Fig. 29.1
Schematic diagram showing the positions of the surgical team, equipments and the patient (Modified with permission from Lopez and Duffy [34])
Cystoscopy is done to evaluate the bladder and ureteral orifices and place the guidewire into the ureter. The placement of guidewire should be done under scopic guidance to ensure the correct localization of the wire and to observe in order to prevent unintentionally pushing the stone upwards. (Trick: If PTFE-coated guidewire does not pass proximal to the stone, a hydrophilic guidewire may be tried to be inserted; if this also fails, then leave the guidewire as close as possible to the stone.)
The choice of caliber of ureteroscope is important. A large ureteroscope will provide a good flow of irrigation fluid and good vision with an increased risk of tissue injury. A fine ureteroscope facilitates entry to the ureter without dilatation and postoperative stent [21, 22], whereas vision might be problematic. Use of instruments ≤8 F is safe, and our experience showed that use of semirigid instruments larger than 8 F is more prone to postoperative complications. A recent study revealed that in children younger than 3 years old, mini-ureteroscope of 4.5 F caliber, the success rate was higher [23].
After the placement of the guidewire, the ureteroscope is inserted through the urethra into the ureter following the lumen of ureter beneath the guidewire. This approach will elevate the guidewire to widen the ureter orifice as a tent and will ease the entrance. (Trick: Especially for the stones located more proximally, it can be difficult to reach the stone. In this case, a second guidewire may be inserted within the ureteroscope so as to straighten the ureter. Trick: If entry to the ureter without dilation manipulations is difficult, first hydrodilatation of the ureteral orifice can be tried [24]; whenever ureter is entered, active squeezing of the hand pump should be stopped in order not to push back the stone. If hydrodilatation is not effective, balloon or coaxial dilatation may be used. Trick: If it is impossible to get into the ureter, then a double J stent can be placed to have passive dilatation, and a second session 2–4 weeks later can be tried [25]. Trick: In patients with a history of cross-trigonal ureteral reimplantation, an angled hydrophilic guidewire can be tried, or suprapubic placement of a guidewire through a puncture needle under direct transvesical endoscopic vision can be helpful, or a flexible cystoscope can be used for guidewire insertion.)
As the stone is reached, disintegration should be done preferably by laser source. Ho: YAG laser is advantageous over pneumatic lithotriptors because of its lesser pushing effect on stone and lower thermal and mechanical injury risk to the surrounding tissue. The power of Ho: YAG laser is usually set at 1–1.5 J and 5–8 pulses/s. The stone will be squeezed gently between the tip of the fiber and ureteral wall. The tip of the fiber should be placed on top of the stone and not in the middle. Fragmentation would be carried on until the particles become as smaller as the tip of the laser fiber that passes spontaneously with no need to extract. (Trick: The tip must be >1 mm away from the urothelium or the guidewire during activation of the laser pulses, as the depth of thermal injury is 0.5–1 mm. Trick: Irrigation pump should be used cautiously.)
If stones are fragmented with laser energy as small as the tip of the fiber, there is no need to extract them. However, if extraction of the stones is required, grasping forceps should be preferred. If basket will be used, fragments should not be larger than the tip of the ureteroscope. (Trick: If a large stone is entrapped within the basket and if the surgeon can’t release the stone from the basket, no attempt must be done to take out the basket in a locked position on a large stone which can cause ureteral avulsion. Instead, a 200-μm fiber can be inserted through the working channel of ureteroscope, and the stone can be fragmented at the hazard of the basket; alternatively, the handle of the basket can be disjoined, the ureteroscope can be taken out when the basket is left in the ureter, then the ureter is entered again, and stone in the locked basket can be fragmented and the basket can be released.)
During the operation, fluoroscopy should be used with consideration to the radiation exposure since it was shown that children receive significant radiation throughout the procedure significantly more than conventional X-rays, cystography, or computerized tomography [26]. Therefore, the surgeon should try his/her best to apply the as low as reasonably achievable (ALARA) principles (to maximize the source to skin distance, proper dose rate setting, judicious use of fluoroscopy, clear communication) during minimally invasive stone surgeries.
If the operation was straightforward with no complication, surgery may be ended without any ureteral stent. However, a ureteral catheter or a DJS with a string exiting from the urethra for a couple of days may be used. There is no consensus on the use of postoperative stenting. In complicated cases with a suspicion of injury or in cases with a high stone burden which necessitated different manipulations during the surgery, a DJS may be left in place for 2–4 weeks for resolution of local edema.
In the postoperative period, the urethral catheter – if placed – may be pulled out at the end of 24 h. Patient and the parents should be informed about the possible voiding problems due to the presence of the internal stent and early infectious complications. Routine analgesic for 2–3 days may be prescribed. Collecting and filtering the voided urine should be suggested to obtain the stone fragments to get analysis of the stone composition.
Success
Complications
Despite the minimally invasive nature of the endoscopic surgery, it is not without complications. A multi-institutional study on the factors affecting the complication rates showed that while operative time, age, institutional experience, orifice dilation, stenting, and stone burden were statistically significant on univariate analysis, operative time was the only statistically significant parameter on multivariate analysis [27]. Complications can be categorized as intraoperative, early postoperative, and late postoperative complications those listed in Table 29.1 [28].
Table 29.1
Review of the literature on complications of semirigid ureteroscopy for treatment of ureteral calculi [28]
Complications | Incidence (%) |
|---|---|
Intraoperative | |
Stone migration | <6 |
Ureteral perforation | <6 |
Inability to access the stone/place guidewire | <12 |
Conversion to open surgery | <13 |
Early postoperative | |
Hematuria | <27 |
Infectious complications | <4 |
Stent migration | <4 |
Late postoperative | |
Stricture | <2 |
Vesicoureteral reflux | 0–17a |
The intraoperative complications are stone migration, ureteral wall injury and avulsion, inability to access the stone, and conversion to open surgery. The stone migration can be prevented by use of fluoroscopy during retrograde guidewire placement, cautious use of irrigation fluid, gentle compression of the stone between the probe and ureteral wall during lithotripsy, and use of cone baskets if available. When proximal migration of the stone to the kidney occurs, retrograde intrarenal surgery or postoperative SWL may be the option. The ureteral wall injury most of the time is secondary to the unintentional contact of the probe to the ureteral mucosa. These injuries are generally minor and heal without any problem with postprocedural stenting. However, hemorrhage due to the injury can disturb the vision and complicate the operation. Inability to access the stone rarely may happen due to the local edematous tissue reaction just distal to the location of the stone. In these cases, making forceful maneuvers to reach the stone may traumatize the tissue that probably became edematous and fragile. Instead, placing a ureteral stent over a guidewire will solve the problem and dilate the ureter which will facilitate an easier second session. If stent placement fails, laparoscopic or open surgery might be indicated. The avulsion of the ureter may be the most devastating complication which occurs secondary to several factors. The forceful attempts to enter into the ureter with an inappropriate size instrument cause the avulsion of the distal end. Lithotripsy under a blurred vision situation may be the other cause. But the most important mistake which should be avoided is capturing a larger stone than the ureteral orifice with a basket and trying to retrieve it in an en bloc fashion. The open surgery as ureteroneocystostomy or ureteroureterostomy is the only option to repair the avulsion of the distal part of the ureter or a short segment. However, in very rare occasions, mostly due to the inappropriate use of basket, a very long segment can be traumatized that primary anastomosis is impossible. In this case, placing a nephrostomy tube and planning further complicated solutions (ileal ureter, autotransplantation) for ureteral replacement may be necessary.
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