Intrinsic
Thrombosis
Stenosis (ex: congenital membranes)
Tumor: primary, invasion from adjacent organ/retroperitoneum
Iatrogenic (central catheter placement, cava filter)
Extrinsic
Compression by retroperitoneal mass (lymph nodes, retroperitoneal fibrosis, tumor, aortic aneurysm)
Enlarged liver
Pregnant uterus
Surgical ligation, clip
Diagnostic imaging is easy as soon as acquisition time is correct. The key imaging is based on the detection of a filling defect within the IVC. However, filling defect in IVC can result from multiple causes including flow-related artifacts, bland thrombus, benign thrombus, or malignant thrombus [11, 12]. Acute thrombus (<1 week) classically appears as intraluminal hyperdensities within the IVC on CT prior to contrast injection, with homogeneous signal intensity on MR, whereas non-acute thrombus can remain undetected on CT prior to injection, with heterogeneous signal intensity on MRI [13]. Acute and non-acute thrombi usually show filling defect on both CT and MRI after contrast injection.
1.3.1.1 Artifactual Filling Defect and Bland Thrombus
Artifactual filling defects are due to incomplete filling of IVC by contrast agents. This is usually caused by flow of enhanced blood from renal veins mixed with non-opacified blood returning from lower limbs [11]. Delayed images as described above may ease the final diagnosis (Fig. 1.1).
Fig. 1.1
Inferior vena cava artifactual filling defect (arrow) (axial CT) on early venous phase (a) with homogenization on late venous phase (arrow) (b)
Bland thrombus is the most common thrombus of IVC. It often extends from pelvic and lower extremity deep vein thrombosis. There is no enhancement of this thrombus after contrast injection (Fig. 1.2). Patients with IVC thrombosis are at high risk of pulmonary embolism. This thrombus can be idiopathic, the consequence of hypercoagulable state or induced by venous stasis (immobility, external compression).
Fig. 1.2
A 55-year-old patient with right common iliac vein thrombus (arrowhead) extending in the inferior vena cava (arrow) on axial (a) and coronal CT (b)
1.3.1.2 Benign Tumor Invasion Within the IVC
1.3.1.3 Malignant Tumor Invasion Within the IVC
Primary and secondary tumor can extend within the IVC. Both often share similar imaging features, characterized by a contiguous adjacent mass, expansion within the lumen vessel and thrombus enhancement after contrast injection [11]. However, neoplastic IVC invasion and bland thrombus induced by neoplastic hypercoagulability state can coexist. If an adjacent mass is not found, IVC-enhancing mass may correspond to primary sarcoma. Extension of thrombus must be perfectly described by radiologist because it affects surgical procedure. Supradiaphragmatic extension must be carefully searched. In this case, IVC resection and cardiopulmonary bypass are required, increasing morbidity and mortality [11, 16].
Primary IVC tumors are rare, and leiomyosarcoma is the most common primary tumor (<1 % of all malignancies) (Fig. 1.3). Differentiation of primary leiomyosarcoma arising from IVC to leiomyosarcoma arising from retroperitoneal space is crucial since surgical treatment differs. Complete surgical resection is the only curative treatment. Cavoplasty or stent graft is required [17]. Distinction between these two entities on imaging is challenging because both masses are predominantly extra-luminal and are supposed to arise from smooth retroperitoneal muscle than from IVC. Some authors have suggested that tumors could be considered as primary IVC leiomyosarcoma if a segment of IVC needs to be resected during surgery. When this tumor is infrarenal and collateral vessels are well developed, IVC ligation is possible. In case of insufficient collateral vessels, edemas of lower limbs are frequent. In this case and in case of suprarenal disease, cavoplasty or stent graft is preferred. Distinction of primary IVC leiomyosarcoma on imaging allows surgery planning with vascular surgeon. The key diagnosis of IVC leiomyosarcoma is the imperceptible cava lumen (75 % of cases in [18]). A positive embedded sign has also been described. Compression of IVC by retroperitoneal mass (negative embedded sign) suggests a non-cava origin.
