Sheila Sheth MD
Elliot K. Fishman M.D.

Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins School of Medicine

Conventional venography, the historical gold standard for diagnosing abnormalities of the inferior vena cava (IVC) has been replaced by non invasive imaging modalities for the diagnosis of venous disorders and is now reserved for therapeutic intervention.

Up until recently, magnetic resonance imaging MR, and to a lesser extent color Doppler ultrasound, were the preferred methods to evaluate the inferior vena cava because of their multiplanar capability. With the availability of high speed multidetector CT (MDCT) scanners allowing for near isotropic data collection, superior spatial resolution is combined with high quality sagittal and coronal reconstructions as well as three-dimensional volumetric rendering (3D_VR) to obtain exquisite depiction of the normal and abnormal IVC. Several recent studies have demonstrated comparable results with (MR) and multidetector CT (MDCT) in staging malignancies affecting the IVC.

The purpose of this exhibit is to illustrate the role of MDCT in the diagnosis of disease processes affecting the IVC.

Currently, CT scans are performed on a 64 slice MDCT scanner (Sensation 64, Siemens Medical Solutions, Malvern PA) using 0.6mm detectors, 120KVp and 150-180mAs. Data is reconstructed with 0.75mm slice thickness at 0.5mm interval.

The inferior vena cava is formed by the confluence of the right and left common iliac veins draining blood from the lower extremities and pelvis. As it ascends in the retroperitoneum, to the right of the abdominal aorta, it receives major tributaries including lumbar veins, the left and right renal veins, the right gonadal vein and hepatic veins. The azygos venous system connects to the IVC either directly or through the renal veins. The IVC and its branches are best demonstrated in the coronal plan.

36 year old woman, renal enal donor. Contrast enhanced CT,coronal reconstruction shows normal anatomy of the IVC and its tributaries.

The IVC is formed between the 6th and 8 weeks by the sequential formation, anastomoses and regression of 3 paired veins, the posterior cardinal vein, the subcardinal veins and the supracardinal veins. It is composed of 4 different segments: infrarenal, renal, suprarenal and hepatic.

Aberrations in the complex embryologenesis of the IVC result in several potential anatomic variants, present in approximately 4% of the population. Anatomic variation in the number and position of the left renal vein are even more common. Most anomalies are found incidentally, although patients with anatomic variations are considered at risk for developing deep venous thrombosis of the common femoral or iliac veins at a younger age. They may pose a special challenge at surgery and should be carefully described in individuals considered for laparoscopic donor nephrectomy. The most common anatomic variants include a retro-aortic left renal vein, double and left sided IVC and a circum-aortic left renal vein. Some anomalies, particularly the azygos continuation, have been associated with significant congenital heart disease.

This is the most common anomaly found incidentally in as many as 8% of the population, Two left renal veins are present, with the superior vein crossing over the aorta anteriorly. The posterior vein often lays much lower then the anterior renal vein, which may be problematic in harvesting a donor kidney. This should be clearly communicated to the surgeon.

41 year old man, renal donor. Contrast enhanced CT, coronal reconstruction: there is an incidentally noted circum aortic left renal vein with the posterior retro-aortic branch coursing inferiorly (arrow).

Persistence of a left supracardinal vein with regression of its right counterpart results in a left sided IVC. The infrarenal IVC is found to the left of the aorta up to the left renal vein which crosses anterior to the aorta to joins the right renal vein and forms a normal right IVC above that level.

This anomaly results from persistence of both supracardinal veins. Typically the left IVC ends at the level of the left renal vein.

In this anomaly, the right supracardinal-hepatic anastomosis does not form, the hepatic IVC is absent and blood from the renal IVC drains into the azygos system to empty in the superior vena cava.

48 year old man with pancreatitis. Contrast enhanced axial CT: a, b. there is an infrarenal left sided IVC. c,d. The hepatic IVC is not seen and the azygos and hemiazygos veins are dilated (arrows). This patient has a left sided IVC with interrupted IVC and azygos continuation.

