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Spectrum of Congenital Anomalies of the Inferior Vena Cava: Cross-sectional Imaging Findings¹

(CME available in print version and on RSNA Link)

¹ From the Department of Radiology, University of Texas Health Science Center, Houston. Presented as a scientific exhibit at the 1998 RSNA scientific assembly. Received March 16, 1999; revision requested May 7 and received July 1; accepted July 8. Address reprint requests to J.E.B., Hermann Imaging and Breast Center, 6410 Fannin, Suite 170, Houston, TX 77030 (e-mail: J.E.Bass@uth.tmc.edu).

	Abstract

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Embryogenesis of the IVC Variations in IVC Anatomy Conclusions References

 
Congenital anomalies of the inferior vena cava (IVC) and its tributaries have become more commonly recognized in asymptomatic patients. The embryogenesis of the IVC is a complex process involving the formation of several anastomoses between three paired embryonic veins. The result is numerous variations in the basic venous plan of the abdomen and pelvis. A left IVC typically ends at the left renal vein, which crosses anterior to the aorta to form a normal right-sided prerenal IVC. In double IVC, the left IVC typically ends at the left renal vein, which crosses anterior to the aorta to join the right IVC. In azygos continuation of the IVC, the prerenal IVC passes posterior to the diaphragmatic crura to enter the thorax as the azygos vein. In circumaortic left renal vein, one left renal vein crosses anterior to the aorta and another crosses posterior to the aorta. In retroaortic left renal vein, the left renal vein passes posterior to the aorta. In circumcaval ureter, the proximal ureter courses posterior to the IVC. Other anomalies include absence of the infrarenal IVC or the entire IVC. These anomalies can have significant clinical implications. Awareness of these anomalies is necessary to avoid diagnostic pitfalls.

Index Terms: Renal veins, 966.134 • Ureter, abnormalities, 82.1439 • Veins, abnormalities, 569.159, 966.134, 982.131, 982.142 • Venae cavae, abnormalities, 569.159, 982.131, 982.142

	LEARNING OBJECTIVES FOR TEST 2

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Embryogenesis of the IVC Variations in IVC Anatomy Conclusions References

 
After reading this article and taking the test, the reader will be able to:

• Name the four segments of the IVC and describe their embryonic origins.

• List at least three anomalous courses of the IVC and the left renal vein and describe the aberrant embryonic vessels and the embryologic errors involved.

• Recognize and describe the appearance of aberrant IVCs and renal veins on cross-sectional images.

	Introduction

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Embryogenesis of the IVC Variations in IVC Anatomy Conclusions References

 
Anomalies of the inferior vena cava (IVC) and its tributaries have been known to anatomists since 1793, when Abernethy (1) described a congenital mesocaval shunt and azygos continuation of the IVC in a 10-month-old infant with polysplenia and dextrocardia. Since the development of cross-sectional imaging, congenital anomalies of the IVC and its tributaries have become more frequently encountered in asymptomatic patients (2). Vascular structures are usually readily identified on computed tomographic (CT) scans of the abdomen and pelvis obtained with intravenously administered contrast material. However, use of intravenous contrast material is occasionally contraindicated. In addition, with helical acquisition, the venous structures may be imaged during the arterial phase, when little or no contrast material is present in the veins. Therefore, familiarity with these variations is essential for correct interpretation of cross-sectional images, to avoid erroneous diagnosis of retroperitoneal and mediastinal masses or adenopathy, and to alert the surgeon and angiographer of potential sources of complications preoperatively.

This article reviews the embryogenesis of the IVC and describes the variations in IVC anatomy. The CT and magnetic resonance (MR) imaging appearances of the more frequently encountered anomalies and some unusual variants are presented. In addition, the clinical relevance of the variations is discussed.

	Embryogenesis of the IVC

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Embryogenesis of the IVC Variations in IVC Anatomy Conclusions References

 
To better understand the etiology of IVC and renal vein anomalies, a concise review of the embryogenesis of the IVC is warranted. For the interested reader, Phillips (3) has published a comprehensive review of the embryogenesis of the IVC. In brief, the infrahepatic IVC develops between the 6th and 8th weeks of embryonic life as a composite structure formed from the continuous appearance and regression of three paired embryonic veins. In order of appearance, they are the posterior cardinal, the subcardinal, and the supracardinal veins (Fig 1).

View larger version (43K): [in this window] [in a new window] [Download PPT slide]   Figure 1.   Conceptual framework for development of the IVC. Composite schematic shows the relative positions and interrelationships of the three paired embryonic vessels that contribute to development of the IVC. The pictured veins are not all present simultaneously. Under ordinary circumstances, the prerenal division is formed from union of the hepatic segment (green area), a vitelline vein derivative, and the right subcardinal vein (magenta area). The renal segment is formed from the suprasubcardinal anastomosis (yellow area) and the postsubcardinal anastomosis (light violet area). The infrarenal segment derives from the right supracardinal vein (goldenrod area). The iliac veins form from the posterior cardinal veins (dark violet area). (Adapted and reprinted, with permission, from reference 4.) card  = cardinal, post  = posterior, SMA  = superior mesenteric artery, v  = vein, 1  = intersubcardinal anastomosis, 2  = intersupracardinal anastomosis.

The next major development is the appearance of the paired supracardinal veins (goldenrod in Fig 1), which lie dorsomedial to the posterior cardinal veins and dorsolateral to the aorta. Initially, multiple anastomoses form between the posterior and supracardinal veins. On each side, a suprasubcardinal anastomosis (yellow in Fig 1) develops from union of the postsupracardinal and the postsubcardinal anastomoses. In addition, intersupracardinal anastomoses develop dorsal to the aorta. The supracardinal veins then separate into cranial (azygos) and caudal (lumbar) ends. Meanwhile, inferiorly, anastomoses develop between the two posterior cardinal veins and between the posterior and lumbar supracardinal veins. With further atrophy of the posterior cardinal veins, blood return from the lower extremities is shunted through the supracardinal system to the suprasubcardinal anastomosis, then to the prerenal division of the IVC. In addition, blood return from the left side of the body is shunted to the right across the intersupracardinal and interpostcardinal anastomoses. Finally, the left supracardinal vein is one of the last veins to disappear, although Huntington and McLure (4) state that the vessel does not so much atrophy as become incorporated into the right supracardinal vein by coalescence of the multiple anastomoses.

