June issue.indd

R. Jegananthan J.A. Reid R.J. Hannon
Vascular Unit, Belfast City Hospital, Lisburn Road, Belfast, BT9 7AB

Correspondence to: J.A.Reid, Vascular Surgical Unit, Level 5, Belfast City Hospital Lisburn Road, Belfast BT9 7AB

Keywords: Inferior vena cava, aneurysm Surg J R Coll Edinb Irel., 1 June 2003, 164-165

Aneurysms of the inferior vena cava (IVC) are extremely rare, with a range of reported presentations including deep venous thrombosis. Computerised Tomography (CT) and Magnetic Resonance Imaging (MRI) scans are suggested appropriate diagnostic imaging modalities, but even then it may not be possible to differentiate between an IVC aneurysm and a retroperitoneal tumour. This case illustrates that an IVC aneurysm should be considered in the differential diagnosis of a retroperitoneal tumour

INTRODUCTION
Aneurysms of the inferior vena cava (IVC) are extremely rare with only 16 cases reported in the literature. ^1-6 These presented with a variety of symptoms and signs. We report a further case, which presented with IVC aneurysm thrombosis mimicking a retroperitoneal tumour.

HISTORY
A 43-year-old woman was admitted with a 10 day history of pain and swelling in her right leg. She had no history of a deep venous thrombosis (DVT) and was otherwise well. On examination, there was gross swelling of the entire right leg with a bluish discolouration, and a firm abdominal swelling to the right of the umbilicus, which clinically didn’t arise from the pelvis. Blood tests revealed that she was slightly anaemic with a haemoglobin of 9.1g/dl. Erythrocyte sedimentation count (ESR) was elevated at 118mm/h and a thrombophilia screen was normal. A venogram confirmed a DVT with no filling of the calf, popliteal, femoral or iliac veins on the right. Ultrasonography (US) and computerised tomography (CT) revealed a 6cm retroperitoneal mass displacing the colon and inferior pole of the right kidney (Figure 1). This mass was felt to be a retroperitoneal tumour compressing the IVC. Pre-operatively an IVC filter was inserted in view of the risk of pulmonary embolus. At laparotomy, the mass was seen to be arising from the IVC and it was diagnosed as a saccular aneurysm. The IVC was controlled proximally and distally and the aneurysm resected. Old organised thrombus was seen within the lumen of the IVC, which extended proximally. No venous reconstruction was attempted, as it was felt that due to the chronic nature of the thrombus and resolving oedema, sufficient collaterals should have developed, and the venotomy was primarily closed.

Post-operatively, the patient recovered well, was prescribed warfarin and discharged with compression stockings. On review, the leg swelling had resolved. Histological examination of the aneurysm demonstrated a thickened venous wall with dilatation and thrombosis of its lumen.

DISCUSSION
Aneurysms of the IVC are a diverse group of anomalies with distinct anatomic and clinical characteristics. They may be saccular or fusiform, with saccular being slightly more common.³ The cause is unknown although it has been suggested that they develop in the anastamoses between the embryological venous systems and that they may be associated with other congenital cardiovascular abnormalities.³ In 1993, Gradman and Steinberg (1993) proposed a classification for IVC aneurysms: type I, aneurysm of the suprahepatic IVC with no venous obstruction; type II, aneurysm associated with interruption of the IVC above or below the hepatic veins; type III, aneurysms confined to the infrarenal IVC without associated venous anomaly. This case would, therefore, fall into the type III category.³

Angiography, CT and magnetic resonance imaging (MRI) have been suggested as appropriate imaging modalities. A “layered gadolinium sign” on MRI strongly suggests a vascular nature of a mass and would, therefore, exclude a neoplastic process.⁵ However, if the lumen of the IVC is completely obstructed by thrombus, the diagnostic value of these images is much reduced and a venous aneurysm could still be easily confused with a retroperitoneal tumour. Therefore, it may not have been helpful in this case.

There are a range of reported presentations including pain, rupture and thromboembolism, the latter being the presenting feature in seven patients including ours.³ Thrombosis usually presents with bilateral leg swelling. In this case, only one leg was symptomatic but there may have been an occult DVT in the other leg. In type II and III aneurysms, surgical repair is advised due to the high incidence of developing symptoms.⁷ In type I aneurysms, as there is a high morbidity and mortality associated with surgery in the thorax and the low incidence of developing symptoms, asymptomatic non-enlarging venous aneurysms can be safely followed-up.⁷

If surgical intervention is required complete excision is recommended with primary venous closure, as was done in this case. Reconstructive surgery with synthetic or vein graft may be necessary to re-establish caval flow if severely symptomatic, but there is a high risk of vena caval graft thrombosis. ^7-8 Reconstruction may not be technically possible if the proximal IVC is thrombosed. In these cases a suprarenal caval filter should be considered.³

In conclusion, IVC aneurysm, although rare, should be considered in the differential diagnosis of retroperitoneal tumours. When the lumen is completely thrombosed, the diagnosis can be very difficult to make pre-operatively even with multiple imaging modalities, hence laparotomy may be the only method of definitive diagnosis. Finally, surgical treatment of abdominal venous aneurysms is advisable in symptomatic cases. In asymptomatic cases, surgery should be considered in fit patients who can undergo a relatively straightforward operation or in other cases where the aneurysm is enlarging.

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