British Journal of Radiology 74 (2001),192-194 © 2001 The British Institute of Radiology
Thrombosed double inferior vena cava mimicking paraaortic lymphadenopathy
J C Evans, MRCP, FRCR1,
J Earis, MD, FRCP2 and
J Curtis, MRCP, FRCR1
1 Departments of Radiology
2 Medicine, University Hospital Aintree, Lower Lane, Fazakerley, Liverpool, Merseyside, UK
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Abstract
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A case is presented of thrombosis of an anomalous left-sided duplication of the inferior vena cava misinterpreted on CT as lymphadenopathy or other retroperitoneal mass. Recognition of this anomaly is important in reaching the correct diagnosis in such cases. The diagnosis by imaging methods is described as well as their pitfalls.
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Introduction
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Anatomical variants of the inferior vena cava (IVC) may be misinterpreted by the radiologist as pathology. Anomalies of the IVC occur in up to 4% of the population and may be complicated by thrombophlebitis, when their appearance may become even more misleading. Lymphadenopathy is the usual misdiagnosis in such cases, often leading to unnecessary biopsy or laparotomy. We present such a case, and discuss the radiological features and methods of imaging that can be employed to confidently diagnose a thrombosed double IVC, thus avoiding unnecessary intervention.
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Case report
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A 68-year-old man was admitted to hospital complaining of pain and swelling of both legs. There was a past history of extensive varicose veins. 6 weeks before admission he had sustained a minor injury to his back. On examination, he looked pale and both legs, including his thighs, were markedly swollen, hot to touch and had a minor degree of pitting oedema. He was apyrexial, with a pulse rate of 90 per min and blood pressure of 140/80. No abnormal physical signs were demonstrated on cardiovascular, respiratory or abdominal examination. Initial investigations showed a low haemoglobin level (7.9 g dl-1), an International Normalized Ratio (INR) of 1.1, normal urea and electrolytes, and a normal chest radiograph. A clinical diagnosis of bilateral deep vein thrombosis was made. Subsequent results confirmed iron deficiency anaemia. He was given a blood transfusion and commenced on intravenous (iv) heparin. Doppler ultrasound confirmed the presence of bilateral iliofemoral thrombosis, although the IVC was not clearly seen.
The possibility of underlying malignancy was investigated as there was no obvious precipitating cause for the extensive venous thrombosis. Gastroscopy and colonoscopy were normal. Ultrasound of the abdomen confirmed the iliofemoral thrombosis. Contrast enhanced CT of the abdomen showed a large left paraaortic soft tissue mass (Figure 1
). This was interpreted as enlarged lymph glands and the possibility of lymphoma was raised. Ultrasound of the testes was normal.
CT-guided biopsy of the retroperitoneal mass was performed using a 20 G co-axial cutting needle. This showed normal tissue, with no evidence of malignancy. Bone marrow aspiration and biopsy was also normal. Thrombus was noted in the IVC at the time of the CT-guided biopsy.
Laparotomy was undertaken to investigate the abdominal mass. No abnormality was found at surgery. In particular, no abnormal lymph nodes and no retroperitoneal mass was found. Nodes sampled at surgery were normal on histological examination.
The patient was discharged on warfarin following recovery from the operation. His legs became less swollen and his general health improved. CT 11 weeks later showed the left paraaortic mass to be tubular in nature and to have decreased significantly in size (Figure 2a). It was then apparent that this mass was thrombus within the lumen of a left-sided IVC, which was contiguous with both common iliac veins (Figure 2b). The patient has subsequently improved further but is left with chronically swollen legs.
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Figure 2. (a) Axial CT 11 weeks later shows a well defined tubular mass with a thrombus-filled lumen to the left of the aorta (arrow). Note the prominent abdominal wall veins (arrowheads). (b) At a lower level, this structure was in continuity with the common iliac veins, which were also filled with thrombus (arrows).
