The case history reported concerns a female patient aged 42 years for whom the clinical picture was that of a blue phlebitis (phlegmatia caerulea dolens), associated with a state of shock evoking a severe pulmonary embolus. The absence of echocardiographic dilatation of the right cavities, and the appearance of a left iliac fossa mass, steered the diagnosis towards internal haemorrhage. Emergency laparotomy allowed diagnosis and treatment of a so-called spontaneous rupture of the left iliac vein, a rare condition for which 20 cases have been reported in the literature. Re-operation performed 24 hours afterwards for the absence of venous return allowed the discovery of Cockett's syndrome with ascending thrombosis, requiring cross-venous bypass associated with the creation of an arterio-venous fistula in order to maintain permeability. One year afterwards the appearance of signs of cardiac insufficiency led to the closure of this fistula.