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Background: Incidence of pediatric nephrolithiasis has been increasing in recent years. Ureteroscopy is the most common surgical intervention, for which fluoroscopy is traditionally used for intraoperative guidance. Children with nephrolithiasis are at increased risk of secondary effects from ionizing radiation in their lifetime due to their risk of stone recurrence and need for repeated procedures, longer life expectancy, high cellular mitotic rate, and close proximity of the operative field to the gonads. Ultrasound guided ureteroscopy has potential to provide a radiation-free, safe and effective approach to stone management in children. We present the first case series demonstrating the safety and success of ultrasound guided ureteroscopy in pediatric nephrolithiasis patients.
METHODS: With IRB approval, a review of consecutive patients that underwent ultrasound guided ureteroscopy at our institution was performed. We collected data on demographics, procedures performed, stone size, operative time, outcomes, and complications.
RESULTS: Eight patients underwent nine ultrasound guided ureteroscopic procedures for nephrolithiasis. One patient had to be pre-stented and subsequently had ureteroscopy and stone extraction. Real time ultrasound guidance was used for guidewire placement, followed by double lumen catheter, second wire access, access sheath, and ureteroscope. All instruments were followed in both bladder and renal ends for confirmation of position. Stones were removed via ultrasound guidance from various locations including lower pole calyx, proximal ureter, and from a calyceal diverticulum. In one patient, ultrasound was used to perform a ureteral balloon dilation of uretero-vesical junction and one patient had ultrasound guided access and dilation of calcyeal diverticulum. Stents were placed under ultrasound guidance. Fluoroscopy was used in the initial six procedures to verify stent location at the end of the procedure during the learning phase of the ultrasound technique. Patient characteristics and outcomes are summarized in Table 1 and 2.
CONCLUSIONS: Ultrasound guided ureteroscopy can be safely and effectively used in pediatric patients to successfully treat urolithiasis with significant reduction or complete elimination of ionizing radiation.

Table 1. Patient characteristics and operative outcomes
Gender (female %)	67%
Age (years) – Median (Range)	13 (3-22)
BMI (kg/m2) – Median (Range)	20.6 (13.7-30.1)
Stone size (mm) – Median (Range)	6 (4-10)
Operative time (mins) – Median (Range)	66 (43-94)

Table 2. Procedural details and outcomes
Patient	Ultrasound Guided Procedure	Operative Time (min)	Outcome	Complications
Patient 1	Ureteroscopy	61	Basket extraction of upper and lower pole stones	none
Patient 2	Ureteroscopy	89	Laser lithotripsy of mid pole stones	none
Patient 3	Ureteroscopy	65	Identification of lower pole Randall’s plaque	Additional pain control (Clavien I)
Patient 4A	Cystoscopy, attempted ureteroscopy, pre-stent placement	44	Failed ureteroscopy, pre-stenting was done	none
Patient 4B	Ureteroscopy	71	Basket extraction of proximal ureteral stone	none
Patient 5	Ureteroscopy	83	Basket extraction of mid pole stone	Additional pain control (Clavien I)
Patient 6	Ureteroscopy	43	Laser lithotripsy and basket extraction of lower pole stone	none
Patient 7	Cystoscopy, Balloon dilation of ureter, attempted ureteroscopy, stent placement	65	Ureteral balloon dilation of UVJ and pre-stent placement	none
Patient 8	Ureteroscopy, laser calycostomy, Stone extraction	94	Calyceal diverticulum-laser calycostomy, removal of stones and stent placement into diverticulum	none