Distinguishing Venous Outflow Insufficiency from Ischemia–Reperfusion Injury Using a Hydro-Manometer: A Case Series

Aim: Venous insufficiency is a cause of failure in microsurgical replantation and free flap surgery and may be difficult to distinguish intraoperatively from ischemia–reperfusion injury. This study aims to introduce a simple, low-cost, and quantitative intraoperative method—the Hydro-Manometer technique—for assessing venous drainage capacity under physiological pressure conditions.Material and Methods: This retrospective case series included seven patients treated between 2024 and 2025 who demonstrated clinically relevant venous drainage pathology. The Hydro-Manometer technique was applied intraoperatively in cases showing compromised tissue perfusion despite technically patent arterial and venous anastomoses. Venous drainage capacity was evaluated using a hydrostatic saline column corresponding to physiological venular pressure (20 cmH₂O).Results: In all cases, arterial and venous anastomoses were confirmed to be patent intraoperatively. Venous thrombosis was identified and treated with thrombectomy in six patients. In one patient, the Hydro-Manometer revealed insufficient venous drainage capacity due to proximal venous pathology, which was successfully managed with venous grafting. All free flaps and replanted tissues survived, with no cases of postoperative venous thrombosis or tissue necrosis during follow-up.Conclusion: The Hydro-Manometer provides an objective, quantitative, and easily applicable intraoperative assessment of venous drainage capacity in microsurgical procedures. By facilitating differentiation between venous outflow insufficiency and ischemia–reperfusion injury, this method may improve intraoperative decision-making and help prevent avoidable tissue loss.