Ureteroneocystostomy (UNC) refers to reimplantation of the ureter into the bladder. In the adult population, ureteroneocystostomy is primarily used for disease or trauma involving the lower third portion of the ureter that results in obstruction or fistula. In children, ureteroneocystostomy it is commonly used for surgical treatment of vesicoureteral reflux (VUR). [1, 2]
Generally, treatment for ureteral injury, stricture, and obstruction depends on the length of the defect, location, etiology, and time of diagnosis.  Ureteroneocystostomy is the procedure of choice to correct distal ureteral injuries in close proximity to the bladder that measure 3-5 cm. These injuries differ from more proximal injuries in that they are frequently associated with disruption of the blood supply from the iliac vessels and are thus best repaired with a ureteroneocystostomy.  Modifications, such as a psoas hitch (tacking the posterior bladder wall to the psoas muscle) and a Boari flap (tubularization of a flap of bladder to extend from the bladder to the ureteral orifice), allow for correction of ureteral defects that are longer than 5 cm. 
Principles for obtaining successful ureteroneocystostomy outcomes include lack of tension, debridement and spatulation of the ureter, and postoperative drainage.  Open and minimally invasive laparoscopic approaches to ureteroneocystostomy have been described. [6, 1]
Injury, stricture, or obstruction of the distal 3-4 cm of the ureter is an indication for ureteroneocystostomy. More extensive loss of the ureter can be bridged with a vesico-psoas hitch or Boari bladder flap. Approximately one third of traumatic injuries and most iatrogenic injuries during pelvic procedures occur in the distal ureter.  Other indications for ureteroneocystostomy include distal ureteral cancers that cannot be removed endoscopically, pelvic malignancies involving the ureter, and renal transplantation and complications arising from transplanted kidneys. 
Indications for psoas hitch
The psoas hitch is a useful technique for bridging a defect involving the lower third of the ureter. Indications include distal ureteral injury, ureteral fistulae secondary to pelvic surgery, segmental resection of a distal ureteral tumor, and failed ureteroneocystostomy. 
Indications for Boari flap
Boari flap is a useful adjunct when the diseased segment of ureter is too long or ureteral mobility is too limited to perform a primary ureteroureterostomy. Boari flaps can be created to bridge a 10- to 15-cm defect. If needed, spiral bladder flaps can be constructed to reach the renal pelvis in some circumstances. 
Indications in the pediatric population
In the pediatric population, VUR is the most common indication for ureteral reimplantation. However, ureteral reimplantation with or without ureteral tapering is also performed for obstructive megaureters.
Significant bladder pathology associated with high intravesical pressures and poor compliance (eg, neuropathic bladder) is a contraindication to ureteroneocystostomy. Individuals with dysfunctional voiding are at an increased risk for complications, including persistent VUR and obstruction. Performing ureteroneocystostomy in an irradiated bladder is also a concern. Ureteroneocystostomy is not recommended in patients with a history of bladder cancer.
The Politano-Leadbetter ureteral reimplantation is contraindicated after puberty or in patients with megaureters. 
Contraindications to psoas hitch and bladder flap
Contraindications to psoas hitch include a small contracted bladder with limited mobilization. In addition, ureteral defects proximal to the pelvic brim usually require more than a simple psoas hitch alone.
Small bladder capacity is likely associated with difficult or inadequate Boari flap creation, warranting considerations of alternative methods. Also, if bladder outlet obstruction, small capacity/high pressure, or neurogenic bladder is possible, urodynamic studies should precede the operation to determine detrusor capacity and compliance. Any existing bladder outlet obstruction or neurogenic dysfunction needs to be addressed preoperatively.
The success rate of ureteral reimplantation with a psoas hitch exceeds 85% in both adults and children. 
In experienced hands, the success rate of ureteroneocystostomy in patients with low-grade primary VUR approaches 100%. 