Bland thrombus in the IVC can be isolated or more often spreads from the veins of the lower extremities. Risk factors include hypercoagulable states, malignancies and venous stasis. Local compression of the IVC by adenopathy, large retroperitoneal masses or fibrosis as well as venous stasis and foreign bodies such as IVC filters or catheters are known to promote local clot formation. The presence of a persistent filling defect within the column of contrast leads to the diagnosis. If IVC thrombosis becomes extensive and long standing, pericaval and periaortic collateral veins form to bypass the obstruction.

50 year old man with history of IVC occlusion. Contrast enhanced CT, coronal reconstruction: there is lack of opacification of the midportion of the IVC, consistent with occlusion by thrombus (arrows). Extensive retroperitoneal collaterals are seen bypassing the occluded segment (arrowheads). There is a stent in the suprarenal portion of the IVC.

57 year old man with abnormal liver function tests Contrast enhanced axial CT:a,b : there is prominent fat posterior to the caudate lobe (arrow). C: this fat projects within the IVC creating an apparent low attenuation filling defect (arrow). D: the IVC is normal, confirming this is a pseudoclot, due to partial volume averaging.

Renal cell carcinoma is the most common malignancy extending into the IVC and producing malignant thrombus. This has been reported in 4 to 10% of patients with renal cell carcinoma. For proper planning of the surgical approach, it is of paramount importance to define the superior extension of the thrombus. According to the TNM classification of renal cell carcinoma, tumor spread into the infradiaphragmatic portion of the IVC is categorized as a T3c stage, while extension into the supradiaphragmatic IVC is classified as T4b. Further subclassification into infrahepatic, hepatic and suprahepatic extension of the tumor thrombus is critical to predict the complexity of the resection and plan the surgical team and surgical approach. While the tumor thrombus is confined to the infra hepatic IVC in approximately 50% of cases with IVC extension, 40% of clots involve the hepatic IVC and 2 to 16% of patients demonstrate clot in the right atrium.

Recent studies comparing MDCT and surgical findings have reported an accuracy of 78 to 93% in predicting the uppermost IVC thrombus extension in patients with renal cell carcinoma. Sagittal and coronal reconstructions reliably delineate the extent of tumor thrombus and allow differentiation between bland and tumor thrombus by demonstrating direct continuity between the primary tumor and the thrombus. In contrast to external compression by a tumor, the vein is generally expanded and dilated. Neovascularity within the thrombus in the arterial phase confirms the malignant nature of the IVC clot.

Left x2: 65 year old man with a large left renal mass. Contrast enhanced CT, coronal reconstruction in the venous phase: there is a large hypervascular mass in the mid-upper pole of the left kidney (arrows). There is thrombus extending into the renal vein and the infrahepatic IVC (arrowheads). Contrast enhanced axial CT in late arterial phase: note hypervascularity in the left renal vein thrombus consistent with tumor thrombus (arrowheads),. The patient underwent a left nephrecomy for a Furhman grade IV clear cell renal carcinoma and thrombectomy of a 2 cm mobile clot in the IVC.

Right x2: 51 year old man with sorthness of breath. Contrast enhanced CT, coronal reconstruction in the venous phase: there is a hypervascular infiltrating mass in the right kidney, extending into and occluding the right renal vein (arrows). The thrombus extends into the IVC, obstructing and expanding it. Note neovascularity within the thrombus and extension into the right atrium (white arrow). Inferior to the level of the right renal vein, the clot in the IVC is lower in attenuation, suggesting a small portion is bland thrombus (arrowhead). There is an embolus in a branch of the right pulmonary artery. In the arterial phase, there is neovascularity in the main thrombus confirming tumor thrombus (arrowheads). The patient underwent a right nephrectomy and removal of tumor thrombus from the IVC and right atrium, confirming a stage T4b tumor.

