Does the body weight influence the outcome in children treated with robotic pyeloplasty?
INTRODUCTION
To investigate the influence of the body weight on peri- and postoperative outcome in a series of pediatric patients with a diagnosis of uretero-pelvic junction obstruction (UPJO) treated with robot-assisted laparoscopic pyeloplasty (RALP) at a single tertiary referral center.


OBJECTIVE
In this study, outcomes of RALP in children divided according to the weight are evaluated.


STUDY DESIGN
Sixty-one consecutive patients treated with RALP from January 2016 to May 2019 were recorded retrospectively and divided according to their weight: group A < 15 kg, group B ≥ 15 kg and were included in this study. Eligible criteria for surgery were symptomatic UPJO, worsening of hydronephrosis, or obstructive pattern at renogram. Success criteria were the reduction of the hydronephrosis at imaging and the absence of flank pain. All procedures were performed by one expert robotic surgeon.


RESULTS
18 patients were included in group A (median weight 12 kg) and 43 patients in group B (median weight 33 kg). The median (IQR) operative was 95 (90-120) for group A compared to 90 (85-110) of control group. No significant difference has been found (P = 0.93). We registered one (5.6%) Clavien 3b complication (omental hernia after removal of the drainage requiring surgical correction) and two (4.7%) Clavien 2 complication in group B (urinary infections). No difference has been found in the length of hospital stay, length of catheterization, and duration of procedure between the groups (P > 0.05). At a median follow-up of 23 months (IQR 9-27 vs 9-33), the success rate was comparable between the two groups (94.4% vs 97.7%; P = 0.51). Relapse was recorded in one child per group and both required nephrostomy placement.


DISCUSSION
Our study tried to fill the gaps in the evidence on the feasibility of RALP in low-weight children reporting favorable peri-operative and long-term outcomes; however, this study shows some intrinsic limitations. The relatively small numbers of patients in the <15 kg may have underpowered the comparison with heavier patients. Moreover, only two patients were <10 kg so that no definitive conclusions on the safety and feasibility of RALP in this cohort of patients can be drawn.


CONCLUSION
RALP in children <15 kg was feasible and effective to treat UPJO with superimposable results to heavier counterparts. In our experience, the need for a different trocar placement and limited space in patients <15 kg did not affect peri-operative and functional outcomes.