Authors: Zeyu Liu, Abiha Abdullah, Mehsa Hashim, Janavi Sethurathnam, James Fleshman, Alessandro Fichera, Aimal Khan
Categories: Original Study, Ureteral injury, rectal surgery, robotic, laparoscopic, surgical outcomes
Source: Annals of Surgery Open
Water Under the Bridge: Ureteral Injury After Robotic Versus Laparoscopic Rectal Surgery
Authors: Zeyu Liu, Abiha Abdullah, Mehsa Hashim, Janavi Sethurathnam, James Fleshman, Alessandro Fichera, Aimal Khan
Abstract
Background:
Robotic surgery is increasingly utilized for rectal surgery due to its favorable ergonomics and perceived superior outcomes compared with laparoscopic surgery. However, it is unclear whether the rates of ureteral injury are lower with robotic rectal surgery. We hypothesized that the robotic approach would be associated with a lower incidence of ureteral injury.
Methods:
This retrospective cohort study used the Nationwide Readmissions Database (2017–2022) to identify adults (≥18 years) who underwent all-cause laparoscopic or robotic rectal surgery. The primary outcome was ureteral injury. Secondary outcomes, defined a priori, included in-hospital mortality, major complications, length of stay, nonhome discharge, and hospitalization costs. Entropy balance adjusted for baseline confounders, multivariable regression models were constructed for evaluating the association between surgical approach and outcomes.
Results:
Of the 33,642 patients included in the study, 18,135 (53.9%) underwent robotic rectal surgery. After entropy balancing and risk adjustment, robotic surgery was not associated with a reduced risk of ureteral injury [adjusted odds 1.12, 95% confidence interval (CI): 0.76–1.66; P = 0.563]. Robotic surgery was associated with lower odds of gastrointestinal complications (adjusted odds 0.57, 95% CI: 0.43–0.76; P < 0.001), a shorter length of stay (β: −0.34 days, 95% CI: −0.51 to −0.17; P < 0.001), and higher costs (β: +4900–$6800; P < 0.001) compared with those who had laparoscopic surgery.
Conclusions:
This cohort study found that surgical approach does not affect the risk of ureteral injury, yet the robotic approach was associated with better short-term clinical outcomes but significantly higher costs compared with laparoscopic surgery.
INTRODUCTION
Ureteral injury is a serious complication of colorectal surgery, occurring in up to 1% of cases, and is associated with significant morbidity, including ureteral strictures, fistula formation, and the need for reintervention.^1–5^ These injuries independently contribute to prolonged hospital stays and increased healthcare costs.^2^ Among colorectal procedures, rectal surgery carries a particularly high-risk of ureteral injury due to the confined nature of pelvic anatomy and the complexity inherent to pelvic dissection.^1,2,6^
Both robotic and laparoscopic techniques are commonly employed for minimally invasive rectal surgery, yet the comparative risk of ureteral injury between them is not well established.^7^ Robotic surgery offers enhanced 3-dimensional visualization, wristed instrumentation, and superior ergonomics, and has been associated with lower rates of major complications and improved oncologic outcomes in colorectal surgeries compared with open and laparoscopic approaches.^8–10^ Although the robotic approach has also been linked to a reduced risk of ureteral injury in colorectal surgery overall, whether these benefits meaningfully extend to rectal surgery, a particularly high-risk subset, remains uncertain.^1^
In this retrospective cohort study, we used contemporary data from the Nationwide Readmissions Database (NRD) to compare the incidence of ureteral injury and associated clinical and financial outcomes between robotic and laparoscopic rectal surgery. We also conducted a subgroup analysis to determine if the initial surgical approach affects outcomes for patients who experience a ureteral injury. We hypothesized that robotic surgery would be independently associated with a lower risk of ureteral injury and better clinical outcomes than the laparoscopic approach, and that this benefit would persist even when a ureteral injury has occurred.
MATERIALS AND METHODS
Study Design and Data Source
We conducted a retrospective cohort study using the NRD to capture patients who underwent all-cause isolated laparoscopic or robotic rectal surgery between 2017 and 2022. As the largest publicly available all-payer inpatient database in the United States, the NRD captures discharge data from 31 participating states, representing nearly 60% of all hospitalizations nationwide with survey weighting.^11^ The NRD allows for longitudinal tracking of individual patients across hospital admissions within a given calendar year, thereby enabling the assessment of readmissions, complications, and short-term outcomes after hospital discharge. Given the de-identified nature of the dataset, this study was deemed exempt from full review by the Institutional Review Board.
