Abstract
With improvements in optics and miniaturization of technology, endoscopic urologic procedures in children have advanced tremendously over the last few decades. Surgeries have become more precise, and smaller instruments now provide safe and effective minimally invasive approaches to uncommon and common urologic diseases of childhood. In this chapter, we describe the outcomes and complications of common cystoscopic interventions and endoscopic stone procedures used in pediatric urology as well as tips for successful endoscopic surgery in children.
Keywords
Nephrolithiasis, Bleeding, Sepsis, Ureteroscopy, Percutaneous nephrolithotomy, Ureterocele puncture, Posterior urethral valve ablation
Chapter Outline
[CR]
Key Points
- 1.
Technological advances and miniaturization have increased the ability to treat certain urologic conditions endoscopically.
- 2.
Though complications are generally less common with endoscopic surgery than corresponding open approaches, they can still be significant and warrant equal caution in preventing.
- 3.
Due to the increasing burden of nephrolithiasis among children, the need for optimizing surgical treatment has never been higher.
Cystoscopic Interventions
The miniaturization of optics and instrumentation has allowed endoscopic approaches to certain urologic pathologies. Common cystoscopic procedures include puncture of ureteroceles, endoscopic injection for vesicoureteral reflux, and ablation of posterior urethral valves.
Puncture of Ureterocele
A ureterocele is a cystic dilation of the distal aspect of the ureter where it enters the bladder. Embryologically, it is thought to be a remnant of Chwalla’s membrane. Ureteroceles are classified into intravesical, extravesical, or ectopic and can be found in both single and duplicated collecting systems. A ureterocele can cause obstruction of the ipsilateral collecting system, leading to loss of kidney function and occasionally obstructive urosepsis if not recognized and addressed in a timely fashion. When intervention is needed, or planned, initial surgery usually entails a cystoscopic ureterocele puncture. Different techniques have been described for ureterocele puncture, but the goal remains the same: Unobstruct and decompress the ureterocele and its accompanying upper tract system, without causing de novo vesicoureteral reflux. The authors prefer incision with a monopolar hot knife or Holmium laser at the base of the ureterocele. Others have described a “watering can” puncture technique with purported lower de novo vesicoureteral reflux, although larger studies are needed for external validation.
Success rates of ureterocele puncture are varied, depending on the number of collecting systems and the type of ureterocele. Some studies report better success – meaning resolution of obstruction and lack of additional procedures – for intravesical ureteroceles compared to extravesical or ectopic ureteroceles. A systematic review and meta-analysis of outcomes following ureterocele puncture revealed a significantly higher risk of reoperation after puncture of an extravesical ureterocele. Rates of reoperation ranged from 0% to 50% for intravesical ureterocele punctures, compared to 48–100% for extravesical ureterocele punctures. This finding remained robust on sensitivity analyses restricting the meta-analysis by duration of follow-up, age at surgery, and duplex systems only. However, heterogeneity and publication bias were both present. Similarly, in the same systematic review and meta-analysis, duplicated systems were at greater risk for reoperation than were single-system ureteroceles after cystoscopic puncture. Rates of reoperation ranged from 0% to 25% for single-system ureterocele punctures, compared to 31–83% for duplicated systems. Heterogeneity was absent, although only three studies were included in this meta-analysis.
One notable complication after puncturing a ureterocele is de novo vesicoureteral reflux into the same collecting system, although most cases are low grade that self-resolve. Two studies published after the aforementioned meta-analysis demonstrate wide variability in rates of new reflux. At a mean follow-up of 3.8 years, one study of 46 duplicated-system ureteroceles noted decompression of the ureterocele moiety in 56% (26 of 46) of patients with a single puncture and an additional 37% (17 of 46) after two punctures, for a cumulative success rate from cystoscopic intervention alone of 93%. However, these authors did not define de novo reflux as surgical failure. New ipsilateral same-moiety vesicoureteral reflux was noted in five patients (four after one puncture, one after two punctures), with three ultimately requiring endoscopic correction of reflux and two experiencing spontaneous resolution. Another single-institution study reviewed 83 patients (26 single-system, 57 duplicated-system) who underwent ureterocele puncture with a mean follow-up of 24 months. Cure rates, including lack of de novo reflux, were 56% and 15% in single-system versus duplicated-system ureteroceles, respectively. New vesicoureteral reflux into the ureterocele moiety was found in 28% and 56% of single-system and duplicated-system ureteroceles, respectively. Spontaneous resolution of the de novo reflux occurred in four of the five single-system patients, compared with six of the 18 duplicated-system patients.
