Feasibility, in terms of efficacy and safety, of video-assisted pyeloplasty (OTAP) in the first 90 days of life
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The uretero-pelvic junction (UPJ) is the most common site of obstruction in the pediatric upper urinary tract, causing hydronephrosis. In our institution, the gold standard approach for hydronephrosis in infants is the One-Trocar-Assisted Pyeloplasty (OTAP). The aim of this study is to evaluate the feasibility of OTAP in terms of efficacy and safety in the first 90 days of life.
We retrospectively reviewed all charts and long-term follow-up of 138 infants treated with OTAP; we selected and examined the ones with a defined diagnosis of severe UJPO and, thus, treated in the first 90 days of life: 28 patients. Indications for early surgery were: antero-posterior pelvic diameter (APD) > 20 mm and an obstructive pattern on renography; impaired echotexture and/or relative renal function < 40% had to be associated.
Out of 23 patients, we witnessed one conversion to open surgery (4.35%) and one recurrence (4.35%) of UPJO. The mean pre-surgery APD was 35.2 mm, while the mean post-surgery APD was 17.32 mm. The mean operative time was 133 min. The mean hospitalization time was 7.71 days. The mean average of follow-up was 46.41 months (minimum 1 year).
Our experience suggests that OTAP is a valid and feasible technique in terms of safety and efficacy for the early treatment of very young infants affected by UPJO.
KeywordsOTAP Pyeloplasty Hydronephrosis Uretero-pelvic junction obstruction (UPJO)
Uretero-pelvic junction obstruction (UPJO) is the most common cause of prenatal hydronephrosis .
The purpose of the procedure is to eliminate the obstruction of the pelvic-ureteric junction and create a new one, wide and functional, in order to allow a correct flow of urine between the pelvis and the ureter. This technique has evolved through time: from an initial open approach to other less invasive. Laparoscopic (LPSc) and retroperitoneoscopic (RPSc) approaches, performed conventionally or even robotically, have been proposed as alternatives to reduce post-operative hospitalization, pain, and scars .
Since 2005, the gold standard approach for hydronephrosis in children younger than 2 years in our institution is the One-Trocar Assisted Pyeloplasty (OTAP) . This procedure combines the advantages of a minimally invasive technique with the high success rate of standard dismembered pyeloplasty . We have treated very young patients affected by severe forms of hydronephrosis for which an early surgical correction can be of some advantage.
The aim of this study in fact is to evaluate the feasibility of OTAP, in terms of efficacy and safety, in infants younger than 90 days.
Number of patients
Mean age, month (range)
Mean weight, kg (range)
All of them presented a prenatal diagnosis of suspected hydronephrosis. Suspicion was confirmed with an ultrasound in the first days of life and repeated after 2 weeks. Voiding cystourethrogram (VCUG) and MAG-3 renogram were performed at 4–6 weeks of age.
Indications for early surgical correction were: antero-posterior pelvic diameter (APD) > 20 mm and obstructive pattern on MAG3 with furosemide. To quantify the severity of UPJO on radionuclide, we adopted a parameter included in HSS score that gives a grade from 0 to 4 for the drainage curve pattern . These indications were not sufficient; impaired echotexture and/or relative renal function (RRF) < 40% had to be associated. For impaired echotexture, we mean a reduction of parenchymal thickness and/or lack of cortico-medullary differentiation and/or flattening of papillae. One diagnosis was not made by renography but by intravenous urography.
Thanks to these criteria, we were sure to operate on actual stenosis, as confirmed by all histological reports. Patients that did not fulfill these criteria were re-evaluated after 3–6 months with ultrasound and a second renography.
Regarding the surgical outcome of the procedure, we considered the minimum period of follow-up to be 1 year after surgery to define success. Patients lost to follow-up (i.e., the lack of a USG or radionuclideMAG3 after at least 1 year from the surgical operation) were not considered in the success rate analysis.
In our center, according to the literature , we evaluate our patients after 1, 3, 6 and 12 months after surgery. Renal scan with MAG3 is performed in selected cases depending on ultrasonic (persistence of pelvic dilatation and/or worsening of echotexture) and clinical (persistent symptoms after surgery) data .
For renal units affected by double congenital urinary malformation such as vesicoureteral reflux (VUR) and vesicoureteral obstruction (VUO), surgical resolution of the UJPO was determined by a renogram performed at least 12 months after the last surgical procedure on the urinary tract.
