Semirigid pediatric ureteroscopes in various sizes from 4.5/6.5 Fr and varying lengths (Karl Storz, top) and Wolf (Middle and Bottom) with offset eyepieces
Eyepieces may either be “in-line” with the ureteroscope or offset. Eyepieces that are “in-line” are more ergonomic and typically allow easy introduction of the scope with greater control. Offset eyepieces require more attention to hand placement but allow for the passage of instruments directly in-line with the scope.
The use of guidewires is critical to any endourologic procedure, adult or pediatric . They are used for gaining access, in dilation procedures, for straightening the ureter, stent placement, and to maintain access via the safety wire. The standard Sensor guidewire measuring 0.035 in. × 150 cm utilized in adults is often used in pediatric cases. Other options include 0.018–0.025 in. × 150 cm glidewire versions when smaller wires are needed. When placing a second wire, dual-lumen ureteral access catheters, typically 10 Fr × 50 cm, can allow rapid and safe deployment of a second wire. After gaining access, ureteral access sheaths placed to protect the ureter from repeated trauma come in 9.5/11 Fr.
Whether performing retrograde ureteropyelography or being used for access, ureteral catheters are requisites in ureteroscopy. Similar to the larger 5 Fr × 70 cm catheters used in adult patients and larger adolescent pediatric patients, pediatric urology benefits from a tailored range of ureteral stents as small as 3–4 Fr × 70 cm.
Despite miniaturization, gaining safe access for primary ureteroscopy is not always easily accomplished even while using pediatric instruments. In such cases the ureter may be dilated to allow safe navigation. Pediatric dilation is most commonly performed using 8/10 Fr coaxial dilators.
Prior to concluding the case, double-J ureteral stents are often deployed to facilitate continued drainage, decompression, and reduce ureteral stricture formation. An array of double-J ureteral stents are available, ranging from 3 to 6 Fr.
6/7.5 Fr semirigid ureteroscope
5/6.5 Fr semirigid ureteroscopes
7 Fr flexible ureteroscope
Endourologic working equipment:
Wires: 0.035 in Sensor™ wire, 0.018–0.025 in ZIPwire™
Ureteral dilators: 8/10 Fr coaxial dilator
Ureteral catheters in various sizes
Dual-lumen ureteral access catheter: 10 Fr
Ureteral access sheath: 9.5/11 Fr
Retrieval Devices: Zero-tip™ or Ngage® baskets as well as others
Double-J Ureteral stents: including 3–6 Fr
Irrigation device: single action pump, pressure bag, or mechanical
Technique for Lower Ureteral Calculi
Management of distal ureteral stones , defined as those located distal to the iliac vessels, is best performed via semirigid ureteroscopy due to advantages in irrigation, visualization, instrument control, and working channel diameter. To begin the procedure, a scout film should be obtained and saved prior to insertion of any instrumentation. Distal ureteral stones are difficult to visualize on fluoroscopy; however this provides documentation of any visible stone burden on plain film prior to removal.
The bladder should be drained prior to initiating ureteroscopy. An age-appropriate pediatric semirigid ureteroscope (4.5–7.3 Fr) is then assembled and advanced alongside the safety wire to the level of the stone. Irrigation can be performed using a pressure bag or mechanical system for continuous flow or manually by an assistant using a hand pump. In some instances the ureter is too narrow to accommodate the ureteroscope requiring ureteral dilation. Practices vary by physician regarding the thresholds for ureteral dilation vs ureteral stent placement and aborting the procedure to return in 7–14 days after a period of passive ureteral dilation. If ureteral dilation is attempted, this can be accomplished using balloon dilating devices (which is controversial), ureteral dilating sheaths, and/or serial ureteral dilators. Dilation should be performed with care as the risk of ureteral perforation is increased, and dilation over the stone can cause extrusion making extraction difficult and increasing the chances of perforation, stone granuloma formation, and eventual development of ureteral stricture. The authors’ preference is to attempt dilation with an 8/10 Fr coaxial dilator if the semirigid ureteroscope does not initially pass through the UO; however, placement of a stent is favored over balloon dilation due to less tactile feedback and increased risk of stricture formation due to ureteral injury/ischemia.
For small stones, basket retrieval can be performed; however, blind basketing and applying pressure due to tight passage through the ureter should not be attempted due to the risk of ureteral perforation and/or avulsion. Larger stones will require lithotripsy which can be accomplished by a number of devices; however, Holmium:YAG laser has emerged as the standard of care for stone fragmentation. Typically, laser lithotripsy is undertaken with a 200-μ laser fiber. Multiple techniques have been described for stone fragmentation including “dusting” or “painting” of the stone, in which it is fragmented into inconsequentially small particles which then easily pass through the urine, and “cracking” the stone into several smaller pieces which are still large enough to remove with a basketing device. For dusting, low-power and high-frequency settings (0.2 J and 30–80 Hz) are preferred, and the leading edge of the stone is contacted and “painted” continuously with the laser fiber such that it disintegrates. Irrigation washes the resulting stone powder out of the field of view. The laser fiber tip should always be in vision to prevent iatrogenic ureteral trauma. Eventually with the dusting technique, the stone will become small enough that the remaining significant stone burden can be removed with a basket device which is preferred due to the ability to send the stone for analysis. For cracking of the stone, which is preferred by the authors for distal stones due to less laser time (and less chance of iatrogenic ureteral injury) and increase in the chances of achieving stone-free status, higher-power and lower-frequency settings are used. For the authors, 0.6 J and 6 Hz is a common starting setting. The power is increased to effect by a factor of 0.2–0.4 J for harder stones with minimal changes in the frequency. The center of the stone is targeted, and the stone is lasered until it cracks into several pieces.