Nerve-sparing robotic extravesical ureteral reimplantation is reported to yield a success rate of 97.6% in the pediatric population. 
Laparoscopic ureteral reimplantation was associated with a success rate of 95.8% in adults undergoing various procedures including psoas hitch, psoas hitch plus Boari flap, and extravesical ureteral reimplantation. 
Although earlier studies of transvesicoscopic ureteral reimplantation demonstrated lower success rates (62%-79%) [14, 15] compared with open techniques, later studies have demonstrated more comparable success rates, ranging from 92%-96%. [6, 16, 17, 18]
The ureters are paired muscular ducts with narrow lumina that carry urine from the kidneys to the bladder. The ureter is roughly 25-30 cm long in adults and courses down the retroperitoneum in an S curve. At the proximal end of the ureter is the renal pelvis; at the distal end is the bladder. The ureter begins at the level of the renal artery and vein posterior to these structures. This ureteropelvic junction usually coincides with the second lumbar vertebra on the left, with the right being marginally lower. The image below depicts the anatomy of the ureters.
In both adults and children, ureteroneocystostomy is performed under general anesthesia. The patient should not have an active urinary tract infection at the time of surgery. Although not routinely performed, cystoscopy may be performed initially for further evaluation of anatomy (ie, confirmation of a complete duplication) or for placement of a guidewire/stent if deemed necessary.
The open procedure is performed with the patient in a supine position, with a roll under the pelvis in children and padding under the knees.
For pediatric reimplantation, a Pfannenstiel incision is used, whereas a Pfannenstiel or lower midline incision is used in adults.
Preparation for Boari flap and psoas hitch
Preoperative measures include complete visualization of the ureter and an evaluation of bladder function. Bladder outlet obstruction and neurogenic dysfunction should be treated preoperatively. The bladder capacity should also be assessed, as small bladder capacity can cause difficulty.
Although ureteroneocystostomy in adults and children is typically performed via an open technique, laparoscopic, transvesicoscopic, and robotic-assisted procedures have been successfully performed in both adults and children. [1, 6, 13, 16, 19]
In the adult population, ureteroneocystostomy is performed for ureteral injury or obstruction affecting the distal 3-4 cm of the ureter and rarely for VUR. In most adults, the repair is performed in a refluxing fashion, except in cases of transplant ureteral reimplantation. In a retrospective review of adults who had undergone ureteroneocystostomy, Stefanovic et al (1991) concluded that there was no difference in preservation of renal function or risk of stenosis with antireflux versus reflux procedures. 
The surgical approach for ureteroneocystostomy in the adult is either through a Pfannenstiel or lower midline incision. In all cases, the bladder is mobilized by freeing the peritoneal attachments. The ureter is identified where it crosses over the iliac vessels and transected proximal to the damaged segment. Various approaches to ureteral reimplantation in the adult can be used, such as a modified Politano-Leadbetter type of repair and an extravesical Lich-Gregoir. The Lich-Gregoir extravesical ureteral reimplantation, as well as modifications thereof, has become the standard technique for management of the ureter during renal transplantation. 
Modified Politano-Leadbetter procedure
The modified Politano-Leadbetter procedure can be approached through a Pfannenstiel or midline lower abdominal incision. Once the bladder is mobilized and the ureter identified and transected, the free end of the proximal ureter is spatulated, the bladder opened on its anterior surface, and the ureter tunneled in the bladder wall in the fashion of Politano-Leadbetter. The origin of the tunnel should be superior and medial to the native ureteral orifice, and the tunnel should be developed in the direction of the bladder neck, with a tunnel length that is at least 3 times the diameter of the ureter. If the ureter is placed in the more mobile lateral bladder, kinking may result.
A double J stent is placed, and the bladder is closed in multiple layers. A Penrose drain and Foley catheter are then placed. The double J stent is typically removed approximately 6 weeks after the procedure.
