Lymphatic drainage efficiency: a new parameter of lymphatic function.

Background Following convection from blood capillaries, plasma proteins are transported to loco-regional lymph nodes in two stages: first, uptake into peripheral lymphatics, and second, transport to nodes. Purpose To introduce a new parameter of lymphatic function that quantifies stage 2 - lymphatic drainage efficiency (LDE). Material and Methods Percentage injected activity (IIQ) in ilio-inguinal nodes 150 min following subcutaneous foot web-space injection of Tc-99 m-nanocolloid was measured in 102 patients undergoing lymphoscintigraphy using a method in which a standard is placed by image guidance over the nodes. Percentage activity leaving the injection depot by 150 min ( k) was measured in 60/102 patients. LDE (%) = 100 × (IIQ/ k). Abnormal lymphoscintigraphy was defined qualitatively as: (i) no activity in ilio-inguinal nodes at 45 min or negligible activity at 150 min (delay); (ii) lymph diversion through skin and/or deep system; and (iii) focal tracer accumulation suggesting cellulitis. Results Scintigraphy was bilaterally normal in 82 limbs, unilaterally normal in 40 limbs and abnormal in 82 limbs. IIQ correlated with k in bilaterally normal (r = 0.86; n = 52), unilaterally normal (r = 0.67; n = 27), and abnormal (r = 0.82; n = 41) limbs. IIQ, k, and LDE were significantly lower in unilaterally normal (9.3 ± 5.4%, 13.8 ± 7.1%, and 65 ± 30%) compared with bilaterally normal limbs (15.4 ± 8.4% [ P > 0.0001], 18.3 ± 8.9% [ P = 0.025], and 84 ± 30% [ P = 0.01]). LDE was lower in limbs displaying skin diversion and/or delay. Conclusion LDE is a new quantitative index that has potential value in clinical research but requires further clinical evaluation. Abnormal quantitative indices indicate that limbs unilaterally normal on lymphoscintigraphy are not functionally normal.

Importance of accurate ilio-inguinal quantification in lower extremity lymphoscintigraphy.

AIMS: The aims of this study were to improve the quantification of lower extremity lymphoscintigraphy, determine its value and lower limit of normal, and determine whether intermediate postinjection time imaging is necessary. PATIENTS AND METHODS: This was a study of 102 consecutive patients undergoing routine lower extremity lymphoscintigraphy using subcutaneous Tc-99m-nanocolloid with imaging at 5, 45 and 150 min after injection. Abnormal imaging criteria were delay (no activity in ilio-inguinal nodes at 45 min or negligible activity at 150 min), lymph diversion (through skin or deep system) and focal accumulation suggesting cellulitis. Lymphatic function was quantified as % injected activity in ilio-inguinal nodes at 150 min (IIQ) using a standard placed, by image guidance, exactly over the nodes. RESULTS: Forty-one patients had bilateral normal scintigraphy. IIQ was normally distributed in 15 limbs, with IIQ of 1-7.5%. In contrast, it was log-normally distributed in 68 limbs, with IIQ of at least 7.5%, suggesting 8% as the lower limit of normal. In 57 limbs, delay was the only scintigraphic abnormality at 45 min. Of these, 33 were abnormal at 150 min. Of the remaining 24 limbs, 17 had reduced IIQ; thus, 50 of these 57 (88%) limbs had lymphatic dysfunction. The seven limbs that remained normal at 150 min were in six patients. The contralateral limb was abnormal in five of these six patients; hence, lymphatic dysfunction would have been missed in only one patient without 45 min imaging. CONCLUSION: IIQ is strongly recommended. Isolated delay at 45 min is abnormal. However, 45 min imaging is not necessary if IIQ is performed.