Underlying Anatomy and Typing Diagnosis of May-Thurner Syndrome and Clinical Significance

STUDY DESIGN Cross-sectional study. OBJECTIVE To explore the underlying anatomy of May-Thurner syndrome (MTS) using computed tomography (CT) and discuss its clinical significance for typing diagnosis. SUMMARY OF BACKGROUND DATA Because the anatomical position of the corpse cannot fully illustrate the actual clinical situation in vivo, the diversity of MTS has not been fully elucidated yet. METHODS We retrospectively analyzed the data of 69 patients with MTS. By CT showing, patients were categorized to simple MTS (sMTS, 22 patients), lumbar degeneration-related MTS (dMTS, 33 patients) and other causes MTS (oMTS, 14 patients); meanwhile, a healthy control group were set. Evaluated indexes were onset age, course of disease, diameter of the iliac vein tunnel (IVTD), lumbar degeneration-related iliac vein compression (IVC), therapeutic effect, and diagnostic cutoff of risk IVTD prone to MTS. RESULTS The onset age of sMTS, dMTS, and oMTS were respectively 42.3 ± 6.5 years, 61.5 ± 10.6 years, and 53.1 ± 16.8 years (P < 0.001); courses were respectively 12.1 ± 9.2 days, 22.5 ± 7.6 days, and 6.8 ± 6.7 days (P = 0.002). IVTDs of sMTS, dMTS, oMTS, and the control were respectively 2.52 ± 0.50 mm, 2.29 ± 0.30 mm, 5.93 ± 2.21 mm, and 4.34 ± 1.61 mm (P < 0.001). Lumbar degeneration-related IVC in dMTS occurred at 41 places, including forward bulging or protruding intervertebral discs (51%,17/33), osteophytes (50%,16/33), and spondylolisthesis (19%, 8/33), but none happened in sMTS, oMTS, and the control. Eighty-six percent of sMTSs, 55% dMTSs, and none oMTSs needed intravenous stent-implanted operation to obtain effective treatment. MTS type (Waldχ = 6.092, P = 0.009), course (Waldχ = 4.618, P = 0.032), and treatment plan (Waldχ = 14.748, P < 0.001) markedly influence the therapeutic result. The cutoff of risk IVTD for sMTS and dMTS was 2.98 mm, which diagnostic sensitivity was 90% and specificity 100%. CONCLUSION Owing to the distinct pathoanatomy and causes, diagnosis in classification of MTS by CT is helpful in accurate treatment program. LEVEL OF EVIDENCE 3.