In summary, cystoscopic puncture of ureterocele offers a minimally invasive approach for initial decompression and the potential for a permanent cure. The rates of success vary by ureterocele location and type of associated collecting system, but repeat puncture can salvage initial failures. New postoperative vesicoureteral reflux may be monitored as with any child with reflux, but spontaneous resolution may be lower in children with duplicated systems.
Endoscopic Correction of Vesicoureteral Reflux
Vesicoureteral reflux is a common urologic anomaly where urine can reflux from the bladder retrograde to the kidneys. It can be treated cystoscopically with injection of material, such as dextranomer/hyaluronic acid or Deflux, that better coapts the ureterovesical junction to prevent urine from passing retrograde up to the kidney. More details about this procedure and its complications are reviewed in Chapter 56 with the other minimally invasive surgical techniques for treatment of vesicoureteral reflux.
Incision of Posterior Urethral Valve
Posterior urethral valves (PUV) are the most common urologic causes of chronic kidney disease renal failure during childhood. They are embryologically related to posterior urethral folds. Because PUV develop early in gestation, the impact on bladder, renal, and pulmonary function can be severe. In a newborn boy with PUV, urethral catheterization is needed to bypass the valves and decompress the urinary system. Once the infant is medically stabilized, he then undergoes a cystoscopic ablation or incision of his PUV. Though there are many methods described of ablating PUV, the follow-up period is critical to monitor for persistent or recurrent obstruction and other complications.
Some experts, including the authors, recommend using a 6Fr or 7.5Fr cystoscope and incising the valves with either a cold knife or monopolar electrode at the 5-, 7-, and 12-o’clock positions to obtain maximum ablation without injuring the external urinary sphincter. The probability of residual valves (i.e., incomplete ablation) ranges from 10% to 33%, and 11% of patients have been reported to develop postablation urinary retention. Over a median follow-up of 6.5 years, one of the largest published retrospective cohorts of PUV patients demonstrated other short-term and long-term complications of PUV ablation. Urinary extravasation was noted in three patients, one of whom experienced a rectal injury and subsequent diverting colostomy during antegrade ablation through a suprapubic tract. Gross hematuria occurred in two patients, one of whom required cystoscopic fulguration. At a mean follow-up of 64 months, six of 291 total patients developed urethral stricture disease, with the strictures developing a mean 24 months after valve ablation. All of the patients were treated with direct vision internal urethrotomy, some requiring multiple rounds of urethrotomy, without any need for formal urethroplasty.
Besides persistent and recurrent obstruction, a rarer but just as significant complication following PUV ablation is injury to the urinary sphincter with subsequent urinary incontinence. This can happen when the ablation extends too distally into the external sphincter. One single-institution retrospective review of 67 boys with PUV noted that 34% (23 of 67) had urinary incontinence on median follow-up of 9 years, with only one of the 23 being directly related to surgical etiology of sphincteric incontinence. The remaining boys were thought to have urinary incontinence secondary to bladder dysfunction. Similarly, in another single-institution retrospective cohort of 50 newborn males with PUV, two of the 50 boys had sphincteric incontinence caused by surgical technique at a mean follow-up of 6.8 years. Thus, though injury to the sphincter happens seldomly during PUV ablation, it can occur and must be carefully prevented. The authors stress the importance of small movements of the scope during ablation, with erring on the side of smaller ablative cuts. Immediately following the ablation, a catheter that passes easily into the bladder should be placed for at least 24 hours to dilate the ablated valves. The authors do not place a Foley catheter due to the potential danger of inflating the balloon in the posterior urethra and the theoretical risk of obstruction of the ureteral orifices from an intravesical balloon. We prefer a coudé mentor catheter appropriate to the size of the patient’s urethra (e.g., 6Fr in a newborn). Should a patient develop persistent inability to void after initial ablation, then the clinical threshold should be low to trigger a repeat cystoscopic evaluation and repeat ablation if necessary, versus a vesicostomy should a repeat ablation be deemed too risky for sphincteric incontinence. Should suspected sphincteric incontinence occur, the authors recommend confirming with a videourodynamics study once the child is toilet-trained. Depending on the severity and progression of bladder dysfunction when the child is older, construction of a catheterizable channel with bladder augmentation and bladder neck closure may be needed.