In summary, the normal IVC is composed of four segments: hepatic, suprarenal, renal, and infrarenal. The hepatic segment is derived from the vitelline vein. The right subcardinal vein develops into the suprarenal segment by formation of the subcardinal-hepatic anastomosis. The renal segment develops from the right suprasubcardinal and postsubcardinal anastomoses. It is generally accepted that the infrarenal segment derives from the right supracardinal vein, although this idea is somewhat controversial (3). In the thoracic region, the supracardinal veins give rise to the azygos and hemiazygos veins. In the abdomen, the postcardinal veins are progressively replaced by the subcardinal and supracardinal veins but persist in the pelvis as the common iliac veins.

Since the embryonic ureter passes posterior to the posterior cardinal veins and anterolateral to the supracardinal vein, formation of the postsupracardinal anastomosis inferiorly and the suprasubcardinal anastomosis at the level of the kidney allows development of a potential periureteric venous ring. The renal collar is formed from the intersupracardinal anastomosis dorsally, the intersubcardinal anastomosis and postsubcardinal anastomoses ventrally, and the suprasubcardinal anastomosis laterally. The embryonic kidneys are initially drained by paired ventral and dorsal limbs. Ordinarily, both dorsal limbs regress. On the right side, the ventral limb is incorporated into the lateral wall of the renal segment of the IVC. On the left side, the ventral limb and the anterior limb of the renal collar form the normal adult left renal vein.

	Variations in IVC Anatomy

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Embryogenesis of the IVC Variations in IVC Anatomy Conclusions References

 
In a study of the development of the IVC in the domestic cat (Felis domestica), Huntington and McLure (4) proposed a classification system for IVC anomalies based on abnormal regression or abnormal persistence of various embryonic veins. These investigators suggested that there could be up to 14 theoretical variations in the anatomy of the infrarenal IVC. They noted that 11 of the 14 variants had been observed in the domestic cat or in humans. In addition, these authors observed that other anomalies seen in humans, such as abnormal development of the prerenal division of the IVC and persistence of the renal collar in the adult, could be explained on a similar basis. In the remainder of this article, we present nine cases that illustrate these and other variations of IVC and renal vein anatomy using CT and MR images.

Left IVC

A left IVC results from regression of the right supracardinal vein with persistence of the left supracardinal vein. The prevalence is 0.2%–0.5% (3). Typically, the left IVC joins the left renal vein, which crosses anterior to the aorta in the normal fashion, uniting with the right renal vein to form a normal right-sided prerenal IVC (Fig 2). The major clinical significance of this anomaly is the potential for misdiagnosis as left-sided paraaortic adenopathy (5). In addition, spontaneous rupture of an abdominal aortic aneurysm into a left IVC has been reported (6). Transjugular access to the infrarenal IVC for placement of an IVC filter may be difficult.

View larger version (29K): [in this window] [in a new window] [Download PPT slide]   Figure 2a.   Partial malrotation and left IVC in a 49-year-old man. (a) Schematic shows a left IVC terminating at the left renal vein. (b-e) CT scans presented from caudal to cranial show the anomaly. (b) Note the left IVC (arrow) inferior to the renal veins. (c) The left IVC joins the left renal vein (arrow). (d) The left renal vein (arrow) crosses anterior to the aorta in the normal fashion. (e) A normal right-sided prerenal IVC is formed from the confluence of the left (straight arrow) and right (curved arrow) renal veins. Note the increased attenuation of the right renal vein relative to that of the left due to absence of dilution from relatively unenhanced lower-extremity venous return.

View larger version (129K): [in this window] [in a new window] [Download PPT slide]   Figure 2b.   Partial malrotation and left IVC in a 49-year-old man. (a) Schematic shows a left IVC terminating at the left renal vein. (b-e) CT scans presented from caudal to cranial show the anomaly. (b) Note the left IVC (arrow) inferior to the renal veins. (c) The left IVC joins the left renal vein (arrow). (d) The left renal vein (arrow) crosses anterior to the aorta in the normal fashion. (e) A normal right-sided prerenal IVC is formed from the confluence of the left (straight arrow) and right (curved arrow) renal veins. Note the increased attenuation of the right renal vein relative to that of the left due to absence of dilution from relatively unenhanced lower-extremity venous return.

View larger version (137K): [in this window] [in a new window] [Download PPT slide]   Figure 2c.   Partial malrotation and left IVC in a 49-year-old man. (a) Schematic shows a left IVC terminating at the left renal vein. (b-e) CT scans presented from caudal to cranial show the anomaly. (b) Note the left IVC (arrow) inferior to the renal veins. (c) The left IVC joins the left renal vein (arrow). (d) The left renal vein (arrow) crosses anterior to the aorta in the normal fashion. (e) A normal right-sided prerenal IVC is formed from the confluence of the left (straight arrow) and right (curved arrow) renal veins. Note the increased attenuation of the right renal vein relative to that of the left due to absence of dilution from relatively unenhanced lower-extremity venous return.

View larger version (136K): [in this window] [in a new window] [Download PPT slide]   Figure 2d.   Partial malrotation and left IVC in a 49-year-old man. (a) Schematic shows a left IVC terminating at the left renal vein. (b-e) CT scans presented from caudal to cranial show the anomaly. (b) Note the left IVC (arrow) inferior to the renal veins. (c) The left IVC joins the left renal vein (arrow). (d) The left renal vein (arrow) crosses anterior to the aorta in the normal fashion. (e) A normal right-sided prerenal IVC is formed from the confluence of the left (straight arrow) and right (curved arrow) renal veins. Note the increased attenuation of the right renal vein relative to that of the left due to absence of dilution from relatively unenhanced lower-extremity venous return.

