Anomalies of the inferior vena cava

Transcription

1 Anomalies of the inferior vena cava Joseph M. Giordano, M.D., and Hugh H. Trout III, M.D., Washington, D.C. The inferior vena cava is formed by a complex process of embryogenesis during the sixth to tenth week of gestation. Improper completion of the process may result in four anatomic anomalies: duplication of the inferior vena cava, transposition or left-sided inferior vena cava, retroaortic left renal vein, and circumaortic left renal vein. The first two anomalies can be diagnosed by sonography and all four anomalies can be seen on CT scan of the abdomen. Duplication and transposition of the inferior vena cava should be further delineated by preoperative phlebography. Preoperative diagnosis of the anomalies should reduce the complication rate of abdominal aortic operations. (J VAse St:g~ 1986; 3:924-8.) Anomalies of the inferior vena cava (IVC) are uncommon but important entities to the radiologist and the vascular surgeon, ls The radiologist must distinguish between an anomalous IVC and a pathologic process such as lymphadenopathy. He must also be aware of the anatomic variability of the renal veins to obtain blood samples for localization of adrenal tumors or for the diagnosis of renovascular hypertension. The vascular surgeon needs to recognize anomalies of the IVC to perform safe dissections of the retroperitoneum in patients undergoing aortic reconstruction or sympathectomy as well as to accurately interrupt or insert a filter in the IVC of patients with pulmonary embolism or deep venous thrombosis. CASE REPORTS Case 1. A 70-year-old man had an abdominal aortic aneurysm shown by sonography to be 8.5 cm. Arteriography showed a large aneurysm 5 cm below the renal arteries. Proximal to this, just distal to the origin of the renal arteries, was a smaller aortic dilatation that measured 3.0 cm. The operative plan was to exclude the entire infrarenal aorta by anastomosis of a synthetic graft to the aorta just below the renal arteries. The operative procedure disclosed a leftsided IVC that crossed to the right side anterior to the smaller aortic aneurysmal dilatation. Efforts to mobilize the IVC were unsuccessful. The graft was anastomosed to the dilated aorta proximal to the larger aneurysm. Ten days postoperatively the patient experienced sudden onset of back pain and hypotension. He underwent an emergency operation that showed an intact suture line but a disruption in the dilated aneurysmal part of the aorta 2 cm above the anastomosis. An intra-aortic occlusion balloon was used to From the Department of Surgery, George Washington University Medical Center. Reprint requests: Joseph M. Giordano, M.D., 2150 Pennsylvania Ave., NW, Washington, DC obtain proximal control and a new graft was sewn from inside the lumen to the aorta just below the renal arteries~ Postoperatively the patient had transient kidney failure bm ultimately did well and was discharged from the hospital. Review of the original sonogram demonstrated a tubular structure to the left of the aorta that retrospectively was diagnosed as a transposition of the IVC (Fig. 1). Case 2. A 66-year-old man came to the hospital with a pulsatile abdominal mass. Computed tomography (CT) of the abdomen confirmed the presence of an abdominal aortic aneurysm and also showed a double IVC that joined anterior and posterior to the aorta just below the renal arteries (Fig. 2). An inferior venacavogram confirmed the duplicated IVC and also demonstrated communications between the iliac venous system (Fig. 3). At operation the IVC was mobilized, which allowed adequate exposure for proximal aortic control. The patient's postoperative course was uneventful and he was discharged on the ninth post operative day. EMBRYOLOGY The IVC forms during the sixth to tenth week of gestation. 6'7 Three parallel pairs of veins appear during different periods of gestation, develop extensive anastomotic channels among themselves, and undergo partial regression (Fig. 4). The remaining parts of these sets of veins coalesce to form the adult IVCand the iliac bifurcation. The first to appear are the postcardinal veins located on the posterior aspect of the fetus. This system completely regresses except for the most distal part, which becomes the iliac bifurcation. The subcardinal veins, located anterior and medial to the postcardinal veins, appear next. The left subcardinal vein completely regresses and the right system forms the suprarenal IVC. The supracardinal veins located directly posterior to the aorta appear last. The left supracardinal system regresses and the right remains to form the infrarenal portion of the IVC. Both the subcardinal and the supracar-