Results of patients undergoing OTAP
No. patients analyzed
Mean operative time, mins (range)
Uretero-pelvic stent (number of patients)
JJ stent (number of patients)
No. conversions (%)
No. complications/recurrence (%)
No. patients cohort success/total no. (%)
Mean hospitalization days (range)
Follow-up of 23 patients
Mean follow-up, months
Mean pre-surgery APD
Mean post-surgery APD
With a mean age of 79.92 days, the youngest was 42 days old and the oldest was 90 days old.
The mean operative time was 133 min (range 60–200 min).
At the end of the procedure, we left a uretero-pelvic stent in 25 patients (18 external uretero-pelvic stent and 7 JJ stents). The remaining three patients had no stents. The JJ stents were left in place for a mean time of 29 days. The external uretero-pelvic stents were removed after a mean time of 5.83 days (range 3–7 days).
The mean hospitalization time was 7.71 days (range 4–16 days).
The mean average of follow-up was 46.41 months. Renal units affected by double congenital urinary malformation were two (7.14%): one was associated with VUR and the other with VUO. These associated anomalies were surgically corrected at 12 months of age.
20 out of 22 patients were evaluated with USG and did not need a post-operative renal scan with MAG3. The other two patients’ outcomes, since they presented an unchanged stable pelvic dilatation, were evaluated with MAG3 renal scan that showed an improvement of the urinary flow, from grade 4 to 1 for one patient and from grade 4 to 2 for the second one.
We registered one conversion (4.35%) to an open procedure because we accidentally opened the peritoneum cavity that did not allow the retroperitoneoscopic phase; one patient (4.35%) had complications due to recurrence of pelvic ureteral junction stenosis, defined as a post-operative worsening of pelvic dilatation on ultrasounds and persistence of impaired urinary flow pattern obstruction on dynamic MAG3 renography at 6 months after surgery.
One patient (4.35%) showed quick improvement in the first 2 years of follow-up on both ultrasound and renography but worsening on renography at 5 years after surgery. This case is at present a matter of discussion among the members of our team.
The remaining 20 patients (87%) presented a good outcome, defined as an improvement of pelvic dilatation on ultrasonography and/or a regular urinary flow on renography.
We also compared pre-operative and 1-year post-operative APD at ultrasonography (USG) in 22 patients (1 patient was converted so he was not included).
Improvement of APD after surgical correction of UPJO
So, 21 out of 22 patients (95.45%) improved their radiological situations at 1-year follow-up.
The uretero-pelvic junction (UPJ) is the most common site of obstruction in the pediatric upper urinary tract.
Obstruction most commonly results from an intrinsic defect in the smooth muscle layer of the PUJ.
Diagnosis is often made in the first months of life, confirming a prenatal diagnostic suspicion.
There is no consensus on how to manage patients with hydronephrosis; the main concerns regard type of treatment, conservative or surgical , the timing of surgical intervention and appropriate technique for each single patient. Management of hydronephrosis due to UPJO is still controversial, especially for those evaluated as “severe” with a Society of Fetal Urology classification (SFU) of 3 or 4 and an APD > 20 mm.
Nowadays, there are two lines of thought: one focusing on early surgery and the other suggesting watchful waiting. Concerns have arisen about early surgery on the urinary tract because of the possibility of anastomotic leakage and stenosis of the reconstructed tract in very young patients. In fact, the majority of surgeons prefer performing pyeloplasty not before 3 months of life in order to work on a bigger structure.
Nevertheless, other authors have stressed on the principle of resolving the obstructions as early as possible in order not to increase post-natal parenchymal damage.
Several authors prefer, at an early stage, a conservative management and they evaluate an RRF deterioration > 5% [10, 11] or > 10%  as indicators for surgery. Chertin recommends expectant management of patients with antenatal diagnosis of UPJO because even if renal function deteriorates, delayed pyeloplasty recovers the initial functional level . On the other hand, Babu et al. reveal that early pyeloplasty leads to a significant improvement of RRF, while delayed pyeloplasty leads to a marginal but significant loss .
Other authors do not recommend an early operation due to the presence of “too small” structures increasing the degree of difficulty.
Once given the surgical indications, the type of surgical approach is also debated.
