Adventitial Cystic Disease of the Common Femoral VeinA Rare Mimic of Deep Venous Thrombosis: A Case Report

Background: Clinicians usually can identify the cause of unilateral lower extremity swelling, but even experienced clinicians can be misled by rare causes of this condition. Objective: To describe unilateral lower extremity swelling that can be mistaken for deep venous thrombosis. Case Report: A 31-year-old woman presented to the emergency department with a 4-day history of painless, progressive right lower extremity swelling and paresthesia. Her medical history was significant for a first-trimester miscarriage and for pulmonary embolism during another pregnancy. She was hemodynamically stable. Her examination was remarkable for tense edema of the entire right leg, accompanied by erythema, calor, and distention of superficial veins, with no evidence of neurologic or vascular compromise. Low-molecular-weight heparin therapy for suspected deep venous thrombosis was administered, and she was discharged home with arrangements for urgent Doppler ultrasonography as an outpatient. Doppler ultrasonography of the right lower extremity demonstrated moderate compression of the right common femoral vein due to a circumferential, hypoechoic, avascular lesion (Figure). The patient was admitted to the hospital for further assessment and management. Computed tomography of the pelvis demonstrated a 2.01. 6cm, fluid-filled structure with almost complete occlusion of the right common femoral vein and associated enlargement of the superficial femoral and greater saphenous veins. Aspiration yielded a viscous, serous, mucinous fluid. She was diagnosed with adventitial cystic disease of the common femoral vein and had surgical resection of the cyst. Pathology tests confirmed a benign, adventitial cystic mass with no epithelial lining of the cyst wall. She tolerated the surgery, and her symptoms resolved. Figure. Ultrasonography and computed tomography findings for 31-year-old woman with unilateral leg swelling. A. Transverse sonographic image of the right common femoral artery (red arrow) and vein (blue arrow), without color Doppler assessment. The common femoral vein is extrinsically compressed by a surrounding anechoic, bilobed structure, corresponding to the adventitial cyst (yellow arrows). B. Transverse sonographic image of the right common femoral vein (blue arrow), with color Doppler assessment. The common femoral vein is extrinsically compressed by a surrounding anechoic, avascular, bilobed structure, corresponding to the adventitial cyst (yellow arrows). C. Transverse axial contrast-enhanced computed tomography image at the common femoral artery (red arrow) and vein (blue arrow). The common femoral vein demonstrates luminal narrowing from extrinsic compression by the surrounding bilobed, fluid attenuating cystic structure, corresponding to the adventitial cyst (yellow arrows). D. Sagittal sonographic image of the right common femoral vein (blue arrow), with color Doppler assessment. The common femoral vein is extrinsically compressed by a surrounding anechoic, vascular, bilobed structure, corresponding to the adventitial cyst (yellow arrow). Discussion: Adventitial cystic disease is a rare disorder that can affect arteries and veins. Arterial disease often presents with claudication, and venous disease manifests as unilateral, painless swelling of the affected limb (1). Disease of the venous system was first described in 1973, and fewer than 40 cases have been reported since (2). Most cases involve the lower limb, particularly the common femoral vein (2). Adventitial cystic disease is commonly mistaken for deep venous thrombosis; however, its symptoms do not resolve with anticoagulation (24). The disease results from a mucinous cyst formed in the vein adventitia that pathologically and structurally resembles ganglion cysts of the musculoskeletal system (5). As the cyst expands over time, it damages the elastic tissue of the vein wall, inducing fibrosis and leading to mechanical compression and obstruction, causing distal edema (5). Ultrasonography can usually identify the cyst (2, 4). Computed tomography and magnetic resonance imaging are helpful in further characterizing the cyst and can assist with surgical planning (2, 4). Management options include simple drainage of the cyst or surgical resection. The latter is preferred given the risk for recurrence after aspiration (25). Resection of larger cysts sometimes warrants prosthetic or autologous vein grafts to restore continuity of the vein (2, 3).