Patient Selection
We included adult patients (≥18 years old) undergoing all-cause isolated rectal surgery by laparoscopic or robotic approaches, identified through previously reported International Classification of Diseases, 10th Revision (ICD-10) procedure codes (Supplemental Digital Content 1, https://links.lww.com/AOSO/A562).^12^ We restricted the cohort to isolated rectal surgery to ensure that any ureteral injuries were attributable specifically to rectal surgery. Patients who underwent rectal surgery in conjunction with any concurrent colectomy procedure were excluded to ensure a more homogeneous cohort.
Surgical approach was determined using a defined set of ICD-10 codes. In brief, the robotic approach was defined as patients with any rectal surgery code (laparoscopic or open), a robotic procedure code, and no conversion-to-open diagnosis code. Similarly, the laparoscopic approach was defined as patients with a laparoscopic rectal surgery code, without a robotic procedure code or conversion-to-open code. This logic ensured mutually exclusive classification of surgical modality. Full code definitions and classification criteria are detailed in Supplemental Digital Content 1, https://links.lww.com/AOSO/A562. Patients with incomplete critical data, including age, sex, cost, income, in-hospital mortality, and elective status, were excluded (Fig. 1).
Exposure and Outcomes
The primary outcome was ureteral injury. Secondary outcomes, defined a priori, included in-hospital mortality, major complications, length of stay, hospitalization costs, 30-day nonelective readmission, and nonhome discharge. Major complications were grouped into neurologic, cardiac, respiratory, gastrointestinal, renal, thromboembolic, and infectious complications, each defined by relevant ICD-10 codes consistent with prior literature.^11^ Gastrointestinal complications encompassed gastrointestinal bleeding, bowel ischemia, intestinal perforation, hemoperitoneum, megacolon, and pancreatic fistula. Hospital costs were computed using hospital-specific cost-to-charge ratios and adjusted for inflation to 2022 US dollars using the Personal Health Care Index, enabling cost comparisons across the 6-year study period.
Exclusions for Readmission Analyses and Frailty Assessment
Due to the NRD’s calendar year structure, which only tracks patients within a calendar year, patients discharged in December were excluded from the 30-day readmission analysis, and those discharged after September were excluded from the 90-day readmission analysis. In addition, patients who died during the index hospitalization were also excluded from the readmission analysis. Frailty was measured using the Hospital Frailty Risk Score, a validated ICD-10-based tool that stratifies patients into low, intermediate, or high-risk for adverse outcomes.^13^ This score has been previously validated in older surgical populations and was selected for its relevance to rectal surgery, which often involves elderly patients.
Statistical Analysis
Baseline patient demographics, clinical characteristics, and hospital data were compared between robotic and laparoscopic groups using Pearson’s χ^2^ tests for categorical variables and Mann–Whitney U tests for continuous variables. Entropy balancing was performed to minimize confounding by matching baseline covariates that were found to be significantly different, including age, sex, Elixhauser comorbidity score, community income percentile, diabetes, obesity, surgical indications, and receipt of neoadjuvant therapy (Supplemental Digital Content 2, https://links.lww.com/AOSO/A562). Covariates for multivariable models were selected using the Least Absolute Shrinkage and Selection Operator method, which included patient demographics, comorbidity burden, frailty status, and hospital characteristics. Multivariable logistic and linear regression models evaluated the independent association between surgical modality and outcomes, reporting adjusted odds ratios (AORs) and beta coefficients (β) with 95% confidence intervals (CI). Model performance was assessed by AUROC c-statistics, calibration plots, and coefficients of determination. All statistical analyses were conducted with Stata 19 (StataCorp LLC, College Station, TX), with statistical significance defined as P < 0.05.
RESULTS
Patient Demographics and Clinical Characteristics
Among the 33,642 patients included, 15,507 (46.1%) underwent laparoscopic rectal surgery, while 18,135 (53.9%) underwent robotic rectal surgery (Fig. 1). Compared with the laparoscopic group, patients in the robotic group were older (median 59 vs 58 years; P = 0.029), less frequently female (46.2% vs 52.9%; P < 0.001), and had higher rates of obesity (16.7% vs 13.4%, P < 0.001) and diabetes (16.0% vs 14.5%; P = 0.028). Robotic surgery patients were also more likely to undergo surgery for rectal cancer (57.8% vs 39.5%; P < 0.001), while laparoscopic surgery was more frequently performed for rectal prolapse (18.6% vs 7.9%; P < 0.001). In addition, robotic patients were more likely to receive neoadjuvant radiation (22.0% vs 12.2%; P < 0.001) and chemotherapy (22.4% vs 13.1%; P < 0.001) compared with laparoscopic surgery. Demographic, clinical, and hospital characteristics of patients stratified by surgical approach are provided in Table 1.