Lich-Gregoir and modified Lich-Gregoir (involving detrusorrhaphy) procedures
A catheter is placed intraoperatively to allow for filling of the bladder. The incision is either a Pfannenstiel or lower midline unless an alternative incision is being used for renal transplantation.
The bladder is moderately filled and then retracted medially to help identify the ureter. The obliterated hypogastric artery is identified and ligated. The ureter is then identified and a vessel loop placed around it. The peritoneum is dissected off of the posterior aspect of the bladder where the reimplantation is intended.
The serosal and muscular layers of the detrusor are opened along a straight course cephalad and lateral to the ureterovesical junction for 4-5 cm, freeing the ureter during the dissection. The detrusor is separated from the underlying mucosa to create the antirefluxing trough. Ureteral continuity is not disrupted. The ureter is placed within the trough, and the detrusor is closed with interrupted absorbable sutures.
A Penrose drain is placed in the perivesical space. The Foley catheter may be left in place overnight.
In the modified Lich-Gregoir procedure, the dissection of the detrusor from the underlying mucosa is carried around the ureter circumferentially, while maintaining the continuity between the ureter and the bladder. The bladder mucosa is further freed in the region of the trigone to create submucosal flaps. A pair of vest-type sutures of absorbable suture are placed that approximate, in succession, the detrusor at the distal limit of the dissected trigone, proximal ureter, and detrusor (inside-out) to advance the ureter into the bladder to create a new, longer submucosal tunnel. The detrusor defect is closed with interrupted absorbable sutures to recede the hiatus and to buttress the submucosal ureter.
As with the unmodified version, a Penrose drain is left in place. In the adult population, a Foley catheter is typically left in place.
The modified Lich-Gregoir (involving detrusorrhaphy) is a common procedure performed for VUR in the pediatric population. It is more commonly performed in children with unilateral VUR and can be performed as an outpatient procedure. [22, 23] Modifications of the Lich-Gregoir reimplantation are the most common forms of ureteroneocystostomy used in renal transplantation.
Cohen cross-trigonal reimplantation
The Cohen cross-trigonal reimplantation is the most common open surgical procedure used to treat pediatric VUR.
A Pfannenstiel incision is made. An anterior cystostomy is performed. The ureter is carefully mobilized transvesically, so as not to devascularize the ureter. The original hiatus is reapproximated to prevent a bladder diverticulum, and a submucosal tunnel is created so that the new hiatus is on the opposite side of the bladder. The tunnel length should be at least 4-5 times the diameter of the ureter.
The anastomosis of the ureter to the bladder should be fixed securely with an anchoring stitch placed through the bladder mucosa and muscle, taking ureteral serosa and mucosa to ensure that the ureter does not retract into the submucosal tunnel. The remainder of the anastomosis approximates ureteral serosa and mucosa to bladder mucosa with interrupted sutures circumferentially. Stents are not routinely placed unless the ureter requires tapering. Placement of a Penrose drain is optional. A Foley catheter is placed at the completion of the procedure.
Politano-Leadbetter ureteral reimplantation
In this procedure, the ureter is initially mobilized intravesically but is then passed extravesically before being brought back into the bladder through a different hiatus.  The new hiatus is located superior and medial to the original orifice; however, it is in the normal anatomic position for later ureteral manipulation if necessary and allows for a long submucosal tunnel.
A Pfannenstiel or lower midline incision can be used for ureteral reimplantation and psoas hitch. Filling the bladder prior to incision may help with the dissection.
The space of Retzius is developed and the bladder is mobilized by freeing the peritoneal attachments. With traction on the ipsilateral dome, the bladder should be able to reach superior to the iliac vessels. If additional mobility is needed, the contralateral superior vesicle artery can be divided.
