Inability to safely access the upper urinary tract for diagnostic or therapeutic purposes is not well reported. Problems with access range from 1.6 to 8.4% [4, 7, 8]. Common locations that may present access challenges include the ureteral orifice, a narrow intramural ureter, and unfavorable calyceal anatomy with acute angles and long narrow infundibula [9]. Ureteral strictures or impacted ureteral wall stones, which may present at any location, can preclude ureteroscopic advancement. Anatomic anomalies and variations such as severe spinal column angulation, external ureteral compression, renal and ureteral ectopia, prior ureteral reimplantation, cystoceles in women, and benign prostatic enlargement in men may also pose access difficulties. Ureteral injury such as mucosal flaps or ureteral perforation can also limit safe retrograde access.

When access problems are encountered, the safest option is to place a ureteral stent and allow for passive ureteral dilation over 1–2 weeks with an attempt at repeat ureteroscopy thereafter. This can reduce the risk of avoidable ureteral injury. In one single-institution retrospective review of 322 ureteroscopies which sought to determine factors predictive of ureteroscopic complications, one third of the ureteral perforations were associated with balloon dilation of the ureteral orifice or trying to manipulate a wire past an obstructing stone [7]. When access to the upper urinary tract is still not possible despite passive ureteral dilation with a stent, a percutaneous antegrade approach may be considered as well.

Bleeding during ureteroscopy is rarely of significant concern and it is only in the exceptional case that intervention is necessary beyond procedure termination and possibly ureteral stenting. Procedure termination is a result of compromised visualization from intraluminal bleeding. Most often bleeding is encountered with ureteral orifice dilation, mucosal, or calyceal injury from wire or ureteroscope trauma, or during stone lasing and manipulation. The incidence of bleeding severe enough to cause premature termination of ureteroscopy has been reported between 0.1 and 2.1% [4, 10–12]. Abdel-Razzak and Bagley reviewed 290 flexible ureteroscopies performed in the late 1980s and early 1990s for urolithiasis and upper tract urothelial carcinoma. They experienced two aborted procedures secondary to bleeding severe enough to limit vision. Geavlete et al., the largest of these series, retrospectively reviewed 2,735 semirigid ureteroscopies at a single center between 1994 and 2005 with three cases prematurely aborted because of bleeding limiting visualization. In all cases a ureteral stent was placed and the bleeding resolved. None of these cases required a blood transfusion.

A single case report described a significant delayed bleed after uncomplicated ureteroscopy and holmium laser lithotripsy for a 0.8  ×  0.9 cm right proximal ureteral stone. The patient required a transfusion of 4 units of packed red blood cells and eventual angioembolization of a lower pole arteriovenous fistula [13]. Interestingly, the patient had undergone failed shockwave lithotripsy (SWL) 2 months prior. Endoureterotomy or endopyelotomy is another instance where significant bleeding may be encountered if a crossing vessel is injured. Prevention of this serious complication is through analysis of preoperative cross-sectional imaging such as computed tomography angiogram, careful selection of incision location away from likely artery location, and thorough ureteroscopic inspection for arterial pulsation at the incision site prior to incision. If bleeding does occur, placement of a large ureteral balloon dilator (24–30 Fr) can help temporize the bleeding to all for further intervention such as angioembolization.

In general, careful technique and fastidious use of lasers and other instruments can help minimize potential bleeding and allow for successful ureteroscopy even in anticoagulated patients and those with bleeding diatheses [14].

Modern ureteroscopes are well insulated and if maintained properly should not cause ureteral thermal injury. Some of the instruments commonly used during uretersocopy, such as lasers and electrohydraulic lithotripters can cause thermal damage to the ureter. This complication is rarely reported. The Holmium:YAG laser was reported to cause a ureteral perforation in 1 patient out of 598 patients (0.2%) undergoing laser lithotripsy in a large prospective study between 1993 and 1999 [15]. Ureteral mucosal spark damage from the electrohydraulic lithotripter was reported to cause ureteral perforations in 2 patients out of 198 patients (1%) with ureteral or renal stones in a separate study between 1985 and 1991 [16]. Three cases (0.1%) of mucosal thermal injury were reported in a more contemporary series of 2,275 semirigid ureteroscopies [4]. Comparisons between the two instruments have shown no difference in complication rates [17].

Proper technique during lithotripsy including avoiding direct contact with the ureteral wall and aiming the energy source parallel rather than perpendicular to the ureteral wall, should minimize thermal tissue damage. If there is concern for thermal injury, ureteral stent placement is prudent. Four to six weeks after ureteral stent removal, renal ultrasound can be used as a screen for ureteral stricture formation, as this has been reported after thermal injuries [18].

Successful ureteroscopy depends on the proper function of multiple instruments and technologies including the endoscope, light source, lithotripsy device, stone basket, biopsy forceps, and digital camera. Any of these may be damaged during surgical use or during processing and ­sterilization. Baskets may break when extracting larger stone fragments that become lodged within the ureter or within the calyces when acute angles are present. Laser fibers may crack within the sheath of the ureterscope and cause unintentional damage to the scope or patient. On very rare occasions the ureteroscope may fracture within the ureter [9].

