Achilles Tendon Xanthomas: Fat-Water Separation at Baseline and after Treatment.

Purpose To investigate the fat-water content of Achilles tendon xanthomas at baseline and after treatment and to compare this assessment with that of ultrasonography (US) and other magnetic resonance (MR) imaging-based parameters. Materials and Methods Forty-eight Achilles tendons with clinically apparent xanthomas in 24 patients with familial hypercholesterolemia (FH) (six men, 18 women; mean age ± standard deviation, 58 years ± 9) were compared with 20 Achilles tendons in 10 control subjects without FH (two men, eight women; mean age, 62 years ± 7). US imaging measurements (thickness, width, cross-sectional area, echogenicity) and 3.0-T MR imaging measurements (thickness, width, cross-sectional area, volume, and fat-water separation) of the Achilles tendons were obtained at baseline and in patients with FH at 3 and 6 months after treatment with probucol, a cholesterol-lowering agent. Nonparametric tests compared baseline data, whereas repeated-measures analyses assessed treatment change. Results At baseline, all US and MR imaging-based parameters were higher in xanthoma tendons compared with those in control tendons (all P < .05). The mean relative water content per unit volume was 71% higher (42.0% ± 6.7) in xanthoma tendons than in control tendons (24.5% 6 5.8; P < .001). After 6 months of cholesterol-lowering treatment, only MR imaging measurements of tendon volume (P = .007), relative fat (P = .041), and relative water content (P < .001) showed significant changes. As relative tendon fat content decreased with treatment, relative water content increased. Conclusion Most of the enlargement of Achilles tendon xanthomas is due to an increase in water content rather than fat. For depicting treatment change, relative tendon water content was the most sensitive parameter, followed by tendon volume and relative tendon fat content. © RSNA, 2017 Online supplemental material is available for this article.