Robotic-Assisted Surgery in Patients Less than 15 kg: A Single Center Review

Introduction

Robotic-assisted surgery (RAS) is being increasingly utilized in both pediatric and adult populations. Growing literature now exists to show that RAS is equally safe and effective compared to laparoscopic (LS) approach.^1–3 RAS affords improved ergonomics, dexterity, and magnification, advantages that have proved useful especially for complex minimally invasive procedures, in addition to the benefits already noted with standard LS surgical approaches including decreased recovery time, postoperative narcotic use, and improved cosmetic outcomes compared to open procedures.^1–3

Limited information exists regarding the feasibility and utility of RAS in infants ≤15 kg. Molinaro et al. evaluated 83 patients who underwent RAS and showed no difference inoperative time for similar surgical procedures in infants <15 kg compared to those >15 kg. ⁴ Similarly, Meehan et al. reported 22 infants weighing less than 10 kg who successfully underwent RAS, with the smallest size of 2.2 kg. ⁵ More rapid utilization of RAS in pediatric patients has been limited by available instrument sizes, lack of experience and training with RAS, and the challenge of doing RAS within a small, confined domain.^6–8 Currently, available port sizes for robotic apparatuses include 8 mm and 5 mm, whereas standard LS instruments include a 3 mm size more suitable for smaller infants and children. ³ Given limited reports with such small patient sizes, we sought to perform a retrospective analysis of all RAS on patients ≤15 kg within our own institution to appreciate the feasibility, and to identify any potential complications associated with these RAS surgical procedures in this select population.

Methods

All research was conducted with institutional review board approval. We performed a single institution retrospective descriptive analysis including all patients undergoing RAS at Nationwide Children's Hospital between January 2013 and July 2021. Data collection included procedure type, age, weight (kg), gender, surgical complications, and readmissions. Cases were further categorized according to preoperative weight (≤15 kg) and surgical specialty: pediatric urology (PU), pediatric surgery (PS), multiple specialties (MS). t-Tests were used for statistical analyses.

Results

The first robotic surgery was performed in 2013 at our institution. Since that time there has been total of 976 RAS that were performed with 492 performed by PU (50.4%), 466 performed by PS (47.8%), and 18 performed as multidisciplinary cases (MS) (1.8%). Of these, 118 (12.1%) were performed on children ≤15 kg, who had a mean weight of 10.7 kg (standard deviation [SD] 2.8). One hundred ten of these were performed by PU (93.2%), while 6 were performed by PS (5.1%) and 2 (1.7%) were MS cases. Procedures in the ≤15 kg cohort were significantly more common in the PU subgroup, with a mean of 12 cases/year (SD 4.0 cases/year), compared to PS subgroup, mean of 0.63 cases/year, (SD 0.71 cases/year) (P < .01), and included a broad case mix. The mean weight of PU patients (10.5 kg, SD 2.7 kg) was significantly less than PS patients (13.9 kg, SD 0.87 kg) (P < .01). Mean age was also significantly lower among PU patients (18.6 months, SD 15.0 months) compared to PS (34.2 months, SD 6.3 months) (P < .01).

As outlined in Table 1, pyeloplasty was the most common procedure with 70 (59.3%), 23 (19.5%) ureteroureterostomy, 14 partial or total nephrectomy (11.9%), 3 nissen (2.5%), 2 bilateral orchiopexy (1.7%), 2 mitrofanoff/malone (1.7%), 2 splenectomy (1.7%), 1 paraspinal mass resection (0.8%), and 1 anterior sagittal vaginoplasty (0.8%). There were no surgical site infections. There were no conversions to open procedures. Four patients (3.4%) experienced port site hernias that were surgically repaired from 1 nephrectomy, 1 pyeloplasty, and 2 ureteroureterostomys.

Discussion

RAS is an evolving and quickly growing tool in pediatric and urologic surgery. ⁹ Literature to support its utilization in smaller patients (≤15 kg) however is limited. This current report outlines 118 RAS at a single center within both PU and PS specialties. Consistent with prior literature, ¹⁰ procedures within this patient population were primarily performed by PU with pyeloplasty being the most common procedure performed. Complications overall were few, and none required conversion to open procedure illustrating these RAS procedures can be performed safely in patients ≤15 kg.

