Indications for therapeutic retrograde ureteroscopy
The modern indications for therapeutic retrograde ureteroscopic approach can be summarized as follows ( ):
extraction of ureteral calculi regardless of their location ( , )
treatment of pyelocaliceal lithiasis (in selected cases)
treatment of the steinstrasse syndrome after extracorporeal lithotripsy
endoscopic treatment of superficial tumors of the upper urothelial field (in selected cases) ( )
endoscopic treatment of symptomatic caliceal diverticula and of intradiverticular lithiasis (in selected cases) ( )
endoscopic treatment of intrinsic or extrinsic ureteral stenoses, benign or malignant ( , )
endoscopic treatment of stenoses of the pyeloureteral junction, congenital or acquired ( )
extraction of intraureteral foreign bodies
treatment of iatrogenic ureteral lesions
The treatment of upper urinary tract stones is the most important indication of retrograde ureteroscopy.
It is likely that the modern urologist’s major dilemma is choosing between the most commonly used therapeutic methods: extracorporeal lithotripsy (SWL) and ureteroscopy. The progress regarding the design of ureteroscopes, as well as the evolution of extracorporeal lithotripsy, has changed the balance between the indications for these methods of treatment in ureteral lithiasis.
According to the guideline of the European Association of Urology (EAU), the therapeutic indications for ureteral lithiasis are differentiated by location, size, degree of obstruction, chemical composition, and potential association of infection ( Tables 5.1–5.4 ).
|Calculi complicated with infection|
|Uric acid calculi|
|Calculi complicated with infection|
|Uric acid calculi|
|Calculi complicated with infection|
|Uric acid calculi|
|Without obstruction||Obstruction and/or existing symptomatology|
The re-evaluation of data available in recent meta-analyses in 2007 led to a consensus between the European and American Urological Associations (EAU/AUA).
According to this consensus, spontaneous elimination of the calculus through pharmacological treatment can be considered a first-line option for ureteral stones smaller than 10 mm with symptoms that can be controlled therapeutically.
The success rate of spontaneous elimination, according to the meta-analyses, is of approximately 68% for calculi smaller than 5 mm and of 47% for those with sizes between 5 mm and 10 mm.
Patients for whom this therapeutic alternative is selected should not present signs of sepsis. They should also have an adequate renal functional reserve and it should be possible for their symptoms to be controlled by pharmacological treatment. These patients should be monitored regularly, active removal of the calculus being recommended in case of persistent obstruction, of colicky pains refractory to treatment, or of the absence of calculus progression.
For calculi larger than 10 mm, the first-line treatment is interventional, both SWL and ureteroscopy being viable alternatives. Patients should be informed about the benefits and risks of each method. A number of parameters must be taken into account when choosing one alternative or another: the “stone-free” rate, the type of anesthesia required, any auxiliary procedures, as well as the risk of complications. The “stone-free” rate is, in turn, dependent on several factors, including the location, size, and chemical structure of the calculi ( ).
The semirigid ureteroscopic approach of distal ureteral lithiasis ensures a success rate of almost 100%, this method being almost unanimously considered as the first therapeutic option. Although the success rates of semirigid ureteroscopy for middle and proximal ureteral calculi are lower, the introduction of flexible instruments has increased the success rate to over 90%. This has recently caused the balance to tilt in favor of ureteroscopy in the detriment of SWL. The introduction of modern methods of lithotripsy, especially the Ho:YAG laser, has contributed significantly to this development.
The development of flexible ureteroscopes has allowed the indications of retrograde approach to include pyelocaliceal lithiasis ( Table 5.5 ). Although these flexible ureteroscopes, together with the new sources of lithotripsy, theoretically allow treatment regardless of size and location, the best results have been recorded in the approach of calculi smaller than 2 cm. Even in these cases, calculi located in the middle or upper calyces may benefit from extracorporeal lithotripsy as a first-line alternative. Lower caliceal lithiasis respresents an elective indication for retrograde flexible approach.
|Single or multiple ureteral, pyelic, and/or caliceal lithiasis|
|Endoscopic alternative in cases in which retrograde rigid ureteroscopy cannot be performed (urinary derivations, etc.)|
|Endoscopic alternative in cases in which extracorporeal lithotripsy, percutaneous nephrolithotomy, or retrograde rigid ureteroscopy are contraindicated|
|Removal of lithiasic fragments remaining after SWL or PNL, or of calculi that ascended during rigid or semirigid retrograde ureteroscopy|
|Intradiverticular lithiasis allowing concomitant treatment of the caliceal diverticula|
The progress regarding ureteroscopic instruments, especially the development of miniaturized and flexible endoscopes, has allowed this method to also be used safely in pregnant women. This indication is even more important as the alternative, SWL, is contraindicated in this category of patients ( ).