This technique has evolved through time: from an initial open approach to others less invasive.
As a matter of fact, laparoscopic (LPSc) and retroperitoneoscopic (RPSc) approaches have been proposed as alternatives to reduce post-operative hospitalization, pain, and scars .
While Garcia-Aparicio et al. support the safety and feasibility of laparoscopic pyeloplasty in patients less than 12 months old , Tan recommends that laparoscopic pyeloplasty not be performed in children younger than 6 months . Also, Piaggio et al. are against the use of laparoscopic approach in children and especially in infants because laparoscopic suturing is challenging, time consuming and associated with a prolonged learning curve . For the same reasons, some authors stress the importance of the surgeon’s and entire team’s expertise limited to selected centers [3, 17].
Hao affirms that the potential advantages of these techniques (LPSc and RPSc) remain controversial and concerns have been expressed regarding the risk of abdominal injuries, the small operative space and technical difficulties .
A retroperitoneoscopic approach allows a more rapid access to the renal pelvis but the unique anatomic orientation and a relatively restricted work space represent recognized limitations .
Pyeloplasty can also be performed robotically. The robotic approach is more precise and allows more movement but is rarely performed prior to 3 months of age due to technical constraints.
This procedure is increasingly being used in re-operative repair for failed pyeloplasty in children .
In our institution, we have been using a retroperitoneoscopic-assisted approach since January 2005. This procedure combines the advantages of a minimally invasive technique with the high success rate of standard dismembered pyeloplasty. This technique has been shown to be safe, feasible and an efficient alternative for the UPJO correction in children. Operative times are similar or even shorten than LPSs or RPSc approaches and aesthetical results are excellent. The main advantage of OTAP is that it overcomes technical difficulties of the completely RPSc approach, especially in small patients .
Indeed, in this study we want to prove the feasibility of OTAP, in terms of efficacy and safety, in infants younger than 90 days (in the first 90 days of life). The indications we chose for early surgical correction were: APD > 20 mm and obstructive pattern on MAG3 with furosemide.
These indications were not sufficient; impaired echotexture and/or RRF < 40% had to be associated.
We, therefore, analyzed surgical outcomes of 23 patients with a minimum period of follow-up of 1 year (mean average of follow-up: 46.41 months). We registered one (4.35%) conversion. This conversion occurred at the very beginning of our experience with OTAP. One patient (4.35%) had complications due to the recurrence of pelvic ureteral junction stenosis. Regarding this complication, it is to say that this patient belongs to the small group in which a stent was not used. This is the reason why we suggest the use of such stents, especially in very young patients. One patient (4.35%) showed quick improvement in the first 2 years of follow-up on both ultrasound and renography but worsening on renography at 5 years after surgery.
The remaining 20 patients (87%) presented a good outcome, defined as an improvement of pelvic dilatation on ultrasonography and/or a regular urinary flow on renography. This case is at present matter of discussion among the members of our team.
We compared pre-operative and 1-year post-operative APD showed that at USG. 21 out of 22 patients (95.45%) improved their radiological situations at 1-year follow-up: the mean pre-surgery APD was 35.2 (range 20–60) mm, while the mean post-surgery APD was 17.32 (range 5–60) mm (Table 2).
Our study lacks a comparison group to determine the advantages of performing OTAP in early life. This was not the aim of the present study that only shows feasibility of the technique, in terms of efficacy and safety in early life. Our next work will compare patients that undergo OTAP early and later in infancy to determine when it is better to correct the malformation.
Even though indications for surgical correction, timing and type of approach are still controversial in patients born with hydronephrosis, our experience evaluated with this retrospective study is aimed at suggesting the one-trocar-assisted pyeloplasty (OTAP) is a valid and feasible approach, in terms of safety and efficacy, for the early treatment of very young infants (first 90 days of life) affected by UPJO.
Compliance with ethical standards
Conflict of interest
No competing financial interests exist.
- 7.Babu R et al (2019) Hydronephrosis severity score: an objective assessment of hydronephrosis severity in children—a preliminary report. J Pediatr Urol 15(1):68.e1–68.e6Google Scholar
- 12.Babu R, Rathish VR, Sai V (2015) Functional outcomes of early versus delayed pyeloplasty in prenatally diagnosed pelvi-ureteric junction obstruction. J Pediatr Urol 11(63):e1–e5Google Scholar