Grade I: any deviation from normal postoperative course without the need for pharmacologic treatment or surgical, endoscopic, or radiologic intervention. The allowed therapeutic regimens include drugs such as antiemetics, antipyretics, analgesics, diuretics, electrolytes, and physiotherapy. This grade also includes wound infections opened at the bedside
Grade II: complications requiring pharmacologic treatment with drugs other than those allowed for grade I complications. The use of blood transfusions and total parenteral nutrition is also included
Grade III: complications requiring surgical, endoscopic, or radiologic intervention
Grade IIIa: intervention required without general anesthesia
Grade IIIb: intervention required with general anesthesia
Grade IV: life-threatening complications, including central nervous system complications, requiring intensive care unit stay
Grade IVa: single organ dysfunction, including requiring dialysis
Grade IVb: multiorgan dysfunction
Grade V: death of the patient
Satava classification system
Grade 1 complications (incidents without consequences)
Grade 2 complications (incidents treated with endoscopic surgery)
Grade 2a complications (incidents treated intraoperatively with endoscopic surgery)
Grade 2b complications (incidents requiring endoscopic re-treatment)
Grade 3 complications (incidents requiring open or laparoscopic surgery)
Ureteral avulsion is one of most devastating complications during ureteroscopy. It is relatively rare, with a reported incidence up to 0.4%. While it may be assumable that avulsion occurs more commonly in the proximal ureter due to its less well-defined muscular wall, a relationship with stone location within the ureter has not yet been found .
The most known mechanism of ureteral avulsion is when stones are tried to be removed with a basket with excessive force while they are too large to be passed through the ureteral lumen. To avoid this complication, stones should not be entrapped in the basket until they are reduced to small fragments. When a basket is impacted in the ureter, one should try to release the stones by opening the basket and pushing it gently against the ureteral wall. In case of failure, a laser fiber should be advanced through the working channel to reduce the size of the stone fragments. Another option is to cut the wires of the basket or to dismantle the handle of the basket.
A less known mechanism is the two-point or “scabbard” ureteral avulsion in which the ureter is wedged in the intramural ureter. It involves a proximal and distal discontinuity of the ureter, with a resultant scabbard, as the ureter is withdrawn as a sheath on the ureteroscope [5–7]. The authors attribute this complication to the tapered design of the endoscope, in which the larger proximal shaft becomes wedged in the intramural ureter. Ureteral avulsion may also occur during removal of a locked ureteroscope . This may occur when a flexible ureteroscope is pulled through a stenotic infundibulum in maximal deflection [8, 9]. In case of locked flexible ureteroscope, one may try to manually straighten the ureteroscope by passing a coaxial dilator alongside the ureteroscope . In case of failure, one may try remove the ureteroscope without damaging the urinary tract by cutting the handle of the flexible ureteroscope or by cutting the distal part through a percutaneous access. To avoid this calamitous complication, the urologist should always be aware of the position of the ureteroscope within the confines of the collecting system by using fluoroscopy.
A ureteral avulsion can be repaired immediately at the time of recognition or in a staged session after discussing the treatment options with the patient. In case of delayed repair, an appropriate urinary drainage should be guaranteed through a ureteral stent or nephrostomy tube. Definitive surgical options include several types of ureteral reimplantation depending of the level of avulsion, ileal interposition, or renal autotransplantation .
Mucosal Erosion, Submucosal Tunnel, and Ureteral Perforation
Endoscopic classification of ureteral wall injury after RIRS using ureteral access sheath 
Grade 0 (low) no lesion found or only mucosal petechiae
Grade 1 (low) ureteral mucosal erosion without smooth muscle injury
Grade 2 (high) ureteral wall injury, including mucosa and smooth muscle, with adventitial preservation (periureteral fat not seen)
Grade 3 (high) ureteral wall injury, including mucosa and smooth muscle, with adventitial perforation (periureteral fat seen)
Grade 4 (high) total ureteral avulsion
Post-Ureteroscopic Lesion Scale (PULS) 
Grade 0 no lesion (uncomplicated URS)
Grade 1 superficial mucosal lesion and/or significant mucosal edema/hematoma
Grade 2 submucosal lesion
Grade 3 perforation with less than 50% partial transection
Grade 4 more than 50% partial transection
Grade 5 complete transection
One may expect that false passages occur more likely at the distal ureter at the medial and posterior side due to the bulky transitional layer, thick muscular backing, and oblique insertion in the bladder. Avulsion may occur more commonly in the proximal ureter where the muscular wall is less well defined. However, this hypothesis has not yet been confirmed .
