Pictorial review of tips and tricks for ureteroscopy and stone treatment: an essential guide for urologists from PETRA research consortium

Introduction

Ureteroscopy (URS) was first described by Marshall in 1964 although it was only in 1987 that Bagley introduced the flexible URS (fURS) (1,2). From treatment of small stones in index patients, the spectrum of ureteroscopic stone surgery has now increased to treat large renal stones, stones in pregnancy, morbid obese, urinary diversion, paediatrics and patients with calyceal diverticula (3-7). Similarly, it is now used as a first line diagnostic tool for upper tract TCC and for its treatment in selected group of patients (8,9).

While there are a few papers that mention the ‘tips and tricks’, they lack the pictorial description of some of the key aspects of URS and stone treatment. In this review article we describe some of these important steps, supplemented with pictures, which enhances the understanding of these steps.

Operating room (OR) set-up and preparation for URS procedure

Under general anaesthesia, with peri-operative antibiotic prophylaxis, the patient is placed in a lithotomy position and the fluoroscopy is set-up. For fluoroscopy, always place the X-ray source under the table and the receptor above but closer to the patient to decrease the zoom effect and the radiation exposure to the surgeon.

As the operator is standing, it is recommended that he/she is not directly facing the patient. The ideal position is a 90-degree rotation in a lateral position. This allows the operator to block and control the ureteroscope (Figure 1). The safety wire is secured inside the plastic sheath of the wire. To avoid displacement, this should be at the same level and as close to the urethral orifice as possible (Figure 1). To maintain a low intrarenal pressure, a simple gravity irrigation using saline should be used with a pressure of no more than 40 cm water (30 mmHg). The outflow can be enhanced by using a ureteral access sheath (UAS). As the laser fiber is 2–2.5 m long, for asepsis and safe handling it should be placed on the working table with saline soaked compresses or gauze on top of the fiber. Its weight will stabilise the fiber. The equipment set-up should allow the radiology C-arm and endoscopic tower to be on the contralateral sides.

Figure 1 Operator position, controlling safety wire and maintaining intrarenal pressure.

Use and ergonomics of the equipment (safety wire, ureteral access sheath)

Guide wires are helpful to get access in the renal collecting system and for passage of scopes and stents. Typically, guide wires have a flexible tip, low friction and a rigid shaft. A ureteral access sheath (UAS) is increasingly used for treatment of large renal stones (10). Whilst it facilitates multiple scope passages, it also helps to reduce the intrarenal pressure thereby improving flow and visibility. Studies have shown a reduction of infectious complications with its use (11).

The selection of UAS is based on the clinical necessity, patient anatomy, type and size of the ureteroscope used as well as surgeon’s preference (12). Intrarenal pressure depends on the inflow via the working channel (typically 3.6 Fr), and outflow via the residual space between the ureteroscope and wall of UAS. It is recommended to use a smaller size UAS and not to apply force while placing it. While it aids flexible URS, care must be taken to ensure its safe placement avoiding injury to the ureter. Long-term use of UAS has a theoretical risk of ureteric stricture although this has not been proven in a recent paediatric study (13). The tip of UAS should be either just below pelviureteric junction (PUJ) or in the upper ureter. If UAS placement encounters resistance, then the scope should either be placed over the guide wire or a temporary ureteral stent is inserted for a secondary URS procedure at a later date (14,15).

Ureteral orifice access

Ureteral access is an important step in endourology and must be done safely. We recommend placement of a safety wire via a cystoscope first. Once the position is confirmed, a semi-rigid URS (R-URS) is then carried out over a working wire using the dominant hand (16,17). If the ureteric orifice (UO) is tight or difficult to access, rotate the scope 90°–180° at the UO to help with access. Semi-rigid URS allows a natural dilatation of the UO and the ureter along with identification and treatment of ureteric stones. Besides, mapping the ureter allows an estimate of the possibility and size of UAS that can be inserted.

Flexible scope manipulation

A flexible URS (F-URS) can either be inserted via a UAS or directly over a guide wire. For the later, an angled guidewire is helpful (Figure 2). Scope manipulation uses a combination of rotation, deflection and in/out movement (Figure 3). With the dominant hand pronation and supination is used to change the direction of the tip of the scope, supination is useful when the scope is in the right renal cavities and pronation is useful when the scope is in the left renal cavities. The exploration of the collecting system is begun with the upper calices followed by middle and lower calices.

Figure 2 Scope and wire manipulation to access the ureteric orifice.

Figure 3 Movements of flexible ureteroscope.

While the macro rotation happens through the dominant hand with scope manipulation, the micro rotation happens with the non-dominant hand at the urethral meatus (Figure 4). The black triangle on the screen denotes the 12 o’clock position and bubble reflects anterior calyces and can be especially useful when using digital F-URS (Figure 4). The scope deflection is also different for the scopes marketed in Europe and USA, whereas deflecting the scope up the tip of scope goes down in Europe, it goes up in USA and vice versa (Figure 4).