View larger version (142K): [in this window] [in a new window] [Download PPT slide]   Figure 2e.   Partial malrotation and left IVC in a 49-year-old man. (a) Schematic shows a left IVC terminating at the left renal vein. (b-e) CT scans presented from caudal to cranial show the anomaly. (b) Note the left IVC (arrow) inferior to the renal veins. (c) The left IVC joins the left renal vein (arrow). (d) The left renal vein (arrow) crosses anterior to the aorta in the normal fashion. (e) A normal right-sided prerenal IVC is formed from the confluence of the left (straight arrow) and right (curved arrow) renal veins. Note the increased attenuation of the right renal vein relative to that of the left due to absence of dilution from relatively unenhanced lower-extremity venous return.

Duplication of the IVC results from persistence of both supracardinal veins. The prevalence is 0.2%–3% (3). The left IVC typically ends at the left renal vein, which crosses anterior to the aorta in the normal fashion to join the right IVC (Fig 3). However, there may be variations in this arrangement (see the section entitled "Double IVC with Retroaortic Right Renal Vein and Hemiazygos Continuation of the IVC"). There may be significant asymmetry in the sizes of the left and right veins. Double IVC should be suspected in cases of recurrent pulmonary embolism following placement of an IVC filter (3). As with left IVC, misdiagnosis of the aberrant vessel as lymphadenopathy should be avoided.

View larger version (34K): [in this window] [in a new window] [Download PPT slide]   Figure 3a.   Lymphoma and double IVC in a 53-year-old woman. (a) Schematic shows left and right infrarenal IVCs. The left IVC terminates at the left renal vein. (b) CT scan obtained inferior to the renal veins shows left (straight arrow) and right (curved arrow) IVCs. (c-e) CT scans show the left IVC ending at the confluence with the left renal vein (arrow in c), which crosses anterior to the aorta in the normal fashion (arrow in d) to join a normal prerenal IVC (arrow in e).

View larger version (131K): [in this window] [in a new window] [Download PPT slide]   Figure 3b.   Lymphoma and double IVC in a 53-year-old woman. (a) Schematic shows left and right infrarenal IVCs. The left IVC terminates at the left renal vein. (b) CT scan obtained inferior to the renal veins shows left (straight arrow) and right (curved arrow) IVCs. (c-e) CT scans show the left IVC ending at the confluence with the left renal vein (arrow in c), which crosses anterior to the aorta in the normal fashion (arrow in d) to join a normal prerenal IVC (arrow in e).

View larger version (130K): [in this window] [in a new window] [Download PPT slide]   Figure 3c.   Lymphoma and double IVC in a 53-year-old woman. (a) Schematic shows left and right infrarenal IVCs. The left IVC terminates at the left renal vein. (b) CT scan obtained inferior to the renal veins shows left (straight arrow) and right (curved arrow) IVCs. (c-e) CT scans show the left IVC ending at the confluence with the left renal vein (arrow in c), which crosses anterior to the aorta in the normal fashion (arrow in d) to join a normal prerenal IVC (arrow in e).

View larger version (124K): [in this window] [in a new window] [Download PPT slide]   Figure 3d.   Lymphoma and double IVC in a 53-year-old woman. (a) Schematic shows left and right infrarenal IVCs. The left IVC terminates at the left renal vein. (b) CT scan obtained inferior to the renal veins shows left (straight arrow) and right (curved arrow) IVCs. (c-e) CT scans show the left IVC ending at the confluence with the left renal vein (arrow in c), which crosses anterior to the aorta in the normal fashion (arrow in d) to join a normal prerenal IVC (arrow in e).

View larger version (126K): [in this window] [in a new window] [Download PPT slide]   Figure 3e.   Lymphoma and double IVC in a 53-year-old woman. (a) Schematic shows left and right infrarenal IVCs. The left IVC terminates at the left renal vein. (b) CT scan obtained inferior to the renal veins shows left (straight arrow) and right (curved arrow) IVCs. (c-e) CT scans show the left IVC ending at the confluence with the left renal vein (arrow in c), which crosses anterior to the aorta in the normal fashion (arrow in d) to join a normal prerenal IVC (arrow in e).

Azygos continuation of the IVC has also been termed absence of the hepatic segment of the IVC with azygos continuation (7). The embryonic event is theorized to be failure to form the right subcardinal–hepatic anastomosis, with resulting atrophy of the right subcardinal vein. Consequently, blood is shunted from the suprasubcardinal anastomosis through the retrocrural azygos vein, which is partially derived from the thoracic segment of the right supracardinal vein. The prevalence is 0.6% (7).

The renal portion of the IVC receives blood return from both kidneys and passes posterior to the diaphragmatic crura to enter the thorax as the azygos vein (Fig 4). The azygos vein joins the superior vena cava at the normal location in the right paratracheal space. The hepatic segment (often termed the posthepatic segment) is ordinarily not truly absent; rather, it drains directly into the right atrium. Since the postsubcardinal anastomosis does not contribute to formation of the IVC, each gonadal vein drains to the ipsilateral renal vein (4).

View larger version (33K): [in this window] [in a new window] [Download PPT slide]   Figure 4a.   Abnormal mediastinum at chest radiography secondary to azygos continuation of the IVC in a 48-year-old man. (a) Schematic shows lack of contiguity between the prerenal segment of the IVC (arrow) and the hepatic segment. The vessel parallel to the aorta under the crus is the azygos vein. (b, c) CT scans obtained at the level of the diaphragmatic crus (b) and the level of the azygos vein arch (c) show the enlarged azygos vein (straight arrow) draining into the superior vena cava (curved arrow in c).

