a 49-year - old woman diagnosed with stage iv ovarian cancer underwent extensive debulking surgery . due to the presence of right hydronephrosis , a right nephrostomy tube was inserted prior to the second surgery . during surgery ,
additional excision was performed because of ovarian tumor invasion of the bladder and right ureter .
her right distal ureter was partly resected ; the distal margin of the remaining ureter was at the l5 level .
as the remaining ureter was not long enough for anastomosis and the level of the injury site was high , ureteroureterostomy or ureterocystostomy were not possible .
therefore , ureter ligation was performed by suturing the ureter three times and clipping it once .
however , four days postsurgery , an antegrade ureterogram through the nephrostomy tube showed contrast extravasation at the site of ligation .
we believed that the ureter was unlikely to seal up spontaneously owing to the relatively large size of the wall defect seen on the ureterogram .
considering the diameter of the ureter at the transection site , the high level of the distal margin of the remaining ureter , and the patient s generally poor condition , an intervention consisting of complete ureter occlusion was planned .
the occlusion stent was made of nickel / titanium alloy , and was super - elastic and self - expandable .
the middle of the stent was constricted in a candy - wrapper configuration , leading to complete obstruction of the central portion ( fig .
when fully expanded , the stent was 10 mm in diameter and 4 cm in length .
the stent was internally coated with a thin silicone membrane , leaving a bare portion at either end ; the bare portion at the distal end was intended to permit tissue growth through the stent interstices and thus prevent stent migration .
the stent was constructed according to our specifications by a local manufacturer ( s&g biotech , seongnam , korea ) . with the patient in a prone position ,
the right nephrostomy tube was replaced with a 9-fr vascular sheath ( pinnacle tif tip , terumo , tokyo , japan ) .
the exact leakage site at the distal margin of the ureter was confirmed with contrast - medium injection through a 5-fr kumpe catheter ( cook , bloomington , in , usa ) . using a guidewire
, an 8-fr introducer sheath was passed through the 9-fr vascular sheath , into the ureter .
stent placement was technically successful and there were no immediate procedure - related complications ( fig .
injection of contrast medium through the ureter showed no contrast material passing beyond the occlusion stent , and no further ureteral leakage ( fig . 2c ) .
an 18-month follow - up antegrade ureterogram showed neither contrast - medium leakage nor migration of the occlusion stent ( fig .
although ureteral leakage is an uncommon complication following abdomino - pelvic surgeries or procedures , it can lead to serious conditions such as ureterovaginal fistula , intra - abdominal sepsis , renal failure , and loss of the ipsilateral kidney .
numerous approaches have been attempted for the management of ureteral leakage , depending on the patient s general condition and the anatomic location of the leakage . in general ,
surgical management should be considered as the final option since repeated surgery could be harmful if the patient is unstable . in many cases , there are very limited reconstructive options available , considering the extent and location of the injury .
transrenal ureter occlusion with permanent urinary diversion may be indicated as a palliative treatment for patients with a surgically or endourologically unmanageable anatomic defect of the ureter .
several techniques have been suggested using tissue adhesive , balloons , coils , electrocautery , stents , and siliconeoccluding devices , but all have varying degrees of success .
the reasons for incomplete occlusion of ureteral leakage have been continuous urinary flow at a blockage site , recanalization of an occlusion , or migration of the inserted materials . in the vascular system ,
the coagulation cascade is triggered around a foreign device , which finally leads to the desired obstruction .
however , as there are no platelets or clotting factors in normal urine , some additional anchoring , such as a fixing component or a self - expandable feature , would be necessary for the device to remain in the urinary tract without migration . here
, we review various techniques reported till date . isobutyl-2-cyanoacrylate has previously been used for intravascular embolization .
gunther et al .   reported its use in several patients , for achieving complete blockage of ureteral fistula via the transrenal approach .
however , moldwin and smith   subsequently announced that the results with isobutyl-2-cyanoacrylate were inconsistent , because the material gradually softens and may allow migration by ureteral peristalsis .
two approaches of balloon occlusion have been reported  using detachable balloons and nondetachable balloons . in 7 patients , gunther et al .  
successfully used detachable balloons inflated with a silicone mixture , and reported complete ureteral occlusion without complications at 16 months .
additionally , papanicolaou et al .   described the application of nondetachable balloons for temporary ureteral occlusion .
although no complications have been reported following the procedures , long - term use of balloons carries potential risks for ureteral necrosis or rupture .
the outcome of using coils and gelatin sponges in 22 patients , were described by farrell et al . .
except for four patients who died owing to progression of underlying malignancy , all the other patients remained symptom - free throughout the follow - up period ranging from 2 to 29 months .
coils may produce foreign body reactions in ureters , namely localized inflammation with the ingrowth of granulation tissues .
ureteral occlusion with coils has been reported to have relatively low complication rates compared with other methods .
recently , the latex - covered amplatzer vascular plug ( avp ) showed promising results in the occlusion of ureteral leakage ; in the study , 9 of 10 ureters were completely sealed off as the expandable characteristics of avps and the latex that covers avps before implantation seemed to provide an effective watertight barrier .
metallic stents have generally been used for retaining the patency of vessels and nonvascular luminal structures .
they have also been applied to the urinary tract , and there is a high tendency for obstruction due to reactive tissue hyperplasia .
we paid attention to this occlusive mechanism and designed our occlusion stent . to our knowledge
, there is no report about the specific shape and function of a ureteral metallic stent designed based on the occlusive principle . in our study ,
the expandable characteristics of the nitinol stent frame , as well as the silicone membrane with midline constriction , resulted in a completely watertight arrangement .
in addition , the bare metallic portions at both ends might precipitate tissue ingrowth through the mesh of the stent , allowing the desirable ureteral occlusion .
moreover , the combination of the expansile feature of the nitinol and the two ends with bare metallic portion in our stent would serve as an antimigration system .
this would make it superior to some other devices using only the expansile characteristic to prevent migration .
in addition , the distinctive candy - wrapper configuration would prevent the separation of the silicone membrane and stent meshes .
the durability and long - term effectiveness of this occlusion stent were confirmed in the 18-month follow - up ureterogram .
a similar kind of occlusion stent with a wine - glass shape has been reported to successfully treat bronchopleural fistulas , following pneumonectomy ; in this study , a silicone - covered occlusion stent with a self - expandable feature and antimigration barbs was used for the remaining left main bronchus .
we propose the use of our specially designed , silicone - covered nitinol ureteral occlusion stent with a candy - wrapper configuration for the treatment of ureteral leakage .
this stent is a less invasive , simple , and practical solution for patients with urinary leakage and in whom surgery is not indicated .
 ureteral fistula is a serious complication of abdomino - pelvic surgeries , often resulting in poor outcomes owing to lack of proper treatment . 
 we report the case of a 49-year - old woman who underwent placement of a silicone - covered ureteral occlusion stent in her right ureter for the management of ureteral leakage after pelvic surgery . 
 a ureterogram obtained 18 months following the stent placement confirmed that there was no stent migration or additional urine leakage . 
 we propose that the silicone - covered ureteral occlusion stent is practical , fast , and safe for the management of ureteral leakage . 
CASE REPORT
DISCUSSION