MR Lymphography of Abdominal and Retroperitoneal Lymphatic Vessels

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1 rrivé et al. MR Lymphography of bdominal and Retroperitoneal Lymphatic Vessels bdominal Imaging Pictorial Essay L. rrivé 1 L. zizi M. Lewin. Hoeffel L. Monnier-holley. Lacombe J. M. Tubiana rrivé L, zizi L, Lewin M, et al. Keywords: abdominal imaging, flow dynamics, lymphatic system abnormalities, lymphatic system, MR lymphography, retroperitoneal imaging DOI: /JR Received February 13, 2007; accepted after revision June 7, ll authors: Department of Radiology, Hôpital St.-ntoine, 184 rue du Faubourg Saint-ntoine, Paris 75012, France. ddress correspondence to L. rrivé (lionel.arrive@sat.aphp.fr). JR 2007; 189: X/07/ merican Roentgen Ray Society MR Lymphography of bdominal and Retroperitoneal Lymphatic Vessels OJETIVE. The abdominal and retroperitoneal lymphatic system is characterized by numerous anatomic variations. Our objective is to review MR lymphographic features of normal anatomy and abnormal conditions. ONLUSION. MR lymphography is a noninvasive technique that is well suited for the examination of abdominal and retroperitoneal lymphatic vessels. he lymphatic system that collects T the lymph from various organs is a closed network of vessels that begins with lymphatic capillaries in soft tissues, extends to larger vessels that pass through lymph nodes, and again collects in another network of vessels. ommunication with the cardiovascular system is through the thoracic duct [1]. The lymphatic system is anatomically complex and difficult to image. For a long time, lymphatic imaging was limited to the use of conventional lymphography, which involved invasive procedures and patient discomfort [2]. MR lymphography based on heavily T2- weighted fast spin-echo sequences and maximum-intensity-projection reconstruction appears to be a useful noninvasive technique to evaluate the lymphatic system [3, 4]. In this article, we review MR lymphographic features of normal anatomy and of various abnormal conditions in the abdomen. MR Lymphography Protocol MR lymphography was performed on a 1.5-T unit (Magnetom Symphony, Siemens Medical Solutions) with a six-channel phased-array body coil. Our protocol includes an axial free-breathing HSTE sequence without fat suppression (TR/TE, 1,200/114; matrix, ; flip angle, 180 ; section thickness, 6 mm; acquisition time, 80 seconds) and a free-breathing 3D high-spatialresolution fast spin-echo sequence with an extremely long TE (1,400/800; flip angle, 180 ). 90 radiofrequency pulse (the socalled restore pulse) is applied at the end of the echo train to flip the transverse magnetization to the longitudinal direction, shorten the spin relaxation time, and accelerate the relaxation of the longitudinal magnetization while maintaining the same contrast resolution and reducing the acquisition time. The matrix is symmetric ( ), the section thickness is 1 mm, and the voxel size is mm. stack of sections is acquired for diagnostic purposes. Postprocessing of the image data is performed to obtain maximumintensity-projection (MIP) images and multiplanar reformatted images. The typical acquisition time is 3 6 minutes for respiratory-triggered navigator-gated acquisitions with the prospective acquisition correction (PE) technique. The 3D imaging technique has potential advantages over 2D imaging, including the capacity to obtain thinner sections with no gap and a higher signal-to-noise ratio. ecause partial volume averaging effects may obscure small structures, thin-section source images must always be reviewed. oth sequences are based on heavily T2-weighted sequences that emphasize static fluid signal in the fluid-containing structures such as lymphatic vessels, whereas solid tissues and flowing blood have no signal. However, these sequences should be performed before the IV injection of gadolinium because gadolinium that is secreted in lymphatic vessels may result in contrast alteration. natomy of the Lymphatic System The abdominal and retroperitoneal lymphatic system is characterized by numerous anatomic variations [1]. The appearance of retroperitoneal lymph trunks markedly varies from thin or prominent thick channels, paral- JR:189, November

