Ureteropelvic junction obstruction (UPJO) describes a disease in which the urine that is produced in the kidney does not drain properly into the ureter, which is the tube that takes the urine to the bladder. It most frequently presents in childhood, or even during pregnancy. However, it can also occur in adults.
Ureteropelvic junction (UPJO) obstruction is generally a congenital (present from before birth) condition caused by narrowing of the connection between the ureter and the renal pelvis, which is part of the kidney. This blockage causes urine to build up in the renal pelvis, damaging the kidney.

Endopyelotomy- UPJO on CT scan. Presented as a abdominal mass
UPJO on CT scan. Presented as a abdominal mass

UPJ obstruction is the most frequently diagnosed cause of urinary obstruction in children. It is now commonly diagnosed during prenatal ultrasound studies that show a dilated renal pelvis or a condition called hydronephrosis.
When recognized before the baby is born, UPJ obstruction may require sugical correction in the first few days after birth. Less severe cases may not require surgery until later in life, and some cases do not require surgery at all.

Endopyelotomy- UPJO in IVP Endopyelotomy- UPJO in IVP

UPJ obstruction may be recognized after birth when an abdominal mass is found on examination, or if the infant develops a urinary tract infection associated with fever. The presenting sign of UPJ obstruction is most commonly pain in the flank region, which may or may not be associated with periods of increased urine output (e.g., after drinking coffee, which increase urine flow). However, it can also present with urinary infection or kidney stones, or can even be found incidentally on an x-ray that is taken for some other condition.In most cases, ureteropelvic junction obstruction seems to be of functional nature. Abnormalities in the development of the innervation of the muscularis of the ureter seem to play an important role in the pathogenesis of ureteropelvic junction obstruction.


Historically, an IVP was used to evaluate patients with possible UPJ obstruction. However, in the evaluation of a child with a hydronephrotic kidney, diuretic renograms have taken the place of the IVP. Those patients with split renal function of less than 40% and obstruction noted by a T 1/2 of greater than 20 minutes appear to be at significant risk of renal deterioration if intervention is delayed.
The vascular anatomy at the UPJ becomes crucial when performing an endopyelotomy. While most associated UPJ vessels lie in the anteromedial plane, accessory vessels may lie posteriorly or laterally. If all endoscopic incisions are made in the posterior-lateral plane, intraoperative hemorrhage may occur. For this reason, a comprehensive vascular evaluation with intraoperative endoluminal ultrasound, preoperative CT scan, or MRI with vascular reconstruction is recommended prior to this form of treatment


The goals in treating patients with UPJ obstruction are to improve renal drainage and to maintain or improve renal function. As mentioned previously, dilation of the intrarenal collecting system or hydronephrosis does not necessarily imply obstruction. Specifically in children, renal pelvic dilation should be followed with serial imaging to assess for changes in dilation, renal parenchymal thickness and/or the presence of scarring, and function. Surgical repair is indicated if a significant differential in serial imaging is present or if progressive deterioration of renal function occurs.
In the past, the only surgical method available to treat UPJ obstruction was an open procedure known as a pyeloplasty. A large incision, which cut through muscle under the rib, was used to expose the kidney and allow for the surgical repair. Success rates of 95 percent have been reported with this surgical technique. However, recent advances in surgical technology have allowed UPJ obstruction to be treated by a variety of minimally invasive surgical techniques. In children, the procedure of choice is an Anderson-Hynes dismembered pyeloplasty. Laparoscopic pyeloplasty offers a minimally invasive treatment option that may be used in patients with either primary or secondary UPJ obstruction and is emerging as a new criterion standard in the treatment of UPJ obstruction. Success rates are comparable with those of open pyeloplasty procedures. Laparoscopic pyeloplasty is a technically demanding procedure that generally requires significant laparoscopic experience. Robotic-assisted laparoscopic pyeloplasty has become increasingly popular as the robots have become more prevalent. An endopyelotomy refers to an endoscopic incision of the UPJ, performed to create a more funneled drainage system and to bring the UPJ more dependent or caudad below areas of pathology.
Endoscopic treatment alternatives include an antegrade or retrograde endopyelotomy, which is an endoscopic incision performed through the obstructing segment. In those patients who fail open pyeloplasty, endopyelotomy is particularly useful, even in the pediatric population. Laparoscopic pyeloplasty is our preferred technique for UPJO treatment and endopyelotomy is offered mainly for patients who fail open pyeloplasty.

Principles of endopyelotomy

It may be performed either antegrade or retrograde, ureteroscopically. A safety guide wire must be placed within the ureter prior to endoscopic incision. Intraluminal ultrasound or preoperative imaging used to define peri-UPJ vascular anatomy is essential.
Endoscopic incision should be performed full-thickness through the UPJ and into perirenal fat with laser energy, electrocautery, or an endoscopic scalpel. To ensure a proper incision, extravasation of contrast should be seen on pyelography during the procedure. The incision most commonly is performed posterolaterally.
Balloon dilation often is performed after the incision to ensure completeness. Ureteral stenting for 4-8 weeks after the endoscopic procedure is common, although no consensus exists regarding size and duration of stents.
Crossing vessels and their relationship to the ureter of the UPJ can also be evaluated. The location of these vessels and their possible contribution to renal obstruction can help the surgeon clinically decide whether endopyelotomy, open pyeloplasty, or laparoscopic pyeloplasty would be the most effective treatment modality.


The general risks of this procedure include, but are not limited to bleeding, transfusion, infection, wound infection/dehiscence, pain, scaring of tissues, failure of the procedure, potential injury to other surrounding structures.