This report describes a case of venous dissecting aneurysm presenting as a popliteal mass, in a 33 year old woman. A 1 × 1 × 0.5 cm lump developed early in the course of a second pregnancy. Primary venous aneurysms are rare vascular abnormalities that can affect either the superficial or deep veins, and have been described throughout the venous system. Most commonly found in the neck and central thoracic veins, they have also been found in visceral veins and extremities. There is a tendency for vascular disturbances to occur during pregnancy. The haemodynamic changes and hormonal milieu may be the cause of vascular alterations, which can lead to new aneurysm formation, or weakening of pre-existing aneurysms. This is the first reported case of a dissecting venous aneurysm, and has the added interest that it occurred during pregnancy.
- venous aneurysm
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A 33 year old woman presented six weeks postpartum with an aching lump in her right popliteal fossa, which developed early in the course of her second pregnancy. The lump was uncomfortable and the symptoms exacerbated by walking and driving. On examination, it was tender on palpation, easily moveable in the lateral planes, but did not move in a proximal or distal direction. An ultrasound scan showed a solid echogenic mass measuring 1 × 0.5 × 0.5 cm. There was no colour doppler flow within the lesion. The lump was considered to be intradermal. The clinical impression was that of a benign lesion, possibly a neurilemmoma. Intraoperatively, a blood filled mass was found arising from a superficial vein of the short saphenous system (fig 1). This was excised and the vein ligated/transfixed.
Macroscopically, there was a blood vessel 8 mm in length and 2 mm in diameter with an attached tan/grey nodule 10 × 15 × 5 mm in size. On slicing the specimen there was a cyst 8 mm in diameter containing brown material.
The plane of dissection was towards the outer aspect of the media. There was a uniform infiltrate of mixed chronic inflammatory cells within the media and adventitia. Most of these were CD3+ T cells. No eosinophils were identified. There was no evidence of mural necrosis or adventitial haemorrhage. Figure 1 shows the histological appearance of the dissecting aneurysm wall.
Primary venous aneurysms are rare vascular abnormalities that can affect either the superficial or deep veins, and have been described throughout the venous system. They occur most often in the neck (jugular vein) and central thoracic veins, and have been found in the visceral veins and the extremities.1 Venous aneurysms can result from trauma (accidental or postoperative), arise in association with varicose veins or arterio-venous shunts, or they can be congenital in origin. In addition, degenerative changes in the venous wall resulting from connective tissue disorders (Marfans, Ehlers-Danlos) can cause aneurysms. Inflammation has also been cited as a possible cause, although in fact inflammation probably results from the mass effect of the aneurysm itself.2 Venous aneurysms arising in the deep veins of the leg (popliteal) commonly present with pulmonary embolism1,3,4 or even sudden death.5
“Venous aneurysms can result from trauma (accidental or postoperative), arise in association with varicose veins or AV shunts, or they can be congenital in origin”
There is a tendency for vascular disturbances to occur during pregnancy (varices, cutaneous spider naevi, pyogenic granuloma) and there is a positive correlation between dissecting arterial aneurysms in young women and pregnancy. Between 25% and 50% of cases occurring in women below 40 years are associated with pregnancy, especially the third trimester.2,6–8 An increase in cardiac output and blood volume, usually found in the later months of pregnancy, are important factors in the precipitation of vascular accidents,7 and are probably precipitating factors in the formation and rupture of dissecting aneurysms. The most commonly reported pregnancy associated ruptured aneurysms include the aorta, and the cerebral, splenic, coronary, renal, and ovarian arteries.2,9 One study reviewed three cases of spontaneous coronary artery dissection in young patients. One of these occurred in the puerperium. The dissection occurred between the tunica media and external elastic lamina, and was associated with a mixed inflammatory infiltrate rich in eosinophils.10
Take home messages
To our knowledge, we describe the first case of a dissecting venous aneurysm
This case occurred as a popliteal mass early in the course of a second pregnancy in a 33 year old woman
There is a tendency for vascular disturbances to occur during pregnancy, but it is unknown whether the aneurysm in our patient was related to her pregnancy
Dissecting venous aneurysms are not documented in the literature. It is unknown whether or not the aneurysm in our patient was related to her pregnancy. There was no history of trauma, varicose veins, AV malformation, hypertension, or collagen vascular disorders and the only risk factor for a vascular disturbance was her pregnancy induced state. Before becoming pregnant for the first time she had been taking the combined oral contraceptive pill for five years, with no adverse effects. Both pregnancies were uneventful, with nothing to suggest occult pulmonary emboli.
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