2 rrivé et al. lel or converging channels, or a plexus (Fig. 1). The lymph trunks receive the lymph from the lower limbs, from the walls and viscera of the pelvis, from the kidneys and adrenal glands, and from the deep lymphatics of the abdominal wall. lternating bands of constriction and dilatation are characteristic of the appearance of lymphatic vessels. reas of constriction correspond to lymphatic valves [5]. Most of the efferent paraaortic vessels converge to form the right and left lumbar trunks, which join the cisterna chyli (Fig. 2). Either a single or two mesenteric lymphatic trunks may be observed. The mesenteric lymphatic vessels, which are very small, unite to form the intestinal trunk, which enters the cisterna chyli (Fig. 3). The intestinal trunk receives the lymph from the stomach and intestine and from the pancreas, spleen, and liver. The size of the intestinal lymphatic vessels varies markedly depending on whether the patient is fasting [1] (Fig. 4). The cisterna chyli receives the two lumbar lymphatic trunks, right and left, and the intestinal lymphatic trunk. The cisterna chyli is described in anatomic studies as a saccular area of dilatation of the lymphatic channels that originates at the L1 L2 level of the vertebral body and extends 5 7 cm in the caudocephalad direction. It is located in the retrocrural space, usually to the immediate right of the abdominal aorta [5]. Despite this classic description, the cisterna chyli has a highly variable appearance. omplex anastomoses of lumbar lymphatics may result in a plexus rather than a single duct (Fig. 1). Several sacculations of the convergent lymphatic channels may be present (Fig. 5). This wide variation of the cisterna chyli has led some authors to prefer the descriptive term abdominal confluence of the lymphatic trunks [6]. The term cisterna chyli is used when a distinctly fusiform or saccular dilatation is present. In addition, the size of the cisterna chyli is markedly variable, with cases of very large cisterna chyli (socalled giant cisterna chyli) reported [7] (Fig. 2). fter gadolinium injection, contrast enhancement of the cisterna chyli may be observed on delayed phase imaging [8] (Fig. 6). The cisterna chyli continues in the cephalic direction as a thoracic duct that enters the thorax through the aortic hiatus of the diaphragm and terminates at the junction of the left subclavian and internal jugular veins, draining lymph into the venous circulation [9] (Figs. 7 and 8). bnormal onditions Dilatation of the lymphatic vessels and of the cisterna chyli may be observed after surgical ligation of the thoracic duct during gastric or esophageal surgery (Fig. 9). MR lymphography easily allows the differentiation between dilated cisterna chyli and retrocrural lymph nodes. Lymphatic dilatation progressively resolves after the formation of multiple collateral lymphatic pathways in the vicinity of the obstruction [10]. Intestinal lymphangiectasis is characterized by tortuosity and marked dilatation of the mesenteric lymphatics (Fig. 10). linically, an extreme loss of protein in the gastrointestinal tract results in hypoalbuminemia, edema, and pleural effusion. MR lymphography directly shows the dilatation of mesenteric lymphatic vessels and associated lymphatic vessel abnormalities. In lymphangioleiomyomatosis, proliferation of smooth-muscle cells in the lymph vessels may produce cystic masses consistent with dilatation of the abdominal lymph vessels due to lymphatic obstruction; these are the so-called lymphangioleiomyomas (Fig. 11). These lymphangioleiomyomas are easily shown on MR lymphography [11]. fter surgery involving the retroperitoneal area, such as esophageal, gastric, or pancreatic surgery, injuries to the lymphatic vessels may be observed [12]. These injuries can result in small lymphoceles. In other cases, important lymphatic leaks may result in chylous ascites (Fig. 12). The leak may sometimes be directly shown on MR cholangiography (Figs D). In summary, MR lymphography based on heavily T2-weighted fast spin-echo sequences and MIP reconstruction appears to be a useful noninvasive technique to evaluate the lymphatic system. It allows adequate evaluation of the abdominal and retroperitoneal lymphatic system, which is characterized by numerous anatomic variations. On T images, anatomic variations such as giant cisterna chyli or abnormal lymphatic dilatation may be mistaken for lymph nodes or fluid collections, whereas MR lymphography easily shows the lymphatic nature of the abnormalities. Finally, MR lymphography is useful for evaluating patients with uncommon diseases of the lymphatic system such as lymphedema, lymphangiectasis, and lymphangioleiomyomatosis, or after injury of the lymphatic vessels during surgery. References 1. louse ME, Wallace S. Lymphatic imaging: lymphography, computed tomography and scintigraphy, 2nd ed. altimore, MD: Williams & Wilkins, Guermazi, rice P, Hennequin, Sarfati E. Lymphography: an old technique retains its usefulness. RadioGraphics 2003; 23: Takahashi H, Kuboyama S, be H, oki T, Miyazaki M, Nakata H. linical feasibility of noncontrast-enhanced magnetic resonance lymphography of the thoracic duct. hest 2003; 124: Laor T, Hoffer F, urrows PE, Kozakewich HPW. MR lymphangiography in infants, children, and young adults. JR 1998; 171: Pinto PS, Sirlin, ndrade-arreto O, rown M, Mindelzun RE, Mattrey RF. isterna chyli at routine abdominal MR imaging: a normal anatomic structure in the retrocrural space. RadioGraphics 2004; 24: Erden, Fitoz S, Yagmurlu, Erden I. bdominal confluence of lymph trunks: detectability and morphology on heavily T2-weighted images. JR 2005; 184: Tamsel S, Ozbek SS, Sever, Elmas N, Demirpolat G. Unusually large cisterna chyli: US and MRI findings. bdom Imaging 2006; 31: Lee KY, assar-pullicino VN. Giant cisterna chyli: MRI depiction with gadolinium-dtp enhancement. lin Radiol 2000; 55: Hayashi S, Miyazaki M. Thoracic duct: visualization at nonenhanced MR lymphography initial experience. Radiology 1999; 212: lalock, Robinson S, unningham RS, Gray ME. Experimental studies on lymphatic blockage. rch Surg 1937; 34: Pallisa E, Sanz P, Roman, Majo J, ndreu J, aceres J. Lymphangioleiomyomatosis: pulmonary and abdominal findings with pathologic correlation. RadioGraphics 2002; 22[spec no]:s185 S Riddell M, Davies D, llum WH, Wotherspoon, Richardson, rown G. High-resolution MRI in evaluation of the surgical anatomy of the esophagus and posterior mediastinum. 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3 MR Lymphography of bdominal and Retroperitoneal Lymphatic Vessels Fig year-old woman who underwent MRI for cholestasis. oronal maximum-intensity-projection image shows prominent lumbar trunks (arrows) on both right and left paravertebral areas. bdominal confluence of lymphatic vessels is shown as complex plexus with no saccular formation. Fig year-old man who underwent MRI for back pain., xial T image obtained after IV contrast injection shows nonenhancing hypodense rounded structure (arrows)., oronal maximum-intensity-projection image shows giant cisterna chyli at confluence of left and right markedly dilated retroperitoneal trunks (arrows). Fig. 3 xial single-shot turbo spin-echo (HSTE) sequence in 63-year-old man who underwent MRI for cholestasis., t lower level, several intestinal trunks (arrows) are seen., t intermediate levels, intestinal trunks converge to form right and left intestinal trunks (arrows)., t upper level, mesenteric trunk is shown coursing from mesentery to retroperitoneal space (arrow). JR:189, November