Others have reported smaller similar series regarding the use of RAS in infants. Kutikov et al. previously described safe pyeloplasty in 9 patients all under 10 kg. ¹¹ Avery et al. reported on 60 patients with a median weight of 8.1 kg undergoing pyeloplasty, with a 91% success rate. ¹² Kawal et al. similarly compared 34 infants to an older population who underwent RAS pyeloplasty with a success rate of 94.1%. ¹³ Rague et al. reported on 101 patients weighing ≤10 kg, who underwent RAS pyeloplasty or ureteroureterostomy, and demonstrated that when stratified by weight within the group there was comparable outcomes, efficiency, and complications regardless of weight. ¹⁴ Andolfi et al. most recently reported on their single institutional experience with RAS pyeloplasty in 44 patients with a mean weight of 6.8 kg with a success rate of 100% and minimal complications. ¹⁵

Within PU, perhaps there is no better example of utility of RAS than pyeloplasty. ¹⁰ LS pyeloplasty was first described in 1993; however, within 10 years, it accounted for <20% of cases in patients ages 13–18. ¹⁶ Since robotic pyeloplasty was described just over 10 years ago, it now accounts for >80% of all cases. ¹⁷ Comparatively, there are significantly fewer reports of RAS approaches in PS surgical procedures in the literature. Xu et al. reported their experience using a RAS platform for diaphragmatic eventration in 20 patients <15 kg. ¹⁸ Nine patients who underwent RAS repair were compared to 11 patients who underwent conventional thoracoscopic repair finding both approaches were similarly effective at achieving repair. Others have published case report using RAS repair of choledochal cysts,^19,20 nissen fundoplications, ²¹ and splenectomies. ²² Most of these included few infants ≤15 kg in their study, but none of these specifically analyzed this population in comparison with larger children and therefore, it is difficult to draw specific conclusions. Each of these articles did report comparable outcomes between RAS and LS or open approaches. Therefore, while the use of RAS for PS cases is in its infancy, our series would constitute the first study specifically evaluating children ≤15 kg undergoing RAS for PS cases.

Despite the advantages of the RAS platform, operating on infants ≤15 kg is not without its challenges. Limited pneumoperitoneum tolerance, diminished three-dimensional operative space, and suboptimal instrumentation for infant operations are just some of the challenges associated with infant RAS operations. Of note, there has yet to be a consensus on a lower weight limit or age of tolerance for infants. Some have suggested optimal abdominal size, specifically noting that robotic arm collisions occurred more frequently if the measurement between bilateral anterior superior iliac spines was less than 13 cm or the pubic bone to xiphoid distance was less than 15 cm. ²³ Furthermore, others have noted that while traditional LS approaches in infants utilize 3 mm ports, the current platforms for RAS only accommodate 5 mm and 8 mm, and typically have a minimum distance (8 cm) required for port separation. ³ Of note, there are systems in development with the ability to accommodate smaller port size. ⁷

This study has several limitations inherent to the design and patient population studied. This study included a small number of patients from a single institute, and analysis was performed in a retrospective manner. Therefore, the conclusions from this study may be subject to confounding, selection bias, and other variables that were not able to be controlled and may not be widely applicable. Data were also acquired from electronic medical records and therefore subject to biases or inaccuracies in the records. Furthermore, the PS and MS groups had fewer patients than the PU group; therefore, future studies with more robust patient numbers are necessary to further validate the findings presented here.

Conclusion

Based on our institutional experience, this report describes collective evidence among both PU and PS groups showing that RAS in infants ≤15 kg is a safe and feasible option. Just as RAS has grown substantially among PU practices, we anticipate a growing trend for its utilization among PS procedures as well. Further studies and technology are needed to help optimize RAS approaches and refine tools to better expand its utilization and improve efficiency given size and space limitations among this very small group.