View larger version (101K): [in this window] [in a new window] [Download PPT slide]   Figure 4b.   Abnormal mediastinum at chest radiography secondary to azygos continuation of the IVC in a 48-year-old man. (a) Schematic shows lack of contiguity between the prerenal segment of the IVC (arrow) and the hepatic segment. The vessel parallel to the aorta under the crus is the azygos vein. (b, c) CT scans obtained at the level of the diaphragmatic crus (b) and the level of the azygos vein arch (c) show the enlarged azygos vein (straight arrow) draining into the superior vena cava (curved arrow in c).

View larger version (94K): [in this window] [in a new window] [Download PPT slide]   Figure 4c.   Abnormal mediastinum at chest radiography secondary to azygos continuation of the IVC in a 48-year-old man. (a) Schematic shows lack of contiguity between the prerenal segment of the IVC (arrow) and the hepatic segment. The vessel parallel to the aorta under the crus is the azygos vein. (b, c) CT scans obtained at the level of the diaphragmatic crus (b) and the level of the azygos vein arch (c) show the enlarged azygos vein (straight arrow) draining into the superior vena cava (curved arrow in c).

Circumaortic Left Renal Vein

A circumaortic left renal vein results from persistence of the dorsal limb of the embryonic left renal vein and of the dorsal arch of the renal collar (intersupracardinal anastomosis). The prevalence may be as high as 8.7% (3). Two left renal veins are present. The superior renal vein receives the left adrenal vein and crosses the aorta anteriorly. The inferior renal vein receives the left gonadal vein and crosses posterior to the aorta approximately 1–2 cm inferior to the normal anterior vein (Fig 5). The major clinical significance is in preoperative planning prior to nephrectomy and in renal vein catheterization for venous sampling. Misdiagnosis as retroperitoneal adenopathy should be avoided.

View larger version (39K): [in this window] [in a new window] [Download PPT slide]   Figure 5a.   Circumaortic left renal vein in a 73-year-old woman. (a) Schematic shows two left renal veins, with the inferior vein crossing posterior to the aorta. (b-e) Contiguous 5-mm-thick CT sections presented from cranial to caudal show the anomaly. (b) The superior left renal vein (arrow) crosses anterior to the aorta. (c-e) The inferior vein (curved arrow) descends approximately 2 cm and receives the left gonadal vein (straight arrow in d) before crossing posterior to the aorta.

View larger version (122K): [in this window] [in a new window] [Download PPT slide]   Figure 5b.   Circumaortic left renal vein in a 73-year-old woman. (a) Schematic shows two left renal veins, with the inferior vein crossing posterior to the aorta. (b-e) Contiguous 5-mm-thick CT sections presented from cranial to caudal show the anomaly. (b) The superior left renal vein (arrow) crosses anterior to the aorta. (c-e) The inferior vein (curved arrow) descends approximately 2 cm and receives the left gonadal vein (straight arrow in d) before crossing posterior to the aorta.

View larger version (123K): [in this window] [in a new window] [Download PPT slide]   Figure 5c.   Circumaortic left renal vein in a 73-year-old woman. (a) Schematic shows two left renal veins, with the inferior vein crossing posterior to the aorta. (b-e) Contiguous 5-mm-thick CT sections presented from cranial to caudal show the anomaly. (b) The superior left renal vein (arrow) crosses anterior to the aorta. (c-e) The inferior vein (curved arrow) descends approximately 2 cm and receives the left gonadal vein (straight arrow in d) before crossing posterior to the aorta.

View larger version (124K): [in this window] [in a new window] [Download PPT slide]   Figure 5d.   Circumaortic left renal vein in a 73-year-old woman. (a) Schematic shows two left renal veins, with the inferior vein crossing posterior to the aorta. (b-e) Contiguous 5-mm-thick CT sections presented from cranial to caudal show the anomaly. (b) The superior left renal vein (arrow) crosses anterior to the aorta. (c-e) The inferior vein (curved arrow) descends approximately 2 cm and receives the left gonadal vein (straight arrow in d) before crossing posterior to the aorta.

View larger version (121K): [in this window] [in a new window] [Download PPT slide]   Figure 5e.   Circumaortic left renal vein in a 73-year-old woman. (a) Schematic shows two left renal veins, with the inferior vein crossing posterior to the aorta. (b-e) Contiguous 5-mm-thick CT sections presented from cranial to caudal show the anomaly. (b) The superior left renal vein (arrow) crosses anterior to the aorta. (c-e) The inferior vein (curved arrow) descends approximately 2 cm and receives the left gonadal vein (straight arrow in d) before crossing posterior to the aorta.

As with circumaortic left renal vein, a retroaortic left renal vein results from persistence of the dorsal arch of the renal collar. However, in this variation the ventral arch (intersubcardinal anastomosis) regresses so that a single renal vein passes posterior to the aorta (Fig 6). The prevalence is 2.1% (3). The clinical significance is preoperative recognition of the anomaly.

View larger version (30K): [in this window] [in a new window] [Download PPT slide]   Figure 6a.   Retroaortic left renal vein in a 27-year-old man. (a) Schematic shows a single left renal vein, which crosses posterior to the aorta. (b, c) CT scans show the left renal vein (arrow) descending to cross posterior to the aorta.

View larger version (130K): [in this window] [in a new window] [Download PPT slide]   Figure 6b.   Retroaortic left renal vein in a 27-year-old man. (a) Schematic shows a single left renal vein, which crosses posterior to the aorta. (b, c) CT scans show the left renal vein (arrow) descending to cross posterior to the aorta.

View larger version (127K): [in this window] [in a new window] [Download PPT slide]   Figure 6c.   Retroaortic left renal vein in a 27-year-old man. (a) Schematic shows a single left renal vein, which crosses posterior to the aorta. (b, c) CT scans show the left renal vein (arrow) descending to cross posterior to the aorta.