By improving accessibility in the entire upper urinary tract, it has become possible to perform retrograde ureteroscopy in an increasing number of patients with urinary malformations or derivations.
Regarding pyelocaliceal diverticula, there is currently a wide range of surgical options available for the treatment of this pathology: open interventions, retrograde ureterorenoscopic approach ( ), direct and indirect percutaneous approach ( ), or laparoscopic approach ( ). The indications of retrograde ureteroscopy are limited to symptomatic diverticula, smaller than 1.5 cm, with or without intradiverticular stones ( ), and especially for those positioned anteriorly, difficult to approach percutaneously ( ).
For tumors of the upper urinary tract, the “gold standard” of treatment is represented by nephroureterectomy with perimeatal cystectomy. However, due to technological progress, ureteroscopic approach may represent a viable therapeutic option in particular situations ( Table 5.6 ).
All symptomatic patients or those with obstruction due to benign ureteral stenosis present an operatory indication in order to preserve renal function.
Open surgical techniques used for the treatment of ureteral strictures (ureteroneocystostomy, kidney mobilization, Boari flap, transureteroureterostomy, bowel interposition, renal autotransplant, nephrectomy) involve abdominal interventions (some major) that are associated with high morbidity and with prolonged hospitalization and social reintegration.
The indications of ureteroscopic approach of ureteral stenoses can be summarized as follows:
benign inflammatory ureteral stenoses
iatrogenic ureteral stenoses
ureteral stenoses under 2 cm
For the treatment of ureteral stenoses by endoscopic approach, the following can be used: cold-knife incision, electroincision, Acucise balloon, balloon dilator, and, more recently, laser.
The technical method of application is individualized according to the characteristics of each case ( Fig. 5.1 ). Regarding the indications of using metallic ureteral stents, these are not yet fully systematized, most authors recommending positioning this type of stent in both malignant and benign ureteral stenoses.
The treatment of ureteropelvic junction stenosis is imposed by the presence of symptoms associated with the obstruction, the progressive deterioration of the ipsilateral or even global renal function, the association of lithiasis, of urinary infection or, in rare cases, of arterial hypertension.
Although, theoretically, retrograde ureteroscopic approach can be used in most cases with ureteropelvic junction stenosis, achieving optimal success rates depends on a careful selection of cases. Thus, the presence of negative predictive factors such as preoperative renal function <20%, increased stenosis length, and association of polar vessels or of severe hydronephrosis indicate that other therapeutic modalities should be used. Other circumstances that would contraindicate retrograde endoscopic approach are represented by the association of renal lithiasis (and especially the voluminous one, which more readily benefits from percutaneous treatment) or by the high insertion of the ureter at the pyelic level (the latter being a controversial negative predictive factor).
Antegrade ureteroscopy has limited indications, usually being reserved for cases with very difficult or impossible retrograde approach, or in those in which it completes the percutaneous approach of some pyelocaliceal injuries.
Technological progress, especially the introduction of flexible ureteroscopes and of modern power sources, has allowed the diversification of the indications for retrograde approach to also include certain particular situations (pregnant women, children, patients with malformations of the upper urinary tract, etc.).
Limitations of rigid and semirigid ureteroscopy
The limitations of rigid and semirigid ureteroscopes derive from their reduced degree of elastic deformation and from their relatively increased diameter.
Thus, the advantages of a working channel that allows the use of a wide range of accessory instruments, superior visibility and reliability, or ease of handling in the distal region of the upper urinary tract are offset by limited access to the pyelocaliceal system and, sometimes, even to the ureter.
The use of rigid ureteroscopes with an increased diameter requires, in a significant percentage of cases, the dilation of the ureteral orifice. This method usually implies post-procedure stenting and, implicitly, an increase in associated morbidity. The coexistence of pathological changes (cystocel, voluminous prostate adenoma, etc.) may limit rigid retrograde access to the pelvic ureter.
