 The Giacomini vein mostly acts as a bypass between the GSV and SSV territories. Usually its flow is in the normal anterograde direction, from bottom to top. However it can become retrograde without pathology. For example, after a GSV stripping, laser ablation or after its ligation at the sapheno-femoral junction, the Giacomini vein will drain into the SSV, with a retrograde flow. When there is a GSV thrombosis or other cause of insufficiency, the Giacomini vein can divert the blood flow to the SSV and from there to the popliteal vein. Where surgery, other than stripping or laser ablation is intended, the examiner will make reference to the blood flow direction in this vein, as it will be of importance.
