Pediatric Ureteroscopy

Indications

The indications for pediatric ureteroscopy mirror those in adults. At our institution, we perform ureteroscopy for obstructing calculi that have a low probability of spontaneous passage. In addition, we perform ureteroscopy for patients with pain unresponsive to oral pain medication, >24 hours of anorexia, or persistent nausea and emesis. In addition, intervention is indicated for stones in a solitary kidney.

Preoperative Considerations

Preoperative antibiotics are given in accordance with the American Urologic Association best practice statement. Thus, in pediatric patients undergoing ureteroscopy, appropriate antibiotics include cephalosporins (first or second generation), ampicillin in conjunction with an aminoglycoside, or trimethoprim-sulfamethoxazole. A preoperative urine culture is obtained and used to document urine sterility and guide preoperative antibiotic use. At our institution, patients with a negative urine culture receive cefazolin preoperatively, whereas those with a pre-existing ureteral stent receive ampicillin and gentamicin or a fluoroquinolone.

Positioning

As for adults, pediatric patients are positioned in the dorsal lithotomy position for ureteroscopy. Appropriately sized boot stirrups are normally used. Candy cane stirrups can also be used, especially for smaller patients. The patient's extremities are adequately padded. Care is taken to avoid exaggerating the lithotomy position. If not using a cystoscopy table, care should be taken to position the patient to allow the c-arm to reach the kidneys without interference from the table.

Surgical Steps

We prefer all patients undergo general anesthesia with paralysis to help prevent patient movement and possible ureteral injury. After performing a sterile preparation, the patient is draped. The rigid cystoscope is advanced to the bladder. A 7.5–8F cystoscope is used in children. Larger cystoscopes of 19F are used in later adolescence. A urine specimen for culture is routinely obtained upon entry into the bladder. A retrograde pyelogram is subsequently performed to map the ureter and collecting system (Supplementary Video S1; Supplementary Data available online at www.liebertpub.com/end).

A wire is then advanced up the ureter under fluoroscopic guidance. We prefer a PTFE-Nitinol wire with a hydrophilic tip. In most cases, regardless of age, a 0.035 inch diameter guidewire can be used. If needed, a smaller hydrophilic Nitinol guidewire of 0.025 inch can be used to pass an impacted ureteral stone.

In the case of semirigid ureteroscopy for ureteral calculi, the 7.5F ureteroscope is now advanced into the bladder and the ureter is cannulated. We find that this ureteroscope can usually be accommodated by the pediatric ureter. A 4.5F semirigid ureteroscope is also available for the smaller ureter of the young patients, yet the 7.5F ureteroscope is preferred for its superior optics.

For upper ureteral calculi or renal calculi, flexible ureterorenoscopy is preferred. In this case, an 8/10F coaxial dilator or dual lumen catheter is advanced over the first or working wire and a second, safety, wire is placed. The 7.5F flexible ureteroscope may then be advanced over the working wire up to the level of the stone or the renal pelvis (Supplementary Video S2). Alternatively, a ureteral access sheath may be placed over the working wire, which is subsequently removed. Compared with adults, the ureteral access sheaths tend to be of shorter lengths, 25–35 cm. In patients in late adolescence, the longer 35 or 45 cm sheaths can be used as necessary. Even in pediatric patients, if possible, we prefer to use the 12/14F sheaths, but the smaller 10/12F sheaths can be used but require stones to be fragmented more completely.

At this point, the stone(s) are identified and intracorporeal lithotripsy or basket extraction can be performed (Supplementary Video S3). When performing flexible ureteroscopy, a 200-μm laser fiber is used with holmium:YAG laser. A larger, 365-μm laser fiber can be used with the semirigid ureteroscope. Isotonic irrigation fluid is used and should be at body temperature. If necessary, any larger fragments are basket extracted using a tipless Nitinol basket, usually 1.9F in size. If fragments are recovered, they are sent for stone analysis.

After complete fragmentation and basket extraction if necessary, the decision is made whether or not to leave a ureteral stent. This is based on the length of the procedure, the number of passes through the ureter, and visible edema, or trauma noted upon removal of instrumentation. The ureteroscope and access sheath, if used, are slowly backed out while examining the ureter and ensuring the safety wire remains in place (Supplementary Video S4).

A 4.7F stent is our stent of choice for the majority of patients. Older adolescents can accommodate a larger 6F stent as is used in adult patients, but usually the smaller diameter stents suffice and may be more comfortable to the patient. The length of the stent will be shorter than that used in adults until the patient reaches late adolescence. One rule of thumb that we have found to be helpful to estimate the stent length is the patient's age plus 10 cm. Normally, a string is left on the stent and brought through the urethral meatus to allow removal of the stent by the patient or family in 3–7 days. If a string is not left, the stent is removed in 7 days under general anesthesia.

The same steps for access are utilized for ureteral and upper collecting system tumors if encountered. The tumor is biopsied using ureteroscopic biopsy forceps or a stone basket. Then, if deemed treatable endoscopically, laser ablation is performed using the holmium laser. A stent is routinely left in place after ablation of ureteral tumors

Postoperative Care

Patients are usually discharged to home on the same day. Discharge medications normally include pain medication, an alpha-blocker, and possibly an anticholinergic. Antibiotic prophylaxis with an indwelling stent is controversial and this decision is made on a case-by-case basis. As mentioned, if a stent is left with a string, the patient is counseled to remove the stent at home in 3–7 days. Otherwise the patient returns for cystoscopy and stent was removed under anesthesia. As per AUA recommendations, patients should follow-up with renal ultrasonography. Patients are also referred to nephrology for a metabolic work-up.

Special Considerations

In pediatrics, the smaller caliber of the ureter can present challenges. As mentioned earlier, this may require smaller instrumentation including smaller ureteroscopes and access sheaths than the instrumentation used in adult patients. This can limit the size of the working channel as well as the optics. In addition, if the ureteroscope or coaxial dilator does not pass easily, ureteral dilation is indicated. This can be performed by balloon dilatation of the ureteral orifice, or, our preferred method, placement of a 3.7F indwelling ureteral stent for a period of 1–2 weeks to allow passive dilatation of the ureter. This period of dilatation will usually allow the larger access sheaths to be passed more easily, thus also improving the ease of the procedure.