Nephrolithiasis
Introduction
Nephrolithiasis is now a disease that is increasingly being diagnosed during childhood. A recent population-based study demonstrated that the annual incidence of nephrolithiasis has increased 5% per year among 15–19 year olds since the 1990s. The rising prevalence of nephrolithiasis has resulted in an increased need for surgical intervention for younger patients. However, there is substantial variability in the utilization of surgical interventions for children with nephrolithiasis, with the hospital where the surgery takes place one of the most important factors in determining which type of surgery is used. Therefore the need to determine optimal interventions – those that maximize efficacy and minimize risk – is great. This section reviews complications of endoscopic stone surgery for children, namely ureteroscopy (URS) and percutaneous nephrolithotomy (PCNL). Shock wave lithotripsy (SWL) is not covered.
While historically most stones in children were treated with SWL, technologic advancements in miniaturization and optics of endoscopy have allowed an increase in utilization of URS and PCNL. According to the American Urological Association 2016 guidelines, URS is considered first-line surgical treatment along with SWL for children with ureteral or renal calculi. PCNL is usually reserved for large staghorn stones, large infection stones where clearance is essential, or renal stones in kidneys with abnormal anatomy, such as patients with horseshoe kidneys or urinary diversions. Although the 2016 guidelines state either SWL or PCNL could be performed for children with renal stones >2 cm, we recommend PCNL for large renal stones because of the higher stone-free rates and lesser need for additional procedures, assuming the treating urologist has the appropriate training and experience with percutaneous renal surgery.
A recent systematic review and meta-analysis comparing SWL, URS, and PCNL in adults for lower pole stones <2 cm in size favored PCNL over SWL and URS over SWL, particularly in stones 10–20 mm in size. Another recent systematic review and meta-analysis compared PCNL to URS in adults for any kidney stone and noted higher stone-free rates with PCNL techniques but also higher complication rates, greater blood loss, and longer hospital stay. Whether these results in adults transfer completely to children remains controversial and certainly warrants higher-quality pediatric-specific studies. Additionally, the comparative effectiveness of newer techniques such as mini-PCNL, ultra-mini-PCNL, and micro-PCNL remains to be determined for children with nephrolithaisis.
Goals of Therapy
The goals of surgical intervention for nephrolithiasis are the same for children as they are for adults, i.e., to render the patient stone free with the minimal number of procedures and complications. The choice of intervention is determined primarily by the size and location of the stone and patient anatomy. Secondary considerations include patient comorbidities, composition of stone (if known), experience of the urologist, equipment availability, and wishes of the parents and patient. Additionally, the choice of SWL versus URS is heavily influenced by the site where the child obtains care. One potential explanation for this variation in care is that URS requires greater technical skill and experience than does SWL.
General Considerations
Radiation
Patients with nephrolithiasis are often exposed to radiation during diagnosis, surgical treatment, and for surveillance after definitive intervention. URS and PCNL both typically use fluoroscopy, which delivers ionizing radiation. Cumulative radiation exposure is a particularly important consideration for children with nephrolithiasis given that they are more likely than adults to require future diagnostic imaging and surgical interventions that use ionizing radiation. Additionally, the cumulative risk of radiation exposure may be higher in children than in adults because of a longer life expectancy and greater sensitivity of developing tissues to the effects of radiation.
Recent studies have quantified radiation exposure during endoscopic surgery for nephrolithiasis in children. Ristau and colleagues performed a cross-sectional study of all children who underwent ureteral stent placement, URS, and PCNL at the University of Pittsburgh between 2005 and 2012. The median fluoroscopy times for unilateral URS, bilateral URS, and PCNL were 1.6 minutes, 2.5 minutes, and 11.7 minutes, respectively. This was equivalent to 3 mSv for URS and 16.8 mSv for PCNL. Importantly, each patient received a median of one (IQR 1-3) CT scan and three (IQR 1-8) abdominal x-rays for the associated stone episode. The average cumulative radiation exposure for a patient who underwent a CT scan, PCNL, and three x-rays in a 1-year period was 32 mSv. The radiation safety concept – as low as reasonably achievable (ALARA) – emphasizes using the minimal amount of radiation necessary to achieve the desired outcome. Current guidelines recommend a maximum dose of 50 mSv in a 12-month period, and an average of <20 mSv/year over a 5-year period. Thus a therapeutic plan for a single large stone requiring PCNL approaches the limits of recommended ionizing radiation exposure.
