47: Urolithiasis—Renal Surgical Management

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Introduction

The overall probability of forming stones differs in various parts of the world and is estimated as 1–5% in Asia, 10–15% in United States and ranges from 1–15% worldwide depending on age, gender, race, and geographic location.1 In the last few decades, there is an increase in the prevalence of kidney stones all over the world. In USA, in adults the prevalence estimate for the period of 2007–2010 was 8.8%. This increase in the stone disease has also been reported among the young people, with girls being more affected by the stone disease as compared to boys.2,3,4 The increase in the incidence of stone disease causes an increase in emergency visits, hospitalisations, surgeries and health care costs. In USA, the health care costs for pediatric urolithiasis amounted to at least 375 million dollars annually.5 Also, the recurrence rates of stones are around 50 % in children within 3 to 5 years of initial episode of development of stone.6,7,8 However, upto 60% children present with stones which are not amenable to spontaneous passage and surgical treatment remains the mainstay of treatment in such individuals.9 However, the surgical treatment has undergone a paradigm shift in the last few decades. There has been a transition from open surgery to ESWL to endourology for pediatric renal stones in last 50 years. Up to 1980s, majority of the renal stones were treated by open surgical methods. However, with the introduction of ESWL and PCNL after 1980s, firstly in the adults, their safety and efficacy were established in the pediatric population too. Currently, with the miniaturization of instruments, endourological management in the form of PCNL and RIRS has vastly improved the access to the pelvicalyceal system of pediatric patients with stones with minimum complications and maximum stone clearance rates.10

Extracorporeal Shock Wave Lithotripsy

Extracorporeal Shockwave Lithotripsy (ESWL) was first used to treat renal stones in adults in early 1980s. After the safety was established in adults, it was soon used in pediatric population by 1986.11,12 Initially, the manufacturers recommended the treatment for patients only with a height greater than 135 cms because of technical challenges for the machines. ESWL is one of the treatment options for treating renal stones up to size 15 mm. For stone size more than 15 mm, the retreatment rates increase substantially and stone clearance rates also decrease in comparison to endourological treatments.

With the improvement in lithotripters with removal of water bath and US guided stone imaging, the acceptance and treatment with ESWL in children increased gradually. Stone free rates are between 65% to 71% in pediatric patients depending upon the location of stone, energy given and machine used.13

Advantages of ESWL

The most important advantage which ESWL provides is that it is a non-invasive procedure. Also, the stone free rates of around 68% to 84% are achieved with a single or a double sitting. This can be attributed to the fact that there is less attenuation of the shock waves, and the shockwaves are better propagated through the small body volume of the child resulting in better fragmentation. Also, the ureters of the children are more accommodative than that of the adults. So, the ureters of children can pass stones more easily than adult population.

Disadvantages of ESWL

The most important drawback is low stone clearance rates in comparison to endourological procedures. Secondly, even ESWL requires general anesthesia in vast majority of pediatric patients (Figure 1). Thirdly, there are concerns regarding effects of ESWL on the growing and developing kidney. Lifshitz et al studied effects of ESWL on 29 for a mean of 9 years, and found that there was a trend towards reduced renal growth in the treated kidneys with one case of hypertension..14 However, the authors believed that the changes were due to abnormal kidneys and changes were not attributable to ESWL. Further follow up of 39 children treated with ESWL had no hypertension or renal scarring on DMSA scan, after a range of 6 months to 8 years.15 Villanyi et al examined in 16 children between the ages of 6 and 14 that there was no deterioration in renal function but there was transient excretion of various surrogate markers of renal damage, such as beta2- macroglobulin for a week. So, the recommendation that an interval of at least 15 days should be left between two successive ESWL treatments.16 However, at present, there is no significant evidence to suggest that ESWL in the pediatric population has any significant long-term effects.

Figure 1 ESWL in pediatric patient under GA

Percutaneous Nephrolithotomy

PCNL has replaced open surgery and at present is considered to be the first line of treatment for renal stones greater than 20 mm with stone clearance rates of more than 90%.17

PCNL was initially described by Johannson and Fernstrom in 1976. Since then, it has become the main stay of treatment for treatment of renal calculi. PCNL in children was described in 1985 as a case series of seven patients aged between 5 years and 18 years using standard adult instruments.18 However, with the continuous decrease in size of optics, nephroscopes and availability of better stone fragmentation technology has allowed the use of smaller tracts for PCNL with decreased complication rates. Mini-PCNL, with tract size up to 20 Fr, ultra-mini PCNL (11 Fr, 13 Fr), mini-micro PCNL (8 Fr), micro-PCNL with sheath size of 4.85 Fr have led to better acceptability of PCNL even in smaller children.

PCNL is performed in general anesthesia. Initially, cystoscopy is performed and a 4 Fr or 5 Fr ureteric catheter is placed in the pelvicalyceal system. It is used for opacification and distention of PCS and irrigation intraoperatively. Then, the child is placed in prone position. The initial puncture can be done using ultrasound guided or fluoro-guided puncture. The initial puncture is most important part of the procedure as the pediatric kidneys are more mobile than the adult kidneys. The pediatric kidneys tend to move away during the initial puncture and dilatation. After confirmation of puncture in the PCS, dilatation can be done using a serial dilator, one step dilator or a balloon dilator. The mini PCNL sheaths are available in different size and tract can be dilated according to the stone size and fragmentation device usage (Figure 2). The stone can be fragmented using conventional lithoclast, lasers like holmium laser or new thulium laser fiber. Use of special devices like Shock pulse and Trilogy has also decreased the operative time and improved the stone clearance rates.

