Residency · Residency · Urology
Ureteroscopy and Laser Lithotripsy
Overview
Ureteroscopy (URS) is the most commonly performed procedure for managing ureteral and renal stones. This technique allows direct visualization of the urinary tract, enabling lithotripsy and extraction of stone fragments. Additionally, URS can be combined with biopsy and laser treatment of urothelial lesions when necessary. The stone-free rates achieved with URS vary depending on stone location: approximately 90-95% for distal ureteral stones, 85-90% for proximal ureteral stones, and 75-85% for renal stones smaller than 2 cm.
Instrumentation
Semi-Rigid Ureteroscope
The semi-rigid ureteroscope typically has a diameter ranging from 6 to 8 French (Fr) and is best suited for stones located in the distal and mid-ureter. Its advantages include superior optics, a larger working channel, and greater durability compared to flexible scopes. However, it has limited deflection capability, making navigation above the iliac vessels challenging. Forced advancement proximally carries a risk of ureteral injury.
Flexible Ureteroscope
Flexible ureteroscopes have a diameter between 7 and 8.5 Fr and offer active deflection up to 270 degrees, which is essential for accessing renal stones and proximal ureteral stones. There are two main types: digital and fiberoptic. Digital scopes provide superior image quality but tend to have a larger diameter and higher cost. Single-use disposable flexible scopes are increasingly adopted as they eliminate reprocessing costs and repair needs.
Working Channel Equipment
The working channel of the ureteroscope accommodates various instruments, including laser fibers ranging from 200 to 550 microns, stone baskets such as nitinol tipless baskets (e.g., Zero Tip, Dakota), biopsy forceps, and guidewires that can be hydrophilic or standard.
<image>Photographs of semi-rigid and flexible ureteroscopes with labeled components including tip deflection mechanism, working channel, and eyepiece</image>
Ureteral Access Sheath (UAS)
The ureteral access sheath is a hydrophilic sheath, typically sized 10/12 Fr or 12/14 Fr, placed over a guidewire into the proximal ureter. Its use facilitates multiple passes of the ureteroscope, reduces intrarenal pressure by improving drainage, enhances visibility through maintaining low-pressure irrigation, and increases stone-free rates for renal stones. However, potential risks include ureteral injury such as ischemia, mucosal stripping, or perforation, occurring in 5-15% of cases, and a debated risk of long-term ureteral stricture estimated at about 1-2%. Pre-stenting the ureter 1-2 weeks prior can facilitate UAS placement in tight ureters. It is crucial to always insert the sheath under fluoroscopic guidance and never force its advancement.
Laser Lithotripsy
Holmium:YAG Laser
The Holmium:YAG laser operates at a wavelength of 2,100 nm, which is strongly absorbed by water, making it the gold standard for ureteroscopic lithotripsy. It is effective against all stone compositions. The laser settings vary depending on the technique used. For fragmentation, high energy (0.6-1.2 Joules) and low frequency (5-10 Hz) are employed to create larger fragments suitable for basket extraction. Dusting uses low energy (0.2-0.4 J) and high frequency (20-80 Hz) to produce fine dust that passes spontaneously. Pop-dusting or pop-corning techniques use moderate energy (0.5-0.8 J) and moderate frequency (10-20 Hz).
| Laser | Wavelength | Fiber Size | Fragmentation Settings | Dusting Settings | Key Advantage |
|---|---|---|---|---|---|
| Holmium:YAG | 2,100 nm | 200-550 μm | 0.6-1.2 J, 5-10 Hz | 0.2-0.4 J, 20-80 Hz | Gold standard; effective on all compositions |
| Thulium Fiber (TFL) | 1,940 nm | 50-150 μm | Lower energy needed | Superior micro-dusting | Less deflection loss; reduced retropulsion |
Thulium Fiber Laser (TFL)
The Thulium Fiber Laser operates at a wavelength of 1,940 nm, which has four times greater water absorption than the Holmium laser. Its advantages include the use of smaller fibers (50-150 microns), which result in less loss of scope deflection, more efficient ablation at lower energy levels, reduced retropulsion, and superior dusting capability often referred to as "micro-dusting." TFL is increasingly adopted and may become the new standard for laser lithotripsy.
Laser Safety
Laser safety is paramount during URS. The laser should never be fired outside the working field of view. The fiber tip must be kept in contact or near-contact with the stone to maximize efficiency and minimize injury. Firing the laser directly on the urothelium should be avoided due to the risk of perforation and stricture formation. Appropriate laser eyewear must be worn in the operating room to protect personnel.
<image>Intraoperative ureteroscopic views comparing fragmentation and dusting techniques during holmium laser lithotripsy of a ureteral calculus</image>
Surgical Technique
Patient Positioning and Setup
Patients are positioned in the supine lithotomy position under general anesthesia or monitored anesthesia care (MAC). Fluoroscopy with a C-arm is available for guidance. Prophylactic antibiotics are administered as a single dose according to the American Urological Association (AUA) Best Practice Statement, typically ciprofloxacin or trimethoprim-sulfamethoxazole if preoperative urine culture is negative.