Nelson and colleagues also demonstrated substantial radiation exposure for children undergoing ureteroscopy. They note that while fluoroscopy time was the most important determinant of radiation exposure, other factors, such as source-to-skin distance, use of ureteral access sheaths, and dose rate setting, also contributed to total radiation dose. Indeed, three of the four categories that determine the patient’s total radiation exposure are modifiable. Of fluoroscopy time, source-to-skin distance, fluoroscopy settings, and patient abdominal wall thickness, only patient abdominal wall thickness cannot be adjusted to decrease delivered radiation. Implementing a 6-item checklist designed to reduce radiation exposure during pediatric URS resulted in a 67% reduction in fluoroscopy time, 78% improvement in skin-to-image intensifier distance, and >90% utilization of appropriate dose settings. Compared to patients who underwent URS prior to implementation of the checklist, radiation exposure was reduced by 87% among patients who were treated after implementation. Additionally, recent techniques that utilize ultrasound for URS and PCNL help to minimize radiation exposure in children. At the authors’ institutions, percutaneous access for PNCL is gained using renal ultrasound. We also use intermittent rather than continuous fluoroscopy when fluoroscopy is needed for URS and PCNL. Fluoroscopy technicians also operate the C-arm and reduce kVp, maximize skin-to-source distance, and narrow the image window to minimize radiation exposure while maintaining image integrity. We avoid routine magnification. Efforts are also ongoing to assess the role of ultrasound-guided URS.
Residual Fragments
Various studies have compared stone-free rates among the surgical treatment modalities. These rates for PCNL range from 70% to 97%, and from 85% to 88% for URS. However, a widespread limitation of the existing literature on endoscopic interventions for pediatric nephrolithiasis means that there is an inconsistency in the definitions of stone-free status after surgery. Often, stone-free rates include ancillary procedures such as SWL. Additionally, different cut-offs for “clinically insignificant” residual fragments are used, which limits effective comparison of outcomes for alternative surgical interventions. Finally, the means by which stone clearance was assessed after surgery are variable. Endoscopy, ultrasound, fluoroscopy, CT scan, and plain film have all been used to define the presence of residual fragments; however, the sensitivity and precision of these methods are highly variable. There is a need to determine a universally accepted and utilized method to define stone clearance after surgical intervention in children.
Ancillary Procedures/Anesthesia
Surgical indications for children with nephrolithiasis are similar to adults. However, the smaller size of children’s ureters and kidneys often require additional ancillary procedures to completely and safely remove stones. For example, the smaller size of children’s ureters often precludes direct access with a ureteroscope secondary to the risk of ureteral perforation and stricture associated with active dilation. Therefore a ureteral stent is often placed prior to the ureteroscopy to allow for passive dilation of the ureter. We routinely “pre-stent” children undergoing URS for kidney stones, particularly if a ureteral access sheath is used; however, we do not typically place a stent prior to URS for ureteral stones. Consequently, the increased stone-free rate with URS compared to SWL needs to be weighed against the greater number of procedures per stone. Future comparative and cost-effectiveness studies should examine the disadvantages and potential harms of surgical interventions along with their efficacy. Such studies will be critical for the development of patients’ decision-making tools and their understanding of the impact of alternative interventions on the quality of life for themselves and their families.
Ureteroscopy
URS has been used to treat children with ureteral and kidney stones since the late 1980s. Initially, the majority of stones extracted were located in the mid-to-distal ureter. Advances in technology, namely miniaturization and improved flexibility, have contributed to the increased use of URS for children and allowed treatment of stones located in the proximal ureter and all areas of the kidney. At our institutions, children undergoing URS are placed in the lithotomy position, similar to adults. However, it is important to use the appropriate-size stirrups to avoid pressure wounds and nerve injuries. We use three sizes of stirrups to provide the appropriate positioning for children of different sizes. For infants, we use gel rolls underneath the knees to provide a modified lithotomy position. Care is taken to ensure all pressure points are padded and the weight of the legs rests on the heels and not the calves or the knees where peroneal nerve injuries may occur.
The success of URS is dependent on stone size. URS should not be considered a first-line treatment for patients with stones larger than 15–20 mm. Additionally, although the efficacy of URS is less dependent on stone position than SWL, consideration must be given to the smaller size of children’s kidneys. Smaller kidneys have less room to maneuver a ureteroscope and have sharper angles, which may make accessing stones in the lower pole difficult. Given these technical considerations, we recommend using 150-µm holmium laser fibers to access stones in the lower pole kidney, which have improved deflection compared to larger fibers. We routinely use a 200-µm fiber for ureteral stones and stones located in the mid and upper pole calyces. Studies that compare the efficacy of stone “dusting” and fragmentation with basketing, which are currently ongoing among adult patients, have not been performed among children or adolescents. The authors frequently use a ureteral access sheath if basketing is required.