The affected ureter is identified as it crosses the iliac vessels and is transected just proximal to the diseased segment. Placement of a stay suture on the healthy proximal ureter and careful mobilization minimizes trauma to the healthy ureter. An anterior cystostomy (vertical, oblique, or horizontal closed vertically) can be used to manually displace the bladder toward the ipsilateral ureter. The ureter is then delivered into the superolateral aspect of the dome of the bladder and the anastomosis performed, either in a refluxing or nonrefluxing (ureter placed through a submucosal tunnel) manner. The ipsilateral bladder dome is then anchored to the psoas minor tendon or the psoas major muscle with several absorbable sutures, taking care to prevent injury to the genitofemoral nerve. If preferred, the psoas hitch can be performed prior to the ureteral reimplantation.
A double J stent is placed, and the bladder is closed in a 2-layer closure with absorbable sutures.
The initial approach to the Boari flap is the same as that for the psoas hitch.
The contralateral bladder pedicle is divided and ligated. The ureter is mobilized, taking care to prevent injury to the adventitia. The ipsilateral superior vesical artery or one of its branches is identified, and a posterolateral bladder flap is outlined based on this artery. The base of the flap needs to be at least 4 cm in width, and the flap is extended obliquely across the anterior bladder wall, with the tip of the flap at least 3 cm in width. The flap length should equal the estimated length of the ureteral defect plus 3-4 cm if a nonrefluxing ureteral anastomosis is to be performed.
The base of the flap is anchored to the psoas minor tendon or psoas major muscle with several absorbable sutures, taking care to spare injury to the genitofemoral nerve when placing the sutures. The ureter is delivered through the posterior flap, and a direct refluxing mucosa-to-mucosa anastomosis is typically performed. However, if deemed necessary, a submucosal tunnel can be created in the flap and the ureter brought through this tunnel and anastomosed, if a nonrefluxing anastomosis is necessary. After the ureteral anastomosis, the tube is rolled anteriorly and closed using absorbable suture. The ureteral adventitia may be anchored to the flap.
Pediatric postoperative management varies based on surgeon preference and the type of procedure performed.
In the extravesical ureteral reimplantation, a drain is not routinely used and a urethral catheter may be left indwelling overnight. However, in many institutions, children are discharged home the same day. [25, 26] In open surgical procedures, a Foley catheter is often placed and left indwelling for 1-2 postoperative days. Children undergoing open reimplantation may develop postoperative bladder spasms, which are treated with oral anticholinergic therapy. Intravenous hydration for the first day or two after the surgery helps prevent clots that may obstruct the Foley catheter.
Children are discharged home when they can tolerate food, are passing flatus, and have voided after the Foley catheter has been removed. Hematuria and bladder spasms are uncommon in children undergoing extravesical reimplantation, and they may be discharged home the same day or the following day, once they can tolerate food and have voided. Children undergoing bilateral extravesical ureteral reimplantation are at a higher risk of voiding dysfunction after surgery, and it is recommended that a Foley catheter be left in place longer than is typical with unilateral extravesical reimplantation.
In all children undergoing reimplantation, postoperative renal ultrasonography is performed about 3 months postoperatively to evaluate for obstruction. Postprocedure voiding cystourethrography (VCUG) is not commonly performed following open ureteral reimplantation because of its high success rates but is usually obtained 3 months postoperative with extravesical ureteral reimplantation. Antibiotic prophylaxis is typically discontinued around 3 months following the procedure or after postoperative VCUG demonstrates resolution of VUR.
In the adult population, a ureteral stent is more commonly placed and has been shown to reduce urologic complications in adult who have undergone kidney transplantation. [27, 28] When stents are placed in the adult population, they are typical removed around 6 weeks after the operation. Similarly, drains are more commonly placed in the adult population and are removed when the drainage ceases. As in children, follow-up ultrasonography is performed in adults after the stent has been removed to evaluate for obstruction.
Acute postoperative complications of ureteroneocystostomy may include the following:
Extravasation of urine
If urine extravasation is identified, typically by persistent output from a drain or rarely from abdominal distention related to urinary ascites, the drain is left in place (or placed if one is not present), and the Foley catheter is left in place until cystography demonstrates resolution of the urine leak.
