CT Evaluation of Anomalies of the Inferior Vena Cava and Left Renal Vein

Transcription

1 CT Evaluation of Anomalies of the Inferior Vena Cava and Left Renal Vein STUART A. ROYAL1 AND PETER W. CALLEN1 Two patients with duplication of the inferior vena cava and two patients with a retroaortlc left renal vein were examined by computed tomography (CT). The characteristic CT appearance of these two entities, as well as circumaortic left renal vein and transposition of the inferior vena cava, is discussed. A scheme by which these anomalies of the inferior vena cava and left renal vein may be distinguished from one another and from pathologic entities such as lymphadenopathy and a dilated gonadal vein is reported. An understanding of the congenital abnormalities of the left renal vein and inferior vena cava is important to both surgeons [1, 2] and radiologists. [3, 4]. Although these anomalies are not common, their recognition is important before performing vascular procedures involving the renal pedicle and to avoid mistaking their unusual appearance on computed tomography (CT) scans as pathologic. We recently examined two patients with a retroaortic left renal vein and two patients with duplication of the inferior vena cava by CT. The CT appearance of these and related anomalies of the inferior vena cava and left renal vein is discussed. Subjects and Methods Four patients with anomalies related to the inferior vena cava were examined by CT on either an EMI 5005 or General Electric CT/I scanner. Patients were examined both before and after intravenous administration of urographic contrast materialinfusion of 300 ml Conray 30%. When delineation of specific vessels was desired, a bolus injection of about ml Conray 60% was administered via the saphenous vein. Scans were performed at 1-2 cm intervals. In three of the four cases, they were reconstructed in the sagittal and coronal planes, in addition to the conventional axial reconstruction. Anatomic Considerations The anatomy [5] and embryology [6, 7] of the normal inferior vena cava and left renal vein have been extensively reviewed in the surgical and radiologic literature and will not be discussed. The anomalies involving both the inferior vena cava and left renal vein can be divided into four major types: (1) transposition of the inferior vena cava (incidence, 0.2%-0.5%); (2) duplication of the inferior vena cava (incidence, 0.2%-3.0%); (3) circumaortic left renal vein (incidence, 1.5%-8.7%); and (4) retroaortic left renal vein (incidence, 1.8%-2.4%) [2]. Each of these conditions may have a retroaortic venous structure as part of its anomaly and thus they form a differential diagnostic gamut. Other congenital anomalies of the inferior vena cava, such as circumcaval ureter, interrupted inferior vena cava with azygous!hemiazygous continuation, and isolated left inferior vena cava, will not be discussed since retroaortic venous structures are not part of their anomaly. Transposition and duplication of the inferior vena cava are related embryologically since they are anomalies of persistence and/or regression of the left and right supracardinal veins [7]. Transposition of the Inferior Vena Cava In transposition of the inferior vena cava, there is a single inferior vena cava that ascends on the left side of the spine and crosses either anterior or posterior to the aorta at the level of the renal veins to further ascend to the right atrium on the right side of the spine [2, 7, 8]. On CT, one would anticipate seeing a single right-side inferior vena cava at levels above the renal veins, a vascular structure crossing either anterior or posterior to the aorta at the level of the renal veins, and a large single venous structure (the transposed inferior vena cava) to the left of the spine at levels below the renal veins (fig. 1). Duplication of the Inferior Vena Cava In duplication of the inferior vena cava [2, 4, 7], there is a normal inferior vena cava along the right side of the spine. In addition, a left-side inferior vena cava ascends to the level of the renal veins to join the right-side inferior vena cava through a vascular structure that may pass either anterior or posterior to the aorta at the level of the renal veins. The characteristic CT appearance (fig. 1) is a single right-side inferior vena cava at levels above the renal veins, a vascular structure crossing either anterior or posterior to the aorta at the level of the renal veins, and a vascular structure to the left (i.e., the duplicated inferior vena cava) and right of the aorta below the level of the renal veins (figs. 1-3). Duplication and transposition of the inferior vena cava may be differentiated by sections caudal to the level of the renal veins. In duplication, the right-side inferior vena cava will be seen as continuous to its bifurcation into the iliac veins, whereas the inferior vena cava will be absent on the right side in transposition of the inferior vena cava. Circumaortic and retroaortic left renal veins compose a series of embryologic abnormalities of the left renal vein. Various combinations of persistence and regres- Received October 2, 1978; accepted after revision January 23, This work was supported in part by National Institutes of Health Training grant Department of Radiology, M-380, University of California School of Medicine, San Francisco, California Address reprint requests to P. W. Callen. AJR 132: , May American Roentgen Ray Society X179/ $0.00