More than one anomaly can coexist in a patient. In the case of a double IVC with a retroaortic right renal vein and hemiazygos continuation of the IVC, the embryologic basis is persistence of the left lumbar and thoracic supracardinal vein and the left suprasubcardinal anastomosis, together with failure of formation of the right sub-cardinal–hepatic anastomosis. In addition, the right renal vein and right IVC meet and cross posterior to the aorta to join the left IVC and continue cephalad as the hemiazygos vein (Fig 7). Thus, there is also persistence of the dorsal limb of the renal collar and regression of the ventral limb. In the thorax, the hemiazygos vein crosses posterior to the aorta at approximately T8 or T9 to join the rudimentary azygos vein. Alternate collateral pathways for the hemiazygos vein include (a) cephalad continuation to join the coronary vein of the heart via a persistent left superior vena cava and (b) accessory hemiazygos continuation to the left brachiocephalic vein (9).

View larger version (32K): [in this window] [in a new window] [Download PPT slide]   Figure 7a.   Spinal dysraphism and double IVC with hemiazygos continuation in a 2-year-old boy. (a) Schematic shows failed development of the right prerenal IVC and hemiazygos continuation of the left IVC. (b-e) MR images presented from caudal to cranial show the anomaly. (b) Note the right (straight arrow) and left (curved arrow) IVCs. (c) The right renal vein (arrowhead) descends to receive the right IVC and crosses posterior to the aorta (arrow) to join the left IVC. (d) The left IVC continues cephalad left of the aorta under the diaphragmatic crus as the hemiazygos vein (arrow). (e) In the thorax, the hemiazygos vein (straight arrow) crosses posterior to the aorta (arrowhead) to join a rudimentary azygos vein (curved arrow) approximately 1-2 cm below the carina.

View larger version (99K): [in this window] [in a new window] [Download PPT slide]   Figure 7b.   Spinal dysraphism and double IVC with hemiazygos continuation in a 2-year-old boy. (a) Schematic shows failed development of the right prerenal IVC and hemiazygos continuation of the left IVC. (b-e) MR images presented from caudal to cranial show the anomaly. (b) Note the right (straight arrow) and left (curved arrow) IVCs. (c) The right renal vein (arrowhead) descends to receive the right IVC and crosses posterior to the aorta (arrow) to join the left IVC. (d) The left IVC continues cephalad left of the aorta under the diaphragmatic crus as the hemiazygos vein (arrow). (e) In the thorax, the hemiazygos vein (straight arrow) crosses posterior to the aorta (arrowhead) to join a rudimentary azygos vein (curved arrow) approximately 1-2 cm below the carina.

View larger version (106K): [in this window] [in a new window] [Download PPT slide]   Figure 7c.   Spinal dysraphism and double IVC with hemiazygos continuation in a 2-year-old boy. (a) Schematic shows failed development of the right prerenal IVC and hemiazygos continuation of the left IVC. (b-e) MR images presented from caudal to cranial show the anomaly. (b) Note the right (straight arrow) and left (curved arrow) IVCs. (c) The right renal vein (arrowhead) descends to receive the right IVC and crosses posterior to the aorta (arrow) to join the left IVC. (d) The left IVC continues cephalad left of the aorta under the diaphragmatic crus as the hemiazygos vein (arrow). (e) In the thorax, the hemiazygos vein (straight arrow) crosses posterior to the aorta (arrowhead) to join a rudimentary azygos vein (curved arrow) approximately 1-2 cm below the carina.

View larger version (95K): [in this window] [in a new window] [Download PPT slide]   Figure 7d.   Spinal dysraphism and double IVC with hemiazygos continuation in a 2-year-old boy. (a) Schematic shows failed development of the right prerenal IVC and hemiazygos continuation of the left IVC. (b-e) MR images presented from caudal to cranial show the anomaly. (b) Note the right (straight arrow) and left (curved arrow) IVCs. (c) The right renal vein (arrowhead) descends to receive the right IVC and crosses posterior to the aorta (arrow) to join the left IVC. (d) The left IVC continues cephalad left of the aorta under the diaphragmatic crus as the hemiazygos vein (arrow). (e) In the thorax, the hemiazygos vein (straight arrow) crosses posterior to the aorta (arrowhead) to join a rudimentary azygos vein (curved arrow) approximately 1-2 cm below the carina.

View larger version (98K): [in this window] [in a new window] [Download PPT slide]   Figure 7e.   Spinal dysraphism and double IVC with hemiazygos continuation in a 2-year-old boy. (a) Schematic shows failed development of the right prerenal IVC and hemiazygos continuation of the left IVC. (b-e) MR images presented from caudal to cranial show the anomaly. (b) Note the right (straight arrow) and left (curved arrow) IVCs. (c) The right renal vein (arrowhead) descends to receive the right IVC and crosses posterior to the aorta (arrow) to join the left IVC. (d) The left IVC continues cephalad left of the aorta under the diaphragmatic crus as the hemiazygos vein (arrow). (e) In the thorax, the hemiazygos vein (straight arrow) crosses posterior to the aorta (arrowhead) to join a rudimentary azygos vein (curved arrow) approximately 1-2 cm below the carina.

Double IVC with Retroaortic Left Renal Vein and Azygos Continuation of the IVC

A double IVC with a retroaortic left renal vein and azygos continuation of the IVC is an interesting combination. It results from persistence of the left supracardinal vein and the dorsal limb of the renal collar with regression of the ventral limb. In addition, the subcardinal-hepatic anastomosis fails to form (Fig 8). A recent study (13) demonstrated that azygos continuation of the IVC can be predicted with ultrasonography by identifying the right renal artery crossing abnormally anterior to the IVC.

View larger version (30K): [in this window] [in a new window] [Download PPT slide]   Figure 8a.   Double IVC with a retroaortic left renal vein and azygos continuation in a 31-year-old woman. (a) Schematic shows the anomalous venous pattern. (b-e) CT scans presented from caudal to cranial show the anomaly. (b) The right IVC receives the right renal vein (straight arrow). Note the left IVC (curved arrow). (c) The left IVC (arrow) receives the left renal vein. (d) The left renal vein (arrow) crosses posterior to the aorta to join the right IVC. (e) The right IVC continues cephalad as the azygos vein (arrow) within the retrocrural space.

