May-Thurner Syndrome Should be Explored As a Possible Existing Risk Factor in Pediatric Patients Presenting with Non-Central Venous Line Associated Deep Vein Thrombosis
Authors: Mamauag Erica , Liang Cynthia , Magnan Katelin , Xavier Frederico 
Published: December 2023

Background:
The compression of the left common Iliac vein (LCIV) by the right common iliac artery is called May-Thurner Syndrome (MTS). The incidence of this anatomic variance is unknown, though it is estimated to be 18-49%. It is currently established that the chronic compression of the iliac vein outflow results in various clinical symptoms including edema, pain, discoloration, skin ulcers and venous thromboembolism. Deep vein thrombosis (DVT) of the LCIV is the most reported presentation of MTS in pediatrics. DVTs in pediatric patients are rare and often provoked by a central venous line (CVL). Patients without a CVL in the context of left lower extremity (LLE) DVT often do not undergo MTS work-up if the DVT does not include the LCIV. To assess if MTS is a risk factor for LLE DVT distally to the LCIV, we describe an institutional incidence of MTS in two pediatric patient populations: those with non CVL-associated LLE DVTs and a control group composed of pediatric patients undergoing imaging that includes the LLE vasculature for unrelated reasons.
Methods:
This was a single center retrospective study. We identified patients with a non CVL-associated LLE DVT seen at our institution using ICD-10 codes as well as a cohort of patients who received imaging of the LLE vasculature for reasons other than DVT using radiology MRI protocol codes.Electronic medical records were reviewed for demographic variables such as age and gender. Patients without DVTs had imaging reviewed for the incidental finding of MTS. Those with DVTs had information collected regarding clinical characteristics such as coagulation panels, thrombosis risk factors (thrombophilic states, oral contraceptive use, obesity), and therapy received. All images were reviewed by a pediatric radiologist.
Results:
A total of 35 patients with non CVL-associated LLE DVTs, and 752 patients without CVL and without LLE DVTs were identified. Of those with LLE DVTs, 19 (54%) were found to have MTS. Of these 19 patients, 5 (26%) were obese, 14 (74%) were on oral contraceptive pills, and 8 (42%) reported prothrombotic risks (7 heterozygous for Factor V Leiden, 1 heterozygous for protein C deficiency). Two patients (10%) had no additional risk factors for thrombosis. Of those without LLE DVTs, 6 patients (0.01%) were incidentally diagnosed with MTS. Interestingly we also described one patient with non CVL-associated LLE DVT distally to the LCIV with MTS.
Conclusions:
In our study, the presence of MTS was significantly higher in the non CVL-associated LLE DVT group than in the control group. This study suggests that MTS should be considered, and associated imaging performed, in pediatric patients with a non CVL-associated LLE DVT, considering the incidence revealed by this single institutional case series. The presence of MTS in pediatric patients may significantly impact the life-long risk of DVT recurrence. Given that aging adversely impacts lower limb venous return (exacerbated by central obesity, sedentary lifestyle, and other risk factors) and that pregnancy is a known trigger of DVT in patients with MTS, knowledge of prior MTS may impact patient care over the lifespan.