Procedural Steps
The procedure begins with cystoscopy to inspect the bladder and identify both ureteral orifices. A safety guidewire, usually 0.035 inches in diameter, is passed into the renal pelvis under fluoroscopic guidance. Ureteroscopy is then performed, advancing a semi-rigid scope for distal or mid-ureteral stones, or a flexible scope via a ureteral access sheath for proximal or renal stones. Stones are identified and treated using laser lithotripsy with fragmentation or dusting techniques. If fragmentation is used, stone fragments are extracted with a basket. A final inspection confirms stone clearance and assesses for ureteral injury. A ureteral stent is placed if indicated.
Tips for Difficult Access
In cases of difficult access, pre-stenting the ureter for 1-2 weeks passively dilates it, facilitating subsequent scope passage. Balloon dilation of the ureteral orifice or intramural ureter can be performed but should be used sparingly. Sequential ureteral dilation with graduated dilators is another option. Importantly, forcing the scope should be avoided due to the risk of ureteral avulsion or perforation.
Stent vs. No Stent After URS
Indications for Stenting Post-URS
Ureteral stenting after URS is indicated in cases of ureteral injury or perforation, significant residual stone burden, solitary kidney, planned second-look procedures, prolonged procedures or significant ureteral edema, bilateral URS, and relative indications such as the use of a ureteral access sheath.
Omitting the Stent
Stent omission is considered safe in uncomplicated URS cases involving small distal ureteral stones without the use of a ureteral access sheath, complete stone clearance, no ureteral injury, and short operative times. Avoiding stenting reduces stent-related symptoms and eliminates the need for a second procedure or string removal. Multiple randomized controlled trials support stent omission in these uncomplicated cases with similar outcomes.
Stent Management
When stents are used, tethered stents with extraction strings allow removal in the clinic without cystoscopy, typically for routine cases. The duration of stenting is usually 3-7 days for routine cases and 2-6 weeks for complicated cases. Stent-related symptoms, including urinary frequency, urgency, flank pain, and hematuria, occur in over 80% of patients. These symptoms can be managed with medications such as tamsulosin and anticholinergics, although evidence for their benefit is limited.
<image>Fluoroscopic image showing a double-J ureteral stent in proper position with proximal curl in the renal pelvis and distal curl in the bladder</image>
Complications
Ureteral injury or perforation occurs in 1-5% of cases and is usually managed conservatively with stenting. Ureteral avulsion is a rare but devastating complication occurring in less than 0.5% of cases, often requiring open or robotic repair such as ureteral reimplantation, ileal ureter substitution, or autotransplantation. Infection and urosepsis occur in 1-3% of patients, with higher risk in those with preoperative positive urine cultures, indwelling stents, or large stone burden. Steinstrasse, or "stone street," refers to a column of stone fragments obstructing the ureter after lithotripsy. Ureteral strictures develop in 1-3% of patients long-term, more commonly associated with ureteral access sheath use, laser injury, or impacted stones. Bleeding is usually self-limited. Retained stone fragments may necessitate a second-look ureteroscopy.
Outcomes and Comparison with SWL
URS achieves higher single-session stone-free rates than shock wave lithotripsy (SWL) for most stone locations. URS is preferred for distal ureteral stones of any size, ureteral stones larger than 10 mm, renal stones measuring 10-20 mm, stones resistant to SWL such as cystine, calcium oxalate monohydrate, and brushite stones, obese patients (BMI >30) where SWL is less effective, and patients with bleeding disorders or on anticoagulation. SWL may be preferred for renal stones smaller than 10 mm located in favorable positions, especially non-lower pole calyces.
Clinical Pearls
It is essential to always place a safety wire before ureteroscopy, as it serves as an insurance policy in case of emergencies. The most dangerous part of URS is forcing the scope through a tight ureter; if the scope does not pass easily, pre-stenting and returning later is the safest approach. The dusting technique avoids the need for basket extraction but requires adequate irrigation flow and patience, with fragment size needing to be less than 1 mm for reliable spontaneous passage. The Thulium Fiber Laser is transforming laser lithotripsy by offering superior dusting efficiency and smaller fibers. Post-URS stent omission is safe and well-supported for uncomplicated distal ureteral stones, reducing morbidity and cost. Ureteral avulsion remains the most feared complication, with the highest risk associated with semi-rigid scopes in the proximal ureter and basket engagement of impacted stones.
References
- AUA/Endourology Society Guideline on Surgical Management of Stones, 2016 (amended 2022)
- EAU Guidelines on Urolithiasis, 2024 Update
- Traxer O, Thomas A. "Prospective evaluation and classification of ureteral wall injuries during ureteroscopy." J Urol. 2013;189(2):580-584.
- Jendeberg J, et al. "Thulium fiber laser versus holmium:YAG laser lithotripsy." World J Urol. 2021.
- Mertz L, et al. "Stenting after uncomplicated ureteroscopy: meta-analysis." J Urol. 2019.
- Campbell-Walsh-Wein Urology, 12th Edition, Chapter on Ureteroscopy
