Surgery in varicose veins is NOT attempted in presence of -

Deep vein thrombosis is a contraindication for t/t of varicose veins. Varicose vein surgery should never be attempted in a case where deep vein thrombosis exists along with varicose veins, because in these cases superficial veins are the only valved venous pathway and excising them will only aggravate the condition. Ref : Bailey & Love 25/e p930