Side-Specific 24 h Pre-Removal Drainage Volume and Fluid-Related Complications After Endoscopic Gynecomastia Surgery

Drain removal after transaxillary single-port endoscopic surgery for gynecomastia remains experience-based, and side-specific drainage thresholds are lacking.

This retrospective cohort study used operated sides as analytic units. Eligible sides had independent negative-pressure drainage and complete follow-up. Exposure was side-specific 24 h drainage volume before removal. Outcome was ultrasonographically confirmed and aspiration-verified seroma or hematoma within 14 days. Discrimination was assessed by receiver operating characteristic analysis with clustered bootstrap confidence intervals, clustered bootstrap cutoff-stability analysis, and likelihood ratios. Associations were evaluated using generalized estimating equation logistic regression with temporal, surgery-type, laterality, intracluster correlation, and effective-information-size sensitivity analyses.

Among 88 patients and 160 operated sides, 32 sides (20.0%) developed fluid-related complications. The area under the receiver operating characteristic curve was 0.729 (95% CI, 0.635-0.815). The raw cutoff was 13.5 mL; 15 mL was selected as the exploratory threshold. At 15 mL, sensitivity was 65.6%, specificity 63.3%, positive predictive value 30.9%, negative predictive value 88.0%, positive likelihood ratio 1.79, and negative likelihood ratio 0.54. Complication rates were 30.9% (21/68) for at least 15 mL and 12.0% (11/92) for less than 15 mL. After adjustment, at least 15 mL remained associated with increased risk (odds ratio [OR], 3.09; 95% CI, 1.28-7.47). Additional temporal and surgery-type/laterality sensitivity analyses were directionally consistent but imprecise, supporting exploratory interpretation.

Side-specific 24 h drainage volume before removal was associated with fluid-related complications. The 15 mL threshold may help identify lower-risk sides in this cohort, but predictive values are prevalence-dependent and the threshold should be interpreted as an exploratory, overall risk-stratification reference rather than a POD-specific or mandatory drain-removal rule.

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