Ureteral injury is a common and serious complication of gynecologic surgery. If not diagnosed and managed in a timely manner, it can often result in adverse outcomes and is a common cause of patient complaints. With the development of surgical treatment of pelvic floor dysfunction in women, ureteral injury in reconstructive pelvic surgery (RPS) has become a clinical problem. Unlike ureteral injuries in traditional major gynecological surgery, ureteral injuries in transvaginal RPS are mostly twisted or obstructed by sutures rather than severed, avulsed, or clamped ureteral injuries. How to timely detect and manage ureteral obstruction in transvaginal RPS is crucial to reduce serious postoperative complications. This article intends to provide a literature review on ureteral obstruction in transvaginal RPS. I. Advances in ureteral anatomy studies related to transvaginal RPS Most ureteral injuries in cathartic surgery are in the lowermost segment of the ureter, between the uterine vessels and the bladder. After entering the deep pelvic floor, the ureter passes along the lateral aspect of the uterosacral ligament and enters the main ligament in an anterior-internal direction and passes under the uterine artery at 1.5 cm lateral to the level of the internal cervical os, then passes forward through the middle of the anterior vaginal fornix to reach and enter the bladder wall, subducting about 1.5 cm and opening at the ureteral crest on both sides of the bladder triangle, which lies just above the middle 1/3 of the anterior vaginal wall. The normal ureteral opening is approximately 2.93 cm apart on both sides, the ureteral opening is approximately 2.83 cm from the internal urethral orifice, and the distance from the internal urethral orifice to the midpoint of the interureteral ridge is approximately 2.4 cm. The ureteral opening is not perfectly symmetrical bilaterally at the cervical site. This was highlighted in one of the first reports on ureteral anatomy by Freund as early as 1869, who noted that the left ureter was closer to the cervix than the right, and in 1982, tomographic fluoroscopic cinematography studied by Hofmeister confirmed the asymmetry of the ureteral ends in the pelvis. Recent autopsy studies have shown that the mean distances of the ureter from the uterosacral ligament at the level of the cervix, middle sacral ligament and sacrum were 0.9 cm, 2.3 cm and 4.1 cm, respectively. Hurd et al. also found by pelvic CT that the ureter was only 0.5 cm or shorter from the cervix in about 12% of women. This means that these women are more likely to have ureteral injuries during pelvic surgery. And when in severe prolapse of the uterus and bladder, the position of the ureter usually changes as well. As the Sampson Classic Institute points out, even in the absence of pathology, the ureter can vary considerably depending on the position of the uterus in the pelvis. As the uterus and bladder move down and descend forward through the vaginal orifice, the bending of the ureter is greatly increased, and DeLancy et al. found as early as 1998 that for every 3 cm of cervical descent in severe uterine prolapse, the ureter descends 1 cm, whereas when the bladder and uterus are completely prolapsed, the ureter may be compressed up to the levator fissure and the edge of the pubic arch, resulting in varying degrees of ureteral obstruction. It was found that 12% to 15% of moderate to severe prolapse had hydronephrosis, of which 3.7% to 5.8% were moderate to severe hydronephrosis. The altered anatomic position of the ureter due to pelvic organ prolapse, the limited field of view and operation of cathodic surgery, and the inherent anatomic features of the ureter all make the ureter more prone to injury and less detectable in transvaginal RPS. The incidence of ureteral obstruction in transvaginal RPS Gustilo-Ashby et al. found an intraoperative ureteral obstruction rate of 5.1% in a study of femoral surgery for anterior and middle pelvic organ prolapse. This type of injury was predominantly in the form of obstruction due to sutures or ureteral distortion due to traction. The rate of ureteral obstruction varies between transvaginal RPS; in 2000, Shull and Barber et al. each reported a 1% and 4% incidence of ureteral injury during vaginal vault uterosacral ligament suspension, respectively; Barbe reported an intraoperative ureteral obstruction rate of up to 11%, of which 60% were relieved by intraoperative removal of supra-ureteral sutures. Because transvaginal RPS requires the patient to shift from a supine to a bladder truncal position, this position change significantly rotates the pelvis and alters the relative anatomy of the soft tissues in the pelvis. This is especially true for patients with pelvic organ prolapse. With this in mind, Aronson et al. in their study of high sacral ligament vaginal suspension noted that because of the rotation of the pelvis in the cystotomy position, a low deep suture should be reflected in the supine cystotomy position as opposed to a high sacral ligament suture in the upright position, i.e., suturing the uterosacral ligament deeper to minimize the distance from the ureter, significantly reducing the rate of ureteral obstruction. There is a paucity of literature on ureteral injury associated with posterior McCall trabeculoplasty, with Stanhope (1991) and Webb (1998) et al. each reporting ureteral obstruction rates of 0.3% and 0.6%, respectively, but neither applied cystoscopy intraoperatively and were only able to detect ureteral obstruction because of postoperative symptoms and elevated serum creatinine. In contrast, Pettit (1994) et al. routinely used cystoscopy during posterior McCall trabeculoplasty, and thus the 3.6% ureteral obstruction rate may be more accurate. In addition, it was found that the rate of ureteral obstruction was lower in the low level plication compared to the high level posterior McCall’s recess plication, which seems to be inconsistent with the local anatomy. It was shown that the ureter is closest to the uterosacral ligament at the level of the cervix and gradually moves away from the uterosacral ligament as it travels toward the sacrum. Furthermore, pulling the uterosacral ligament at the cervical level can lead to higher ureteral pressure than at the sacral level, thus making it more likely to cause ureteral obstruction. It is thus speculated that the reason for this may be that the closer to the sacrum the uterosacral ligament is sutured, the greater the midline deviation of the ureter produced by the suture and the greater the peritoneal tension covering the ureteral surface may be, thus predisposing the ureter to distortion or obstruction. The rate of ureteral obstruction in vaginal closure has