Application of probit method for the elastographic evaluation of venous obliterating material after sclerotherapy procedure

Purpose: Status after sclerotherapy constitutes a good clinical model for venous thrombosis with known age. The aim of this study was to compare elastographic parameters of material obliterating the great saphenous vein at 7-21 days after polidocanol sclerotherapy. Material and methods: The study included 60 patients subjected to sclerotherapy due to venous insufficiency (45 women and 15 men, mean age 51.2 ± 14.7 years, range 27-77 years). Elastographic parameters of obliterating material: total area of vessel cross-section (mm2), relative areas (%) covered by tissues with highest, intermediate, and lowest elasticity, were determined 7 ± 1, 14 ± 2, and 21 ± 2 days post-sclerotherapy, respectively. Mean time to partial and complete organisation of the obliterating material was estimated during probit regression analysis. Results: The relative area of vessel cross-section covered by tissues with the lowest elasticity underwent a statistically significant enlargement, either between the first and the second (Z = 6.725, p < 0.001) or between the second and the third control visit (Z = 6.717, p < 0.001). This corresponded to a change in the structure of the obliterating material from elastic during the first visit (in all patients) to mixed (fibro-elastic) or fibrous during the third visit (71.7% and 28.3% of patients, respectively). Mean time after which the obliterating material reached mixed and fibrous structure on elastographic images was estimated at 14.3 days and > 21 days, respectively. Conclusions: Ultrasound elastography may accurately reflect the age of venous thrombosis in polidocanol sclerotherapy model. Mixed, fibro-elastic structure of a 14-day-old obliterating material visualised by elastography probably corresponds with chronic thrombus.