Mucosal ureteral erosions , false passages, and ureteral perforations may also be further complicated by submucosal or extra-ureteral stone migration. This was reported by Georgescu et al. in 0.15% of semirigid ureteroscopies for ureteral stones . Ideally, every effort should be made to remove residual submucosal fragments or in order to prevent later stricture formation.
Most authors suggest continuing the intervention despite the lesions and leaving a ureteral stent afterward in a retrograde or antegrade way. In case of extensive extravasation, a conversion may be appropriate with drainage of the extravasation, ureteral stent insertion, and ureterorrhaphy [12, 16–18].
Bleeding After Endoureterotomy or Endopyelotomy
Instrument Malfunction or Breakage
Intraoperative bleeding frequently occurs during ureteroscopy. Ureteral wall trauma is usually iatrogenic after inappropriate instrument usage. It may also occur as a consequence of forniceal rupture because of increases intrarenal pressure. Minor bleeding usually stops spontaneously after a couple of minutes of low-pressure irrigation. In case of prolonged poor vision caused by bleeding, it may be better to place a ureteral stent and postpone the intervention.
Following the MCCS, Mandal et al. considered hematuria lasting less than 6 h not as a complication. Hematuria resolving spontaneously by 48 h was considered as “transient hematuria.” “Persistent hematuria” was defined as it lasted for more than 48 h and when additional medication or interventions were needed . Transient hematuria and persistent hematuria are reported with an incidence up to 20% and 3%, respectively. This may result in urinary clot retention. In up to 1% of ureteroscopic cases, a blood transfusion is given . Seldom, endourological of angiographic techniques are necessary to treat life-threatening bleeding .
To prevent mucosal tears, submucosal trauma, or more severe ureteral injuries, it is recommended to use small-size ureteroscopes and access sheaths. Instruments should always be adapted to the patient’s anatomy and not the other way around. In case of ureteral narrowing, it is recommended to place a ureteral stent and postpone the intervention for at least 1 week, allowing passive ureteral dilatation . Baskets should be used with great care under direct vision, and ureteral stones should be fragmented or dusted from the center toward the periphery in order to reduce the risk of accidental laser activation on the mucosa. Vaporizing urothelial carcinoma of the upper tract may be less bloody with the “no touch technique” with a low energy, low frequency, and long pulse duration.
Bleeding due to forniceal rupture may be prevented by keeping the intrapelvic pressure as low as possible (below 40 cm H2O or 30 mmHg). This may be achieved by applying low-pressure irrigation and using a ureteral access sheath that lowers irrigation pressures transmitted to the renal pelvis. The rate of decrease in pressure will depend on the outer diameter of ureteroscope and the inner diameter of the sheath . Increasing irrigation pressure during bleeding may further worsen the situation. As well, active aspiration should be avoided since negative intrarenal pressure may provoke bleeding as well.
Westerman et al. studied the effect of anticoagulation and antiplatelet agents on bleeding-related complications following ureteroscopy. They found that continuing antiplatelet therapy in patients on chronic therapy does not increase the risk of bleeding-related complications . In contrast, continuation or bridging of anticoagulants increases the risk of perioperative bleeding .
Early Postoperative Complications
Even if ureteroscopy is generally considered as a safe procedure, fatal events may occur. Most frequent reported cause of dead is urosepsis . Other causes include multiorgan failure, arrhythmia, cardiac death, and lung embolism. These complications are frequently secondary to less severe complications at first sight like infected urolithiasis, bleeding, or perirenal hematoma [15, 21, 26]. Chang et al. reported a gas embolism as a cause of death . Possible explanatory mechanisms may be air bubbles generated during Ho:YAG laser lithotripsy, air pushed into the upper urinary tract during repeatedly ureteroscope extraction and insertion, air bubbles during irrigation, or peripheral venous catheter-related air embolism.
A renal pseudoaneurysm is a serious uncommon condition that is caused by an arterial perforation that is only surrounded by connective tissue and a hematoma. This vascular lesion may become life-threatening when the arterial pressure surpasses the tamponade effect of the surrounding tissue. It has been reported after rigid and flexible ureteroscopy after endopyelotomy or lithotripsy with various energy sources techniques (laser fragmentation and electrohydraulic energy), and with or without the use of a ureteral access sheath. It may be asymptomatic or present as unexplained anemia, abdominal pain, fever, or hematuria. A renal pseudoaneurysm is diagnosed with contrast-enhanced CT or renal angiography. Treatment consists of embolization or surgery in case of treatment-refractory bleeding [28–32].
A few authors reported the initiation of intrarenal arteriovenous fistula after Ho:YAG or electrohydraulic lithotripsy. These fistulae are probably caused by damage of tissue and small interlobar arteries and veins during lithotripsy, leading to a connection between a high-pressure artery and a low-pressure vein. All cases presented with hematuria and were treated by embolization [33–35].