Reno-ureteral malformations, stenosis, or important bends may prevent the ascent of the (semi)rigid endoscopes at different levels of the upper urinary tract.
Limiting access to the entire pyelocaliceal system may require interrupting the intervention in certain circumstances (e.g., ascending migration of a proximal ureteral stone).
The physical characteristics of rigid ureteroscopes (especially those of high caliber), as well as the use of more robust accessory instruments, is associated with an increased incidence of upper urinary tract traumatic complications.
Despite the continuous efforts to overcome these obstacles by improving the semirigid endoscopes (miniaturization, introduction of digital optical systems, etc.), the development of flexible ureteroscopes seems to offer, at least in perspective, much more efficient and versatile solutions.
Limitations of flexible ureteroscopy
The Fragility and Increased Cost of Instruments
Flexible ureteroscopes are expensive endoscopes compared to their rigid or semirigid counterparts. In addition, this method requires the use of certain types of accessory instruments or energy sources for lithotripsy (flexible, with a low caliber in order to be inserted into the working channel, etc.), which in turn contribute to the increased costs of flexible ureteroscopy.
The miniaturization of flexible ureteroscopes, with the purpose of reducing operatory trauma on the urinary tract, has unfortunately resulted in their increased fragility. The low caliber, the existence of the deflection system, and the insertion of instruments into a working channel that is not straight, all create the conditions for damaging these endoscopes.
Some of the most common causes of destruction of flexible ureteroscopes are represented by the accidental discharge of the laser fibers in the working channel, perforation as a result of the insertion of accessory instruments, or excessive twisting. Laser fibers are the accessories with the greatest potential for damaging the working channel. Seto and Ishiura evaluated this effect in an in vitro study that involved inserting various accessory instruments 100 times through the endoscope with 0, 30, 60, 90, and 120˚ deflections. The occurrence and severity of potential injuries were subsequently determined by testing the tightness of the working channel and evaluating its internal surface with a small caliber fiberscope. Thus, the repeated insertion of 3 F forceps or of 2.4 F basket catheters produced no significant damage, regardless of the deflection angle. Fiberscopic assessment of the internal surface of the working channel after inserting 200 and 250 μm laser fibers revealed minor abrasions for angles of 0 and 30° and deep imprinting for deflections of 60 and 90°. Advancing laser fibers into the working channel of the ureteroscope with a 120° deflection was not possible nor produced perforations ( ).
Even when used carefully, avoiding the accidents presented earlier, a phenomenon of “fatigue” has been described in flexible ureteroscopes, with their performance steadily decreasing over time.
Older models had a period of functioning of approximately 3–13 h or 6–15 uses before requiring repairs, the reduction of the maximum amplitude of active deflection being the problem that occurred most frequently, especially after interventions that required a prolonged approach of the lower caliceal group ( ).
In a study conducted with four 7.5 F flexible ureteroscopes, an average number of 50.3 passages was reported (varying between 42 and 66) until losing 25° of deflection ( ).
Despite technological progress, this phenomenon continues to appear, although more slowly, in new-generation flexible ureteroscopes. Traxer and coworkers evaluated a Storz 11278 AU1 Flex-X flexible ureteroscope; after a number of 50 procedures consisting of a total of 17 h and 15 min, the authors registered a decrease of the maximal ventral deflection from 270° to 208°, of the maximal dorsal deflection from 270° to 133°, and of the flow of the irrigation fluid at a pressure of 100 cm H 2 O from 50 mL/min to 40 mL/min ( ).
Monga and coworkers in a prospective and randomized trial evaluated the durability of seven models of flexible ureteroscopes: Storz 11274AA and Flex-X, ACMI DUR-8 and DUR-8 Elite, Wolf 7330.170 and 7325.172, respectively Olympus URF-P3. According to the results of this study, the ACMI DUR-8 Elite and Olympus URF-P3 models appear to have superior resistance. Thus, the longest functioning period without repair (494 min) was registered for the DUR-8 Elite model, the longest period of lower caliceal approach was registered for the URF-P3, while both models presented the longest working period with inserted accessory instruments ( ).