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Discussion
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Anomalies of the IVC are present in 0.4–4% of the population [1]; the lower percentage representing the radiological detection rate, with the higher figure of 4% being that found at post-mortem. The commonest reported anomalies are duplication of the IVC and left-sided IVC. Absence of the suprarenal IVC with azygos continuation, retrocaval ureter, and retroaortic or circumaortic left renal vein occur less frequently. All of these anomalies appear during venous development between the sixth to eighth week of fetal life. The retroperitoneal venous system develops from three pairs of veins, the posterior cardinal, subcardinal and supracardinal veins. The posterior cardinal veins are the first to appear, lying in the paravertebral gutters and related to the primitive renal structures. The subcardinal veins then form anteromedial to the posterior cardinal veins. A rich set of anastomoses develops between ipsilateral veins, leading eventually to involution of most of the posterior cardinal venous system in synchrony with the disappearance of the mesonephros. An important midline anastomosis develops between opposite subcardinal veins. Finally, the supracardinal veins form medial and parallel to the posterior cardinal veins. Subcardinal–supracardinal anastomoses develop between ipsilateral veins and these segments later become the renal segment of either a right or left IVC, depending on whether the left or right infrarenal supracardinal vein involutes. If neither involute, then a double IVC develops. An outpouching of the right subcardinal vein anastomoses with the hepatic veins to form the suprarenal portion of the IVC. The suprarenal portions of the right and left supracardinal veins become the azygos and hemiazygos veins, respectively.
Without an awareness of their existence or appearance, such venous anomalies may mislead the radiologist. CT without contrast enhancement may lead to the most common misdiagnosis of paraaortic lymphadenopathy [2]. This is not surprising, as paraaortic lymph nodes are a common site for metastases from local and distant tumours and for diseases of the reticuloendothelial system. Other differential diagnoses for a soft tissue mass lying to the left of the aorta in the upper abdomen include enlargement of the left gonadal or hemiazygos vein, a circumaortic or retroaortic left renal vein, an extrarenal pelvis or post-operative herniation of either stomach or bowel after a nephrectomy or splenectomy [3]. Misinterpretation of venous structures as lymphadenopathy will usually be avoided by the use of iv contrast medium and recognition of the tubular configuration, but if CT is performed in the equilibrium phase it may be very difficult to appreciate venous enhancement. In the case presented here, contrast enhancement was poor owing to a combination of non-dynamic contrast medium injection and the use of a relatively slow non-spiral CT, both contributing to the misdiagnosis. Although spiral CT allows more dynamic acquisition, it is likely that enhancement will be negligible if images are acquired only in the arterial phase. Many authors have advocated injecting contrast medium into a lower limb vein when a venous anomaly is thought to be present [4]. This has the advantage of producing improved opacification of the IVC.
Thrombophlebitis of anomalous venous pathways is well documented [5], including, as in this current report, the left side of a double IVC [6]. The appearance of the left IVC in this situation may assume a dilated, lobulated appearance or become ectatic and thus resemble a chain of nodes. Contrast enhancement is usually absent but may occasionally occur around the periphery of the thrombus or in the wall of the vein. Stranding of the surrounding fat may be seen if inflammation is present. Biopsy reports in such cases usually state that either the sample is inadequate or that only thrombus is present. The radiologist, not unreasonably, assumes that the biopsy has missed the area of interest, and may offer to repeat the biopsy, or the patient undergoes a laparotomy.
To avoid this unnecessary chain of events, we suggest that awareness of venous anomalies and their radiological appearances is vital to avoid misdiagnosing these patients. Lower limb iv contrast medium injection and CT during the venous phase should both be applied if such an abnormality is thought a possibility. Magnetic resonance or digital subtraction venography should also be considered. Occasionally, as in this case, a thrombosed vein may recanalize after a few weeks and reveal its true identity.
Received for publication June 30, 2000.
Revision received October 16, 2000.
Accepted for publication October 25, 2000.
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Abstract
Introduction
