In the adult patient with urgent need for venous access (in the emergency room, in the operating room, in emergency wards, etc.) it is necessary to distinguish the patients with ease of venous access (well palpable/visible veins in the upper limbs) vs. patients with 'difficult' access (DIVA).

The patient "without veins" obviously does not exist, but nonetheless in many patients (up to 10% of patients who arrive in the emergency room) the patrimony of the superficial veins of the upper limbs is limited or exploited, so that these veins are hardly visible and/or palpable. This category of patients has recently been classified with the English acronym 'DIVA' (Difficult IntraVenous Access), normally referring to the difficulty of accessing the superficial veins (i.e. located less than 6-7 mm deep) of the upper limbs .

In case of difficulty in accessing the superficial veins of the upper limbs, it is also possible to insert a short cannula in a superficial vein of the neck (external jugular vein in the cervical tract) or in a superficial vein of the lower limbs: these accesses must be removed within 24 hours, due to the high risk of dislocation (external jugular vein) or venous thrombosis (veins of the lower limbs).