56 year old woman with right sided back pain and abdominal distention. Contrast enhanced CT, coronal reconstruction in the venous phase: There is a large heterogeneously enhancing mass displacing the right kidney inferiorly. There is a filling defect in the hepatic portion of the IVC. On the arterial phase, the mass is hypervascular. Note subtle vascularity in the IVC thrombus indicating tumor thrombus. The appearance is most suggestive of an adrenocortical carcinoma with IVC extension. This diagnosis was confirmed at surgery and pathology. The large right adrenal mass was excised and the IVC thrombus removed.

Primary tumors of the IVC are exceedingly rare. Leiomyosarcoma of the IVC is a tumor of mesenchymal origin arising from the smooth muscle cells found in the vessel wall and is associated with a poor prognosis with a reported 10 year survival of 14%. Most leimyosarcomas are quite large at presentation and manifest with non specific complaints of abdominal pain, a palpable right upper quadrant mass or progressive lower extremity edema. Occasional patients present with ascites or Budd Chiari syndrome if the tumor extends into the hepatic veins. Wide surgical excision, combined with adjuvant radio and chemotherapy therapy offers the only potential for cure or prolonged survival.

Leiomyosarcomas of the IVC are classified according to their location. Data gathered form a compiled review of 218 cases from the world literature reveals that approximately 37% of tumors occur in segment I, below the level of the renal veins and above the iliac vein bifurcation, 43% involve segment II, between the renal veins and the level of the hepatic veins and 20% form in segment III at or above the hepatic veins level and may extend into the right atrium . Tumors affecting segment II may be associated with a slightly better prognosis .Over two thirds of tumors exhibit a predominantly extraluminal growth while the reminder are growing within the IVC.

At imaging, exophytic leiomyosarcomas appear as large retroperitoneal masses with heterogeneous contrast enhancement. Cystic necrotic areas are not uncommon. As the origin of these large tumors may be quite difficult to ascertain on imaging, percutaneous biopsy is very valuable to achieve a definitive diagnosis. The predominantly intraluminal leiomyosarcoma focally dilates and usually obstructs the IVC and may display homogeneous contrast enhancement.

50 year old woman with right flank mass: Contrast enhanced CT, coronal reconstruction: a. there is a very large heterogeneously enhancing mass displacing the right kidney inferiorly (arrows). Note calcifications within the mass (arrowheads). b. The IVC is not visualized. Because of its large size, the origin of this tumor could not be definitely ascertained. Differential diagnosis included adrenocortical cancer, GIST tumor or retroperitoneal sarcoma c. The diagnosis of leimyosarcoma was obtained by ultrasound guided percutaneous biopsy: the prebiopsy ultrasound shows a large heterogeneous mass with calcifications. d. At surgery, the tumor engulfed the IVC and portion of the right kidney.

54 year old man with newly developing hypertension. Contrast enhanced axial CT:a, b there is a homogeneous mass expanding the suprarenal IVC. C The diagnosis of caval high grade leiomyosarcoma was confirmed at surgery.

75 year old man with history of bilateral lower extremity edema and shortness of breath. Contrast enhanced axial CT: a. there is a large homogeneous soft tissue mass expanding the infrarenal IVC (arrows). b. The mass is arising from the anterior IVC below the level of the renal veins, is partially exophytic, compressing the adjacent duodenum (arrowhead). Contrast enhanced CT, coronal reconstruction: c.The large, partially exophytic soft tissue mass is occluding the IVC and extends from below the renal veins to the hepatic IVC (arrows). Note the superior border of the mass in the hepatic IVC does not extend into the right atrium. This was confirmed on axial CT (not shown). d. There is abundant neovascularity within the IVC mass (arrowheads). Note the early enhancement of the distal IVC and extension into the left renal vein (arrow). The diagnosis of leiomyosarcoma was established by percutaneous biopsy.

