(Radiographics. 1999;19:1683-1685.)
© RSNA, 1999
Cases of the Day1
General Case of the Day
Salah M. Khader, MD,
Samy F. Saleeb, MD and
Steven K. Teplick, MD
1 From the Department of Radiology, University of South Alabama College of Medicine, 2451 Fillingim St, Mobile, AL 36617. Received April 22, 1999; revision requested May 10 and received June 15; accepted June 21. Address reprint requests to S.K.T.
Index Terms: Aneurysm, venous, 966.73 • Renal angiography, 966.122 • Renal veins, aneurysm, 966.73 • Renal veins, CT, 966.12912
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HISTORY
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A 40-year-old man presented with chronic midabdominal pain. Contrast material–enhanced computed tomography (CT) of the abdomen and late-venous-phase left renal arteriography were performed.
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FINDINGS
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A contrast-enhanced abdominal CT scan obtained at the level of the left renal hilum demonstrated a well-defined, homogeneous mass that appeared to arise from the left renal sinus and extend medially (Fig 1). A contrast-enhanced CT scan obtained at a comparable level showed the mass with attenuation similar to that of other vascular structures (Fig 2). Late-venous-phase abdominal aortic angiography demonstrated a large, rounded, bilobed mass (Fig 3).
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Figures 1, 2. (1) Contrast-enhanced abdominal CT scan obtained at the level of the left kidney demonstrates a well-defined, homogeneous mass arising in the renal sinus (long arrow). The mass is isoattenuating relative to muscle, and a small rim of calcification is seen along its lateral aspect. Short arrow indicates residual renal tissue along its superolateral aspect. (2) Contrast-enhanced abdominal CT scan obtained at about the same level as Figure 1 shows the mass with homogeneous enhancement similar to that of other vascular structures (single arrow). Residual renal tissue is again seen (double arrows).
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Figures 1, 2. (1) Contrast-enhanced abdominal CT scan obtained at the level of the left kidney demonstrates a well-defined, homogeneous mass arising in the renal sinus (long arrow). The mass is isoattenuating relative to muscle, and a small rim of calcification is seen along its lateral aspect. Short arrow indicates residual renal tissue along its superolateral aspect. (2) Contrast-enhanced abdominal CT scan obtained at about the same level as Figure 1 shows the mass with homogeneous enhancement similar to that of other vascular structures (single arrow). Residual renal tissue is again seen (double arrows).
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Figure 3. Late-venous-phase abdominal aortic angiogram obtained with the catheter tip at the level of the renal arteries shows a rounded, bilobed mass with moderate enhancement, a finding that is consistent with a renal vein aneurysm.
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DIAGNOSIS: Left renal vein aneurysm.
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DISCUSSION
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Renal vein aneurysm is a very rare entity: Less than 10 "pure" renal vein aneurysms have been reported. The left renal vein is involved more often than the right renal vein, perhaps because of its greater length (1,2).
Idiopathic or primary renal vein aneurysms are usually found incidentally during routine abdominal imaging or laparotomy (2). These aneurysms can be detected with color Doppler ultrasonography (US) (1), contrast-enhanced
CT, and magnetic resonance (MR) imaging. At US and CT, primary renal vein aneurysms usually demonstrate findings similar to those in aneurysms in other anatomic locations. At MR imaging, a gradation in signal intensity is seen following administration of gadolinium contrast material ("layered gadolinium sign"). This phenomenon has been ascribed to very slow flow in the aneurysm, which results in poor mixing of inflowing blood with the stagnant blood within the aneurysm (3).
The nutcracker phenomenon consists of distention of the left renal vein compared with the right renal vein in healthy subjects. This phenomenon has been attributed to compression of the left renal vein as it courses between the superior mesenteric artery anteriorly and the aorta posteriorly. This compression causes dilation of the more proximal part of the vein. Dilation up to four times the diameter of the distal vein has been reported as normal (4).
Renal vein aneurysms should be differentiated from varices of the renal veins, which is a more common condition with diverse causes. Varices have been classified as primary and secondary; most reported cases are secondary varices. Varices of the renal veins may result from renal vein dilation caused by an acquired arteriovenous fistula, congenital arteriovenous malformations, portal hypertension with splenorenal collateral vessels, and shunting of blood into the renal vein caused by renal cell carcinoma (1,2). Other entities may also be confused with renal vein aneurysm, including renal artery aneurysm (5,6).
Acquired arteriovenous fistulas are usually the result of trauma, most commonly penetrating injuries. Iatrogenic arteriovenous fistulas sometimes follow renal biopsy. In such cases, the renal vein is usually seen in its normal anterior position, and the correlation of clinical findings with imaging findings is usually sufficient to make the diagnosis. A rare but well-recognized cause of left renal vein dilation due to arteriovenous shunting is the "silent left kidney, abdominal pain, hematuria" syndrome. This syndrome consists of penetration or fistulization between an abdominal aortic aneurysm and a retroaortic left renal vein and is thought to be related to pressure necrosis of the renal vein as it is compressed between the pulsating aneurysm and the spine. The aberrant course of the left renal vein appears to be an important factor in the development of this entity, which, as its name implies, is associated with diminished renal function (7,8).
True renal vein aneurysms can be differentiated from arteriovenous fistulas both radiologically and histologically. True renal vein aneurysms demonstrate lack of development of the tunica media, which weakens the vessel wall, whereas fistulas demonstrate hypertrophy of the tunica media with fibrotic thickening (2).
A renal vein aneurysm that is incidentally encountered during laparotomy should be repaired. If the aneurysm is encountered during diagnostic evaluation of an unrelated pathologic condition, surgery is still advised, especially if this unrelated condition requires surgical exploration and repair of the aneurysm does not entail significant additional risks (2).
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References
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Kabaalioglu A, Yilmaz S, Apaydin A, Sindel T, Ozkaynak C, Luleci E. Renal aneurysm: diagnosis with color Doppler sonography. AJR 1997; 168:645-646.[Free Full Text]
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Krinsky G, Johnson G, Rofsky N, Shapiro R, Yang B, Weinreb J. Venous aneurysms: MR diagnosis with the "layered gadolinium" sign. J Comput Assist Tomogr 1997; 21:623-627.[Medline]
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Buschi AJ, Harrison RB, Norman A, et al. Distended left renal vein: CT/sonographic normal variant. AJR 1980; 135:339-342.[Abstract]
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Kurtz AB, Dubbins PA, Zegel HG, Cole-Beuglet C, Goldberg BB. Normal left renal vein mimicking left renal artery aneurysm. J Clin Ultrasound 1981; 9:105-108.[Medline]
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Mansour MA, Rutherford RB, Metcalf RK, Pearce WH. Spontaneous aorta–left renal vein fistula: the "abdominal pain, hematuria, silent left kidney" syndrome. Surgery 1991; 109:101-106.[Medline]
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Jabbour N, Radulescu OV, Flogiates T, Stahl W. Hemodynamics of an aorta–left renal vein fistula: a case report and a review of the literature. Crit Care Med 1993; 21:1092-1095.[Medline]
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HISTORY
FINDINGS