Figure 4 Micro and macro rotation of the scope and identification of screen position.

Improving vision

Vision is the key for achieving good results during URS and there are certain tricks to improving it. Focusing the scope, adjusting brightness and white balance is the key before beginning the procedure. UAS enhances irrigation and potentially provides a better vision. Similarly, use of pressure irrigation devices can also help improve vision although it should be used carefully and judiciously to avoid complications related to haemorrhage and infections (18-20). Contrast can be useful to clear debris, blood or dust during the procedure and improve vision, although sometimes it might helpful to be patient and wait for the vision to improve naturally. The newer digital scopes also offer a better vision than the older fiberoptic scopes (21).

Laser use and settings

Lasers play a big role in modern endourology with holmium:yttrium-aluminum-garnet (Ho:YAG) proving its safety and efficacy over the last 2 decades (22). Pulse duration, energy and frequency can all be adjusted to either fragment, dust or popcorn the stone (Figures 5,6). While ureteral stones are treated from center to surface, kidney stones are treated from the surface to the center. Fragmentation uses a short pulse duration with high power and low frequency, dusting uses a long pulse duration with low power and high frequency, and popcorning uses a long pulse duration with relatively high power and frequency. Recently, pop-dusting (0.3–0.6 J and a frequency of 20–50 Hz) has also gained momentum which can treat large stones in a single setting (23).

Figure 5 Laser settings for stone treatment.

Figure 6 Laser settings for fragmentation, dusting and popcorning.

Stone clearance

Irrespective of the technique is used for lasering the stone, it must be remembered that stone volume is not proportionate to the diameter (Figure 7). Larger stones have significantly larger volumes, and this should be recognised while counselling patients for their treatment. It is therefore practically impossible to remove all stone fragments while treating larger stones.

Figure 7 Stone volume, laser fiber introduction in lower pole, glue-clot technique.

While treating lower pole stones, it might be beneficial to reposition the stone to a more accessible place such as the upper pole before it is treated. In case the stone cannot be repositioned, the laser fiber should ideally be introduced in an undeflected (straight) scope and the F-URS deflected after the fiber is at the tip of the scope (Figure 7). This technique avoids the potential for scope damage although with the disposable scopes and the ball-tip laser fiber the risk is minimised and it is possible to insert the fiber in a deflected scope, albeit at a higher cost (22,24,25). It is also possible to insert the laser fiber and the basket simultaneously via the working channel of the F-URS. After the procedure is completed, the glue-clot technique (24,26) allows the autologous blood to seal the lower pole and to remove the dust and small fragments which become trapped in the clot.

URS for upper tract TCC

Ureteric biopsy has gained importance in the last two decades and correct characterisation seems to be fundamental for diagnosis and patient selection for endoscopic management (8,27,28) (Figure 8). For papillary lesions, the nitinol basket achieves a good histological characterisation (27). Even tumours >1 cm and multifocal tumours can be managed conservatively with laser photoablation (8).

Figure 8 Upper tract tumour biopsy and ablation.

Use of URS in special situations

Flexible URS has been used to treat parapelvic cysts, calyceal diverticuli and ureteric/PUJ strictures (29-31). Once the F-URS is in the renal pelvis, the cyst is identified, and incision and drainage of renal cyst wall is done with a laser (29) (Figure 9). A post-incision ureteric stent is placed in the cyst and removed after 4 weeks. For a diverticulum, contrast with indigo carmin is injected to identify the diverticular neck under fluoroscopic guidance. Once the collecting system is washed with saline, the leakage of dye from the diverticulum is seen endoscopically and the neck of the diverticulum is incised with a laser (14,24). For ureteral stricture, this needs to be located and a full-thickness incision into fat is performed. To avoid vascular injury this is done posterolaterally for proximal stricture and anteromedially for distal strictures (30,31) (Figure 9).

Figure 9 Treatment of parapelvic cyst, calyceal diverticulum and ureteral stricture.

Strengths, limitations and areas of further research

While there are a few reviews on tips and tricks of F-URS, a pictorial guide helps to explain the steps and provides a better understanding of the procedure. These technical principles are our own suggestions and there may be other effective ways to accomplish many of the tips and tricks’ we describe. Although we have tried to explain the important steps, we were not able to explain the procedure on its entirety. This is not a step-by-step guide for how to perform URS, rather an opportunity to refine technical steps of the procedure. It has been shown that URS is more cost effective than shockwave lithotripsy but in future more needs to be done for simulation-based training in URS so that the training is standardised, and this translates into better clinical outcomes (32,33).

Conclusions

Flexible URS has revolutionised the treatment of kidney stones with expanding indications and safer outcomes. We hope that these ‘tips and tricks’ will help in guiding endourologists for an effective and safe treatment for upper urinary tract surgery.

Acknowledgments

None.

Footnote

Conflicts of Interest: The authors have no conflicts of interest to declare.

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