TY - JOUR T1 - Lymphatic drainage efficiency; a new parameter of lymphatic function. JF - Journal of Nuclear Medicine JO - J Nucl Med SP - 1651 LP - 1651 VL - 57 IS - supplement 2 AU - Georgia Keramida AU - Luisa Pereira AU - Emma Wroe AU - Mark Aplin AU - Nicola Winterman AU - Adrien Peters Y1 - 2016/05/01 UR - http://jnm.snmjournals.org/content/57/supplement_2/1651.abstract N2 - 1651Objectives Lymphoscintigraphy with s.c. Tc-99m-nanocolloid is routinely used to assess lymphatic function in limb swelling of unknown cause. Diagnostic accuracy is improved by quantification, of which 2 methods are in use: measurement of ilio-inguinal nodal uptake (IIQ) and disappearance rate of activity from the injection depot (k). The former is difficult to perform accurately and the latter generally regarded as unhelpful, probably because it is also technically difficult. We describe a new simple method for IIQ and its combination with k to yield a new parameter of lymphatic function - lymphatic drainage efficiency (LDE).Methods Lymphoscintigraphy was performed in 74 patients with lower limb swelling. Tc-99m-nanocolloid (20 MBq; GE) was injected s.c. into the 1st webspace of each foot followed by imaging at 5, 45 and 150 min. Abnormal lymphatic function per limb, qualitatively assessed, was diagnosed if there was transport delay (no ilio-inguinal nodal activity at 45 min or negligible activity at 150 min) and/or lymph diversion (dermal backflow and/or popliteal node visualisation). IIQ was performed at 150 min from the geometric mean of nodal counts recorded anteriorly and posteriorly before and after anterior placement, guided exactly by the nodal activity, of a standard over the nodes with subtraction to obtain standard counts. k was obtained as the % decrease in depot counts at 150 min. LDE is the % of activity leaving the depot that arrives in the ilio-inguinal nodes at 150 min.Results From qualitative assessment, 148 limbs were divided into 3 groups: 1. bilateral normal scintigraphy (n = 58); 2. unilateral normal scintigraphy (n = 29); 3. abnormal scintigraphy (n = 61). k was measured in 36/58, 17/29 and 29/61 of groups 1-3 limbs. Co-efficients of correlations between k and IIQ in groups 1-3 were 0.86 (p less than 0.0001), 0.58 (p = 0.015) and 0.81 (p less than 0.0001), respectively. In group 1, 6 limbs had IIQ of between 2% and 5%. All other limbs in this group had IIQ greater than 8%, suggesting a lower limit of normal of 8%. Therefore, 6/58 limbs in group 1 and 11/29 limbs in group 2 with IIQ less than 8% were re-classified as abnormal and 2 limbs in group 1 with IIQ unilaterally greater than 8% were moved to group 2. In the remaining scintigraphically normal limbs, mean IIQ was significantly higher in group 1 (19.0 ± 7.0; n = 50) compared with group 2 (12.8 ± 3.5%; n = 20; p = 0.0003) but there was no significant difference in k (22.2 ± 7.9% vs 17.8 ± 5.0%; p = 0.09). Accordingly, LDE was significantly higher in group 1 (90 ± 27%) than group 2 (68 ± 28%; p = 0.027). LDE in abnormal limbs was highly variable but less than 90% in all 29 of them.Conclusions Lymphedema occurs when there is an imbalance between lymph production rate, reflected by k, and drainage capacity, reflected by LDE. IIQ reflects both. Scintigraphically normal limbs with a contralateral abnormal limb have impaired lymphatic function, reflecting the commonest cause of lymphatic dysfunction, which is constitutional lymphatic weakness (latent lymphedema). Follow-up is needed to see how many unilaterally normal limbs develop lymphedema. LDE is a new marker of lymphatic function. ER -