View larger version (113K): [in this window] [in a new window] [Download PPT slide]   Figure 8b.   Double IVC with a retroaortic left renal vein and azygos continuation in a 31-year-old woman. (a) Schematic shows the anomalous venous pattern. (b-e) CT scans presented from caudal to cranial show the anomaly. (b) The right IVC receives the right renal vein (straight arrow). Note the left IVC (curved arrow). (c) The left IVC (arrow) receives the left renal vein. (d) The left renal vein (arrow) crosses posterior to the aorta to join the right IVC. (e) The right IVC continues cephalad as the azygos vein (arrow) within the retrocrural space.

View larger version (111K): [in this window] [in a new window] [Download PPT slide]   Figure 8c.   Double IVC with a retroaortic left renal vein and azygos continuation in a 31-year-old woman. (a) Schematic shows the anomalous venous pattern. (b-e) CT scans presented from caudal to cranial show the anomaly. (b) The right IVC receives the right renal vein (straight arrow). Note the left IVC (curved arrow). (c) The left IVC (arrow) receives the left renal vein. (d) The left renal vein (arrow) crosses posterior to the aorta to join the right IVC. (e) The right IVC continues cephalad as the azygos vein (arrow) within the retrocrural space.

View larger version (116K): [in this window] [in a new window] [Download PPT slide]   Figure 8d.   Double IVC with a retroaortic left renal vein and azygos continuation in a 31-year-old woman. (a) Schematic shows the anomalous venous pattern. (b-e) CT scans presented from caudal to cranial show the anomaly. (b) The right IVC receives the right renal vein (straight arrow). Note the left IVC (curved arrow). (c) The left IVC (arrow) receives the left renal vein. (d) The left renal vein (arrow) crosses posterior to the aorta to join the right IVC. (e) The right IVC continues cephalad as the azygos vein (arrow) within the retrocrural space.

View larger version (115K): [in this window] [in a new window] [Download PPT slide]   Figure 8e.   Double IVC with a retroaortic left renal vein and azygos continuation in a 31-year-old woman. (a) Schematic shows the anomalous venous pattern. (b-e) CT scans presented from caudal to cranial show the anomaly. (b) The right IVC receives the right renal vein (straight arrow). Note the left IVC (curved arrow). (c) The left IVC (arrow) receives the left renal vein. (d) The left renal vein (arrow) crosses posterior to the aorta to join the right IVC. (e) The right IVC continues cephalad as the azygos vein (arrow) within the retrocrural space.

A circumcaval ureter is also termed a retrocaval ureter. The right supracardinal system fails to develop, whereas the right posterior cardinal vein persists. With one reported exception (14), the anomaly always occurs on the right side. The proximal ureter courses posterior to the IVC, then emerges to the right of the aorta, coming to lie anterior to the right iliac vessels (Fig 9). Patients with this anomaly may develop partial right ureteral obstruction or recurrent urinary tract infections. Therapeutic options include surgical relocation of the ureter anterior to the cava (3).

View larger version (36K): [in this window] [in a new window] [Download PPT slide]   Figure 9a.   Hematuria and circumcaval ureter in a 65-year-old man. (a) Schematic shows the right ureter encircling the IVC. (b-d) CT scans presented from cranial to caudal show the anomaly. (b) The right ureter (arrow) is positioned posterior to the IVC. (c) The ureter (arrow) then courses to the left of the IVC. (d) Finally, the ureter (arrow) crosses anterior to the IVC. (Courtesy of Akira Kawashima, MD, Lyndon B. Johnson General Hospital, Houston, Tex.)

View larger version (87K): [in this window] [in a new window] [Download PPT slide]   Figure 9b.   Hematuria and circumcaval ureter in a 65-year-old man. (a) Schematic shows the right ureter encircling the IVC. (b-d) CT scans presented from cranial to caudal show the anomaly. (b) The right ureter (arrow) is positioned posterior to the IVC. (c) The ureter (arrow) then courses to the left of the IVC. (d) Finally, the ureter (arrow) crosses anterior to the IVC. (Courtesy of Akira Kawashima, MD, Lyndon B. Johnson General Hospital, Houston, Tex.)

View larger version (88K): [in this window] [in a new window] [Download PPT slide]   Figure 9c.   Hematuria and circumcaval ureter in a 65-year-old man. (a) Schematic shows the right ureter encircling the IVC. (b-d) CT scans presented from cranial to caudal show the anomaly. (b) The right ureter (arrow) is positioned posterior to the IVC. (c) The ureter (arrow) then courses to the left of the IVC. (d) Finally, the ureter (arrow) crosses anterior to the IVC. (Courtesy of Akira Kawashima, MD, Lyndon B. Johnson General Hospital, Houston, Tex.)

View larger version (90K): [in this window] [in a new window] [Download PPT slide]   Figure 9d.   Hematuria and circumcaval ureter in a 65-year-old man. (a) Schematic shows the right ureter encircling the IVC. (b-d) CT scans presented from cranial to caudal show the anomaly. (b) The right ureter (arrow) is positioned posterior to the IVC. (c) The ureter (arrow) then courses to the left of the IVC. (d) Finally, the ureter (arrow) crosses anterior to the IVC. (Courtesy of Akira Kawashima, MD, Lyndon B. Johnson General Hospital, Houston, Tex.)

