Underlying Anatomy and Typing Diagnosis of May-Thurner Syndrome and Clinical Significance: An Observation Based on CT

Abstract

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.

Figure 1

CT image of a female of age 40 years of control group. The map displayed the diameter (white line) of the left iliac vein tunnel (IVT, big red arrow) 6.20 mm, which was measured on the central cross-sectional CT image of the left iliac vein stretching across the anterospine from right to left. The anterior border of the IVT is the posterior wall of the right iliac artery (the front small red arrow); the posterior border is the anterior margin of the vertebral body (the rear small red arrow).

Figure 2

Low lumbar lordosis angle (red arrow) 132.62° measured on the reconstructed sagittal plane image from the same object as Figure 1. One side of the angle is perpendicular to the superior border of the third lumbar and the other is the vertical of the superior margin of the first sacral vertebrae.

Figure 3

Diameter of the iliac vein tunnel (IVTD) 2.83 mm (arrow) of a 46-year-old female with simple MTS. No signs of degenerative changes oppressing the left iliac vein were found on the transection CT image. Therefore, the IVTD of the patient was deemed primary stenosis.

Figure 4

Low lumbar lordosis angle 123.33° (arrow) of the same patient as Figure 3. In addition, no signs of low lumbar degeneration-related iliac vein compression were found on the sagittal plane image.

Figure 5

CT from a 68-year-old female with lumbar generation-related MTS presenting the diameter of the iliac vein tunnel 2.78 mm (arrow).

Figure 6

Low lumbar lordosis angle 117.86°of the same patient as Figure 5. The sagittal plane image demonstrated degenerative lower lumbar slippage (bifid arrow). The iliac vein tunnel (IVT) became narrow owing to the forward shift intervertebral disc of the fourth and fifth vertebral bodies, which caused the iliac vein compression (arrow). Thus, the IVT of the patient was considered secondum stenosis.

Figure 7

CT from a patient of age 67 years with lumbar degeneration-related MTS and presented the osteophyte (arrow) at the right front of the fifth lumbar protruding forward the iliac vein tunnel (IVT), which caused an acquired (or secondum) stenosis of the IVT.

Figure 8

Map of intravenous balloon dilatation by digital subtraction angiography of the same patient as Figure 7, and showed a stenosis of the vein cavity corresponding to the osteophyte site (arrow).