The complications of URS include ureteral injury, urinary tract infection, and bleeding. Serious complications (greater than Clavien III) are, in most reports, uncommon. In a recent systematic review, the overall stone-free rate for URS was 85.5% and complications occurred in 12% of patients. Only 2% were greater than Clavien grade III. However, the definition of “success” is ill defined and varies substantially among studies. The method of assessing stone-free status ranges from visual inspection at the time of ureteroscopy to postoperative ultrasound or CT. It is thus difficult to directly compare the results and complications associated with different techniques, stone sizes, and stone locations. Generally, stone-free rates are lower for renal compared to ureteral stones ( Fig. 55.1 ).
Although the comparative effectiveness of pre-stenting versus active ureteral dilation to allow primary passage of the ureteroscope has not been systematically examined, adverse outcomes such as ureteral perforation and stricture may be more common if placement of a ureteral stent is not placed prior to the URS to allow for passive ureteral dilation. Complications that occurred among patients in whom a ureteral stent was not placed prior to URS include ureteral injury, ureteral stricture, and conversion to open surgery. In one recent report, 19% of children undergoing URS who did not have a ureteral stent placed prior to URS required open ureterotomy with or without ureteroneocystostomy due to a small ureteral orifice. As mentioned above, if the scope or access sheath cannot be advanced easily up the ureter, a 4.6 or 4.7Fr ureteral stent is placed to passively dilate the ureter for at least 2 weeks before returning for the formal URS. We recommend against active dilation of the distal ureter because of the risk of ureteral injury and because the diameter of the ureter proximal to the ureteral orifice also limits safe ureteroscopy, particularly if an access sheath is used.
If a ureteral stricture is encountered or develops after ureteroscopy, a retrograde pyelogram can show the degree, length, and location of narrowing. Short midureteral strictures can undergo prolonged stent placement. Balloon dilation is used sparingly by the authors, with laser incision being preferred. We recommend formal reconstruction, which can often be performed robotically, for longer, denser, or recurrent strictures. Distal strictures may be treated with a ureteroneocystostomy. Proximal or midureteral strictures may necessitate pyeloplasty or excision and primary anastomosis, respectively.
A selection of contemporary studies on URS among children is shown in Table 55.1 along with a selected few studies from early in the URS experience to allow comparison of patients and stone characteristics, ureteroscopes, outcomes, and complications.
| Author | Patients | Procedures/Patient | Age in Years Mean (Range) | Stone Size, in mm Mean (Range) | Stone Location | Type of URS | Size of URS | Primary SFR | Pre-stent (%) | Ureteral Dilation | Post-operative Stent | Ureteral Injury (%) | Fever and/or UTI |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Al Busaidy | 43 | 1.2 | 6.2 (0.5–12) | 12.6 (4–22) | Ureteral | Rigid | 8.5–11.5 | 84 | 0 | balloon | NR | 1 (2) | 12(24) |
| Satar | 33 | 1.1 | 7.4 (0.8–15) | 5.3 (3–10) | Ureteral | Rigid | 6.9–10 | 94 | 0 | balloon | 12 (34) | NR | NR |
| Nerli | 80 | 1.1 | 9.5 (6–12) | 10 (7–16) | 70% ureteral 30% kidney | Flexible | NR | 90 | 0 | Metal dilators | NR | 0 | 5 (6) |
| Dogan | 642 | 1.1 | 7.4 (0.3–17) | 8.9 (NR) | Ureteral | SR | 4–10Fr | 90 | 207 (31) | balloon irrigation pump | ??? | 2 (1) | 0 (0) |
| Yucel | 48 | 1.1 | 7.6 (0.8–18) | 6.6 (4–20) | Ureteral | SR | 7.5 | 84 | 2 (4) | balloon | 31 (61) | 1 (2) | NR |
| Tiryaki | 32 | 1.7 | 5.9 (0.6–17) | 8.8 (4–18) | Ureteral | Rigid and flexible | 4.5–7.5 | 57 | 8 (20) | none | 29 (71) | 9 (20) | NR |
| Erkurt | 65 | 1.1 | 4.3 (0.5–7) | 26 (7–30) | Kidney | Flexible | 7.5 | 83 | 17 (8) | sheath | NR | 2 (3) | 10 (15) |
| Kocaoglu | 36 | 1 | 5.3 (1–13) | 8.4 (4–18) | Ureteral | SR | 4.5 | 97 | 0 | None | 16 (42) | 0 | 1 (3) |
| Chedgy | 21 | 1.5 | 8.6 (1.4–16) | 9.6 (5–20) | Kidney Ureteral | SR Flexible | NR | 13 (62) | 18 (50) | 0 | 18 (50) | 0 | 1 (3) |
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