Ureteroscopy is the most common procedure performed to treat urolithiasis.¹ Though it is generally safe and effective, it is not without complications. One of the major complications that can occur is ureteral injury. Ureteral injury can range from a mucosal injury of the ureteral wall to ureteral avulsion. The implications of ureteral injury can be repeat procedures and ureteral stricture formation. Ureteral strictures have been reported to occur in up to 2.9% of patients who have undergone ureteroscopy for stone disease.¹ Though the cause of a ureteral stricture can be multifactorial, including patient- and stone-related factors, strategies to help avoid ureteral injury can help reduce stricture rate and overall morbidity after ureteroscopy. There are a number of ways to avoid ureteral injury, and I will describe the top 5 ways I go about trying to avoid ureteral injury (Figure 1).

Figure 1. Five ways to avoid ureteral injuries during ureteroscopy. Preop indicates preoperative.

The most important way to avoid ureteral injury is to have adequate preparation and counseling for ureteroscopy. This starts with patient counseling. All patients who undergo ureteroscopy should be counseled they may have a staged procedure. If a tight, unaccommodating ureter is encountered, a ureteral stent can be placed to allow passive dilation. During the procedure, if visibility is poor either due to stone impaction, bleeding, or debris, a stent can be placed and the procedure can be staged. Counseling patients that when this occurs it is for their safety allows them to be prepared for this eventuality and should make the decision to stage easier for the urologist. For patients with complex anatomy, contrasted imaging such as a CT urogram can help with surgical planning. It is better to recognize complex anatomy preoperatively to allow for appropriate counseling and to ensure the appropriate tools are available in the operating room.

Figure 2. Always ensure the stone and basket are clearly visible and are at a slight distance proximal to the ureteroscope all the way down the ureter.

Ureteral avulsion injuries are rare but devastating complications of ureteroscopy. These most commonly occur when too much force is applied in removing a fragment that is too large to fit through the ureter.² When removing fragments with a basket, minimal force should be applied to pull the stone out. In addition, it is critical to ensure the basket and stone are always visible and kept a distance from the ureteroscope (Figure 2). This allows clear and immediate recognition if the stone is stuck. If the basket gets stuck, a small laser fiber can be placed through the working channel of the ureteroscope alongside the basket and the stone can be further fragmented. Alternatively, the basket can be cut outside the ureteroscope and the ureteroscope can be reinserted alongside the basket to allow fragmentation of the stone.

When performing ureteroscopy, particular attention should be paid to the amount of force being applied to the ureteroscope. Excessive force can lead to either ureteral wall injury or ureteral avulsion. Ureteral avulsion can occur when withdrawing a rigid ureteroscope if the larger more proximal portion of the scope gets stuck in the intramural ureter.² If a ureteroscope will not advance up the ureter with minimal force, a consideration should be made to place a stent and allow passive dilation of the ureter.

Ureteral access sheaths are frequently used for flexible ureteroscopy to facilitate access to the proximal ureter and collecting system. Force may also be a contributing factor in ureteral wall injuries that occur with placement of ureteral access sheaths. These injuries have been characterized as grade 1, mucosal flap; grade 2, involving the mucosa and smooth muscle; grade 3, full thickness with fat visible; and grade 4, avulsion.³ Low grade injuries make up the majority of these. Access sheaths should be placed with minimal force to avoid these injuries. Prestenting was found to be associated with reduced risk of injury.³ Use of smaller access sheaths (10/12F vs 12/14F) may also reduce the risk of these injuries.⁴ Finally, there are some data to support use of preoperative alpha blockers such as tamsulosin to increase the compliance of the ureter and reduce the force needed for insertion of the access sheath.⁵ If a ureteral access sheath will not easily advance, the safest option is to either proceed without the sheath or place a stent and stage the procedure.

It is frequently necessary to fragment ureteral stones prior to removing them with the basket. The laser, either holmium:YAG or thulium, is the most common energy source used to fragment stones in the ureter. These lasers can generate heat when firing which could in turn cause damage to the ureter. It is important to moderate the total power (watts) used in the ureter to mitigate heat generation, irrespective of which laser is used. The lowest energy settings possible, preferably 10 W or below, should be used in the ureter. Irrigation is also effective at dissipating and reducing temperature elevation during laser lithotripsy in the ureter.⁶

Ureteroscopy is a minimally invasive, effective treatment for stones in the kidney and ureter. Though ureteral injury is uncommon, care should be taken to try and avoid these injuries as they can have significant impact on patients. Adequate preparation, appropriate basket extraction techniques, minimal insertion force for scopes and access sheaths, and low laser power for lithotripsy are all ways to reduce the likelihood of ureteral injury.