Fig. 1.3
A 58-year-old patient with an inferior vena cava leiomyosarcoma. Axial and coronal T2 (a, b), axial diffusion (c), apparent diffusion coefficient (d), and coronal contrast-enhanced T1-weighted MR images (e) show an inferior vena cava leiomyosarcoma (arrow) with liver invasion (arrowhead)
Secondary involvement of IVC by retroperitoneal sarcoma or neoplasm (renal carcinoma, hepatocellular carcinoma, or adrenocortical carcinoma for the most common neoplasms) is more common, and complete resection of this segment should be done by a surgeon.
Invasion of IVC is frequently seen in renal cell carcinoma (RCC) (4–10 % of cases [19]) (Fig. 1.4). In a Mayo Clinic report, complications occurred in 15 % of nephrectomy with thrombectomy of the IVC [20]. These complications included hemorrhage, pulmonary embolism (PE), acute renal failure, ileus, and wound infection. IVC extension of RCC must be screened on preoperative imaging [21, 22]. The Mayo classification [23] describes four levels of venous extension: level I when extension only concerns the renal vein and/or the IVC <2 cm, level II corresponds to extension within the IVC >2 cm below the hepatic veins, level III corresponds to retro-hepatic IVC and/or hepatic vein involvement, and level IV corresponds to extension above the diaphragm with or without atrial thrombus. Imaging should be performed no longer than 30 days and preferentially 14 days before resection for optimal surgical planning [24]. MRI is usually considered as the gold standard for thrombus evaluation, but MDCT is as accurate as MR and more available [25]. It also allows simultaneous thoracic screening. Furthermore, imaging features may predict the need for IVC resection during nephrectomy: anteroposterior IVC diameter >24 mm, a right-sided tumor, and complete occlusion of the IVC at the ostium of the right renal vein [26].
Fig. 1.4
Right renal cell carcinoma (arrow) with malignant thrombus (arrowhead) in a 64-year-old patient. Axial (a and c) and coronal CT (b and d) show a right renal heterogeneous mass (arrow) with contrast enhancement, extending to IVC through the renal vein (arrowhead)
1.3.1.4 IVC Obstruction Consequences and Therapeutic Implications
IVC obstruction can be asymptomatic or can lead to bilateral lower limbs edema, pulmonary embolism, the Budd-Chiari syndrome (BCS), or venous collateral formation [27–30].
Budd-Chiari Syndrome
The Budd-Chiari syndrome (BCS) is a clinical and biological syndrome due to a lack of hepatic venous drainage. The etiology of BCS can be located at any portion of the hepatic venous drainage path from hepatic venules to IVC. In Europe, BCS is most of the time the consequence of hepatic vein thrombosis or of extrinsic compression. In Asia and South Africa, IVC webs (described below) are common BCS etiology [31]. The rapidity and extension of venous obstruction determine the severity of clinical and biological symptoms. BCS can be fulminant, acute, subacute, and chronic.
Imaging features of BCS include parenchyma abnormalities, ascites, signs of portal hypertension, and confirmation of venous outflow obstruction. Doppler US is the easiest imaging modality used for diagnostic confirmation with good sensitivity and specificity (approximately 85 % [32]). In acute BCS, hepatic parenchyma can be heterogenous, with an enlarged caudate lobe and ascites. Splenomegaly reflecting portal hypertension is also described. On color Doppler US, hepatic vein or its confluence with the IVC is non-visualized; flow can also be diminished or reversed [33]. In chronic BCS, collateral veins can be seen. Portal vein flow can be slow and hepatofugal. On MDCT, heterogenous enhancement is present on arterial-parenchymal phase, with regenerative nodular lesions and caudate lobe hypertrophy. Ascites, splenomegaly, and venous collateral pathways are seen. Thrombosis, stenosis, or webs in hepatic veins or in the IVC can also be seen. Liver cirrhosis may be present on chronic BCS. Liver analysis must be carefully done to depict hepatocellular carcinoma. MRI displays the same imaging features than that of MDCT. Regenerative nodular lesions show hyperintensity on T1-weighted images, isointensity on T2-weighted images, and hyperenhancement on arterial phase, persisting on portal phase [34]. Specific treatment of BCS includes medical treatment with anticoagulation or interventional management in case of medical treatment failure [35].
