A 17-year-old healthy girl presents to the pediatric emergency department (ED) with a 1-week history of diffuse, achy lower back pain. She reports that the pain began after dance practice. Two days ago, she developed sharp pain radiating down her left leg, which is now causing difficulty walking. She denies fever, recent illness, changes in bowel habits, abdominal pain, dysuria, hematuria, numbness and tingling in extremities, or vaginal discharge. Her medications include monthly medroxyprogesterone acetate injections for contraception. She denies recent trauma and recent travel and is up to date on vaccinations. She has no personal or family history of coagulation disorders.In the pediatric ED, the patient is well appearing and in no acute distress. Initial vital signs include a temperature of 37.8 °C, heart rate of 132 beats/min, respiratory rate of 20 breaths/min, blood pressure of 135/89 mm Hg, and oxygen saturation of 100% on room air. Her examination is notable for diffuse tenderness of the lower back, most pronounced in the left paraspinal region, with mild midline tenderness in the lumbar region, and no overlying skin changes. The patient’s entire left lower extremity is erythematous and edematous, with mild calf tenderness. Her dorsalis pedis pulses are 3+ bilaterally, and capillary refill is less than 2 seconds. Her straight leg test does not elicit any pain or limitation. A neurological examination reveals mild weakness in left leg elevation and hip extension, with normal sensation. She ambulates independently with a mild limp.Her initial laboratory test results are notable for leukocytosis with a white blood cell count of 18.6 × 103/μL (reference range, 4.4–10.5 × 103/μL) with a neutrophil predominance of 85.8% (reference range, 41.2% 76.7%). Her prothrombin time is 16.3 seconds (reference range, 12.3–14.9 seconds), C-reactive protein (CRP) is 180.7 mg/L (reference range, 0.0–5.0 mg/L) and D-dimer greater than 20.00 μg/mL fibrinogen equivalent units (FEU) (reference range, 0.00–0.49 μg/mL FEU). A urinalysis is unremarkable, and her urine pregnancy test is negative. Considering her persistent tachycardia, further studies are obtained. Her thyroid studies, creatine kinase, troponin I, and pro-BNP levels are all within normal range. An electrocardiogram is obtained, which shows sinus tachycardia without signs of right heart strain.Venous Doppler ultrasonography of the left lower extremity reveals an extensive occlusive thrombus in the left femoral popliteal venous system. A computed tomography (CT) angiogram of the chest reveals extensive pulmonary emboli (PE) involving the left main pulmonary artery and segmental branches (Figure 1). The patient is admitted to the pediatric intensive care unit (PICU) for anticoagulation treatment. Additional testing confirms the diagnosis.This 17-year-old girl who presents with 1 week of lumbar back pain and 2 days of left lower extremity pain was subsequently found to have a deep vein thrombosis (DVT) and PE. Venous thromboemboli (VTE) are an uncommon finding in healthy pediatric patients and often signal an underlying pathologic condition that disrupts one or more components of Virchow’s triad: blood stasis, endothelial injury, and/or a hypercoagulable state.1The patient is on monthly medroxyprogesterone acetate injections for contraception. Although some studies demonstrate a slightly increased risk of thromboembolic events,2 its progesterone-only composition carries a lower VTE risk compared with estrogen-containing contraceptives.3Occult malignancy is a key consideration for unexplained VTE in the pediatric population,4 particularly acute lymphoblastic leukemia.5 However, this is less likely given the patient’s complete blood count results and the lack of systematic symptoms like fever, fatigue, and weight loss.Infections, particularly bacteremia, can increase VTE risk by promoting inflammation and endothelial injury.6 A primary spinal infection such as osteomyelitis, discitis, and spinal epidural abscess may explain the patient’s back pain, leukocytosis with neutrophilia, and potential embolic phenomena; however, this is made less likely by the patient’s lack of fever.Underlying chronic inflammatory conditions, such as systemic lupus erythematosus, inflammatory bowel disease, or rheumatoid arthritis, may predispose to VTE by creating a hypercoagulable state.6 This patient’s elevated white blood cell count and CRP raise the possibility of an inflammatory condition, but the absence of fever, systemic symptoms, or additional findings makes this diagnosis less likely.Genetic or familial hypercoagulable disorders may contribute to VTE risk.7 Of particular consideration is factor V Leiden, a genetic disorder characterized by a poor anticoagulant response to activated protein C and the most common inherited form of thrombophilia.8 Although the patient lacks a family history of hypercoagulability, further evaluation is necessary to exclude an inherited predisposition.Anatomic abnormalities and vascular malformations can lead to venous stasis and increase the risk of thromboemboli.7 These conditions often require further imaging and should be strongly considered.After admission to the PICU, a CT venogram (CTV) revealed compression of the left common iliac vein by the right common iliac artery and lumbar vertebrae at L4, consistent with May-Thurner syndrome (MTS) (Figures 2 and 3). The patient was maintained on twice-daily enoxaparin in the