Several reports have described absence of the entire IVC (15–17) or absence of the infrarenal IVC with preservation of the suprarenal segment (Fig 10) (18,19). Absence of the entire posthepatic IVC suggests that all three paired venous systems failed to develop properly. Absence of the infrarenal IVC implies failure of development of the posterior cardinal and supracardinal veins. Since it is difficult to identify a single embryonic event that can lead to either of these scenarios, there is controversy as to whether these conditions are true embryonic anomalies or the result of perinatal IVC thrombosis (15,18,19). In the case presented herein (Fig 10), the common iliac veins are also absent. The external and internal iliac veins join to form enlarged ascending lumbar veins, which convey blood return from the lower extremities to the azygos and hemiazygos veins via anterior paravertebral collateral veins. A normal suprarenal IVC is formed by confluence of the renal veins. Patients with absent IVC may present with symptoms of lower-extremity venous insufficiency (16–18) or idiopathic deep venous thrombosis (19,20). The collateral circulation may simulate a paraspinal mass (15).

View larger version (41K): [in this window] [in a new window] [Download PPT slide]   Figure 10a.   Hepatitis C and absent infrarenal IVC in a 48-year-old woman. (a) Schematic shows absence of the IVC below the renal veins. Collateral flow from the lower extremities reaches the azygos vein via paravertebral collateral veins. (b) CT scan obtained inferior to the aortic bifurcation shows absence of the common iliac veins. Enlarged ascending lumbar veins are present (black arrow). Note the iliac arteries (white arrow). (c) CT scan obtained inferior to the kidneys shows absence of the IVC (white arrow). Enlarged ascending lumbar veins are present (black arrow). (d) CT scan obtained at the level of the renal veins shows a normal prerenal IVC formed at the confluence of the renal veins (arrow). (e) CT scan obtained at the level of the prerenal IVC (white arrow) shows prominent paravertebral collateral veins (black arrow), which lead to a prominent azygos vein (arrowhead). (f) Coronal T1-weighted MR image shows the enlarged ascending lumbar veins (arrow). (g) Lateral maximum-intensity projection reconstruction of two-dimensional time-of-flight MR images shows formation of enlarged ascending lumbar veins at the confluence of the internal and external iliac veins (solid straight arrow). Note the anastomoses between the ascending lumbar veins and the azygos vein (open straight arrow) via prominent anterior paravertebral veins (white curved arrow). Also note the prerenal IVC (black arrowhead) posterior to the portal vein (black curved arrow), as well as prominent anterior abdominal wall collateral veins (white arrowheads). (Figs 10b, 10c, and 10g reprinted, with permission, from reference 19.)

View larger version (104K): [in this window] [in a new window] [Download PPT slide]   Figure 10b.   Hepatitis C and absent infrarenal IVC in a 48-year-old woman. (a) Schematic shows absence of the IVC below the renal veins. Collateral flow from the lower extremities reaches the azygos vein via paravertebral collateral veins. (b) CT scan obtained inferior to the aortic bifurcation shows absence of the common iliac veins. Enlarged ascending lumbar veins are present (black arrow). Note the iliac arteries (white arrow). (c) CT scan obtained inferior to the kidneys shows absence of the IVC (white arrow). Enlarged ascending lumbar veins are present (black arrow). (d) CT scan obtained at the level of the renal veins shows a normal prerenal IVC formed at the confluence of the renal veins (arrow). (e) CT scan obtained at the level of the prerenal IVC (white arrow) shows prominent paravertebral collateral veins (black arrow), which lead to a prominent azygos vein (arrowhead). (f) Coronal T1-weighted MR image shows the enlarged ascending lumbar veins (arrow). (g) Lateral maximum-intensity projection reconstruction of two-dimensional time-of-flight MR images shows formation of enlarged ascending lumbar veins at the confluence of the internal and external iliac veins (solid straight arrow). Note the anastomoses between the ascending lumbar veins and the azygos vein (open straight arrow) via prominent anterior paravertebral veins (white curved arrow). Also note the prerenal IVC (black arrowhead) posterior to the portal vein (black curved arrow), as well as prominent anterior abdominal wall collateral veins (white arrowheads). (Figs 10b, 10c, and 10g reprinted, with permission, from reference 19.)

View larger version (96K): [in this window] [in a new window] [Download PPT slide]   Figure 10c.   Hepatitis C and absent infrarenal IVC in a 48-year-old woman. (a) Schematic shows absence of the IVC below the renal veins. Collateral flow from the lower extremities reaches the azygos vein via paravertebral collateral veins. (b) CT scan obtained inferior to the aortic bifurcation shows absence of the common iliac veins. Enlarged ascending lumbar veins are present (black arrow). Note the iliac arteries (white arrow). (c) CT scan obtained inferior to the kidneys shows absence of the IVC (white arrow). Enlarged ascending lumbar veins are present (black arrow). (d) CT scan obtained at the level of the renal veins shows a normal prerenal IVC formed at the confluence of the renal veins (arrow). (e) CT scan obtained at the level of the prerenal IVC (white arrow) shows prominent paravertebral collateral veins (black arrow), which lead to a prominent azygos vein (arrowhead). (f) Coronal T1-weighted MR image shows the enlarged ascending lumbar veins (arrow). (g) Lateral maximum-intensity projection reconstruction of two-dimensional time-of-flight MR images shows formation of enlarged ascending lumbar veins at the confluence of the internal and external iliac veins (solid straight arrow). Note the anastomoses between the ascending lumbar veins and the azygos vein (open straight arrow) via prominent anterior paravertebral veins (white curved arrow). Also note the prerenal IVC (black arrowhead) posterior to the portal vein (black curved arrow), as well as prominent anterior abdominal wall collateral veins (white arrowheads). (Figs 10b, 10c, and 10g reprinted, with permission, from reference 19.)