Budd Chiari syndrome results from obstruction of the hepatic vein outflow tracts, usually at the hepatic veins level and most commonly associated with a hypercoagulable state. Obstruction of the hepatic portion of the IVC, either by a congenital web, stenosis, clot or tumor invasion is a relatively rare cause of Budd Chiari syndrome. More frequently, the IVC is narrowed and compressed by a massively enlarged caudate lobe.

The CT appearance of Budd Chiari syndrome is well recognized. In the acute phase, there is preferential enhancement of the hypertrophied caudate lobe in the arterial phase, followed by heterogeneous enhancement of the liver with peripheral linear low attenuation bands and areas of infarction in the portal venous phase. In chronic Budd Chiari syndrome, patchy hepatic enhancement is best depicted in the portal venous phase. Low attenuation thrombus may be visible in the hepatic veins and IVC. In addition, enlarged and tortuous collateral veins from the azygos, hemi azygos and lumbar venous system can be seen bypassing the occluded IVC.

21 year old woman with coagulopathy. Contrast enhanced CT, coronal reconstruction, venous phase: a: the liver is enlarged and demonstrates heterogeneous enhancement with enlarged caudate lobe and peripheral fatty infiltration. Regenerating nodules are seen in the right lobe. The hepatic veins are not visualized. b. The hepatic and infra hepatic IVC is not visualized. Note prominent periaortic venous collaterals (arrowheads). The diagnosis of Budd Chiari syndrome was confirmed by histologic analysis of the liver at the time of liver transplantation.

IVC stents are placed routinely to bypass areas of occlusion or stenosis. Placement of long standing indwelling venous catheters or creation of surgical anastomoses in patients undergoing liver transplants increase the risk of IVC stenosis. MDCT with volume rendering can exquisitely display the stent and confirm patency. Similarly, MDCT can accurately display the location of IVC filters, their relationship with the renal veins and potential complications such as migration and embedding in the wall of the IVC.

Left x1: 50 year old man with history of recurrent deep vein thrombosis and ulcerative colitis.Contrast enhanced CT, coronal reconstruction: there is an IVC filter in place with its tip at the level of the renal veins, which are patent. A small thrombus is present just above the tip of the filter (arrowhead). There is thrombus in the IVC distal to the filter (arrow).

Right x2: 56 year old woman with history of IVC filter migration. Contrast enhanced CT, coronal reconstruction: a.the bird cage IVC filter is in the suprarenal IVC, with its tip extending into the hepatic IVC. Its inferior portion is very close to the junction with the renal veins (arrows). b. One of the prongs may be embedded in the medial wall of the IVC (arrow).

Retrograde opacification of the IVC and hepatic veins during contrast enhanced CT has been associated with right sided heart disease causing reflux of brightly enhanced blood from the right atrium into the IVC. This has been shown to be a specific (98%) but relatively insensitive (31%) sign of right heart dysfunction. However, the frequency of this finding varies with the rate of contrast injection as retrograde opacification of the IVC is observed more commonly at injection rates above 3cc/sec.

21 year old woman with congestive heart failure. Contrast enhanced CT,axial (a) and coronal reconstruction (b): there is extensive reflux of contrast into the IVC and hepatic veins.

A flattened IVC defined as a transverse to antero-posterior diameter ratio of 3/1 or more seen at multiple levels has been associated with significant hypotension and / or impending shock in trauma patients. A surrounding hypodense halo as well as small caliber of the abdominal aorta are useful adjunct signs. A recent retrospective study of this sign in a non trauma situation reported that although this sign was associated with hypotension in one third of cases, the majority (66%) of patients were normotensive and normovolemic. The authors concluded a flat IVC can be a normal variant, particularly in elderly women.

27 year old woman with multiple pelvic fractures. Contrast enhanced CT,axial: the distal IVC is flattened. Note dilated small bowel loops.