PICU. Echocardiography showed normal segmental anatomy without cardiac strain. She underwent thrombectomy of the left common iliac vein and iliac vein stenting in the interventional radiology suite. A thrombectomy for the PE was not performed due to the absence of cardiac strain. Her thrombophilia workup was negative including testing for prothrombin gene mutation, factor V Leiden, protein S, protein C, antithrombin III, and antiphospholipid antibodies.MTS is a vascular anatomic anomaly where the left common iliac vein is compressed between the lumbar spine and the overlying right common iliac artery (Figure 4). Chronic arterial pulsations induce shear stress on the venous endothelium, leading to fibrotic intraluminal bands, or spurs.9 Over time, this results in impaired venous return, and an increased risk of venous insufficiency, obstruction, or DVT, most commonly affecting the left iliofemoral vein.10,11MTS accounts for 2% to 5% of all DVT cases11,12 but is identified in up to 76% of patients with left-sided iliofemoral DVT.9,13 Women aged 20 to 50 years are disproportionately affected.11,12 Hormonal factors—including oral contraceptive use and pregnancy—as well as immobilization, recent surgery, or trauma can further increase susceptibility to thromboembolic events in patients with MTS anatomy.14–16MTS anatomy is common and is most often asymptomatic due to compensatory venous collaterals.17–19 When symptomatic, acute presentations include sudden left lower extremity pain and swelling, often aggravated by venous claudication and relieved with rest or elevation. Chronic symptoms may include persistent venous claudication, hyperpigmentation, varicose veins, or venous ulcers. Rarely, patients with MTS may present with back pain in the lumbar area, at the location of the venous obstruction.20 In this case, the patient’s predominantly left-sided back pain overlying L4 to L5 corresponds with the anatomical location of iliac vein compression. Women more commonly present with acute DVT or PE, whereas men often report chronic pain or edema.12MTS should be suspected in any young, healthy patient presenting with a left lower extremity DVT. Initial imaging with color venous duplex ultrasonography (CVDU), a noninvasive tool with high sensitivity and specificity for detecting proximal DVT, can identify proximal DVT but may not adequately visualize venous collaterals or the inferior vena cava or iliac vein compression in patients with larger body habitus or other obstructive factors.14,21–24When CVDU results are inconclusive, CTV or magnetic resonance venography (MRV) is recommended for detailed visualization of venous anatomy, including intraluminal spurs, stenosis, and collateral pathways.25–28 Both modalities offer more than 95% sensitivity and specificity for diagnosing MTS.25,29,30 Although CTV is preferred due to its widespread availability and superior imaging clarity, it may overestimate stenosis in dehydrated patients and is contraindicated during pregnancy.25,27 MRV, although safe for pregnant patients and better at visualizing soft tissues, is less readily accessible and more expensive.26,31Management of MTS is determined by the severity of symptoms and the presence of thrombosis. For asymptomatic or mildly symptomatic patients without thrombosis, conservative measures such as compression stockings and elevation of the affected limb are sufficient, along with prothrombotic risk counseling and close monitoring.32–34For symptomatic nonthrombotic MTS, angioplasty and venous stenting are the primary treatments to relieve venous compression and restore proper blood flow (Figure 5).21,32 These interventions have proven effective in improving symptoms and preventing further complications.35,36Patients with thrombotic MTS typically require anticoagulation therapy, beginning with unfractionated heparin followed by low-molecular-weight heparin or direct oral anticoagulants.37–39 Severe cases may require catheter-directed thrombolysis or mechanical thrombectomy prior to stenting to resolve the thrombus and reduce the risk of post-thrombotic syndrome.40,41 If thrombolysis is contraindicated, mechanical or open surgical thrombectomy followed by angioplasty and stenting is recommended.21,33,42,43In rare cases where endovascular procedures fail, reconstructive surgical options such as saphenofemoral crossover bypass, cross-pelvic venous bypass, femoro-femoral prosthetic bypass, and other reconstructive techniques may be necessary to address persistent venous obstruction.11,32 Long-term anticoagulation is advised after interventions to prevent recurrence.11,44Although MTS typically presents with left lower extremity pain and swelling, the mild neurologic deficit noted in this patient—specifically weakness in leg elevation and hip extension—is atypical and not commonly described in the literature as a presenting symptom. Regardless, the patient recovered well, regained full strength of her bilateral lower extremities, and was discharged home on twice-daily enoxaparin.Consider May-Thurner syndrome in the differential diagnosis of back and leg pain in otherwise healthy patients (especially young female patients). A thorough history and physical examination is the first step in differentiating musculoskeletal pain and/or sciatica from more serious etiologies.Any young, healthy patient with a DVT of the left lower extremity should raise suspicion for May-Thurner syndrome.
Grubner et al. (Sun,) studied this question.