Superficial vs. Deep Venous System in DIEP Flaps: Lessons from 25 Years of CTA-Guided Planning.

: Venous congestion is a major contributor to complications in DIEP flap breast reconstruction. Beyond superficial venous dominance, the presence or absence of anatomical connections between the superficial and deep venous systems may influence drainage physiology. This study investigates how preoperative CTA and targeted superdrainage impact outcomes over a 25-year period. : A retrospective analysis was conducted on 208 DIEP flaps performed from 2000 to 2024 at a single center. From 2006, computed tomographic angiography (CTA) was routinely used to evaluate venous anatomy, focusing on the presence, trajectory, and connection of the superficial inferior epigastric vein (SIEV) with the deep system. Superdrainage was performed when superficial venous dominance was evident or drainage was judged insufficient intraoperatively. Primary outcomes included venous congestion, partial necrosis, and reoperations; secondary outcomes included hospital stay and safety of superdrainage. : Venous complications decreased significantly after CTA implementation (37.5% vs. 8.0%; < 0.001). Superdrainage was performed in 40.9% of post-CTA cases, with 90% preoperatively planned based on CTA findings. No complications were associated with second venous anastomosis. Flap outcomes correlated not with perforator number or flap size but with venous drainage physiology. Mean hospital stay was shorter post-CTA (6 vs. 9 days; < 0.001). : Evaluating the anatomical connection between superficial and deep venous systems via CTA enhances venous planning and allows for safer, physiology-driven decisions. In the absence of such connections, intraoperative evaluation remains essential. Drainage physiology-rather than anatomical metrics alone-should guide surgical strategy in DIEP flap reconstruction.