Collateral Pathways
Chronic obstruction of IVC promotes collateral pathway development through deep and superficial venous collateral vessels. Four major pathways have been described [28]. The deep pathway, the most common, concerns the ascending lumbar veins, anastomosing with the azygos vein on the right side and the hemiazygos vein on the left side. Blood flow can also join vertebral, paraspinal, and extravertebral plexus. In the intermediate pathway, blood flow returns through the periureteric plexus bilaterally and the left gonadal vein to the left renal vein. The superficial pathway is constituted with the inferior epigastric and the abdominal wall veins, anastomosing with the superior epigastric veins and internal mammary veins to join the subclavian veins and the superior vena cava. Finally, the portal pathway concerns blood arising from lower extremities through the internal iliac veins to the hemorrhoidal plexus to join the inferior mesenteric vein and the portal system (Fig. 1.5).
Fig. 1.5
Collateral pathway. A 56-year-old patient with IVC leiomyosarcoma, who underwent surgery. IVC occlusion leads to portal collateral pathway development (arrow) (axial CT (a) and coronal CT (b))
Identification of these collateral pathways is essential before surgery to decrease hemorrhagic risk during procedure and to avoid pitfalls.
1.3.2 IVC Anatomical Variants
Anatomical variants of the IVC can be explained by aberrations of regression of embryologic veins described above. They are present in approximately 4 % of the population and are most of the time asymptomatic [1, 3]. Correct identification of these variants is essential before vascular interventions.
The most common variants are left IVC, double IVC, retroaortic and circumaortic left renal vein, interruption of the IVC with azygos continuation, and portocaval shunt [1–5, 36].
1.3.2.1 Left IVC
During embryologic development, the persistence of the left supracardinal vein combined with regression of the right supracardinal vein leads to the persistence of a left IVC. The left IVC joins the left renal vein. Then the left renal vein joins the right renal vein to form the IVC. Its prevalence is around 0.2–0.5 % [2] and can also be seen in patients with situs inversus. This variant can be mistaken with left-sided para-aortic adenopathy on non-contrast injection imaging. It is of primary importance during left-sided donor nephrectomy [36].
1.3.2.2 Double IVC
Both of the supracardinal veins (left and right) persist, leading to a double IVC. On imaging, the IVC presents bilaterally. The left renal vein joins the left IVC, which crosses anterior to the aorta in the normal location to join the right IVC (Fig. 1.6). This variant is asymptomatic and its prevalence is about 0.2–3 % [2]. Its knowledge is important during kidney nephrectomy or vena cava filter placement to avoid pulmonary embolism recurrence. Some authors recommend contrast injection in the left and the right common iliac veins during cavography before inferior vena cava filter placement to diagnose this anomaly. Preoperative imaging is essential to correctly plan surgery and avoid vascular complications.
Fig. 1.6
A 55-year-old patient with double IVC (arrow) (axial, (a); coronal CT (b))
1.3.2.3 Retrocaval Ureter
The infrarenal segment develops from the right posterior cardinal vein, which lies anterior and lateral to the ureter instead of the right supracardinal vein, which is located posterior and medial to the ureter. This results in the compression of the ureter, leading to hydronephrosis or tract infections.
1.3.2.4 Retroaortic and Circumaortic Left Renal Vein
Retroaortic renal vein (2.1 %) is classically asymptomatic but has been involved in the nutcracker syndrome with hypertension or in hematuria.
Circumaortic renal vein (5–7 %) is characterized by two renal veins: one anterior to the aorta and the other posterior to the aorta. Its clinical implication is fundamental in renal transplantation and should be known before varicocele treatment by radiologist (as it is technically impossible in this case).
1.3.2.5 Interruption of the IVC and Azygos/Hemiazygos Continuation
It results from a failure to form the right subcardinal-hepatic anastomosis. The right subcardinal vein becomes atrophic. Blood is redirected through the retrocrural azygos vein or the hemiazygos vein and then the azygos vein. As a result, the azygos vein is enlarged and joins the superior vena cava at its normal location in the right paratracheal space. The hemiazygos can also drain directly in the coronary sinus or in the left brachiocephalic vein [37–39]. The prevalence is 0.6 %. The hepatic segment drains usually directly in the right atrium. The gonadal veins drain directly to the ipsilateral renal vein [1].
