ObjectiveKlippel-Trenaunay syndrome (KTS) is a congenital mixed mesenchymal malformation syndrome that includes varicose veins, capillary and venous malformations, lymphatic abnormalities, and hypertrophy of various connective tissue elements. The purpose of the present study was to describe the clinical characteristics and outcomes in a subset of patients with KTS in whom venous interventions, including iliofemoral venous stenting, were performed after failure of conservative therapy. MethodsA single-center retrospective data review of 34 patients with KTS who had undergone interventions for venous disease between January 2000 and December 2020 was performed. ResultsTheir mean age was 38.4 ± 17.5 years (range, 12-80 years). No gender predilection was found. Of the 34 patients, 61% had had all three features of the classic triad for KTS. Varicose veins were present in all 34 patients (100%), and 30% had had a history of bleeding varicosities. Most patients (79%) had CEAP (Clinical, Etiology, Anatomy, and Pathophysiology) class ≥C4. Of the 34 patients, 30% had a history of deep vein thrombosis and/or pulmonary embolism. Factor VIII elevation was the most common thrombophilia condition (12%). The venous filling index was elevated at baseline (5.9 ± 5.1 mL/s) and did not normalize despite intervention (3.5 ± 2.3 mL/s; P = .04). The superficial venous interventions (n = 35) included endovenous laser therapy; stripping of the great saphenous vein, small saphenous vein, anterior thigh vein, or marginal vein; ultrasound-guided sclerotherapy; and stab avulsion of varicose veins. One coil embolization of a perforator vein was performed. Deep interventions (n = 19) included endovenous stenting (n = 15), popliteal vein release (n = 3), and valvuloplasty (n = 1). The venous clinical severity score had improved from 9.4 ± 4.5 to 6.2 ± 5.6 (P = .04). The visual analog scale for pain score had improved from 5.5 ± 2.7 to 2.5 ± 3.3 (P = .008). Healing of ulceration was noted in 75% of the patients. Significant improvements in the total pain (P = .04) and total psychological (P = .03) domains were noted in the 20-item chronic venous disease quality of life questionnaire. ConclusionsSuperficial and deep venous interventions are safe and effective in patients with KTS when conservative therapy has failed. Iliofemoral venous stenting is a newer option that should be considered in the treatment of chronic deep venous obstructive disease in patients with KTS in the appropriate clinical context. An aggressive perioperative deep vein thrombosis prophylaxis protocol should be in place to reduce thromboembolic complications in these patients.