Historical background and definition
As early as 1851,
Virchow noted a striking five-fold left-sided preponderance for lower extremity deep venous thrombosis (DVT).
[1] It was not until the seminal cadaveric study by May and Thurner in 1957 that comprehensive description of the anatomy underlying this peculiarity was provided.
[2] Namely,
compression of the left common iliac vein (LCIV) by the overlying right common iliac artery (RCIA,
Fig.
1,2).
The authors postulated that venous 'spurs' arose through a combination of chronic mechanical compression and endothelial disruption from adjacent arterial pulsations.
Thus,
by fulfilling two elements of Virchow's triad,
this entity represents an anatomical substrate for DVT.
Fig. 1: CT venography below the level of the common iliac artery and vein bifurcation. Note the reduced enhancement of the left common iliac vein (LCIV) compared to the right (RCIV), indicating thrombosis, and its position below the right common iliac artery (RCIA). The left common iliac artery is marked (LCIA).
Fig. 2: Multiplanar line-of-flow CT scan reconstructions of the inferior vena cava and left iliac vein demonstrate compression of the left iliac vein by the right iliac artery against the fifth lumbar vertabra. Arrow, Right iliac artery; arrowhead, = left iliac vein.
References: Kibbe M et al. (2004) Iliac vein compression in an asymptomatic patient population. Journal of Vasc Surg 39(5):937-943
May-Thurner,
or iliac vein compression,
syndrome (MTS) now encompasses a wider spectrum of pathology; rarer variants have been described,
including compression of the right common iliac vein by the right common iliac artery.
Epidemiology
MTS prevalence is unknown due to its potentially silent nature,
and is often overlooked in the investigation of left iliofemoral DVT.
It most commonly occurs in females,
and in the 2nd-4th decades of life.
Studies suggest that MTS is an under-appreciated syndrome; up to 15% of patients with left chronic venous disease have evidence of MTS.
[3]
Current Issues
The existing evidence for radiological MTS diagnosis is heterogeneous with often small-scale,
retrospective studies,
and little consensus regarding diagnostic algorithms.
A key shortcoming is failure to ascertain what constitutes a significant narrowing and the apparent dynamic nature of LCIV compression.
[4]
Knowledge of the variety of existing imaging modalities,
their applications,
and how to address negative findings is particularly important in this cohort.