A 57 year-old woman presented with an 18- month history of unilateral painless left leg swelling exacerbated by prolonged standing. USG showed a 3cm cystic lesion in the inguinal region and no evidence of DVT (Figure 1). CT demonstrated a thin-walled, well-defined 3 x 2 cm oval structure just posterior to the left common femoral vessels (Figure 2).

Figure 1: Hypoechoic 3 cm cystic structure
identified on USG.

Fig 2: CT showing cystic lesion (arrowed)
compressing left femoral artery and vein.

Exploration of the left groin was performed demonstrating a cyst medial to the femoral vessels at the level of the SFJ. Mucinous fluid was evacuated from the cystic mass.

Fig 3: Intra-operative exploration showing
cyst, femoral artery and femoral vein.

Histology showed marked paucicellular proteinaceous material with macrophages and fat necrosis, suggestive of synovial origin. Surgical resection was able to resolve patient’s symptoms and follow-up was unremarkable.

Cystic compression of the femoral vein can be of two separate etiologies: adventitial versus synovial. The difference lies in the pathophysiology and operative strategies (AS5/S1). ACD is more common arterial, with popliteal artery being the most common (ACS1-2-6). Venous ACD is rare and mostly seen in the ileofemoral veins (ACS 2-3-6-7).

Joint synovial cysts are more frequently found at the wrist, ankle or knee, with hip being rare (S2). Proposed etiologies have been attributed to underlying connective tissue disorders, repetitive trauma and aganglionosis of synovial cells (ACS2- 7). Synovial cysts are proposed to develop secondary to chronic effusion, such as RA and osteoarthritis (AS5).

In most cases, a communication with the hip joint can be identified (AS5/S3). Both can be uniocular or multiocular, and contain mucin-rich material (AS5, ACS7). The cyst wall has been described as being composed of fibrous connective tissue devoid of any epithelial lining (AS5, ACS1-4-5-6-7S4). ACD of femoral veins and joint synovial cysts usually present similar to DVT (ACS6). Usual presentation is that of insidious onset of edema in the lower limb associated with or without a painless, non- pulsatile inguinal mass (ACS4-5/S1).

Phlebography is the diagnostic modality of choice, which shows proximal extrinsic compression of the vein with distal dilation

(ACS4). However, these findings are also similar for synovial cysts, and definitive diagnosis can only be done during surgery (ACS4). CT/MRI have also been successful (AS5/S1/ACS6).

In the case of adventitial cysts, treatment choices range from ultrasound-guided percutaneous aspiration to simple resection (ACS 2-3-5). In the case of synovial cysts, needle aspiration or surgical resection are treatment options (S1).

Even though unilateral leg swelling almost always points to DVT as a strong clinical suspicion, it is important to identify rarer causes. Differentiating between synovial and adventitial cysts becomes important in their operative strategy, and can be done by thoroughly examining the patient’s history, radiological studies and intra-operative findings.

1. ACS 1:(S) Sugimoto T, Yamamoto K, Tanaka S, Saitou N, Kikuchi C, Motohashi S, et al. Adventitial cystic disease vein presenting as deep vein thrombosis: a case report and review of the literature. J Vasc Surg 2006; 44:871-874
2. ACS 3: Jayaraj A, Shalhub S, Deubner H, Starnes BW, Washington S. Cystic Adventitial disease of the common femoral vein. Ann Vasc Surg 2011; 25: 558.e9- 558.e11
3. ACS6: Johnson JM, Kiankhooy A, Bertges DJ, Morris CS. Percutaneous image- guided aspiration and sclerosis of adventitial cystic disease of the femoral vein. Cardiovasc Intervent Radiol 2009; 32:812- 816 jerafsonline@gmail.com Fall Ed. 2013 6.
4. ACS7: Lee C-H, Lin S-E, Chen C-L. Adventitial cystic disease. J Formos Med Assoc 2006; 105(12):1017-1021.
5. S3: Huang H-T, Tsai I-C, Cheng S-B, Chen C C-C. Unilateral lower limb swelling caused by a synovial cyst of the hip joint. Tzu Chi Med J 2012; 22(1): 65-67.
6. S4: Bhan C, Corfield L. A case of unilateral lower limb swelling secondary to a ganglion cyst. Eur J Vasc Endovasc Surg 2007; 33:371-372