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Lipomas are benign, encapsulated, soft-tissue tumours composed of well-differentiated adipocytes. They arise in the subcutaneous tissue typically on the back, shoulder and neck. Lipomas have been known to cause symptomatic obstruction to venous flow by compression. We report a case of venous obstruction syndrome due to a small lipoma within the femoral sheath.
Lipomas are benign, encapsulated, soft-tissue tumours composed of well-differentiated adipocytes. They are the most common soft tissue tumour arising in the subcutaneous tissue typically on the back, shoulder and neck. They can also originate in more atypical sites as long as adipose tissue is present. Lipomas have been known to cause symptomatic obstruction to venous flow by compression. There are reports of pelvic lipomas,1 pelvic lipomatosis2 and intravascular femoral vein lipomas3 all causing significant venous outflow obstruction. We report a case of venous obstruction syndrome due to a small lipoma within the femoral sheath.
A 47-year-old man presented with a 12-month history of noticeable unilateral swelling of his left leg. The swelling had been fairly constant and the only exacerbating factor in his history was intermittent, long-distance flights. There was no past history of deep vein thrombosis or trauma to his leg. He was a type 1 diabetic on insulin and had had spinal surgery 11 years previously for right-sided sciatica, which had left him with some residual weakness on the right side. Nine months previously, he had sustained trauma to his chest by falling onto his left side. At this time, an ultrasound scan and computed tomography (CT) identified two fractured ribs but no other pathology.
On examination, he weighed 92 kg with large legs. There was obvious asymmetry of his legs, and circumferential measurements of his calves 10 cm below the tibial tuberosity and 10 cm above the medial malleolus revealed the left side to be 2 cm greater than the right. The left calf also had a brawny discolouration in the gaiter area with pitting oedema, but no varicose veins or other stigmata of venous hypertension. Peripheral pulses were normal and the only neurological deficit was some residual weakness of plantar flexion on the right side from his spinal surgery.
A duplex scan was performed and identified normal long and short saphenous veins with no perforator incompetence. There was no evidence of new or old deep vein thrombosis or venous reflux, and no lymphadenopathy. The only detectable abnormality in the left leg was loss of the normal variation of venous flow with ventilation when the patient was supine. A provisional diagnosis of lymphoedema was made but this did not fit with the duplex findings and clinical picture. A CT scan was, therefore, performed.
The CT scan confirmed normal abdominal organs and no pelvic mass or lymphadenopathy. The iliac veins were patent but the left common femoral vein was severely compressed as it passed over the left superior pubic ramus (Fig. 1). The cause appeared to be a 2.5 × 2 cm lipoma lying immediately anterior to the vein and medial to the left common femoral artery. The probable lipoma was of slightly lower attenuation than the surrounding fat and was contained by a thin capsule.
Surgery was performed through a groin incision. The left common femoral vein was exposed within the femoral sheath. The lipoma was found within the sheath, wedged under the inguinal ligament, causing compression of the vein. On removing the lipoma, the left common femoral vein expanded to a normal appearance. The patient made a fairly uneventful recovery apart from a superficial wound infection. Four weeks postoperatively, the left leg was feeling much improved with resolution of the calf swelling. A repeat duplex scan showed a return to normal flow pattern within the left common femoral vein.
Histology showed a well circumscribed piece of fatty tissue measuring 6 × 3 × 1.5 cm consistent with a benign lipoma.
A lipoma occurring within the femoral sheath causing symptomatic venous outflow obstruction is rare and, as far as we are aware, unreported in the medical literature. Unilateral leg swelling can be a result of venous obstruction syndrome, post-thrombotic syndrome, lymphoedema or arteriovenous fistulae. Venous obstruction commonly occurs from compression on the iliac or femoral veins secondary to pelvic tumours, retroperitoneal fibrosis, aneurysms, femoral hernia, pregnancy or, as in our case, a lipoma. Lipomas causing venous outflow obstruction have been previously reported. They may either cause obstruction by direct extrinsic compression1,4 or they originate from the vessel wall and cause intraluminal flow impedance.3,5 In our case, the lipoma was contained within the fairly non-expandable femoral sheath and, therefore, produced a significant compression effect to venous flow in the common femoral vein resulting in leg swelling.
This case also highlights the usefulness of a careful duplex examination to identify variations in the normal venous flow. During breathing, the venous flow will vary with inspiration and expiration. On inspiration, the venous flow will reduce and can even reverse slightly, on expiration venous flow will increase (Fig. 2). The degree of swing will depend on how deeply the patient is breathing. In this case, the swing was dampened due to the lipoma within the femoral sheath. When analysing the venous duplex trace, identification of the normal variation due to breathing or, indeed, its attenuation can be a useful diagnostic clue. CT and MRI scanning also provide additional information for diagnosis and planning of treatment.