Another problem is represented by the fracturing of the fibers that compose the optical system of conventional flexible ureteroscopes. Each broken fiber generates a black dot in the endoscopic field ( Fig. 5.2 ), and when there is a significant number of these, they can alter visibility, preventing the interventions from being carried out in good conditions.
Assessing four older models of flexible ureteroscopes, Pietrow and coworkers reported an average of 15.3 passages (varying between 12 and 20) until the breaking of over 20 optical fibers was recorded ( ). In order to extend the lifespan of the optical system, it is recommended to avoid any external trauma to the working region of the flexible ureteroscope, as well as excessive torsioning or bending.
The optical systems of the latest-generation conventional flexible ureteroscopes seem to have superior durability; Traxer reported only six broken fibers after 50 procedures with the Storz Flex-X model ( ). In the case of the new models of digital flexible ureteroscopes, the fragile optical fiber system has been removed, the image being transmitted from the distal sensor to a proximal processor through a single wire.
The great variability regarding the results of durability studies indicates the influence of various factors (related to the operator, handling and storage conditions, the treated pathology, etc.) on this phenomenon. When adequately handled, the new generation of ureteroscopes, although still having a high potential for being damaged, presents a superior durability, offering a greater number of hours of use before requiring repairs, compared to previous models.
Different methods and technical artifices have been studied and devised in order to prolong the functioning period of flexible ureteroscopes. Thus, the routine use of nitinol accessory instruments, with an increased flexibility, which are less demanding on the deflection mechanism, has been proposed ( ). In addition, these present a reduced aggressiveness on tissues and superior durability.
Also, some authors believe that the routine use of the ureteral access sheath reduces the aggression on flexible ureteroscopes, the operating time, and the costs of the interventions ( ).
In order to protect the working channel, advancing the 200 μm laser fiber through a previously inserted 2 F catheter has been proposed. Although the flexible ureteroscope’s deflection does not seem to be diminished by the insertion of this catheter, the flow of the irrigation fluid is reduced ( ).
The application of a ceramic protective layer on the distal region of the new models of ureteroscopes is part of the effort to prolong the working period of flexible endoscopes. Thus, the Storz 11278AU1 Flex-X presents a layer of Laserite™ ceramic material on a 1.5 cm distal part of the working channel, which has the role of protecting the area from accidental discharges of the laser fibers and of allowing lithotripsy in the immediate proximity of the endoscope. Similarly, the Olympus URF-P5 model presents a ceramic piece in the distal part, with a protective role during electrohydraulic lithotripsy. In order to prevent the fatigue phenomenon, it is recommended to limit the working period at the level of the lower calyx. For this purpose, the displacement of calculi at this level and their fragmentation in the renal pelvis will be preferred instead of in situ lithotripsy ( ).
Visibility during flexible ureteroscopy is reduced, compared with rigid or semirigid endoscopic interventions. This phenomenon is the result of several factors:
small size of the endoscopic field
poor image resolution
low irrigation flow
lack of clarity of the pyelocaliceal environment (hematuria, pyuria)
The miniaturization of flexible ureteroscopes has imposed the reduction of the dimensions of the optical systems and of the working channel, with direct implications on intraoperative visibility ( Fig. 5.3 ).
The currently used conventional flexible ureteroscopes generally have an endoscopic visual field area of 20–22 cm 2 . An exception is represented by the Olympus URF-P3 model, which has the widest endoscopic field, measuring 25 cm 2 ( ).
Conventional models have optical systems consisting of a coherent beam of glass fibers. This structure generates the previously described images with a honeycomb aspect (or moire effect), with a lower resolution than that obtained by the optical systems of rigid or semirigid ureteroscopes. The flow of the irrigation fluid is one of the essential parameters of obtaining sufficient visibility for performing endoscopic interventions in good conditions. Most flexible ureteroscopes in use today have a working channel of 3.6 F, providing a reduced irrigation flow compared to the rigid or semirigid models.
The Wolf 7330.072 flexible ureteroscope has a 4 F working channel, allowing an increased flow of the irrigation fluid, which leads to better visibility, but with the disadvantage of a higher caliber of 9 F at its tip.
The insertion of the various accessory instruments, probes, or lithotripsy fibers into the working channel further reduces the irrigation flow ( Table 5.7 ). There is a correlation between the dimensions of the instruments used and the reduction of the irrigation flow.