Hematuria is not uncommon after reimplantation but is typically self-limiting and rarely requires catheter irrigation.
Bladder spasms are managed with anticholinergic therapy while the catheter is indwelling and after adequate bladder emptying is demonstrated (with bladder scan postvoid residual determination or abdominal palpation) after catheter removal. The bladder spasms and associated urinary frequency and urgency typically resolve by the end of the first postoperative week but may be prolonged if an indwelling stent is placed.
Acute ureteral obstruction is most commonly related to edema of the bladder mucosa; however, it can result from kinking of the ureter in rare cases. If the obstruction is unilateral and the patient’s creatinine level is stable, short-term watchful waiting may be considered. Persistent pain, nausea, vomiting, and/or elevated creatinine levels should prompt stent placement. The method of stent placement varies with the procedure performed and varies from endoscopic to percutaneous nephrostomy tube placement and subsequent internalization of a double J stent.
A study by Houle et al (1992) showed that up to 26% of children who underwent bilateral extravesical ureteral reimplantation experienced transient voiding dysfunction, which resolved after a maximum of 4 weeks of clean intermittent catheterization. 
A study by Wenske et al assessed functional outcomes and complications of 100 ureteral reimplantations with or without psoas hitch or Boari flap in the reconstruction and repair of the ureter. The study reported that postoperative complications included stent-related dysuria, urinary tract infection, and contrast-extravasation on cystogram necessitating prolonged urethral and ureteral catheter drainage. 
Long-term complications of ureteroneocystostomy may include the following:
Persistent reflux is related to not achieving an adequate submucosal tunnel and/or elevated intravesical pressure.
Ureteral obstruction presenting as a long-term complication is related to ureteral ischemia, tension on the anastomosis, or kinking and often requires surgical management. Ureteral kinking may occur if the ureter is placed in the more mobile lateral bladder wall. 
Ureteral fistula may be related to ischemia, tension, and a lack of a water-tight anastomosis.
During extravesical ureteral reimplantation, if a ureteral advancement suture is being placed, care must be taken to avoid excessive angulation, which could lead to obstruction. In the Politano-Leadbetter repair, the ureter must be freely mobilized off the peritoneal reflection for 6-8 cm. Failure to do so may lead to excessive angulation. It is also recommended that this part of the procedure be performed under direct vision to avoid perforating the peritoneum, ileum, or colon.
Postoperative reflux after ureteral reimplantation may be persistent, new, or newly onset contralateral. Newly onset VUR is observed in up to 22% of open unilateral ureteral reimplants and tends to resolve over time. A true association between contralateral reflux and the type of reflux repair has not been demonstrated. 
Complications of psoas hitch
Care should be taken to avoid injuring the genitofemoral nerve and the femoral nerve in the vicinity when placing sutures that attach the bladder dome to the psoas hitch. Other complications include urinary fistula, ureteral obstruction, iliac vessel injury, and voiding difficulties. 
Complications of bladder flap
The most common complication is recurrent stricture formation, resulting from either ischemia or extension tension on the anastomosis. Uncommonly, development of pseudodiverticulum has been reported. 
Medications and Medical Devices
In children with VUR undergoing open ureteral reimplantation, antibiotic prophylaxis is maintained for several months postoperatively and then discontinued.
In the immediate postoperative period, children undergoing open intravesical procedures often require anticholinergic agents to help the transient detrusor overactivity associated with the procedure.
Cystoscopy and endoscopic injection of dextranomer/hyaluronic acid (Deflux) is a minimally invasive alternative to open surgical correction of reflux. This is an outpatient procedure and, although it is associated with a success rate ranging from 51% for grade V VUR to 90.7% with 2 injections, [33, 34] it is associated with a lower risk of obstruction and morbidity. Newly onset contralateral VUR develops in 10% of patients undergoing unilateral endoscopic treatment.