Primary Outcome
The incidence of ureteral injury was comparable between the laparoscopic (1.2%) and robotic (1.1%) groups (Supplemental Digital Content 3, https://links.lww.com/AOSO/A562). After entropy balancing and multivariable regression to account for confounders, surgical approach—robotic versus laparoscopic—was not significantly associated with a decreased risk of ureteral injury (AOR: 1.12, 95% CI: 0.76–1.66; P = 0.563).
Secondary Outcomes
In the analysis of secondary clinical and financial outcomes, the robotic approach was associated with lower odds of gastrointestinal complications, including gastrointestinal bleeding, bowel ischemia, intestinal perforation, hemoperitoneum, megacolon, and pancreatic fistula (AOR: 0.57, 95% CI: 0.43–0.76; P < 0.001) and a shorter length of stay (β: −0.34 days, 95% CI: −0.51 to −0.17; P < 0.001). There was no significant association with in-hospital mortality compared with the laparoscopic approach (AOR: 1.08, 95% CI: 0.65–1.79; P = 0.777). However, robotic surgery was independently associated with higher hospitalization costs (β: +4900–$6800; P < 0.001) and increased odds of nonhome discharge (AOR: 1.15, 95% CI: 1.05–1.25; P = 0.002) (Fig. 2). Unadjusted results are provided in Supplemental Digital Content 3, https://links.lww.com/AOSO/A562.
Subgroup Analysis: Patients With Ureteral Injury
In the subgroup of patients who sustained ureteral injury, undergoing robotic as the initial rectal surgery modality was not associated with significant differences in length of stay (β: +0.7 days, 95% CI: −1.6 to 3.0; P = 0.554), odds of nonhome discharge (AOR: 1.21, 95% CI: 0.48–3.07; P = 0.682), or 30-day nonelective readmission (AOR: 1.10, 95% CI: 0.30–3.50; P = 0.934), compared with laparoscopic surgery, after entropy balancing and risk adjustment. However, robotic surgery remained independently associated with significantly higher hospitalization costs in this subgroup (β: +9300–$29300; P < 0.001) (Table 2). Unadjusted results are provided in Supplemental Digital Content 4, https://links.lww.com/AOSO/A562.
DISCUSSION
In this contemporary comparative analysis of a nationally representative cohort, we found no significant difference in ureteral injury rates between laparoscopic and robotic approaches in isolated rectal surgery (1.2% vs 1.1%, respectively), even after adjusting for confounders using entropy balancing and multivariable modeling. Despite the lack of difference in ureteral injury risk, the robotic approach was associated with fewer gastrointestinal complications and a shorter length of stay, though these benefits came at a significantly higher cost. Importantly, among patients who sustained ureteral injuries, the initial use of robotic surgery was not associated with increased length of stay, higher odds of nonhome discharge, or greater 30-day readmission rates compared with laparoscopy. However, it remained independently associated with substantially higher hospitalization costs.
Although laparoscopic and robotic approaches are widely used in colorectal surgery, existing literature offers conflicting evidence regarding their comparative risks of ureteral injury. Prior findings remain Mayo et al^1^ reported reduced risks of ureteral injury for robotic [odds ratio (OR) 0.50] and laparoscopic (OR 0.81) methods compared with open surgery across all colorectal surgeries using the 2006–2016 NRD. Similarly, Halabi et al^2^ demonstrated modest risk reductions with laparoscopy relative to open surgery using data from 2001 to 2010. Conversely, Andersen et al^3^ found an increased risk of ureteral injury associated with laparoscopic procedures compared with open surgery specifically in colorectal cancer resections (OR 2.67, 95% CI: 1.26–5.65). This variability may, in part, reflect differences in study design, case mix, and temporal context. For example, many analyses grouped colon and rectal procedures together, potentially masking key distinctions in anatomical complexity and ureteral injury risk.^14^ Additionally, earlier studies examining robotic techniques frequently overlapped with their initial introduction period, a time during which surgeons were still progressing along the learning curve.^15^ To specifically address these gaps, our study uniquely focuses on isolated rectal surgery and leverages a contemporary, nationally representative database to provide procedure-specific insights. We observed ureteral injury rates of approximately 1.1%–1.2%, slightly higher than the previously reported general colorectal surgery incidence of 0.3%–1.0%, possibly due to the inherently elevated risks associated with rectal procedures (1–3). Crucially, our findings demonstrate no significant difference in ureteral injury risks associated with robotic and laparoscopic approaches for isolated rectal surgery, thus clarifying previously uncertain comparative risks and providing valuable, updated insight for clinical modality decision-making in rectal surgery.
While the overall incidence of ureteral injury was low and comparable between surgical approaches, its occurrence following robotic rectal surgery was associated with a markedly higher financial burden. Specifically, median hospitalization costs increased from 46,200 when a ureteral injury occurred. In contrast, costs for laparoscopic rectal surgery remained relatively stable regardless of injury status. This disparity persisted even after entropy balancing and multivariable adjustment, with robotic-associated ureteral injury independently contributing to an additional 9300–$29,300, P < 0.001). These findings are consistent with prior studies demonstrating that postoperative complications are among the most significant drivers of increased healthcare expenditures.^16^ Moreover, recent literature suggests that the cost gap between robotic and laparoscopic surgery continues to widen over the years, raising concern about the escalating financial burdens associated with ureteral injuries in robotic cases.^17^ Given these economic implications, it is imperative that surgeons approach robotic surgery with thoughtful cost-awareness—reserving its use for cases where the anticipated clinical benefit clearly justifies the added expense. Integrating both clinical judgment and resource stewardship is essential to advancing high-value, equitable surgical care while minimizing unnecessary financial strain on patients.
Notably, in our study, robotic rectal surgery was associated with a 48% lower likelihood of overall gastrointestinal complications (AOR: 0.57, 95% CI: 0.43–0.76; P < 0.001) and a modestly shorter hospital stay (β: −0.34 days, 95% CI: −0.51 to −0.17, P < 0.001) compared with the laparoscopic approach. These findings are consistent with prior literature suggesting that robotic systems, through enhanced 3-dimensional visualization and wristed instrumentation, may improve surgical precision and reduce tissue trauma—particularly within the confined pelvic space.^18,19^ At the same time, the demonstrated perioperative advantages of robotic surgery reinforce the importance of individualized modality selection. In patients with greater anatomical complexity or elevated risk for complications, the technical benefits of robotic platforms may offer meaningful improvements in outcomes that support their use despite higher upfront costs.
This study has several limitations. First, the use of administrative claims data introduces the possibility of coding errors and lacks the clinical granularity needed to assess operative detail and patient lab values. Second, we were unable to determine the laterality or grade of ureteral injuries, which may have implications for clinical and financial outcomes. Third, the NRD does not indicate whether ureteral injuries were identified intraoperatively or postoperatively, a distinction known to influence morbidity and management. Additionally, the database does not capture data on intraoperative preventive strategies, such as ureteral stenting or the use of fluorescence imaging, which may influence injury rates. Fourth, cost estimates derived from hospital-specific cost-to-charge ratios may not fully capture indirect institutional expenses or long-term costs. Finally, regarding study scope, our analysis intentionally focused on rectal surgery to ensure procedural and anatomic homogeneity. We acknowledge that excluding sigmoid and other segmental colectomies may omit cases where ureteral dissection is particularly challenging—such as in diverticular disease with dense adhesions near the pelvic brim. However, this restriction was necessary to isolate the risk of ureteral injury inherent to rectal surgery itself, without confounding from proximal colorectal procedures that differ in anatomy and surgical approach. Future studies directly comparing proximal and distal colorectal resections could help delineate whether the mechanisms and preventive strategies for ureteral injury vary by operative field. Despite these limitations, our findings provide timely and procedure-specific insights into the comparative risks, outcomes, and economic implications of robotic versus laparoscopic rectal surgery in the modern surgical era.
In conclusion, our study offers contemporary, rectal surgery-specific evidence on the comparative risks and outcomes associated with robotic and laparoscopic approaches. While the risk of ureteral injury remains low and comparable between modalities, its occurrence, particularly after robotic surgery, carries significant financial implications. At the same time, robotic surgery offers distinct clinical benefits, including fewer gastrointestinal complications and shorter hospital stays. These findings underscore the importance of individualized surgical decision-making that balances technical advantages, patient-specific risk factors, and economic considerations. As robotic platforms continue to evolve and expand in colorectal surgery, future research should focus on refining patient selection criteria, optimizing perioperative strategies to prevent ureteral injury, and evaluating long-term outcomes to ensure the delivery of high-quality, cost-effective care.
ACKNOWLEDGMENTS
Z.L.: Conception and design of study; data acquisition and analysis; drafting of manuscript; critical revision. A.A.: Conception and design of study; drafting of manuscript. M.H.: Drafting of manuscript. J.S.: Drafting of manuscript. J.F.: Critical revision of manuscript; supervision. A.F.: Critical revision of manuscript; supervision. A.K.: Conception and design of study; critical revision of manuscript; supervision.