2 760 ROYAL AND CALLEN AJR:132, May 1979 TRANSPOSITION DUPLICATION Cl RCUMAORTIC OF THE IVC OF THE 1VC LRV RETROAORTIC LRV Fig. 1.-CT sections of aorta (Ao). inferior vena cava (IVC), and left renal vein in anomalies of inferior vena cava and left renal vein. In transposition and duplication of inferior vena cava venous structure may pass either antenor or posterior (dashed lines) to aorta at level of renal veins. A Fig. 2.-Patient with duplication of inferior vena cava. A, At level just caudad to renal veins. After bolus intravenous injection of contrast material, left inferior vena cava (arrow) appears as rounded enhanced structure prior to entrance into left renal vein. a = aorta, i = normal right-side inferior vena cava. B, Inferior vena cavogram. Both inferior vena cavas can be seen (*), as well as vascular connection (arrow) at level of kidneys. B

3 AJR:132, May 1979 CT OF VASCULAR ANOMALIES 761 I 1.. V Fig. 3.-Patient with duplication of inferior vena cava. A, At level of renal veins. Entry of duplicated inferior vena cava unites into left renal vein seen as focal dilatation (arrow) of left renal vein. B, just caudad to renal veins. Duplicated inferior vena cava (arrow) continues as large vascular structure immediately left of aorta (a). C, Immediately cephalad to bifurcation of iliac veins. Duplicated inferior vena cava (large arrow) seen as prominent vascular structure left of common iliac artery (small arrow). 0, Coronal reconstruction. Continuous nature of duplicated inferior vena cava ( ) from level just cephalad iliac veins to entrance into left renal vein. Li = liver, a = aorta, i = normal right-side inferior vena cava.

4 762 ROYAL AND CALLEN AJR:132, May 1979 I sion of the left supracardinal (posterior to the aorta) and left subcardinal (anterior to the aorta) veins that occur during embryogenesis produce the anomalies [6]. Circumaortic Left Renal Vein In circumaortic left renal vein, there is a true vascular ring about the aorta. The preaortic left renal vein crosses from the left kidney to the inferior vena cava at the expected level of the renal veins. The retroaortic vein connects the preaortic vein to the inferior vena cava by descending caudally and crossing the spine behind the aorta, usually one to two vertebral levels below the level of the preaortic left renal vein [3, ]. In this situation, CT will demonstrate the preaortic left renal vein in the expected course of the normal left renal vein and the anomalous retroaortic left renal vein in a more caudal position (fig. 1). Retroaortic Left Renal Vein In retroaortic left renal vein, the anterior subcardinal veins regress completely and only the retroaortic supracardinal veins remain to connect the left kidney to the inferior vena cava. The course of the left renal vein can be either retroaortic at the level of the normal left renal vein or it may course obliquely caudad behind the aorta to enter the inferior vena cava as low as the confluence of the iliac veins (fig. 1) [2, 9, 10]. In both of our cases, the retroaortic left renal vein crossed at the level of the normal renal vein (figs. 4 and 5). An unopacified segment of the third part of the duodenum must not be mistaken as the normal left renal vein, thus suggesting the incorrect diagnosis of a circumaortic left renal vein in the presence of a retroaortic left renal vein. Since both transposition and duplication of the inferior vena cava may have venous structures that pass postenor to the aorta at the level of the renal veins, they may be confused with simple circumaortic and retroaortic left Fig. 4.-Patient with retroaortic left renal vein (A, arrow). B, Sagittal reconstruction. Retroaortic left renal vein (arrow) courses posterior to aorta. A = aorta; I = inferior vena cava. renal veins. However, they should be easily distinguished on CT, since circumaortic and retroaortic left renal veins have no associated inferior vena cava anomaly. Thus, in the presence of a retroaortic vascular structure at the level of the renal veins on CT, the inferior vena cava anatomy below the level of the renal veins should help distinguish isolated left renal vein anomalies from transposition and duplication of the inferior vena cava. Discussion Other diagnostic considerations may be entertained when evaluating the patient with an infrarenal left inferior vena cava by CT. On a single tomographic section, the left inferior vena cava may look like an enlarged lymph node. The continuous nature of the inferior vena cava anomaly on consecutive sections, or as seen with sagittal or coronal reconstructions (fig. 3D), should be apparent and serve to distinguish this from an enlarged lymph node. In addition, intravenous contrast enhancement of the inferior vena cava should further help distinguish these two structures. A second differential consideration would be an enlarged left gonadal vein, since its distal portion can simulate a left inferior vena cava by joining the left renal vein and coursing along the left side of the spine. However, these two can be distinguished anatomically since, proceeding caudally, the proximal left gonadal vein crosses the psoas muscle to enter the inguinal canal; whereas the left inferior vena cava will continue to run along the left side of the spine to join the left common iliac vein (fig. 2B). These two structures can be differentiated by observing the effect of intravenous contrast enhancement after a bolus injection into the left saphenous vein using sequential rapid scans. The left inferior vena cava should show immediate contrast enhancement as opposed to delayed enhancement (after the aorta) of the left gonadal vein.