4 rrivé et al. D Fig year-old man who underwent MRI for follow-up of biliary enteric anastomosis. oronal maximum-intensity-projection image shows abdominal confluence of lymphatic vessels as bilateral right and left saccular dilatations (arrows) that continue in cephalic direction as thoracic duct (arrowheads). E Fig year-old woman who underwent MRI for cholangitis., xial single-shot turbo spin-echo (HSTE) sequence after 8 hours of fasting shows small intestinal (arrow) and retrocrural (arrowhead) lymphatic trunks., fter regular meal, marked dilatation of both intestinal (arrows) and retrocrural (arrowhead) lymphatic trunks is seen. and D, oronal thin-section source images of 3D sequence show marked dilatation of lymphatic trunks after regular meal (D) and with fasting (). E, oronal maximum-intensity-projection image shows confluence of dilated lymphatic trunks JR:189, November 2007

5 MR Lymphography of bdominal and Retroperitoneal Lymphatic Vessels Fig year-old woman who underwent MRI for cholestasis., xial single-shot turbo spin-echo (HSTE) T2- weighted image shows cisterna chyli as uniformly high-signal-intensity saccular collection (arrows) in prevertebral location., oronal maximum-intensity-projection image shows cisterna chyli (arrows) clearly. and D, xial MR images obtained at arterial () and delayed (D) phases show contrast enhancement of cisterna chyli (arrows) at delayed phase after gadolinium injection. D Fig year-old man who underwent MRI for cirrhosis., oronal true fast imaging with steady-state free precession image shows origin of thoracic duct at cisterna chyli (arrow). and, Tortuous course of thoracic duct at right side of aorta (arrows) is well shown. JR:189, November

6 rrivé et al. Fig year-old man who underwent MRI for pancreatitis. oronal maximum-intensity-projection image shows right and left proximal thoracic trunks (arrows) that join to form distal thoracic duct (arrowhead). Fig year-old man who underwent MRI after surgery for gastric cancer., xial contrast-enhanced T scan shows nonenhancing round structure (arrows) with low attenuation. and, xial single-shot turbo spin-echo (HSTE) () and coronal maximum-intensity-projection () images show marked dilatation of cisterna chyli after surgical ligation of thoracic duct. Fig year-old man with intestinal lymphangiectasis and history of chylous ascites. and, xial single-shot turbo spin-echo (HSTE) images show dilatation (arrows) of both right () and left () intestinal lymphatic vessels. (Fig. 10 continues on next page) 1056 JR:189, November 2007

7 MR Lymphography of bdominal and Retroperitoneal Lymphatic Vessels Fig. 10 (continued) 41-year-old man with intestinal lymphangiectasis and history of chylous ascites., t upper level, marked dilatation of main intestinal trunk is shown during its course from mesentery to retrocrural space. D, oronal maximum-intensity-projection image clearly shows marked dilatation of lymphatic trunks. Fig year-old woman with lymphangioleiomyomatosis., xial contrast-enhanced T scan shows several round hypodense structures (arrows) around iliac vessels. and, oronal true fast imaging with steady-state free precession () and coronal thin-section source image of 3D sequence () show marked dilatation (arrows) of both iliac lymphatic trunks () (so-called lymphangioleiomyomas) and retroperitoneal lymphatic trunks (). = bladder. D JR:189, November

8 rrivé et al. D Fig year-old man who underwent MRI for chylous ascites after cephalic pancreaticoduodenectomy for chronic pancreatitis., oronal true fast imaging with steady-state free precession (FISP) image shows chylous ascites (asterisks) and retroperitoneal chylous collection (arrows). and, xial true FISP images show small leak (arrows) from retrocrural lymphatic trunk that pierces diaphragmatic crus () between inferior vena cava and aorta and diffuses in peritoneal cavity (). D, oronal thin-section source image of 3D sequence shows small leak (arrows) from retroperitoneal lymphatic trunk (arrowhead) JR:189, November 2007