 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 . 
