Transurethral Holmium Laser Cystolithotripsy in Children: Single Center Experience

Abstract

Purpose:

To evaluate prospectively safety and efficacy of transurethral cystolithotripsy (CL) in children using holmium:yttrium-aluminum-garnet (Ho:YAG) laser. This is important in developing countries, because the risk of bladder stones in children is high. Open cystolithotomy (OC) was the main line of treatment. A gradual shift has occurred toward endourologic treatment after improvement of pediatric endoscopes.

Patients and Methods:

Between January 2010 and May 2011, 33 children <12 years old with vesical calculi were treated. Children with orthopedic deformities, urethral stricture, history of urethral operations or bladder reconstruction, or stones >4 cm were excluded. Cystoscopies were performed under general anesthesia using 9 to 11F cystoscopes. Stones were completely fragmented under video guidance. Ho:YAG was applied at a power of 30 W.

Results:

Median age was 3 years (0.5–11). Mean stone size was 2.02±0.82 cm (1–4 cm). Mean operative duration was 31.21 minutes (20–50). All children were discharged within 24 hours. A single operative session was performed for each patient. No complications were detected. After a mean follow-up of 16.87±4.08 months, all children were stone free, without development of any urethral stricture or recurrence of stones. Operative duration was significantly longer in stones >20 mm (P<0.001).

Conclusion:

Ho:YAG laser CL is a safe and successful minimally invasive treatment option for bladder stones in children. Success rate was 100% without development of any complications or recurrence.

Introduction

Voiding dysfunctions, posterior urethral valves, urethral strictures, foreign bodies, and vesicoureteral reflux predispose children to bladder stones.^1

–5 In developing countries, the risk is increased because of presence of infection and poor nutrition.⁶ In the Middle East and Africa, low-protein and high-carbohydrate diets with nutritional deficiencies predispose to this condition. This is enhanced by decreased urine production because of the higher incidence of dehydration, diarrhea, fever, and infection.⁷ Although there is a gradual decrease in the incidence of bladder stones because of improvement in nutrition and healthcare services,⁸ our hospital still receive a relatively large number of children with bladder stones because our hospital is the largest pediatric hospital in Egypt. Open cystolithotomy (OC) has been the main line of treatment for those with pediatric bladder stones in our hospital alternating with percutaneous suprapubic cystolithotripsy (PCCL). After improvement of the pediatric cystoscopes and ureteroscopes together with the introduction of the holmium:yttrium-aluminum-garnet (Ho:YAG) laser as a novel modality of lithotripsy, a gradual shift has occurred in the main line of treatment in our center to become transurethral cystolithotripsy (CL). The aim of this study is to evaluate prospectively the safety and efficacy of pediatric CL using Ho:YAG.

Patients and Methods

Between January 2010 and May 2011, a total of 33 children with vesical calculi were treated at Cairo University Children's Hospital using Ho:YAG CL. Children <12 years old who presented with vesical stones were included in our study. We excluded children with severe orthopedic deformities, urethral stricture, stones >4 cm, history of urethral operations, bladder reconstruction, or bladder augmentation. Written informed consent was obtained in all cases. All patients underwent clinical evaluation, urine analysis with additional urine culture and sensitivity (C&S) if needed, determination of serum creatinine level, abdominal ultrasonography (US) and plain radiography. Additional noncontrast CT was performed for radiolucent stones. The upper urinary tract and urethra were evaluated for the presence of other stones. The size of the stones was determined by measuring the longest diameter. In patients with multiple stones, we added the length of these stones. Children were admitted on the operative day. Cystoscopies were performed under general anesthesia with the patient in the lithotomy position using 9 to 11F pediatric cystoscopes (Karl Storz, Germany) with Ho:YAG lithotripsy (Sphinx 30 W-LISA laser products OHG, Germany.) Ho:YAG was applied at a power of 30 W (energy: 2.75 J, pulse: 11 Hz). In younger children with smaller urethra, a 7.5F semirigid ureteroscope was used.

