Keywords
May-Thurner syndrome - venous compression - osteophyte - thrombolysis - stent
Introduction
May-Thurner syndrome (MTS) classically refers to symptomatic venous outflow obstruction
of the left lower extremity, with or without venous thrombosis, due to external compression
of the left common iliac vein (LCIV) by the right common iliac artery (RCIA).[1]
[2] Chronic compression and pulsatile biomechanics lead to venous intimal injury, which
in turn causes obstruction and stenosis and can precipitate deep vein thrombosis (DVT).[1]
[2] This article presents an MTS variant in which prominent vertebral osteophytes compress
the involved iliac veins with or without contribution from the RCIA and LCIA. We highlight
the importance of considering different clinical and technical aspects when diagnosing
and treating this distinct MTS variant.
Classic Presentation and Treatment
Patients with MTS are typically teenagers or young adults and more commonly female.
They may present acutely with left lower extremity pain and swelling or with signs
of chronic venous insufficiency. When suspected, the presence and extent of DVT are
often initially assessed with Duplex ultrasound (US). Additional imaging can be considered
to confirm any underlying anatomic compression, including computed tomographic venography
(CTV), magnetic resonance venography (MRV), and/or catheter venography.[3] Pulmonary arterial phase computed tomographic arteriography (CTA) or magnetic resonance
arteriography (MRA) may be added if pulmonary embolism is suspected. Management of
patients with MTS with DVT includes anticoagulation, catheter-directed thrombolysis,
and/or angioplasty and stent placement at the obstructed site[4] ([Fig. 1]). Axial intravascular ultrasound (IVUS) is a useful adjuvant to plan stent placement
and subsequently evaluate treatment.
Fig. 1 A 16-year-old girl presented with acute left iliofemoral deep vein thrombosis. Iliac
digital subtraction venography (DSV) following thrombolysis demonstrated (A) extrinsic compression of the central aspects of the left common iliac vein (LCIV)
(arrowhead). Intravascular ultrasound (IVUS) (Volcano Corporation) confirmed (B) compression between the right common iliac artery (RCIA) (dashed outline) and lumbar
vertebral body (open star). Following angioplasty and placement of a 14 × 60-mm self-expanding
bare metal stent (Wallstent, Boston Scientific) (C), DSV demonstrated (D) reestablished in-line outflow. Completion intravascular ultrasound confirmed (E) venous expansion between the RCIA and lumbar vertebral body.
Clinical Consideration: Variant Demographics
Multiple studies have shown that classic MTS occurs more often in women of reproductive
age.[5]
[6] Although the relative frequency of osteophytic MTS variant across different demographic
groups is unknown, its incidence is expected to be higher in older patients, who are
more likely to experience degenerative spondylosis. When an older adult presents with
the first episode of unprovoked unilateral lower extremity DVT, particularly if iliofemoral
in distribution, an osteophytic MTS variant should be considered ([Fig. 2]).
Fig. 2 A 68-year-old man with a history of left lower extremity deep vein thrombosis presented
for inferior vena cava (IVC) filter placement given the need to withhold anticoagulation
prior to his spine surgery for thoracic compression fractures. During initial venography,
an obvious displacement and compression of the left common iliac vein (LCIV) by a
bulky lumbosacral osteophyte (open star) was noted along with transpelvic collaterals
(A, B). Retrospective review of a prior CT confirmed (C) compression of the LCIV between the osteophyte (open star) and the left common iliac
artery (LCIA) (black star).
Clinical Consideration: Variant Laterality
Outside of situs inversus anatomy, classic MTS occurs on the left side due to the midline crossing of the RCIA
and LCIV. Because of variable patterns of degenerative spondylosis, right-sided presentation
of iliofemoral venous occlusion does not exclude a variant of MTS. The clinical features
may be otherwise indistinguishable from classic MTS ([Fig. 3]).
Fig. 3 A 67-year-old man with a remote history of right lower extremity deep vein thrombosis
presented with symptomatic progressive right lower extremity varicose veins. Doppler
ultrasound demonstrated chronic occlusion of the right external iliac vein with valvular
incompetence of the right great saphenous vein. Physical examination showed diffuse
varicosities in the right lower extremity, groin, and pubic regions. Axial image from
the computed tomography (CT) venogram demonstrated (A) focal compression of the right common iliac vein (RCIV) between a bulky osteophyte
(open star) and the right common iliac artery (black star). Coronal 3DRA image from
a CT venogram demonstrated (B) inguinal and pubic varicosities as seen on physical examination. Initial catheter
venography demonstrated (C) near occlusion of the entire RCIV (open arrows) with a small residual channel and
abundant pubic collaterals. Digital subtraction venogram image post angioplasty and
stent placement demonstrated (D) reestablished in-line outflow.