Broken or entrapped baskets can be challenging problems. This is most often encountered during stone basket extraction of larger stones or fragments. Tipped baskets that break often have wire fragments extending out toward the ureteral wall [19]. Tipless baskets have less of a tendency to do this and are safer from this perspective. Many strategies have been suggested. Clearing the engaged stone first can allow safer manipulation of the basket. Cutting or lasering the remaining intact basket wires can help disengage most of the basket. Then grasping the remaining portion of the basket may be easier. The remaining portion of the basket can also be carefully manipulated so that the tip of the basket is angled down the ureter and then removed tip first. In this orientation ureteral injury is less likely. Alternatively, trying to backload a small catheter over the basket may sheath the broken wire fragments and protect the ureter with basket removal through the catheter [19].

Ureteroscopy accessories such as basket retrieval devices and laser fibers are usually easily replaced. Malfunctioning or damaged ureteroscopes often require manufacturer repair, which are expensive and can represent a majority of the cost of a flexible ureteroscopy program over time [20]. Instrument malfunction is likely underreported, and has ranged in incidence from 0.7 to 1.9% [4, 7, 10]. Unfortunately all ureteroscopes require repair at some point, and a prospective comparison of four contemporary ureteroscopes showed three of the four to have relatively similar durability with approximately 17–18 uses before repair was necessary [21]. However, the fourth ureteroscope required repair after only approximately five uses, though the authors did not comment further as to the differences.

Proper technique during ureteroscope use is important to reducing preventable damage to instruments. The ureteroscope should be straight when advancing and removing instruments through the working channel. Ureteral access sheaths and small laser fibers and baskets can minimize deflexion strain on ureteroscopes and improve longevity [22].

Ureteroscope processing, sterilization, and storage is another source of preventable damage and has been of increased interest recently. Specific causes of ureteroscope damage include overcurling of the scope during storage, improper cleansing techniques, and closing the storage case onto the ureteroscope shaft [23]. Developing a dedicated and well educated team responsible for ureteroscope cleansing and storage has been shown to reduce ureteroscope damage and increase ureteroscope lifespan [24].

When broken or damaged instruments are detected they should be removed from the surgical field and no longer used. In some cases this may require early termination of the current procedure and a repeat procedure at a later time. This approach is preferred to the possible major complications that may occur when continuing with poorly functioning or broken equipment.

Some degree of ureteral mucosal abrasion occurs routinely with most ureteroscopy cases. It is rarely of clinical significance and because of this likely underreported. Moreover, no standard definition of mucosal abrasion exists further complicating the understanding and impact of this problem.

A recent retrospective series of 2,275 semirigid ureteroscopies reported ureteral abrasions in 1.5% of cases while using a variety of ureteroscopes between 6 and 10 F [4]. An older series compared the complications of 248 rigid ureteroscopies using ureteroscope diameters between 9.5 and 11.5 F to 49 semirigid ureteroscopies with ureteroscope diameters between 6 and 7 F. Ureteral mucosal abrasions were reported in 24% of the rigid ureteroscopies and in only 6% of the cases using the smaller caliber semirigid ureteroscopes [25]. Principles to help minimize abrasions includes careful technique, avoiding rapid jerky movements while in the ureter, keeping the ureteral lumen in view when advancing and withdrawing the ureteroscope, and not advancing the ureteroscope with accessories protruding from the working channel. The use of ureteral access sheaths when expecting multiple passes with the ureteroscope should also help minimize mucosal injuries.

An infrequent but devastating complication of ureteroscopy, ureteral intussusception, occurs when the ureteral mucosa circumferentially tears away from the underlying submucosa and then invaginates as a sleeve along the intact ureteral lumen. Described another way, it can be thought of as avulsion of the ureteral mucosa while the underlying ureteral layers remain intact. It has only rarely been described, and has been associated with stone manipulation, retrograde pyelography, and during diagnostic endoscopic management of urothelial cell carcinoma [32–34]. In the case of intussusception after retrograde diagnostic ureteroscopy, ureteral dilation with a 12 Fr peel-away sheath was believed to be the inciting factor.

Prompt recognition requires a high index of suspicion, and should be considered in cases of ureteral obstruction after recent instrumentation or stone extraction. Inability to place a ureteral stent after stone extraction or ureteral dilation should serve as an alert to possible intussusception. Retrograde pyelogram may show a “bell-shaped” ureter [35]. If not found intraoperatively, it can present as ureteral obstruction at a later time. Cross-sectional imaging with contrast can show an inner contrast-filled lumen surrounded concentrically by the intussuscepted ureteral mucosa and an outer ring of contrast. On coronal sections a narrow line of contrast, recently dubbed the “line sign,” can be appreciated [36].

If possible, a ureteral stent should be placed once the injury is identified. If retrograde stenting is unsuccessful, then percutaneous nephrostomy tube placement is advised. These are only temporizing measures to drain the kidney, as the intussuscepted segment can be expected to fibrose and stricture off rather than heal with any meaningful lumen. Ultimately, resection of the intussuscepted nonviable segment is required with ureteroneocystotomy, ureteroureterostomy, ureteropyelostomy, or ureteral substitution depending on the location and length of intussuscepted ureter.