5 AJR:132, May 1979 CT OF VASCULAR ANOMALIES 763 alies can be categorized by CT and can be differentiated from other pathologic entities. REFERENCES Fig. 5.-Patient with retroaortic I ft renal vein. Left renal vein (arrows) points posteriorly prior to course behind aorta (A). I = inferior vena cava. The importance of diagnosing left renal vein and inferior vena cava anomalies has been documented. Surgically, these anomalies can affect decisions regarding shunt placement for portal hypertension, choosing prospective renal transplant donors, choosing the site for inferior vena cava ligation for thromboembolic disease, repairing aortic aneurysms, and performing other retroperitoneal surgery [1, 2, 9, 11]. Angiographically, awareness of this anomaly is important in performing adrenal venography, renal vein sampling, and in avoiding the false interpretation that a mass lesion is causing the inferior displacement of the retroaortic left renal vein [3, 6]. Using the framework presented here, these anom- 1. Thomas TV: Surgical implications of retroaortic left renal vein.arch Surg 100: , Brener BJ, Darling RC, Frederick PL, Linton RR: Major venous anomalies complicating abdominal aortic surgery. Arch Surg 108: , Kottra JJ, Castellino RA: The circumaortic left renal vein: angiographic appearance. Radiology 95 : , Berkow AE, Henkin RE: Double inferior vena cava or iliac vein occlusion? A diagnostic problem in radionuclide yenograms.ajr 130: , Pick JW, Anson BJ: The renal vascular pedicle. An anatomical study of 430 body-halves. J Uro! 44 : , Chuang VP, Mena CE, Hoskins PA: Congenital anomalies of the left renal vein: angiographic consideration. Br J Radio! 47: , Chuang VP, Mera CE, Hoskins PA: Congenital anomalies of the inferior vena cava. Review of embryogenesis and presentation of a simplified classification. Br J Radio! 47: , Pillari G, Wind ES, Wiener SL, Baron MG: Left inferior vena cava.ajr 130: , Thomford NR: Abnormal left renal vein. No barrier to Warren shunt. Am J Surg 129: , Davis CJ, Lundberg GD: Retroaortic left renal vein-a relatively frequent anomaly.am J Clin Pathol 50: , Bosniak MA, Madayag M: Angiographic appearance of the circumaortic left renal vein.j Urol 108:18-20, Mitty HA: Circumaortic renal collar: a potentially hazardous anomaly of the left renal vein. AJR 125 : , Lien HH, Kolbenstuedt A: Nonmalignant venographic abnormalities of the inferior vena cava. Radio!ogy 122: , 1977