently. Delvecchio et al. found a similar ureteral stricture rate, 1.4%, in patients who had a ureteral access sheath utilized during their ureteroscopy [39]. However, there is a theoretical risk of ischemic effects with the use of a ureteral sheath, and, therefore, it is best not to use large sheaths for long periods of time.

Ureteroscopy is typically performed with the use of a safety wire, meaning an extra wire that is not used to insert the ureteroscope or ureteral access sheath. This allows for continuous access into the kidney even if the ureteroscope or access sheath is removed. Furthermore, in the event of a ureteral injury or avulsion, it can provide a means to place a ureteral stent. If the use of a safety wire is preferred, then prior to insertion of the ureteroscope, a dual lumen catheter, or an 8/10 F dilator, may be inserted over the guidewire and a safety wire may be placed at that time. However, there are several publications documenting the advantage of not using a safety wire in experienced hands. Omitting the safety wire allows for greater ease when inserting the ureteroscope and decreases overall disposable equipment costs [40–43].

Lithotripter Options and Techniques

Historically, several technologies have been used to fragment urinary stones, including ultrasonic lithotripsy, electrohydraulic lithotripsy (EHL), laser lithotripsy, or pneumatic lithotripsy [44, 45] The holmium:YAG laser has been used since the early 1990s and is currently the most commonly used and studied modality as it is effective against all stone compositions, can be delivered through small laser fibers, and causes minimal damage to surrounding tissues [3, 46]. It fragments stones through a photothermal mechanism (Fig. 13.5) [47].

Multiple techniques have been described using the holmium:YAG laser. Wolf et al. described different approaches for stone fragmentation utilizing the holmium laser [48]. One commonly used technique is dusting the stone into small enough fragments that may spontaneously pass. This can be accomplished by using the dancing or chipping technique, as described by Wolf et al., in which the laser fiber is either brushed back and forth across the stone to ablate in layers or directed toward the periphery of the stone until small fragments of the stone are chipped off [48]. An alternative method, the popcorn technique, does not require the laser fiber to be in direct contact with the stone. Instead, the laser fiber is positioned near a collection of stones within a dependent portion of the calyx. The laser is fired continuously, creating rapid stone motion within the calyx and, ablation of the stone results from the collision of the stone fragments with the laser fiber [48].

In general, when one desires to fragment the stone with the goal of primarily extracting the pieces, a higher-energy setting (0.8–1.2 J) is used with a lower frequency (6–12 Hz) [49, 50]. If the goal is to primarily dust the stone into small enough fragments to pass, then lower energy settings (0.2–0.5 J) are used with higher frequency settings (40–80 Hz) [51, 52]. One significant innovation in laser technology has been the introduction of longer pulse widths and other stabilization methods to decrease stone retropulsion during treatment. The pulse width is the length of time that the laser energy is transferred to the stone. Increasing the pulse width results in decreased stone retropulsion [53–55]. It should be mentioned that laser settings across different lasers are not necessarily comparable, and therefore urologists should adjust the settings based on the observed and desired outcomes [53]. Furthermore, treatment efficiency is increased by increasing the overall wattage of laser settings. Therefore, if lower energy is to be used, higher frequency settings can decrease treatment time [54]. There is also growing data evaluating the heat produced by lasers. Therefore, higher pulse energies should be minimized when possible and irrigation should be used to decrease heat buildup [56, 57].

There has been much debate recently regarding the practice of fragmenting renal stones with subsequent basket extraction versus “dusting” the stone into small enough fragments for spontaneous passage. The EDGE consortium has recently published their data comparing dusting and extraction [58]. This was a multiinstitutional study where urologists performed the technique with which they were most comfortable. Their data showed that basket extraction increased the mean operative time by 38 min compared to the dusting group. There was no difference in the rate of complications, hospital readmissions, or additional procedures between the dusting and basket extraction groups. The authors utilize a combination of dusting and basket extraction, depending on anatomical features and stone characteristics. Stones that have a hard composition may not dust well and may require basket extraction. For larger stone burden in cases where PCNL is contraindicated, the authors prefer to perform a staged approach in which dusting is utilized for the initial procedure, and then on the second look procedure 2–3 weeks later a ureteral access sheath is utilized to basket extract fragments that did not pass. Furthermore, treating large volumes of stones may produce a large amount of debris, which may increase the risk of complications. The choice of technique also varies depending on the experience of the surgeon and available equipment.

The size of the laser fiber should be minimized in order to allow for better irrigation flow through the ureteroscope and deflection of the scope [52, 59]. Fortunately, there does not appear to be a significant difference in ablation volume or energy transmission between laser fibers from 200 and 365 μm [52, 59]. Moreover, there is significant variability between the advertised diameter and the actual diameter of laser fibers [60]. The authors prefer to use a 200–270 μm laser fiber for both semi-rigid and flexible ureteroscopy. This decreases the need to order and stock different sizes based on technique. When treating hard stones or performing prolonged laser lithotripsy surgeries, the tip of the laser fiber can degrade. This is commonly referred to as “burn-back.” The use of long pulse widths and lower pulse energy helps to minimize this fiber tip degredation [52]. If the tip of the fiber does begin to fray or break, this can be cleaved to create a fresh tip. Stripping the end of the laser fiber has often been advocated. However, this practice has been shown to decrease the efficiency of laser energy transmission [52]. This is partly because the coating helps to redirect laser energy toward the tip of the fiber and not out of the sides. The laser fiber should be positioned about 3 mm from the tip of the ureteroscope in order to minimize any damage to the ureteroscope. This distance can be estimated endoscopically by advancing the fiber at least 25% from the edge of the screen toward the middle [61].

Ureteral Stents

Most urologists place a ureteral stent at the conclusion of ureteroscopy. Pais et al. performed a meta-analysis demonstrating a twofold increase in unplanned visits after ureteroscopy when a ureteral stent was omitted in randomized trials. However, when trials were examined that left stent placement up to the surgeon, there was no difference in unplanned visits [62]. These data were corroborated by an analysis of the CROES (Clinical Research Office of the Endourological Society) database [63]. Therefore, the authors recommend routine placement of a ureteral stent for a duration of less than 7 days. However, the stent may be safely omitted after uncomplicated ureteroscopy, particularly when the stone is primarily extracted from the distal ureter without the need for ureteral dilation [64–66]. However, stents should be placed if there is evidence of ureteral trauma, injury, or stricture, if a large residual stone burden was treated, or in the case of patients with a solitary kidney, renal insufficiency, and coagulopathies.

The authors generally use a 5 or 6 F diameter stent. The length of the stent can be estimated based on the patient’s height or measured endoscopically using a ureteral catheter or by measuring the length of the ureter on preoperative imaging [67, 68]. Most ureteral stents come with an extraction string attached. This can be left in place or removed prior to inserting the stent. Leaving the string on the stent allows the patient to remove the stent or is for stent removal in the clinic without the need for cystoscopy. However, leaving the string, while more convenient, places the patient at a higher risk for accidental premature removal of the stent. A string should only be left if the stent is needed for 7 days or less. One technique is to leave the string shorter in the male so that it is in the anterior urethra, facilitating cystoscopic removal without having to enter the bladder while also eliminating premature stent removal. The stent is typically left in place between 3 and 7 days following routine ureteroscopy and for longer duration, 2–6 weeks, following ureteral injury or dilation of ureteral stricture.

Placement of the stent may be accomplished with the use of the rigid cystoscope under direct visualization or fluoroscopically. For placement under direct visualization, the stent pusher is inserted through the working channel of the cystoscope. The guidewire is then “backloaded” through the pusher. Then the pusher is removed, leaving the guidewire in the cystoscope. The cystoscope is then advanced into the bladder in order to visualize the ureteral orifice. The stent is advanced through the cystoscope with the pusher until the distal black marker on the ureteral stent is at the ureteral orifice and the proximal end of the stent is in proper position within the renal pelvis. At this point, the guidewire is withdrawn enough to see the proximal end of the stent coil into good position under fluoroscopic visualization. Attention is then turned to the distal end of the stent. The cystoscope is withdrawn to the bladder neck, and the stent is advanced until the distal end is at the bladder neck. The guidewire is completely removed, and the distal end of the stent will subsequently be curled within the bladder. In cases with a narrow renal pelvis, the extraction string may be used to set the proximal curl and then subsequently removed, if desired, before setting the distal curl.

The second approach to the placement of the ureteral stent is under fluoroscopic visualization alone; see Fig. 13.6, which outlines the steps as described below. The ureteral stent is advanced over the guidewire using the pusher. The C-arm should be positioned over the bladder, and the pusher should be advanced until the radiopaque marker is at the mid-pubic symphysis. Maintaining the pusher in the same position, the C-arm is moved to the kidney to ensure that the proximal end of the stent is in good position. The guidewire is withdrawn enough to see the proximal end coil within the renal pelvis. The C-arm is then relocated over the bladder, and fluoroscopy is used to ensure that the marker on the pusher is still in the proper location. Once verified, the guidewire is completely removed, deploying the distal end of the stent to coil within the bladder.

Difficult Ureteral Access

An impacted ureteral stone or ureteral stricture may make placement of the guidewire into the renal collecting system difficult. If this occurs, then the ureteral access catheter should be passed over the guidewire just distal to the level of the obstruction, and a retrograde pyelogram should be performed. Using the imaging gained from the retrograde pyelogram, a hydrophilic guidewire, such as the glidewire, should then be readvanced through the ureteral access catheter to negotiate past the obstructing stone or stricture. It is important to carefully manipulate the guidewire with care so as not to perforate the ureter. Glidewires are often able to bypass an impacted stone and are less likely to cause a false passage or ureteral perforation. There are both straight and angled glidewires available. Once the glidewire is coiled within the renal pelvis, the ureteral access catheter should be passed over the wire and above the area of obstruction. If the urine draining from the access catheter appears to be infected, then the procedure should be abandoned, a stent should be placed, and treatment should be performed after appropriate antibiotics have eradicated the infection. Otherwise, the glidewire should then be exchanged for a stiffer guidewire to avoid the glidewire from inadvertently being removed. If access is not possible by this point, it may be safer to have a nephrostomy tube placed and refer to a more experienced center.

However, in experienced hands, another option is to place a wire under direct visualization using a ureteroscope. A guidewire should be left in place just below the impacted stone, and the ureteroscope, either semi-rigid if within the distal ureter or flexible if within the mid/proximal ureter, should be passed to the level of the obstruction. Under direct visualization, the degree of stone impaction and/or ureteral stricture may be assessed. The guidewire may then be directed around the obstruction at a favorable appearing location. If stone impaction prevents this, then laser lithotripsy may be carefully performed until a guidewire is able to be passed. It is not recommended to attempt basketing the stone without a safety wire in place. In cases of failed retrograde access, a percutaneous nephrostomy tube should be placed with plans for antegrade ureteroscopy.

For a ureteral stricture, after successful retrograde access, the next step is determined by the location of the stricture that is compromising access to the stone. Due to the fragility of the proximal ureter, it is best to stent and allow for passive dilation rather than active dilation with a ureteral balloon dilator. A second-look URS may be done in 1–2 weeks, typically with an easily accessible ureter. For distal ureteral strictures, a safety wire should be placed prior to balloon dilation. The safety wire may be placed with a dual lumen catheter, 8/10 dilator, or under direct visualization with the ureteroscope.

Ureteral balloon dilators can be used for the dilation of distal ureteral strictures that compromise access to the ureteral stone. The balloon has radiopaque markers at the proximal and distal ends, which is used to position the balloon over the working guidewire using fluoroscopy (Fig. 13.7). They should never be inflated over an obstructing ureteral stone due to the risk of ureteral perforation. Once the balloon is in proper position, it is inflated with half-strength contrast using a pressure gauge syringe. The balloons typically can withstand inflation pressures up to 17–20 atm; however, dilation of the ureter typically can be achieved at lower pressures (4–6 atm). The lowest pressure necessary to dilate the ureter should be used to avoid ureteral perforation, and therefore it is important to inflate the balloon under fluoroscopic guidance. Typically, a “waist” is seen in the balloon at the location of the stricture, and one should continue to inflate slowly until the “waist” disappears. The balloon is then deflated and removed, leaving the guidewire in place. Ureteroscopy may then be performed to treat the stone.

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