been reported differently, with Gustilo-Ashby et al. showing an obstruction rate of 4.2%, whereas earlier ureteral obstruction associated with vaginal closure has not been reported by several authors such as Delancy. The exact mechanism of ureteral obstruction in these procedures is not fully understood and may be related to excessive distortion of the bladder triangle caused by the anterior vaginal wall during closure. The conventional wisdom is that the rate of ureteral injury in anterior vaginal wall folding sutures is low; however, this is not the case, and the reported rate of obstruction is approximately 0.5% to 2%. Hofmeister (1982) used fluoroscopic cinematography during anterior vaginal wall folding suturing and found that the operator’s needle in the upper third of the vagina was the closest point to the ureter. Rahn et al. also showed that the shortest distance between the suture and the ureter at the level of the sciatic spine in the repair of paravaginal defects was 0.5 cm, and even shorter after knotting, in a cadaveric study without preservatives. The placement of a ureteral stent prior to complex transvaginal RPS has been proposed, but there is no conclusive evidence that this measure ensures avoidance of ureteral injury, and the obvious disadvantage is the increased cost, time, and complications of the procedure. Intraoperative diagnosis of ureteral obstruction Impairment or loss of urinary drainage function after ureteral obstruction will lead to hydronephrosis and renal function impairment, and local obstruction and urinary extravasation will easily induce local infection, which may lead to death of the patient in severe cases due to renal function loss or local and systemic infection. Studies have shown that timely intraoperative detection and management of ureteral injury can reduce the rate of postoperative disease and minimize the loss of renal function as well as the need for late nephrostomy. Its early detection also reduces the incidence of ureterovaginal fistula compared to delayed diagnosis of ureteral injury postoperatively. Usually, ureteral injuries suspected during open or laparoscopic surgery can be explored along the ureteral walk under direct vision, a point that is difficult to perform in the negative procedure. Intraoperative palpation of the ureter has been suggested, which is a good approach for those with experience in negative surgery. The role of cystoscopy in anti-incontinence procedures has been progressively used by gynecologic urologists, but there is no consensus on whether it is routinely used in transvaginal RPS. Visco et al. have stated that if the rate of intraoperative ureteral injury exceeds 1.5%, the benefit costing of routine intraoperative cystoscopy is worthwhile. In fact most of the literature reports intraoperative ureteral obstruction rates exceeding this value in transvaginal RPS. Moreover, the relatively simple, time-consuming and less invasive nature of cystoscopy has led to an increasing number of recommendations for the inclusion of intraoperative cystoscopy in pelvic reconstructive surgery. Although there are occasional reports that intraoperative cystoscopy may miss some cases, numerous publications have shown that intraoperative cystoscopic intravenous indocyanine to assess ureteral integrity is a safe and accurate test with a sensitivity and specificity of 94.4% and 99.5%. Ureteral patency can be assessed by giving 5 to 10 ml of indigo rouge intravenously prior to the ureteral patency examination and assessing its integrity by observing the blue urine ejected from the bilateral ureteral openings. Sometimes subtle differences in urine ejection from both ureters also suggest the possibility of partial obstruction on one side. However, false positive results due to pre-operative pre-existing renal or ureteral disorders should be taken into account. In cases of older age, poor renal function, and inadequate blood volume, the time to observe blue urine is relatively long. The excretion of the dye can be accelerated by giving diuretics with adequate rehydration. It is worth noting that excessive urine production and rapid urine flow in a short period of time may mask some cases of incomplete ureteral obstruction. Although intraoperative intravesical cystoscopic injection of indocyanine is highly accurate and specific for the diagnosis of ureteral obstruction, false-negative results have indeed been reported clinically. Therefore, patients still need to be closely monitored for postoperative abnormalities such as fever, lumbago, persistent leakage, pyelonephritis, peritonitis, intestinal obstruction, anuria, and elevated serum creatinine and urea nitrogen. Even so, about 5% of patients are asymptomatic and are diagnosed in advanced stages due to hydronephrosis or non-functioning kidneys. IV. Treatment of ureteral obstruction The aim of treatment of ureteral injury is to restore normal urinary access and protect renal function, and to restore ureteral integrity while minimizing the formation of local stenosis and urinary fistula. When the ureter is slightly damaged or transiently damaged and basically does not affect the function, it can recover on its own. Sutures that are too close to the ureter may cause mild distortion and obstruction of the ureter, but usually recover in time. In contrast, in cases where intraoperative cystoscopy clearly diagnoses obstruction, the suture needs to be removed and repositioned immediately intraoperatively. In approximately 90% of cases, the sutures can be cut intraoperatively to relieve the obstruction. In cases of postoperative symptoms and confirmed partial ureteral obstruction, sutures are often removed and a retrograde ureteral stent is placed to ensure patency. However, due to severe prolapse and local anatomic distortion caused by the repair procedure, placement of the ureteral stent may be difficult or fail before removal of the sutures. Forced placement can easily lead to ureteral perforation. If retrograde ureteral stent placement fails, a percutaneous pyelostomy can be used to drain the ureter and place the stent in line. The stent can be selected from a double J catheter that is not easily moved up and down and maintained for 4 to 6 weeks. In conclusion, transvaginal RPS has an increased chance of ureteral injury. Familiarity with the corresponding changes in ureteral anatomy after pelvic organ prolapse, good cathodic surgical technique, and constant awareness of possible ureteral injury are the best ways to prevent ureteral injury in transvaginal RPS. Intraoperative cystoscopic intravenous indocin can accurately detect the majority of such ureteral injuries, thus allowing timely management and reducing serious postoperative complications.