2 Volume g Number 6 June 1986 Anomalies of the inferior vena cava 925 Fig. 1. Tubular structure to left of aorta is left-sided inferior vena cava (case 1). dinal system form extensive anastomotic channels at the level of the renal vein. These channels coalesce to form a large vein anterior and posterior to the aorta that drain the left kidney and unite with the IVC. Eventually the vein posterior to the aorta regresses but the vein anterior to the aorta persists to become the left renal vein. In summary then, the right subcardinal vein forms the suprarenal segment of the IVC, the right supracardinal vein forms the infrarenal segment, the postcardinal veins form the iliac bifurcation, and both the subcardinal and supracardinal systems contribute to the formation of the renal veins. With such a complex process of embryogenesis it should not be surprising that anomalies of the IVC occur. Fifteen types of anomalies have been reported but many of these are minor variations and some have been reported only in animals. Four IVC anomalies with a range of incidences are clinically important. 2's'6'8 Duplication or a double WC, with an incidence of 0.2% to 3.0%, consists of large veins on both sides of the aorta that join anteriorly at the level of the renal arteries to become the suprarenal IVC. The anomaly occurs because the left supracardinal vein fails to regress. Transposition or left-sided IVC, with an incidence of 0.2% to 0.5%, consists of an IVC to the left of the aorta that crosses to the right side, usually anterior to the aorta at the level of the renal arteries. It is a true transposition so that the IVC on the left side is a mirror image of a normal right-sided IVC. Therefore, the gonadal and adrenal veins that normally empty into the left renal vein instead empty into the IVC in a patient with a left- sided IVC. The right gonadal and adrenal veins that usually drain into the IVC instead join the right renal vein in a patient with a left-sided IVC. A retroaortic left renal vein, with an incidence of 1.2% to 2.4%, consists of the left renal vein crossing posterior to the aorta to join the inferior vena cava. This anomaly occurs because, during gestation, the vein anterior to the aorta regresses while the vein that is posterior persists, the opposite of the normal occurrence. A circumaortic left renal vein, with a reported incidence of 1.5% to 8.7%, consists of a left renal vein anterior and posterior to the aorta that join just before entering the IVC, forming a venous collar around the aorta. This anomaly occurs when the vein posterior to the aorta does not regress. It should be noted that both duplication and transposition of the IVC are associated with anomalies of the renal veins. M- though the IVCs in both anomalies usually join or cross anterior to the aorta at the level of the renal arteries, either one may cross posterior with a retroaortic left renal vein or may be associated with a circumaortic left renal vein. DISCUSSION Anomalies of the IVC are unusual manifestations of a complex process of embryogenesis. No individual surgeon accumulates a large experience. Nevertheless, lack of awareness of these anomalies can cause serious clinical problems. The first case presented illustrates this and both patients indicate the opportunity for preoperative diagnosis by CT scan or sonography. Previously the diagnosis of IVC anomalies was

3 926 Giordano and Trout Journal o VASCULAR SURGERY Fig. 2. CT shows tubular structure on both sides of aorta indicating duplication of inferior vena cava (case 2). made during operative procedures on the retroperitoneum. Recently reports in the literature have now shown that CT scan or sonography of the abdomen can often diagnose these anomalies. TM For patients with duplication or transposition, the abdominal CT scan shows tubular structure on both sides or just to the left of the aorta. At times these structures can be confused with lymphadenopathy but differentiation can be made by opacification of the anomalous structure with a bolus of intravenous contrast material. The abdominal CT scan, if carefully evaluated, can also indicate the relation of the left renal vein to the abdominal aorta whether it is anterior as normally found, posterior as in retroaortic left renal vein, or on both sides of the aorta as in circumaortic left renal vein. Sonography of the abdomen can also diagnose both duplication and transposition. The course of the IVC is usually best demonstrated by showing a tubular structure on coronal sonographic sections. With the use of real-time sonography, pulsations in the structure confirm it to be vascular in nature. Sonography is not as helpful for the diagnosis of anomalies related to the renal vein. Once the diagnosis of IVC anomalies is made by abdominal CT scan or sonography, an inferior venacavogram should be performed to confirm and delineate the precise anatomy. Venous communications between both IVCs in patients with duplication and the relation of duplication or transposition to the configuration of the renal vein should be determined. The venacavogram should be performed through a left femoral puncture, since this approach will more likely opacify both IVCs if duplication is present and the left IVC if transposition exists. Fig. 3. Phlebogram perfbrmed through left femoral vein shows opacification of both inferior vena cavae. Note venous communication between lilac veins (case 2). Retroaortic and circumaortic left renal veins are the most common IVC anomalies. If these are unsuspected during reconstruction of the abdominal aorta, an inadvertent injury, of the vein can occur. To avoid this the left renal vein should be identified before the proximal aorta is dissected. If the vein is not located anterior to the aorta, the patient may have a retroaortic left renal vein. Another useful technique is to limit dissection to the anterior surface and sides of the aorta. The posterior surface is not dissected, an umbilical tape is not placed around the aorta, and control of the aorta is attained with a straight vascular clamp. Exposure of the aorta just below the level of the renal arteries is the major technical problem associated with transposition or double IVC. A double IVC usually unites anterior to the aorta, which can complicate exposure. Because communication between both lilac veins is usually present in this anomaly, the left IVC may be ligated and divided to facilitate exposure. This will leave the right IVC to drain both lilac veins. Transposition presents greater technical problems. The left-sided IVC usually crosses to the right side anterior to the aorta at the level of the renal arteries although occasionally it crosses posterior or is part of a circumaortic renal collar. As in case 1, this anomaly prevents adequate

