The lymphoscintigraphic investigation (LySc) of the superficial lymphatic system (SLS) remains the gold standard for the diagnosis of lower limb lymphoedema. However, LySc of the deep lymphatic system (DLS) may be useful for diagnosing deep lymphatic system insufficiency in patients with lower limb oedema (LLE) but normal and/or paradoxical LySc of the SLS. The purpose of this study was therefore to evaluate a new LySc of the deep lymphatic system in patients presenting with a normal and/or paradoxical SLS exam showing LLE. In all, 15 patients with unilateral and 17 with bilateral LLE underwent 3-phased deep LySc of the lower limb via the injection of 99 mTc-labelled human serum albumin (HSA) nanocolloids in the Kager's triangle. The absence of popliteal lymphatic node visualization after phase 2 of DLS LySc to diagnose a deep lymphatic insufficiency has a specificity and a sensitivity of 89% in patients with unilateral LLE and without associated venous symptoms. An insufficiency of the DLS was observed in 67% of cases with unilateral LLE and 59% of patients with bilateral LLE of venous and/or lymphatic origin. In conclusion, the lymphoscintigraphic visualization of the popliteal lymphatic nodes after the injection of 99 mTc-labelled HSA nanocolloids in the Kager's triangle seems to be an effective way to diagnose DLS insufficiency in patients with LLE but normal findings in the SLS.