View larger version (116K): [in this window] [in a new window] [Download PPT slide]   Figure 10d.   Hepatitis C and absent infrarenal IVC in a 48-year-old woman. (a) Schematic shows absence of the IVC below the renal veins. Collateral flow from the lower extremities reaches the azygos vein via paravertebral collateral veins. (b) CT scan obtained inferior to the aortic bifurcation shows absence of the common iliac veins. Enlarged ascending lumbar veins are present (black arrow). Note the iliac arteries (white arrow). (c) CT scan obtained inferior to the kidneys shows absence of the IVC (white arrow). Enlarged ascending lumbar veins are present (black arrow). (d) CT scan obtained at the level of the renal veins shows a normal prerenal IVC formed at the confluence of the renal veins (arrow). (e) CT scan obtained at the level of the prerenal IVC (white arrow) shows prominent paravertebral collateral veins (black arrow), which lead to a prominent azygos vein (arrowhead). (f) Coronal T1-weighted MR image shows the enlarged ascending lumbar veins (arrow). (g) Lateral maximum-intensity projection reconstruction of two-dimensional time-of-flight MR images shows formation of enlarged ascending lumbar veins at the confluence of the internal and external iliac veins (solid straight arrow). Note the anastomoses between the ascending lumbar veins and the azygos vein (open straight arrow) via prominent anterior paravertebral veins (white curved arrow). Also note the prerenal IVC (black arrowhead) posterior to the portal vein (black curved arrow), as well as prominent anterior abdominal wall collateral veins (white arrowheads). (Figs 10b, 10c, and 10g reprinted, with permission, from reference 19.)

View larger version (115K): [in this window] [in a new window] [Download PPT slide]   Figure 10e.   Hepatitis C and absent infrarenal IVC in a 48-year-old woman. (a) Schematic shows absence of the IVC below the renal veins. Collateral flow from the lower extremities reaches the azygos vein via paravertebral collateral veins. (b) CT scan obtained inferior to the aortic bifurcation shows absence of the common iliac veins. Enlarged ascending lumbar veins are present (black arrow). Note the iliac arteries (white arrow). (c) CT scan obtained inferior to the kidneys shows absence of the IVC (white arrow). Enlarged ascending lumbar veins are present (black arrow). (d) CT scan obtained at the level of the renal veins shows a normal prerenal IVC formed at the confluence of the renal veins (arrow). (e) CT scan obtained at the level of the prerenal IVC (white arrow) shows prominent paravertebral collateral veins (black arrow), which lead to a prominent azygos vein (arrowhead). (f) Coronal T1-weighted MR image shows the enlarged ascending lumbar veins (arrow). (g) Lateral maximum-intensity projection reconstruction of two-dimensional time-of-flight MR images shows formation of enlarged ascending lumbar veins at the confluence of the internal and external iliac veins (solid straight arrow). Note the anastomoses between the ascending lumbar veins and the azygos vein (open straight arrow) via prominent anterior paravertebral veins (white curved arrow). Also note the prerenal IVC (black arrowhead) posterior to the portal vein (black curved arrow), as well as prominent anterior abdominal wall collateral veins (white arrowheads). (Figs 10b, 10c, and 10g reprinted, with permission, from reference 19.)

View larger version (160K): [in this window] [in a new window] [Download PPT slide]   Figure 10f.   Hepatitis C and absent infrarenal IVC in a 48-year-old woman. (a) Schematic shows absence of the IVC below the renal veins. Collateral flow from the lower extremities reaches the azygos vein via paravertebral collateral veins. (b) CT scan obtained inferior to the aortic bifurcation shows absence of the common iliac veins. Enlarged ascending lumbar veins are present (black arrow). Note the iliac arteries (white arrow). (c) CT scan obtained inferior to the kidneys shows absence of the IVC (white arrow). Enlarged ascending lumbar veins are present (black arrow). (d) CT scan obtained at the level of the renal veins shows a normal prerenal IVC formed at the confluence of the renal veins (arrow). (e) CT scan obtained at the level of the prerenal IVC (white arrow) shows prominent paravertebral collateral veins (black arrow), which lead to a prominent azygos vein (arrowhead). (f) Coronal T1-weighted MR image shows the enlarged ascending lumbar veins (arrow). (g) Lateral maximum-intensity projection reconstruction of two-dimensional time-of-flight MR images shows formation of enlarged ascending lumbar veins at the confluence of the internal and external iliac veins (solid straight arrow). Note the anastomoses between the ascending lumbar veins and the azygos vein (open straight arrow) via prominent anterior paravertebral veins (white curved arrow). Also note the prerenal IVC (black arrowhead) posterior to the portal vein (black curved arrow), as well as prominent anterior abdominal wall collateral veins (white arrowheads). (Figs 10b, 10c, and 10g reprinted, with permission, from reference 19.)

View larger version (168K): [in this window] [in a new window] [Download PPT slide]   Figure 10g.   Hepatitis C and absent infrarenal IVC in a 48-year-old woman. (a) Schematic shows absence of the IVC below the renal veins. Collateral flow from the lower extremities reaches the azygos vein via paravertebral collateral veins. (b) CT scan obtained inferior to the aortic bifurcation shows absence of the common iliac veins. Enlarged ascending lumbar veins are present (black arrow). Note the iliac arteries (white arrow). (c) CT scan obtained inferior to the kidneys shows absence of the IVC (white arrow). Enlarged ascending lumbar veins are present (black arrow). (d) CT scan obtained at the level of the renal veins shows a normal prerenal IVC formed at the confluence of the renal veins (arrow). (e) CT scan obtained at the level of the prerenal IVC (white arrow) shows prominent paravertebral collateral veins (black arrow), which lead to a prominent azygos vein (arrowhead). (f) Coronal T1-weighted MR image shows the enlarged ascending lumbar veins (arrow). (g) Lateral maximum-intensity projection reconstruction of two-dimensional time-of-flight MR images shows formation of enlarged ascending lumbar veins at the confluence of the internal and external iliac veins (solid straight arrow). Note the anastomoses between the ascending lumbar veins and the azygos vein (open straight arrow) via prominent anterior paravertebral veins (white curved arrow). Also note the prerenal IVC (black arrowhead) posterior to the portal vein (black curved arrow), as well as prominent anterior abdominal wall collateral veins (white arrowheads). (Figs 10b, 10c, and 10g reprinted, with permission, from reference 19.)

	Conclusions

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Embryogenesis of the IVC Variations in IVC Anatomy Conclusions References