Intraoperative bleeding represents a rare complication of ureteroscopy and it rarely represents the cause of termination of the procedure due to compromised visualization of the ureteral lumen. Causes of bleeding include trauma of the ureteral orifice during the insertion of the ureteroscope, pelvis or caliceal over-distension, mucosal injury during insertion of stiff guidewires or stone manipulation with basket.

Tepeler et al. reported and categorized the intraoperative complications in 1,208 patients who underwent ureteroscopy for stone removal [1]. The authors reported that the incidence of intraoperative bleeding was 1.9 % and none of the cases needed blood transfusion. Although bleeding was minor in most of the cases, four of them (0.33 %) were terminated due to loss of vision.

Geavlete et al. retrospectively reviewed 2,735 ureteroscopic procedures operated in a single center between 1994 and 2005 [2]. The incidence of significant bleeding during the ureteroscopic procedure was 0.1 % with three of the cases having to be terminated due to limited visualization. All cases were managed with stent placement and no blood transfusion was required.

Toepfer et al. compared the clinical outcome of rigid ureteroscopy between patients who receive antiplatelet and anticoagulant therapy and patients who did not [3]. They reported no differences in bleeding complications. Similarly, Watterson et al. reviewed 29 stones of patients with known bleeding diathesis who were treated with holmium laser intracorporeal lithotripsy [4]. All procedures were finished uneventfully, apart from one case in which a blood transfusion was required due to a significant retroperitoneal hemorrhage. Of great interest, in this specific patient he was treated with laser and concomitant electrohydraulic lithotripsy (which has a higher rate of ureteral perforation and ureteal damage compared to the Holmium laser).

In the contemporary era, smaller diameter ureteroscopes have decreased the need for ureteral orifice dilation and thereby the incidence of significant bleeding [5]. The surgeon may also decrease the risk of intraoperative bleeding by decreasing the use of extraction tools, like baskets, and stiff wires. A flexible instrument should be used in cases that there is an increased resistance to pass proximal the ureter. Whenever, the visualization is low and manipulations inside the ureter are not safe, a ureteral stent should be placed and the procedure should be terminated. Bleeding is then generally controlled within a few hours. In the rare case of uncontrolled bleeding, a tamponade balloon catheter may be used intraoperatively. Persistent, life-threatening hemorrhage should be managed with immediate angioembolization.

Some of the devices used for intracorporeal lithotripsy, mainly electrohydraulic and laser lithotripters, produce thermal energy during stone fragmentation. As a result of the above phenomenon, thermal injury of the ureteral wall, even if it is rare, represents a potential complication of the procedure. Direct contact of the electrohydraulic probe to the ureteral wall may lead to ureteral perforation due to coagulative necrosis. The same results can be produced by the Holmium laser fiber which has a penetration depth of 0.5 mm. However, when the tip is located adistance of at least 2 mm away from the ureteral wall, the possibilities of thermal injury are rare.

Sofer et al. reported a thermal injury incidence of 0.2 % in 598 patients who were treated with Holmium laser lithotripsy [6]. On the other hand, this rate was significantly higher (1 %) in a series of 198 patients who were managed with electrohydraulic lithotripsy by Basar et al. [7].

In depth knowledge of the technical characteristics of ureteroscopic instruments, surgical experience and appropriate instrumentation during lithotripsy are the mainstays for decreasing the potential of ureteral wall thermal injury. In cases of ureteral wall injury or ureteral perforation, a stent should be placed to allow for mucosal healing. Future CT urography may be helpful for early identification of ureteral stricture and obstruction.

Mucosal abrasion represents the most common complication of ureteroscopic procedures. There is no standardized definition and it is rarely of clinical significance apart from technical difficulties that can be produced during the operation mainly due to obstruction of the lumen and decrease of visibility. It is obvious that any instrument that passes through the ureter can produce a certain degree of abrasion. This degree is higher when rigid and semirigid instruments are used, and multiple entries of the ureteroscope are needed for stone disintegration and removal. Butler et al. reported a 0.3 % rate of mucosal abrasion in a study of 2,273 ureteroscopies. They reported that the ureteroscope itself was the cause of mucosal abrasion in all cases [8]. Similarly, Geavlete et al. reported that mucosal abrasion was noticed in 1.5 % of 2,735 ureteroscopic procedures made with semirigid instruments of variable diameter ranged from 6.5 to 10F [2].

The flexibility and size of the ureteroscope can be correlated to the degree of mucosal abrasion [9]. Francesca et al. thus compared the safety of conventional rigid ureteroscopes with a diameter from 9.5 to 11.5Fr and semirigid ureteroscope with a diameter ranging between 6 and 7Fr [9]. Ureteral mucosal abrasion was observed in 24 % of 248 rigid ureteroscopies and in 6 % of 49 semirigid procedures. The authors conclude that small caliber semirigid ureteroscopes are safer compared to conventional instruments.

Theoretically, small abrasions will not affect the procedure in terms of technical aspects and clinical outcome. They usually do not need any adjuvant procedure since they will heal fast without long term complications.

False passage represents a common complication during endoscopic maneuvers. The reported rate is widely varied and ranges from 1 to 18.3 % [2, 10]. Although it is characterized as a minor complication, it can be transformed into a serious complication if it is not identified and left untreated. It is generally caused during the insertion of a guidewire and it is more common to happen at sites of ureteral inflammation or impacted stones. Ureteral strictures, tight ureteral orifice, tortuous ureters and excessive force during the insertion of the ureteroscope may also lead to false passage. Blind manipulations of any endoscopic equipment, such as baskets, laser fibers and forceps may lead to creation of false passage, as well.

Suspicious clinical signs such as difficulty in advancing the wire through the ureter should be carefully noted and if the manipulation is continued may lead to a false passage. The fluoroscopic identification of the wire inside the pelvis and the caliceal system does not exclude the presence of a false passage, since the wire may re-enter the ureteral lumen after a short sub-mucosal course. The latter situation may lead to tract dilatation with a ureteral catheter or with the ureteroscope. Dilatation of a false passage with a balloon can lead to disaster as it can then lead to ureteral perforation and increased ureteral damage.