Discussion
May-Thurner syndrome (MTS) is a condition in which the left common iliac vein is compressed between the right common iliac artery and the lumbar vertebrae. The chronic pulsatile pressure on the vein leads to endothelial damage, intimal proliferation, and fibrin replacement, resulting in luminal stenosis and fibrosis, and in severe cases, complete occlusion would be expected (6). The prevalence of this anatomical variation is reported as up to 20% in the general population (7), and Over 25% of the asymptomatic population show more than 50% stenosis of LCIV in their screening CT-scan (8). The symptoms could include a range from asymptomatic iliac vein stenosis, to symptoms of chronic vein stasis of the lower limb such as pain, swelling, varicose veins, and pelvic congestion syndrome. It’s also possible to develop acute deep vein thrombosis (DVT), with the following complications such as post-thrombotic syndrome (9). MTS often occurs in women in their 20 and 30s, and is more common in the left leg, although some cases of the right side or bilateral MTS have been reported (10). The diagnosis of MTS is based on initial duplex ultrasound for assessment of the presence of any DVT, but the optimal visualization of the venous system is made by CT or MR venography, which let us directly visualize the compressive effect of the artery on the vein, and also the possible collateral formation due to chronic obstruction of the venous return flow (11). However, the gold-standard test for diagnosis is invasive venography, especially with IVUS usage, where we can preciously determine the intraluminal area and diameters (12). Most of the patients initially have lower limb venous hypertension but haven’t any symptoms, but gradually they would experience some tightness and heaviness in their legs, especially after long hours of standing. The recommended treatment for MTS is venoplasty with a stent implantation (13). In a systematic review of 1569 patients with an established diagnosis of MTS, the endovascular interventions were performed more than surgical procedures or medical treatment, while the results showed open surgery was associated with significantly higher complications compared to interventional procedures (p=0.021) (14). In a study by Khalid Bashar et al., five years follow-up of 782 patients after stenting of the CIV due to symptomatic non-thrombotic iliac vein lesions, showed a 94% of stent patency rate (15).
We faced a previously unknown case of MTS, with several pelvic collaterals, which led to the misdirection of the wire into the renal parenchyma. Jenab et al. reported a 40 years old lady with a previously known history of symptomatic MTS, who had undergone iliac venoplasty with stenting, and during the procedure, a secondary spinal epidural hematoma was developed because of the misdirection of a 0.035-inch hydrophilic stiff wire into the paraspinal space throughout the collateral network of vertebral-pelvic venous plexus. The patient complained of severe back pain 12 hours after the procedure and developed an abrupt loss of sensory-motor function in the upper and lower extremities. MRI showed the epidural hematoma from cervical to lumbar spaces, which was treated with emergent laminectomy and hematoma removal (16). In our case, as a result of the inappropriate wiring, severe hematuria was developed, due to continuous blood flow, from a higher-pressure space of the iliac vein into a lower-pressure space of the renal pelvis. Lattimer et al. studied the hemodynamics of the femoral vein in individuals with venous outflow resistance (such as MTS patients) and concluded that in these circumstances, hemodynamic velocity parameters of the femoral vein are markedly increased (17). With this regard, the heart team decided to perform balloon venoplasty of the left CIV. After the procedure, the collateral vessels were gone, possibly due to a significant decrease in the femoral vein pressure. A few hours later, hematuria was stopped as a result of the cessation of collateral blood flow.