May-Thurner syndrome (MTS) is characterised by compression of the left external iliac vein by overriding right common iliac artery resulting in venous stasis. It carries a higher risk of left iliofemoral deep vein thrombosis (DVT), however the prevalence and management guidelines are unclear in pediatrics. We reviewed the prevalence of MTS in children diagnosed with left iliofemoral DVT at our center, associated prothrombotic risk factors and their clinical outcomes.


This is a retrospective audit of pediatric patients (<18 years) with left iliofemoral DVT treated at the IWK Health Center from January 1 2008 to December 31 2020.


Twelve pediatric patients with left iliofemoral DVT were identified at our center and all patients except one had MRV/CTV during their course of anticoagulation to evaluate for MTS. MTS was diagnosed on imaging in 8 of the eleven evaluable patients with DVT and one patient had an incidental diagnosis of MTS with no DVT. The median age at diagnosis of MTS was 15 years (13-16), male:female ratio of 1:8. The overall prevalence rate was of MTS was 72.72% (8/11) in patients with left iliofemoral DVT. All patients with iliofemoral DVT and MTS had at least one other prothrombotic risk factor- initiation of estrogen containing contraceptive pills in the preceding 3 months of the DVT (n=5), inherited thrombophilia (n=2) and obesity (n=2).

All patients with MTS were referred to vascular surgery. Only one patient required catheter directed thrombolysis and stenting at presentation of DVT, the remaining 7 patients were managed with anticoagulation alone. Complete (n=1) or partial (n=7) resolution of the thrombus was seen in all 8 patients. Median duration of follow up was 3 years. Recurrent DVT was seen in 1 patient and two patients came off anticoagulation at 6 months post therapy. Post thrombotic syndrome was seen in 4 patients, mild in 3 and moderate in 1; as per modified Villalta score.


We observed a high prevalence of MTS in patients with left iliofemoral DVT which may be due our screening approachwith upfront radiographic evaluation for MTS in all patients with left iliofemoral DVT. A second pro-thrombotic risk factor was identified in all patients, which raises the possibility of a "two hit theory" for the occurrence of DVT in MTS. Compared to published adult studies, majority of our pediatric patients were managed conservatively with anticoagulation therapy alone.


No relevant conflicts of interest to declare.

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