Incidence, Predictors, and a Bedside Risk Score for Chylous Ascites after Open Abdominal Aortic Surgery: A 20-Year Population-Based Cohort Study.

BACKGROUND

Chylous ascites is a rare but morbid complication of retroperitoneal vascular dissection, associated with prolonged hospitalization and reported mortality of 11-18%. No population-based incidence data or risk stratification tool exists. We aimed to estimate procedure-specific incidence, identify independent predictors, and derive an internally validated bedside risk score.

METHODS

Retrospective cohort study of 6,382 consecutive open abdominal aortic procedures (2003-2022) across 3 centers in Vojvodina, Serbia. The mean age was 69.1 ± 8.6 years; 79.8% were male. Chylous ascites required milky drainage fluid with triglyceride ≥200 mg/dL. Multivariable logistic regression identified predictors; coefficients informed a points-based score. Internal validation used 1,000 bootstrap resamples (TRIPOD type 1b).

RESULTS

Chylous ascites occurred in 47 patients (0.74%; 95% confidence interval [CI]: 0.54-0.98%), five-fold more frequently after ruptured (2.51%) than elective abdominal aortic aneurysm (AAA) repair (0.43%; P < 0.001). Five predictors reached significance: hostile retroperitoneum (aOR 4.21), suprarenal clamping (3.44), redo surgery (3.02), rupture (2.53), and operative time ≥240 min (2.38). Three additional predictors were retained on clinical grounds. The bedside score (0-10 points) stratified observed risk 22-fold (0.26-5.79%). The optimism-corrected area under the ROC curve was 0.79 (95% CI: 0.72-0.86); calibration slope 0.92.

CONCLUSION

Chylous ascites is rare but clinically significant, particularly after ruptured AAA repair. A bedside score calculable within 24 hours of surgery identifies patients who may benefit from targeted drain-fluid monitoring and early dietary intervention. The score is most applicable to aneurysm surgery. External validation is required before routine use.