Development and validation of a preoperative nomogram for predicting postoperative high drainage output after robot-assisted Roux-en-Y hepaticojejunostomy for children with choledochal cysts: based on cyst diameter, age, and other indicators

Robot-assisted Roux-en-Y hepaticojejunostomy (RYHJ) is the standard treatment for choledochal cysts (CDC). Routine abdominal drainage is typically placed, but no reliable preoperative tool exists to identify patients at risk of high drainage output (≥ 2 mL·kg⁻¹·d⁻¹), limiting early drain removal or selective omission under close monitoring. This study aimed to develop and validate an intuitive preoperative nomogram using readily available clinical indicators (e.g., cyst diameter, age) to predict high-drainage risk after robot-assisted RYHJ and support individualized drainage management.

This single-center retrospective cohort study enrolled 129 children with CDC who underwent da Vinci robot-assisted RYHJ. Based on weight-adjusted daily drain output, patients were divided into low-drainage (< 2 mL·kg⁻¹·d⁻¹, n = 30) and high-drainage (≥ 2 mL·kg⁻¹·d⁻¹, n = 99) groups. Potential predictors were identified via univariate and multivariate logistic regression and incorporated into a nomogram. Model performance was assessed using the area under the receiver operating characteristic curve (AUC) and calibration plots.

Multivariate analysis identified younger age as an independent predictor of high drainage output (OR = 0.983, 95% CI: 0.972–0.994), and larger cyst diameter as a potential predictor showing a trend toward association (OR = 1.321, 95% CI: 0.979–1.783). The final nomogram, incorporating cyst diameter, age, body mass index (BMI), hemoglobin (HGB), and globulin (GLB), showed good discrimination (AUC = 0.753) and calibration. The optimal risk threshold was 79.88%, yielding a specificity of 75.9%, and, using an optimal threshold, identifies low-risk patients suitable for early drain removal protocols to guide individualized drainage management.

We have developed and validated a nomogram model based on "cyst diameter + age" (supplemented by BMI, HGB, and GLB) that enables noninvasive, precise assessment of high-drainage risk following robot-assisted RYHJ. Notably, the model identifies a low-risk subset—older children with smaller cysts—for whom early drain removal (e.g., within 24–48 h) is safe, and in whom selective drain omission could be prospectively evaluated under rigorous monitoring. This risk-stratified approach has the potential to reduce drain-related complications and optimize ERAS pathways following robot-assisted RYHJ. As this is an internal validation only, external validation in independent cohorts is warranted before clinical implementation.