1.3.2.6 Absence of the IVC
Absence of the IVC [40, 41] or only the infrarenal segment [42] is rare, and its cause is unknown. It may result from complete failure of embryonic vein development or perinatal venous thrombosis with atrophy. Collateral circulation may also be present on imaging, and patients are prone to develop deep venous thrombosis (DVT) [42] and chronic venous insufficiency (CVI) [43].
1.3.2.7 Portocaval Shunt
Portocaval shunt (Abernethy malformation) is classified into two categories. The first one is characterized by absence of the portal vein with complete shunting of portal blood in IVC. It is associated with polysplenia and biliary atresia. The second one is a partial end to side anastomosis between the portal vein and IVC [44].
1.3.2.8 IVC Webs
IVC webs are uncommon anomalies, either congenital or sequel of thrombosis. This entity is more frequent in Asian and South African populations [45]. Images show complete or fenestrated membrane in the lumen of the IVC [3]. It can lead to congenital Budd-Chiari syndrome and its complication (hepatocellular failure, HCC). Intra- and extrahepatic collateral circulations are present. Treatment depends on liver function and can be angioplasty, stenting, or creation of a transjugular intrahepatic portosystemic shunt (TIPS).
1.3.3 IVC Trauma
In trauma, IVC can be flattened reflecting hypovolemia or hypotension and should not be misdiagnosed as IVC trauma.
IVC trauma is rare and responsible of major blood loss. Multiple injuries are common, and most of the patients arriving at the hospital with IVC injury die [46]. Most IVC bleeding is compressed by adjacent structures in case of integrity of the retroperitoneum. Surgery is advocated in patients with persistent bleeding. Diagnosis is easily made on CT: retroperitoneal hematoma around the IVC, irregular vessel contour, and extravasation of contrast on venous phase (Fig. 1.7). Retro-hepatic IVC injury must be carefully searched because of its high mortality in a patient paradoxically stable. This injury is raised in case of liver laceration extending to the IVC with irregular contour of this one [47].
Fig. 1.7
Inferior vena cava trauma: a 25-year-old patient injured in a motor vehicle accident. Arterial and portal contrast-enhanced axial CT (a, b) show hepatic contusion involving the IVC (arrow) with contrast extravasation on delayed venous phase (c)
1.3.4 Postoperative Imaging
1.3.4.1 Post-Liver Transplantation
Vascular complications involving the IVC can be seen after liver transplantation. Anastomosis of recipient and donor IVCs can be end to end or with the “piggy back” technique. Regarding living donor transplantation, the donor hepatic vein is anastomosed to the recipient IVC. Knowledge of the type of anastomosis is important as stenosis often concerns the anastomotic site. Liver transplantation complications of the IVC are thrombosis and stenosis, which concern only 1–2 % of liver transplantations. IVC stenosis is due to anastomotic narrowing or extrinsic compression by fluid, hematoma, or graft swelling. On US, flow velocity is increased by three- to fourfold when compared to normal flow, with Doppler aliasing. Hepatic veins are enlarged and their phasicity disappeared. Focal narrowing can be seen either on MDCT or MRI. Imaging features of the Budd-Chiari syndrome or portal hypertension can also be found [48]. This anomaly can be treated with angioplasty or stent placement.
1.3.4.2 Post-Portocaval Shunt
Uncontrollable variceal bleeding with failure of radiological and surgical TIPS placement can be treated by creation of a shunt between the superior mesenteric vein and the IVC. Radiologist should be aware of this atypical shunting to verify its patency.
1.4 Interventional Imaging of the IVC
1.4.1 Inferior Vena Cava Filter
Surgical ligation of the IVC was the first technique for IVC interruption in prevention of PE. IVC thrombosis and lower limb edema were frequent complications of surgical ligation. IVC interruption by endovascular approach was possible in 1967, thanks to the Mobbin-Udin filter. Vena cava filter indications are listed in Table 1.2. It prevents passage of emboli from systemic to pulmonary circulation by trapping venous emboli. Vena cava filter does not treat or prevent DVT [49–51].
Table 1.2
Society of Interventional Radiology guidelines for use of inferior vena cava filter
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