The main objective of this study is to test the hypothesis that a 3 week intensive course of spa therapy can reduce the risk of leg ulcers in patients with advanced chronic venous insufficiency (C4a-b and C5 of the CEAP classification) at one year.

Chronic venous insufficiency affects to differing extents half of the French population. The most advanced forms, with skin changes (CEAP clinical classes C4-5-6) affect 5% of the population and are those most often indicated for spa treatment. A venous condition is recognized as justifying spa therapy by 12 spa resorts in France. However, no specific or global benefit has been clearly scientifically shown for such therapy. One methodologically sound study (Carpentier 2009) demonstrated a benefit of spa therapy using a non-clinical intermediate endpoint (severity of skin changes). No study has shown efficacy of spa therapy in the primary and secondary prevention of the major and most common complication of advanced chronic venous insufficiency: leg ulcers.

Vascular hemodynamics and in particular venous return from the lower limbs is subject to the laws of physics. Thus, the roles of the calf muscle venous pump and hydrostatic pressure in venous insufficiency rationalizes the use of balneotherapy techniques in the management of this pathology.

The spa therapy techniques used in the context of venous insufficiency have well-defined physiopathic targets and the hemodynamic and microcirculatory effects of some of them have been demonstrated. The high degree of satisfaction of patients taking the waters annually for venous conditions indirectly testifies to their enhanced well-being. Among venous indications, the prevention of post-thrombotic syndrome is one of the best recognized by the medical profession.Nevertheless, there has been no real validation of this indication with an acceptable methodology that meets the canons of evidence based medicine.

Inclusion Criteria:

• Both sexes, more than 18 years old patients with a phlebological indication of spa treatment, with advanced chronic venous insufficiency, class C4a, or b or C5 of CEAP classification (leg ulcers must be healed since 3 months at least)
• Available for a spa treatment during 18 days (immediate or late spa)and a follow-up period of 18 months
• Voluntary to participate to the study,informed consent form signed after appropriate information
• Affiliation to the social security system or equivalent

Exclusion Criteria:

• Pregnancy, parturient or breast feeding
• No psychiatric illness or social situation that would preclude study compliance
• Leg ulcer in progress
• Leg ulcer healed for less than 3 months
• Refusal to consent
• Refusal of spa treatment
• Contra-indication of spa treatment(cancer in progress, psychiatric disorders, immunodeficiency)
• Arteriopathy of lower limb with an Ankle Brachial Pressure Index (ABPI)< 0.7, symptomatic neuropathy, erysipelas within 5 years prior to inclusion
• Surgical or endovascular treatment of the venous disease planned during the first year or during the six months prior to inclusion
• No previous phlebological spa treatment within 6 months prior to inclusion