Initial urethrocystoscopy was performed to exclude urethral stricture, posterior urethral valves, or any other abnormalities. Ho:YAG was applied through reusable 420 micron Flexifib fiber (LISA laser products, Germany). Stones were completely fragmented under video guidance. A 6 to 8F silicone catheter was inserted postoperatively. Analgesics were given when needed. The patients were evaluated 3, 12, and 18 months postoperatively. This was performed using US in addition to clinical assessment to confirm the stone-free status and to exclude the development of any urethral stricture. Uroflowmetry was performed when indicated. Success was defined as no evidence of residual stones >2 mm in diameter in the postoperative US.

Data were statistically described in terms of median, range, mean±standard deviation, frequency, and percentages when appropriate. Comparison of numeric variables between the study groups was performed using independent sample t test for parametric data or Mann Whitney U test for nonparametric data. A probability value (P value)<0.05 was considered statistically significant. All statistical calculations were performed using SPSS (Statistical Package for the Social Science; SPSS Inc., Chicago, IL) version15 for Microsoft Windows.

Results

Two experienced surgeons treated 33 children. All patients had no history of previous stone intervention, bladder or urethral operations. Preoperative urinary tract infection (UTI) was detected in 12 (36%) children and treated according to C&S. The causative organisms for UTI were Escherichia coli in five children, Pseudomonas in one child, Klebsiella in three children, and Proteus vulgaris in three children. The age, stone size, operative duration, and other perioperative data are presented in Table 1. Isolated bladder stones were present in 29 patients (including the 2 patients with neurogenic bladder). The remaining four patients had associated renal stones. Mini-perc was performed to clear renal stones for two patients in the same session of cystolithotripsy while it was staged in the other two patients. All operations were completed. No equipment failure occurred (no lithotripsy malfunction or damage to laser fibers). One laser fiber was used for all cases. All children were discharged within 24 hours. Urethral catheters were removed before discharge. In most patients, the bladder catheter was removed within a few hours. It was maintained for a longer time in some children with prolonged operative time. It was removed in all patients within 24 hours, however, except the two children with associated renal stones treated by mini-perc and the two girls with associated neurogenic bladder. The urethral catheterization was maintained for 3 to 4 days in these four patients. The two girls with associated neurogenic bladder were maintained preoperatively on CIC. There were no challenges with stone clearance in these two girls compared with the normal males. The stones were fragmented completely by laser with easier manipulation and bladder wash using the 11F sheath. A single operative session was performed for each patient. No bladder perforation, mucosal abrasions, hematuria, fever, urinary retention, or other complications were detected. After a mean follow-up of 16 months (range 12–24), all children were stone free, without development of any urethral stricture or recurrence of stone disease. The operative time was analyzed in relation to different sizes of stones and also in relation to radiolucency (Tables 2 and 3).

Table 1.

Perioperative Data

Parameter	Result
No. of patients:	33 (100%)
Male	31 (94%)
Female	2 (6%)
Median age (range) (years)	3 (0.5–11)
Presenting symptoms:
Urinary retention	11 (33%)
Obstructive symptoms	13 (39%)
Hematuria	9 (27%)
Stones:
Total number of stones	39
Mean size±SD (range) (cm)	2.02±0.82 (1–4)
Patients with multiple stones	5 (15%)
Patients with radiolucent stones	21 (63%)
Mean operative time±SD (range) (min)	31.21±9.01 (20–50)
Associated bladder disease:
Myelomeningocele (neurogenic bladder)	2 (6%)^a

These two patients were the only girls in our study.

SD=standard deviation.

Table 2.

Operative Time in Relation to Stone Size Groups

Size groups	No. of patients (%)	Median operative time (range)	P value
1–2 cm	21 (63%)	25 (20–40) min	<0.001^*
2– cm	12 (36%)	40 (25–50) min

Significant.

Table 3.

Operative Time in Relation to Stone Radiolucency

			95% confidence interval of the difference
	Patients with radiolucent stones 21 (63%)	Patients with radioopaque stones 12 (36%)	Lower	Upper	P value
Operative time (min)	32.85±8.59	28.33±9.37	−2.03	11.07	0.169

Discussion

OC, CL, shockwave lithotripsy (SWL), and PCCL are used for the treatment of children with bladder stones.⁹ Although strong scientific evidence regarding the optimal approach is lacking, various minimally invasive endourologic approaches have become the mainstay of treatment with minimization of tissue trauma and surgical morbidity while attaining good results.^10,11 Each method has its advantages and disadvantages. The choice of treatment depends mainly on the availability of equipment, surgical expertise, anatomy of the patient, and the number and size of stones.^10,11 OC has been the traditional treatment of children with bladder stones,¹² but it is associated with a scar, prolonged catheterization, extended hospital stay, and risk of infection.¹³ SWL is one of the least invasive methods, but there are few data concerning SWL in pediatric bladder stones, limiting its use in many centers. Some authors argue that SWL may be associated with difficulty in passing the stone fragments, incomplete fragmentation of calculi, and the need for more than one session to reach a high success rate. This may increase the chance for complications, recurrence from residual fragments as well as the necessity for auxiliary procedures to manage fragments impaction in the urethra with repeated exposure to general anesthesia. Furthermore, the late bioeffects of SWL in children remain controversial.^14
–16 This is important in developing countries because the cost of multiple SWL sessions with the possibility of auxiliary procedures may exceed the cost of one session of CL in addition to the lack of healthcare service within reasonable distance for adequate follow-up of SWL.¹⁷

PCCL has been developed to prevent trauma to the urethra and bladder neck that may occur with the transurethral route in children. It has been recommended for large stone burdens.^6,11 Salah and colleagues¹⁸ performed PCCL in 155 children. The mean age was 4.5 years (range, 8 mos–14 y) while the mean size of stones was 2.3 cm (range 0.7–4 cm). They concluded that this procedure is safe and effective. The disadvantages were the presence of a scar and the relatively long catheterization and hospitalization time (3–5 d).¹⁸ PCCL has been used successfully, even in infants. Gan and associates¹⁹ successfully treated 15 infants (range 3–11.5 mos) with PCCL. The mean age was 8.2 months, and the mean stone size was 1.4 cm (range 0.9–2.2 cm). All children were free of calculi, with average operative time of 25 minutes and mean hospital stay of 2.8 days.¹⁹ PCCL has important disadvantages, however, such as the presence of an incision, the need to dilate a tract, the insertion of a suprapubic tube, and the need for a urethral catheter, which leads to a relatively longer hospital stay when compared with CL. There are other reported complications including paralytic ileus, abdominal distention from escape of irrigating fluid into the abdominal cavity, fever, and urine leakage. It also carries a risk of bowel perforation and vascular injury, especially if there is a history of abdominal or pelvic surgery.^18,20
–22 Furthermore, PCCL is initiated with urethrocystoscopy to exclude any subvesical obstruction or to push back the urethral stones into the bladder. In addition, some authors dilate the suprapubic tract under imaging. This adds to the operative time, the required instruments, and the total cost.²⁰ For patients with previous abdominal surgery or reconstructed bladders, intraoperative imaging-guided percutaneous access (using US or CT) is recommended to minimize the risk of bowel injury.¹¹

Al-Marhoon and coworkers²⁰ compared retrospectively PCCL (27 patients), and OC (53 patients) in 80 children with bladder stones. The age means were 5.9±4.6 years and 7.2±3.8 years while the stone size means were 3.1±1.6 cm and 1.8±0.8 cm in OC and PCCL groups, respectively. Operative time was comparable in both groups. The hospital stay was significantly shorter after PCCL compared with OC (2.6 vs 4.8 d). In the OC group, one patient had a small intestinal injury, while in the PCCL group, three patients had intraperitoneal bladder perforation and one patient had persistent urinary leakage from the suprapubic site treated by prolongation of catheterization. The authors concluded that endourologic management offers a shorter hospital stay but OC seems to be safer. They recommended to perform PCCL under radiologic control and to prolong urethral catheterization in cases with difficult tract creation. They also recommended close postoperative follow-up after PCCL to detect any missed bladder perforations, especially in patients experiencing prolonged ileus, abdominal discomfort, and distention.

The gradual decrease in endoscopic sizes and the development of effective lithotripters allowed intracorporeal lithotripsy in children.²³ CL has been developed to avoid the scar of open surgical and percutaneous approaches and to achieve early discharge making it a day care procedure. The long time necessary for fragmentation and the urethral caliber remain the main challenges during CL in children, however.⁶

Pneumatic lithotripsy is relatively cheaper and simple in use than Ho:YAG; hence, it can be used even in small centers.²⁴ This technique was applied to children after miniaturization of endoscopes without development of any urethral stricture.²⁵ Isen and colleagues²⁵ reported their experience with pneumatic CL in children with a mean age of 7.6 years (range 3–14). The mean stone size was 14 mm (range 8–20 mm). The operative time was 22 minutes (range 10–46 min). The mean hospitalization was 1.2 days (range 1–3 d). They had no cases of urethral stricture or recurrence. They concluded that pneumatic lithotripsy using an ureteroscope is an effective and safe minimally invasive treatment with reduced hospital stay and overall cost when compared with PCCL. They reported, however, acute retention in 7.4% of patients because of failure of fragments to pass through the urethra. A second procedure was performed on these patients. They also reported mild hematuria and fever in 7.4% of patients. All patients were stone free at 2 weeks postoperatively.²⁵ They used stone forceps to retrieve large stone fragments (5–6 mm) during the procedure in 37% of the patients to reduce potential spontaneous passage problems. The repeated passage of the forceps with stones through the urethra may increase the risk of urethral complications, however. These problems can be minimized by using Ho:YAG CL, because it achieves small stone fragments of about 2 mm.^24,26

The Ho:YAG has emerged as the device of choice for intracorporeal lithotripsy for all stone types. It has revolutionized intracorporeal lithotripsy because it can fragment stones with minimal trauma to the bladder mucosa and minimal hematuria.^11,23 CL is widely used in adults and older children and has a high stone-free rate and short hospital stay, thus making it the preferred management option for bladder stones.²⁷ The procedure, however, takes a longer time than other methods, especially for large and multiple bladder stones, and this may increase the risk of urethral trauma and subsequent strictures because of the small urethra in younger children.²⁸ Arrabal Martin and associates²⁹ recommended that the Ho:YAG CL offers the best results with a low percentage of complications while PCCL should be reserved for cases with greater complexity, including large calcular masses or pathologic urethra. Studies discussing Ho:YAG CL in children are still very few. Ramakrishnan and coworkers²⁴ treated 23 children 2 to 12 years old (mean 7.8 y) with bladder stones using an 8F ureteroscope and Ho:YAG CL. The mean size was 27 mm (range 9–40 mm). The applied energy was 0.6 to 1.8 J in a frequency of 5 to 12 Hz using 550 microns end-firing fiber under video guidance. The mean operative time was 38 minutes (range 19–62 min). The calculi were pulverized into 2 to 3 mm fragments. An 8F urinary catheter was placed for one night in all patients. The mean length of hospital stay was 2.2 days (range 2–3 d). All the children were stone free following a single session. There were no residual stones or any other important complications. During the follow-up (mean 42 mos), stone recurrence, UTIs, or urethral strictures did not develop in any child. The authors concluded that Ho:YAG CL was an efficient and safe modality in children.²⁴