Technical Consideration: “Pseudothrombus”
Bulky osteophytes may cause marginal extrinsic compression, mimicking mural thrombus
on digital subtraction venography ([Fig. 2]). Alternatively, a central impression on the vein may mimic the appearance of nearly
occlusive thrombus ([Fig. 4]). Failure to recognize the nature of this problem may result in delayed IVC filter
removal or prolonged anticoagulation therapy. When suspected, comparison to unsubtracted
images and/or repeat imaging in various obliquities may be clarifying. If those tactics
are insufficient, intravascular ultrasound or cone-beam CTV are useful problem-solving
tools.
Fig. 4 A 77-year-old man presented in cardiac arrest and was found to have pulmonary embolism.
Anticoagulation was complicated by intra-abdominal hemorrhage and an inferior vena
cava (IVC) filter was placed. One month later, the patient subsequently tolerated
oral anticoagulation and returned for filter removal. Venography prior to planned
filter removal demonstrated (A) an apparent filling defect within the left common iliac vein (LCIV) (open arrow)
with transpelvic collaterals (open arrowheads). This was interpreted as a residual
thrombus and the filter was left in place. He presented 1 month later for possible
filter removal at which time venography demonstrated the same finding. Intraprocedural
cone-beam computed tomography venography confirmed (B) compression and fenestration of the LCIV by a bulky vertebral osteophyte (open star)
and left common iliac artery (white star) causing a “pseudothrombus” appearance. The
filter was removed.
Technical Consideration: Stent Construct Reinforcement
Stent placement across the area of occlusion is widely considered a standard therapy
for MTS. The bony projections associated with the osteophytic MTS variant create a
smaller surface area of compression and fulcrum effect. As a result, the compressive
lesion may not respond as well to the same endovascular techniques. Despite initial
apparent technical success, excessive extrinsic compression may promote early stent
failure ([Fig. 5]). A stent or stent construct with higher radial force may be required to achieve
durable patency. Alternatively, analogous to stent failures seen in venous thoracic
outlet syndrome, the underlying musculoskeletal compressive etiology may need to be
addressed surgically.[3]
[7]
Fig. 5 A 75-year-old man with a history of peripheral artery disease status post aortobifemoral
graft placement presents with chronic left lower extremity swelling. Prior axial computed
tomography (CT) image demonstrated (A) compression of the left common iliac vein (LCIV) by a prominent lumbar disc-osteophyte
complex (open star). Initial venogram demonstrated (B) LCIV occlusion (open arrowheads) and prominent transpelvic collaterals. Venogram
post angioplasty and placement of a self-expanding bare metal stent (LifeStar Vascular
Stent, C. R. Bard, Inc.) demonstrated (C) restoration of in-line flow but thinning of the contrast column. On Doppler ultrasound
examination 1 week later, however, the LCIV stent was noted to be thrombosed. Sagittal
image from a subsequent CT venogram demonstrated (D) severe compression of the stent between a prominent lumbar disc-osteophyte complex
(open star) and the aortobifemoral bypass graft (black star). Following successful
pharmacomechanical thrombolysis, the stent was relined with a larger diameter self-expanding
bare metal stent (Wallstent, Boston Scientific) (E). Subsequent venogram demonstrated (F) restoration of in-line outflow. The stent complex remained patent on a follow-up
ultrasound at 5 months.
Conclusion
We present a classic case of MTS as well as four examples of osteophytic variants
with various clinical manifestations. In all cases, catheter venography confirmed
hemodynamically significant iliac venous stenosis or occlusion with visualization
of prominent collateral channels. Correlation with cross-sectional imaging demonstrated
degenerative vertebral osteophytes disc herniation as the culprit compressive lesions.
Various causes of iliac vein compression leading to MTS have been reported, including
gravid uterus,[5] ectopic kidney,[8] right iliac artery stent,[9] and orthopaedic hardware.[10] To the best of our knowledge, this variant of MTS in which bony structures are primarily
responsible for the iliac vein compression is underreported. This underrecognized
entity presents distinct diagnostic and therapeutic challenges compared with classic
MTS.
Main Points
-
MTS classically refers to symptomatic venous outflow obstruction of the left lower
extremity, with or without venous thrombosis, due to external compression of the LCIV
by the RCIA.
-
Typical treatment of MTS involves thrombolysis (when applicable) and placement of
a self-expanding bare metal stent across the compressive lesion.
-
An osteophytic variant of MTS may affect common iliac veins on either side, result
in venographic pseudolesions, and require placement of stent constructs with additional
radial force.
Ethical Approval and Conflict of Interest
All procedures performed in studies involving human participants were in accordance
with the ethical standards of the institutional and/or national research committee
and with the 1964 Helsinki declaration and its later amendments or comparable ethical
standards with waiver of consent. Each author declares that he/she has no conflict
of interest.
D. S. S., M. M., S. A., and E. J. M. have no financial disclosures or conflicts of
interest.