Use of suction devices in sheath or device have added a new dimension for the stone free rates and discussion between dusting and fragmentation in PCNL. A nephrostomy tube can be kept at the end of the procedure. The overall success rates in PCNL range from 81–100% after ancillary procedures (Table 1).19,20,21,22

Table 1 Overall success rates after PCNL range from 81–100% (includes ancillary procedures).

Study	Renal units	Mean age	Tract	Stone size	Complications	Success rate (after auxiliary procedures)
Mahmud M et al23	30	3.8 years (1.4–5)	< 22 Fr	2.3–5 cm (1.3-6 cm)	Overall=6%	100%
Zeren et al24	67	10–14 years (7.9)	24–30 Fr	25–2075 mm2	Hemorrhage=23.9%	96.7%
Manohar et al25	35	11 months to 4.5 years	< 22 Fr	140 mm2	Transfusion rate=5%	86%
Salah et al26	138	8–14 years (8.9)	26 Fr	124–624 mm2 (507 mm2)	Urine leak=8%, Bleeding=0.7%, Retroperitoneal collection=0.7%	98.5%
Nouralizadeh et al27	20	3.1 years	26 Fr	33 (20–46)	Overall=15.38%	91.67%

Figure 2 Miniperc nephroscope sheath in place (left), nephroscopy being performed (centre) and intracorporeal lithotripsy with Holmium laser (right)

Disadvantages of PCNL

The PCNL has its own set of complications ranging from 15% to 39%. Most common complications are fever and blood loss requiring transfusions. Since the organs in pediatric patients are crowded and near, they are prone to complications like hemothorax, hydrothorax or colonic injury. However, with the use of US guided puncture and meticulous technique, these complications can be avoided.

Flexible Ureteroscopy (fURS/RIRS)

Due to continuous advancements in miniaturization of flexible ureteroscopes, RIRS is now possible in pediatric patients with minimal complications. Historically, RIRS was avoided in children owing to complications like ureteral ischemia, ureteric perforation and stricture formation. However, the flexible scopes are now available in sizes as small as 7.5 Fr which can be easily accommodated in pediatric ureters. Also, development of small laser fibers as small as 200 microns with good fragmentation and dusting capabilities has improved the stone clearance rates substantially up to 85% to 90%. Maximum complications are seen in children who weight less than 20 kgs.28 AUA guidelines also suggest that in stones less than 20 mm, URS or ESWL is recommended. fURS has to be performed under general anesthesia in children. The child has to be placed in modified lithotomy position like adults with adequate padding of pressure points. Firstly, a guide wire is placed in under c arm guidance into the ureter using a cystoscope. The ureter can be dilated up to 10 Fr serial dilators. Ureteral access sheath (10/12, 11/13, 12/14 Fr) can be used. Access sheath facilitate the flexible ureteroscope during a tortuous ureter. If any point the ureter does not accommodate. Ureter should not be overdilated. Often sheathless procedure can be performed. In very small children, it is better to do presenting. Care must be taken not to damage the ureter as well as the urethra.

The advent of disposable flexible ureteroscopes of size up to 7.5 Fr has ushered a new interest in flexible endoscopy. Additionally, newer lasers are coming up like high powered holmium laser, thulium laser fiber which claim to have better dusting and fragmentation than a conventional low powered holmium laser.

Disadvantages of fURS

The complications of fURS include infection, sepsis, bleeding, ureteric injuries and strictures. If a ureteric injury is identified, then the procedure should be abandoned and a ureteral stent should be placed.

Role of Laparoscopy and Open Surgery

The AUA and Endourological society does not recommend routine use of open, laparoscopic or robotic assisted surgeries for renal stones in pediatric patients except in cases of congenital PUJ Obstruction.28

Conclusion

The endourological treatment remains the mainstay of pediatric stone disease in the present era. Pediatric renal stones, though uncommon can present unique challenges to the urologist. However, the principles guiding the treatment essentially remain the same with minor modifications. First and foremost, aim remains complete stone clearance with minimum re treatment sessions thus minimizing complications.

The use of ESWL has reduced substantially due to low success rates than endourology and miniaturization and improved optics of instruments. ESWL can be used as an adjunct to endourology treatment.

The advent of mini PCNL, micro PCNL and mini-micro PCNL, sleek and slender instruments, US guided punctures have paved way for a better acceptance and low complication rates in pediatric patients.

RIRS with flexible ureteroscopes has also become a routine and can become the standard of care for renal stones in due course of time owing to decreased diameters of flexible ureteroscopes, improved imaging and better availability of different lasers for stone fragmentation.

The management of ureteric and bladder stones are discussed in the relevant chapters of the book.

Key Points

1. The endourological treatment remains the mainstay of pediatric stone disease in the present era. Pediatric renal stones present unique challenges to the urologist. Primary aim is complete stone clearance with minimum re-treatment session and minimal complications.
2. ESWL is still a treatment option for renal stones with stone free rates between 68% to 84%. Though the use of ESWL has reduced substantially due to lower success rates than endourological management, it can be used as an adjunct to the endourology treatment.
3. The advent of mini PCNL, micro PCNL and mini-micro PCNL, sleek and slender instruments, US guided punctures have paved way for a better acceptance and low complication rates in pediatric patients. Additionally, energy sources like high power holmium laser, thulium laser fiber (TLF), Trilogy and Shockpulse have improved stone clearance rates. Use of sheaths with suctions has an added advantage.
4. Flexible ureterorenoscopes are now thinner and can be accommodated in pediatric ureters. Additionally, they also have better optics in comparison to their older counterparts. Care should be taken that ureter should not be over dilated. Often, sheathless procedure can be performed.

References

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最近更新时间: 2023-02-22 15:40