Our patients were younger with nearly similar stone size, operative duration, and comparable results. Al-Marhoon and associates²⁰ treated 10 patients with Ho:YAG CL and 17 patients with pneumatic CL using 10 to 12F pediatric cystoscopes. Mean patient age was 6.5±4.1 years. Stone size was 1.2±0.6 cm. One patient had urinary extravasation because of urethral rupture after Swiss lithoclast CL. Bulbous urethral stricture was diagnosed 1 year after CL. The urethral catheters were removed on postoperative day 1 with discharge on the second postoperative day. These authors recommended the use of a laser fiber through fine flexible cystoscopes or ureteroscopes to reduce the risk of urethral damage in young patients.²⁰ In our study, the operative duration was significantly longer in stones >20 mm, but this did not affect the outcome. We did not analyze the stones because they were completely fragmented. We used radiolucency of stones as an indicator of the effect of stone composition on operative duration, but there was no statically significant difference.

The cost and the complications of the procedure were minimized by different factors in our study. (1) One laser fiber was used for all cases. (2) No equipment failure occurred. (3) A single operative session was performed for each patient. (4) Stones were completely fragmented without the need of any extraction that may lead to urethral injuries from multiple entries. At the same time, complete fragmentation protected against any possibility of postoperative retention during passage of fragments through the urethra. (5) All children were discharged within 24 hours, decreasing the hospital stay. Isen and colleagues²⁵ recommended that patients with stones <4 cm with a patent and nonreconstructed urethra/bladder neck are well treated with CL. Those with a greater stone burden and/or coexistence of previous lower urinary tract surgeries, however, are better treated percutaneously.

According to our experience, Ho:YAG CL is a safe and successful minimally invasive treatment option for bladder stones in children with the advantages of the lack of any scar and the short hospital stay. The success rate was 100% without development of any complications or recurrence. The operative time was significantly affected by the size of stones, but a single operative session was performed for each patient. Stones were completely fragmented without the need of any extraction. One laser fiber can be used for a large number of cases, decreasing the cost. The use of small caliber pediatric endoscopes, appropriate experience, and caution are the key to success. It should be the preferred treatment for bladder calculi up to 4 cm. Our study has some limitations, mainly because of lack of a control group, so our results were compared with other published papers on different lines of treatment for bladder stones in children. Another limitation was the exclusion of stones >4 cm and children with a history of a previous stone intervention or bladder or urethral operations. We excluded these patients from the present study; they were not the majority of patients presenting to our department because most of the stones were because of infection and poor nutrition. In addition, we decided to avoid the special complications related to these cases during reporting of our initial experience with laser CL including complications related to the reconstructed bladder neck or continent stoma of the augmented bladder. The absence of stone analysis because of intraoperative complete fragmentation of stones is also a limiting factor. In a previous study in our center, it was reported that the epidemiologic profile of urinary stones in Egyptian children can be considered as an intermediate between those of developing countries, where dietary deficiencies are the main causes in addition to infection and other causes, and developed countries, where only infectious and metabolic calculi are observed. This was most probably because of gradual improvement of dietary habits and nutritional status of children.

Regarding the composition of bladder stones in that study, the ammonium acid urate was found in 27% of stones, struvite in 27%, calcium carbonate in 22%, calcium oxalate in 13%, calcium phosphate in 9%, and pure uric acid in 4%. The authors assumed that a low and fixed urinary pH at the time of stone formation, coupled with low urine volume, was the mechanism responsible for the development of endemic stones composed of ammonium acid urate, which have almost disappeared in the Western world, probably as a result of a balanced diet.⁸ On the other hand, the prospective evaluation of this reasonable number of relatively young children adds to the strength of our study. Because the size of stones in our study was <4 cm, other methods of intervention including PCCL and OC should be compared with CL in bladder stones >4 cm. This comparison is also needed in infants and in children with reconstructed bladder.

Conclusion

Ho:YAG CL is a safe and successful minimally invasive treatment option for bladder stones in children with the advantages of the lack of any scar and the short hospital stay. The success rate was 100% without development of any complications or recurrence. It should be the preferred treatment for bladder calculi up to 4 cm.

Footnotes

Disclosure Statement

No competing financial interests exist.

Abbreviations Used

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