4 Volume 3 Number 6 June 1986 Anomalies of the inferior vena cava 927 Pr~cardinel vein f J *') I P Subcardinal veins "~ Postcardinel vein (L) Postcardinal vein regresses ==.-. Subcardinal veins =~. Supraeardinal / ~ri ~ i=jmi i ~Both Subcardinal vein Postcardinal Renal vein ~ t ll!... dina, vein '/ Key: ~e~l IJ ~/, S ube..s, dlnllll v.in s [] Pretn-sand i:,oetcardlnal [] I ~? ~ SvUP~a" and eubcarclinal Fig. 4. A, Gestation at 6 weeks; posterior cardinal veins dominant. B, Gestation at 7 weeks; subcardinal veins dominant, postcardinal veins begin to regress. C, Gestation at 8 weeks; supracardinal veins dominant; subcardinal system forms prerenal IVC. D, Adult inferior vena cave. exposure of the abdominal aorta. Ligation and division of the IVC as it crosses the aorta would facilitate exposure but would probably cause lower leg edema. Division and subsequent repair of the IVC following aortic reconstruction is possible but may present formidable technical problems because the IVC, as it crosses the aorta, is wide and under tension from the aneurysmal wall. Replacement of the aneurysm with a graft will relieve some of this tension and may facilitate reanastomosis of the IVC. Division of the right renal vein might free up enough of the IVC to allow exposure of the proximal aorta? Since the right gonadal and adrenal veins empty directly into the right renal vein in a patient with transposition of the IVC, division of the right renal vein might be done as safely as division of the left renal vein in a patient with normal venous anatomy. The use of an intra-aortic occlusion balloon to obtain proximal control of the aorta as was done in case 1 is a final option. The graft may then be sewn

5 928 Giordano and Trout to the proximal aorta from inside the lumen of the artc U. A surgeon must be aware of other potential problems from anomalies of the IVC. Nephrectomy, adrenalectomy, and sympathectomy may be hazardous in a patient with unsuspected anomalies of the IVC. Interruption of the IVC with either a filter device or plication to prevent pulmonary emboli may be unsuccessful if the patient has a double IVC and only the right side is interrupted. Collection of blood samples from the renal vein to diagnose renovascular hypertension may give inaccurate results if anomalies of the renal veins are not appreciated. Finally for patients undergoing portal decompression, accurate assessment of the venous anatomy is essential. Although uncommon, anomalies of the IVC may present formidable challenges to the surgeon operating on structures within the retroperitoneum. Accurate depiction of the anomalies preoperatively by sonography or CT scanning is important in planning a safe operation. If these anomalies are not detected preoperatively, then the surgeon must at least bc aware of the various anatomic configurations that are possible. REFERENCES 1. Babian RJ, Johnson DE. Major venous anomalies complicating retroperitoneal surgery. South Med J 1979; 72: Chaung VP, Mena CE, Hoskins PA. Congenital anomalics of the left renal vein: Angiographic consideration. B r J Radiol 1974; 47: Dardik H, Loop FD, Cox PA, Keshishian JM. C-pattern inferior vena cava. JAMA 1967; 200: Kolbenstvedt A, Kolmannskog F, Lien HH. The anomalous inferior vena cava--another structure between the aorta and the superior mesenteric artery. Br J Radiol 1981; 54: Brener BJ, Darling C, Frederick PL, Longton RR. Major venous anomalies complicating abdominal aortic surgery. Arch Surg 1974; 108: Mayo l, Gray R, St Louis E, Grossman H, McLoughlin M, Wise D. Anomalies of the inferior vena cava. AJR 1983; 140: Chaung VP, Mena E, Hoskins PA. Congenital anomalies of the inferior cava: Review of embryogenesis and presentations of a simplified classification. Br J Radiol 1974; 47: Royal SA, Collen P. CT evaluation of the anomalies of the inferior vena cava and left renal vein. Am J Radiol 1979; 132: Faer MI, Lynch RD, Evans HO, Chin FK. Inferior vena cava duplication: Demonstration by computed tomography. Radiolo~ 1979; 130: Richardson ML, Richard ICE, Levesque PH. Inferior vena cava duplication: Demonstration by sonography. J Clin Ultrasound 1983; 11: Siegfried M& Rochester D, Bernstcin JR, Miller JW. Diagnosis of inferior vena cava anomalies by computerized tomography. Comput Radiol 1983; 7: