- Email: [email protected]
A primer on linear array endosonographic anatomy
35. 36. 37.
38.
cystectomy and common bile duct stones. The utility of planned perioperative endoscopic retrograde cholangiography and sphincterotomy: experience with 63 patients. Ann Surg 1993; 218:61-7. Cotton P, Lehman G, Vennes J, et al. Endoscopic sphincterotomy complications and their management. An attempt at consensus. Gastrointest Endosc 1991;37:383-93. Cotton PB. Endoscopic retrograde cholangiopancreatography and laparoscopic cholecystectomy. Am J Surg 1993;165:474-8. Leitman IM, Fisher ML, McKinley MJ, et al. The evaluation and management of known or suspected stones of the common bile duct in the era of minimal access surge1:r Surg Gynecol Obstet 1993;176:527-33. Cabrera O, van Sonnenberg OE, Wittich GR, et al. Sonography of gallstones and biliary dilatation without a visible aetiology: the ~nfrequency of obstructing choledocholithiasis. Eur J Radiol 1988;8:34-6.
A primer on linear array endosonographic anatomy Kenneth J. Chang, MD Richard A. Erickson, MD
Endoscopic ultrasound (EUS)-guided fine-needle aspiration (FNA) has now been shown in a number of published series 1-6 to be an effective modality for establishing a tissue diagnosis of primary malignant lesions within and adjacent to the gastrointestinal tract and for documenting malignant spread to lymph nodes, fluid, and liver. EUS-guided FNA is performed using a curved linear array echoendoscope (Pentax Precision Instrument Corp., Orangeburg, N.Y.). In addition, color flow mapping and Doppler ultrasound, which are used to assess vascular invasion by tumor, are currently limited to the linear array echoendoscope. Because most endosonographers are using radial scanning echoendoscopes (Olympus America, Inc., Lake Success, N.Y.) and there is a paucity of published linear array images, the purpose of this primer is to provide some basic concepts of linear array anatomy. Radial scanning EUS has a 360 degree ultrasonographic field, which is oriented perpendicular to the long axis of the scope. Thus, with the probe in the esophagus the images obtained are similar in orientation to a CT or magnetic resonance image (MRI) of the chest. Linear array EUS has a 100 degree ultrasonographic (wedge-shaped) field, which is oriented paralFrom the Clinical Cancer Center, the University of California, Orange. Reprint requests: Kenneth J. Chang, MD, UCI Clinical Cancer Center, 101 The City Drive, Building 23, Route 81, Orange, CA 92668. 0016-5107/96/4302-0S4355.00 9 0 GASTROINTESTINAL ENDOSCOPY Copyright 9 19.96 by the American Society for Gastrointestinal Endoscopy 37/0/70317 VOLUME 43, NO. 2, P A R T 2, 1996
39. Amouyal P, Amouyal G, Mompoint D, et al. Endosonography: promising method for diagnosis of extrahepatic cholestasis. Lancet 1989;II:1195-8. 40. Canto M, Cooper G, Chak A, Sivak MV Jr. Clinical and endosonographic predictors of choledocholithiasis [Abstract]. Gastroenterology 1995;108:A7. 41. Barkun A, Barkun J, Fried G, et al. Useful predictors of bile duct stones in patients undergoing laparoscopic cholecystectomy. Ann Surg 1994;220:32-9. 42. Denis B, Bas V, Goudot C, et al. Accuracy of endoscopic ultrasonography (EUS) for diagnosis of common bile duct stones (CBDS) [Abstract]. Gastroenterology 1993;104:A315. 43. Palazzo L, Girollet P, Salmeron M, et al. Value of endoscopic ultrasonography in the diagnosis of common bile duct stones: comparison with surgical exploration and ERCP. Gastrointest Endosc 1995;42:225-31.
lel to the long axis of the scope. Therefore, images obtained with the linear array transducer are oriented 90 degrees from images obtained with the radial scanner in the same position. GASTROINTESTINAL WALL
The five echolayers of the esophagus, stomach, duodenum, and rectum are the same for both linear array and radial scanning transducers. However, the linear array transducer has 7.5 and 5.0 MHz frequencies but not the higher 12 MHz frequency available with the radial scanners. Thus the five echolayers of the esophagus cannot be visualized well with the linear array transducer. Filling the gastrointestinal lumen with water (water-fill method) or injecting water while imaging/freezing (dynamic water-fill) are techniques used to enhance the imaging of the echolayers. MEDIASTINUM
As shown in Figure 1, A, most of the structures in the mediastinum visible by EUS are anterior to the esophagus, thus necessitating the learning of anatomy from a posterior perspective. On deep intubation of the esophagus, that is, 30 to 35 cm from the incisors (station 1, Fig. 1, A), the linear array echoendoscope most naturally orients toward the patient's left. The landmark structure throughout the mediastinum is the descending aorta, which is located at station 1 by rotating the shaft of the echeendoscope a little to the right (clockwise) or left (counterclockwise). The descending aorta is easily recognized as a large echolucent longitudinal structure with a very bright deep wall secondary to the air interface with the left lung (Fig. 2, A). From the descending aorta, rotating the shaft of the echoendoscope to the right will then sequentially bring into view the left lung, right atrium, right lung, azygous vein, and spine. Rotating to the right from the descending aorta will bring into view GASTROINTESTINAL ENDOSCOPY
S43
Neck
and
Mediastinum
/ I I I I I I I l
echoendoscope to station 3 of Figure 1, A will bring the arch of the aorta into view as a large circular structure adjacent to the esophagus (Fig. 2, D). By rotating the scope slightly right and left, the takeoffs of the left subclavian and sometimes the left common carotid arteries can be seen. Deep to the arch is the occasionally visible left innominate (brachiocephalic) vein. Just distal to the arch is the aortopulmonary window, another important area for FNA of mediastinal lymph nodes, especially in staging patients with lung cancer. 7 While withdrawing the echoendoscope into the neck, one can usually see little because the esophagus is wedged between the impenetrable trachea anteriorly and the spine posteriorly. However, longitudinal views of the left and occasionally right common carotid arteries and the deeper internal jugular veins can be seen when the scope is oriented left or right. ABDOMEN
1
8
~
Figure 1. A, Posterior view of periesophageal mediastinal anatomy. B, Anterior view of perigastroduodenal anatomy. Endosonographic station numbers are discussed in the text.
the left atrium as a contracting thin-walled echolucent chamber (Fig. 2, B). Through the left atrium, the mitral and aortic valves can be visualized. Starting from the descending aorta, when rotating the echoendoscope shaft to the right, the mitral valve is seen before the aortic valve (Fig. 2, B). Further rightward rotation and slight withdrawal of the echoendoscope will follow the aortic outflow tract of the left ventricle, bringing the aortic valve and ascending aorta into view deep to the left atrium. Rotation to the left from the descending aorta will promptly bring the azygous vein into view as a thin longitudinal echolucency close to the wall of the esophagus. Repositioning the echoendoscope over the mid left atrium and withdrawing it a few centimeters will place the scope in the subcarinal region (station 2, Fig. 1, A). Here, the large pulsatile cephalad portion of the left atrium or upper pulmonary veins just distal to a round cross-sectional view of the pulmonary artery will be visible (Fig. 2, C). Depending on the exact orientation, the ascending aorta may be seen deep to these structures. This is an important view for localizing subcarinal lymph nodes for fine-needle aspiration. Further withdrawal of the S44
GASTROINTESTINAL ENDOSCOPY
The abdominal organs and vascular structures are imaged through the stomach and duodenum. Finding landmarks and organs through the stomach is more difficult than through the esophagus because of the former's larger capacity and greater anatomic variation (different shapes and sizes of the stomach in relation to surrounding organs). Again the major landm a r k or "home base" for imaging through the stomach is the abdominal aorta and the mesenteric vessels. The survey from the stomach begins at the gastroesophageal junction. With the transducer positioned in the cardia, the scope is rotated until the abdominal aorta is imaged longitudinally coming down from the thorax (station 1, Fig. 1, B). By advancing the scope a few centimeters along the aorta, the celiac trunk will then come into view as a longitudinal structure at about a 45 degree angle. Color flow and Doppler ultrasound can be used to verify the celiac artery, which has a typical mesenteric arterial waveform with a sharp upstroke followed by a substantial diastolic flow from the low resistance of the mesenteric vascular bed (Fig. 3, A). Finding the celiac artery is important both for identifying celiac nodes for EUS-guided FNA s and for performing celiac nerve blocks. 9 Advancing the scope I to 2 cm farther will image the superior mesenteric artery (SMA) coming off at about a 30 degree angle. Between the celiac trunk and the SMA (station 2, Fig. 1, B) the body of the pancreas can be imaged in cross section, with the pancreatic duct appearing as a small echolucent circle (Fig. 3, B). To view the distal pancreas (station 3, Fig. 1, B), left kidney, and spleen, rotate your shoulders to the right and fine-tune the image using the left/right control knob and a slight withdrawal of the scope. The tail of the pancreas can be seen with the splenic vein and artery below. The splenic artery is generally serpiginous, cephalad to the pancreas, and tends to be more circuVOLUME 43, NO. 2, P A R T 2, 1996
Figure 2. Linear array endosonographic views of mediastinum using Pentax-Hitachi FG32UA system at 7.5 MHZ (all station numbers refer to Fig. 1, A). A, Descending aorta at station 1. B, View from left atrium of mitral valve (M. V.) into the left ventricle and aortic outflow tract, station 1. C, View of subcarinal region, station 2, with cephalad portion of left atrium, pulmonary artery (P.A.), and the ascending aorta. D, View of arch with the take-off of the left subclavian artery (LSCA) at station 3. Deep to these structures is the innominate vein (IN. V.).
lar than the splenic vein, which is more oval and of a larger diameter. Deep to these vessels, the renal vein and artery can be imaged with the vein larger and closer to the transducer (station 4, Fig. 1, B). Further rotation and tip deflection will allow imaging of the left kidney and spleen (Fig. 3, C). The left adrenal gland can sometimes be seen medial to the left kidney (station 5, Fig. 1, B). After imaging the structures of the upper abdomen, the scope is advanced into the duodenum. From here, the pancreatic uncinate, head, and neck are imaged by withdrawing the scope in a continuous sweep from the duodenum to the a n t r u m and body of the stomach. After the ampulla of Vater is identified endoscopically, the transducer is placed against the mucosa with the water balloon inflated. The uncinate process is identified here (station 6, Fig. 1, B). All endosonographers, especially those embarking on EUS-guided FNA, VOLUME 43, NO. 2, P A R T 2, 1996
should be aware that the ventral pancreas is often hypoechoic and can mimic a "pseudotumor. ''1~ At the level of the ampulla, the head of the pancreas is imaged, with the common bile duct (CBD) and the pancreatic duct running parallel (Fig. 3, D). The CBD is always closer to the transducer. The extrapancreatic CBD is usually imaged adjacent to the distal duodenal bulb and appears in cross section. This is the ideal location for performing EUS cholangiogram where the EUS-guided fine-needle injection of contrast is performed through the duodenal wall into the CBD in patients with difficult ERCP cannulation. The portal vein confluence (PV) is imaged at the level of the proximal second portion of the duodenum or duodenal bulb and is deep to the pancreatic head and neck. Portal vein and splenic vein Doppler waveforms are similar and are characterized by a continuous venous hum that extends throughout the systole and diastole GASTROINTESTINAL E N D O S C O P Y
S45
E
C Figure 3. Linear array endosonographic views of abdomen. (all station numbers refer to Figure 1, B). A, Celiac artery with characteristic pulsewave, station 1. B, Body of pancreas with pancreatic duct demarcated, station 2. C, Tail of pancreas, kidney, and spleen, station 4.
(Fig. 3, E). Color flow at this level may enhance the endosonographer's ability to assess portal vein invasion in patients with pancreatic head cancer. The neck of the pancreas is imaged from either the duodenal bulb or the antrum. Decreasing the amount of water in the balloon will help facilitate the transition from S46 G A S T R O I N T E S T I N A L E N D O S C O P Y
Figure 3. Cont'd D, Head of pancreas at level of ampulla. C, Common bile duct; P, pancreatic duct; PV, portal vein, station 6. E, PV, Portal vein; characteristic venous hum on Doppler, station 6 or 7. F, Neck/body of pancreas with SMA, Superior mesenteric artery; PV, merging of superior mesenteric vein with splenic vein to form portal vein, station 8.
the bulb to the antrum and prevent "popping" out of the pylorus. At the pancreatic neck, the superior mesenteric vein (SMV) and splenic vein (SV) may be seen merging into the portal vein; the SMA is usually seen longitudinally and running parallel below the SMV/PV (Fig. 3, F). When the scope is further withdrawn into the body of the stomach, the pancreatic body is imaged. Occasionally one can orient the transducer to VOLUME 43, NO. 2, P A R T 2, 1996
image the pancreas and splenic vein transversely; the SMA then appears in cross section (similar to radial scanning). The inferior vena cava (IVC) and abdominal aorta can be imaged from the duodenum. The IVC has a typical pulsatile "sawtooth" waveform with some reversal of flow due to right atrial contraction. The gallbladder is best imaged from the duodenum or antrum. EUS imaging of the gallbladder may be important in patients with idiopathic biliary pain. 11 CONCLUSION Linear array endosonography, with its capacity to perform EUS-guided FNA and EUS-guided injections, as well as color mapping and Doppler ultrasonography, is becoming an important instrument for the endosonographer. Familiarity with linear array anatomy, as introduced here, is the critical foundation on which these diagnostic and therapeutic procedures can be performed safely and effectively. REFERENCES 1. Chang KJ, Katz KD, Durbin TE, et al. Endoscopic ultrasoundguided fine-needle aspiration. Gastrointest Endosc 1994;40: 694-9. 2. Wiersema MJ, Kochman ML, Cramer HM, et al. Endosonography guided real-time fine-needleaspiration biopsy. Gastrointest Endosc 1994;40:700-7.
VOLUME 43, NO. 2, P A R T 2, 1996
3. Wegener M, Adamek RJ, Wedmann B, Pfaffenbach B. Endosonographically guided fine-needle aspiration puncture of paraesophagogastric mass lesions: preliminary results. Endoscopy 1994;26:586-91. 4. Vilmann P, Hancke S, Henriksen FW, Jacobsen GK. Endoscopic ultrasonography guided fine-needle aspiration biopsy of lesions in the upper gastrointestinal tract. Gastrointest Endosc 1995;41:230-5. 5. GiovanniniM, Seitz JF, Monges G, et al. Fine-needleaspiration cytology guided by endoscopic ultrasonography: results in 141 patients. Endoscopy 1995;27:171-7. 6. Chang KJ, Albers CG, Nguyen P. Endoscopic ultrasoundguided fine-needle aspiration of pleural and ascitic fluid. Am J Gastroenterol 1995;90:148-50. 7. Gress F, Savides T, Ikenberry S, et al. A prospective comparison study of endoscopic ultrasound (EUS), computed tomography (CT) and EUS directed fine-needle aspiration biopsy (EUS/FNA) of the mediastinum in the preoperative staging of non-small cell lung cancer (NSCLCA) [Abstract]. Gastrointest Endosc 1995;41:304. 8. Chang K, Durbin T, Katz K, et al. Endoscopic ultrasound (EUS) guided fine-needle aspiration (FNA) of upper gastrointestinal peri-luminal and celiac lymph nodes (LN) [Abstract]. Gastrointest Endosc 1994;40(Pt 2):62. 9. Wiersema M, Sandusky D, Carr R, et al. Endosonography guided celiac plexus neurolysis (EUS CPN) in patients with pain due to intra-abdominal (IA) malignancy [Abstract]. Gastrointest Endosc 1995;41:315. 10. Savides TJ, Gress FG, Zaidi SA, et al. EUS detects the pancreatic ventral anlage [Abstract]. Gastrointest Endosc 1995;41: 312. 11. Dill J. Comparative accuracy of endoscopic ultrasound, transabdominal ultrasound and biliary drainage in the diagnosis of cholecystitis [Abstract]. Gastroenterology 1995;108:A414.
GASTROINTESTINAL ENDOSCOPY
S47
38.
cystectomy and common bile duct stones. The utility of planned perioperative endoscopic retrograde cholangiography and sphincterotomy: experience with 63 patients. Ann Surg 1993; 218:61-7. Cotton P, Lehman G, Vennes J, et al. Endoscopic sphincterotomy complications and their management. An attempt at consensus. Gastrointest Endosc 1991;37:383-93. Cotton PB. Endoscopic retrograde cholangiopancreatography and laparoscopic cholecystectomy. Am J Surg 1993;165:474-8. Leitman IM, Fisher ML, McKinley MJ, et al. The evaluation and management of known or suspected stones of the common bile duct in the era of minimal access surge1:r Surg Gynecol Obstet 1993;176:527-33. Cabrera O, van Sonnenberg OE, Wittich GR, et al. Sonography of gallstones and biliary dilatation without a visible aetiology: the ~nfrequency of obstructing choledocholithiasis. Eur J Radiol 1988;8:34-6.
A primer on linear array endosonographic anatomy Kenneth J. Chang, MD Richard A. Erickson, MD
Endoscopic ultrasound (EUS)-guided fine-needle aspiration (FNA) has now been shown in a number of published series 1-6 to be an effective modality for establishing a tissue diagnosis of primary malignant lesions within and adjacent to the gastrointestinal tract and for documenting malignant spread to lymph nodes, fluid, and liver. EUS-guided FNA is performed using a curved linear array echoendoscope (Pentax Precision Instrument Corp., Orangeburg, N.Y.). In addition, color flow mapping and Doppler ultrasound, which are used to assess vascular invasion by tumor, are currently limited to the linear array echoendoscope. Because most endosonographers are using radial scanning echoendoscopes (Olympus America, Inc., Lake Success, N.Y.) and there is a paucity of published linear array images, the purpose of this primer is to provide some basic concepts of linear array anatomy. Radial scanning EUS has a 360 degree ultrasonographic field, which is oriented perpendicular to the long axis of the scope. Thus, with the probe in the esophagus the images obtained are similar in orientation to a CT or magnetic resonance image (MRI) of the chest. Linear array EUS has a 100 degree ultrasonographic (wedge-shaped) field, which is oriented paralFrom the Clinical Cancer Center, the University of California, Orange. Reprint requests: Kenneth J. Chang, MD, UCI Clinical Cancer Center, 101 The City Drive, Building 23, Route 81, Orange, CA 92668. 0016-5107/96/4302-0S4355.00 9 0 GASTROINTESTINAL ENDOSCOPY Copyright 9 19.96 by the American Society for Gastrointestinal Endoscopy 37/0/70317 VOLUME 43, NO. 2, P A R T 2, 1996
39. Amouyal P, Amouyal G, Mompoint D, et al. Endosonography: promising method for diagnosis of extrahepatic cholestasis. Lancet 1989;II:1195-8. 40. Canto M, Cooper G, Chak A, Sivak MV Jr. Clinical and endosonographic predictors of choledocholithiasis [Abstract]. Gastroenterology 1995;108:A7. 41. Barkun A, Barkun J, Fried G, et al. Useful predictors of bile duct stones in patients undergoing laparoscopic cholecystectomy. Ann Surg 1994;220:32-9. 42. Denis B, Bas V, Goudot C, et al. Accuracy of endoscopic ultrasonography (EUS) for diagnosis of common bile duct stones (CBDS) [Abstract]. Gastroenterology 1993;104:A315. 43. Palazzo L, Girollet P, Salmeron M, et al. Value of endoscopic ultrasonography in the diagnosis of common bile duct stones: comparison with surgical exploration and ERCP. Gastrointest Endosc 1995;42:225-31.
lel to the long axis of the scope. Therefore, images obtained with the linear array transducer are oriented 90 degrees from images obtained with the radial scanner in the same position. GASTROINTESTINAL WALL
The five echolayers of the esophagus, stomach, duodenum, and rectum are the same for both linear array and radial scanning transducers. However, the linear array transducer has 7.5 and 5.0 MHz frequencies but not the higher 12 MHz frequency available with the radial scanners. Thus the five echolayers of the esophagus cannot be visualized well with the linear array transducer. Filling the gastrointestinal lumen with water (water-fill method) or injecting water while imaging/freezing (dynamic water-fill) are techniques used to enhance the imaging of the echolayers. MEDIASTINUM
As shown in Figure 1, A, most of the structures in the mediastinum visible by EUS are anterior to the esophagus, thus necessitating the learning of anatomy from a posterior perspective. On deep intubation of the esophagus, that is, 30 to 35 cm from the incisors (station 1, Fig. 1, A), the linear array echoendoscope most naturally orients toward the patient's left. The landmark structure throughout the mediastinum is the descending aorta, which is located at station 1 by rotating the shaft of the echeendoscope a little to the right (clockwise) or left (counterclockwise). The descending aorta is easily recognized as a large echolucent longitudinal structure with a very bright deep wall secondary to the air interface with the left lung (Fig. 2, A). From the descending aorta, rotating the shaft of the echoendoscope to the right will then sequentially bring into view the left lung, right atrium, right lung, azygous vein, and spine. Rotating to the right from the descending aorta will bring into view GASTROINTESTINAL ENDOSCOPY
S43
Neck
and
Mediastinum
/ I I I I I I I l
echoendoscope to station 3 of Figure 1, A will bring the arch of the aorta into view as a large circular structure adjacent to the esophagus (Fig. 2, D). By rotating the scope slightly right and left, the takeoffs of the left subclavian and sometimes the left common carotid arteries can be seen. Deep to the arch is the occasionally visible left innominate (brachiocephalic) vein. Just distal to the arch is the aortopulmonary window, another important area for FNA of mediastinal lymph nodes, especially in staging patients with lung cancer. 7 While withdrawing the echoendoscope into the neck, one can usually see little because the esophagus is wedged between the impenetrable trachea anteriorly and the spine posteriorly. However, longitudinal views of the left and occasionally right common carotid arteries and the deeper internal jugular veins can be seen when the scope is oriented left or right. ABDOMEN
1
8
~
Figure 1. A, Posterior view of periesophageal mediastinal anatomy. B, Anterior view of perigastroduodenal anatomy. Endosonographic station numbers are discussed in the text.
the left atrium as a contracting thin-walled echolucent chamber (Fig. 2, B). Through the left atrium, the mitral and aortic valves can be visualized. Starting from the descending aorta, when rotating the echoendoscope shaft to the right, the mitral valve is seen before the aortic valve (Fig. 2, B). Further rightward rotation and slight withdrawal of the echoendoscope will follow the aortic outflow tract of the left ventricle, bringing the aortic valve and ascending aorta into view deep to the left atrium. Rotation to the left from the descending aorta will promptly bring the azygous vein into view as a thin longitudinal echolucency close to the wall of the esophagus. Repositioning the echoendoscope over the mid left atrium and withdrawing it a few centimeters will place the scope in the subcarinal region (station 2, Fig. 1, A). Here, the large pulsatile cephalad portion of the left atrium or upper pulmonary veins just distal to a round cross-sectional view of the pulmonary artery will be visible (Fig. 2, C). Depending on the exact orientation, the ascending aorta may be seen deep to these structures. This is an important view for localizing subcarinal lymph nodes for fine-needle aspiration. Further withdrawal of the S44
GASTROINTESTINAL ENDOSCOPY
The abdominal organs and vascular structures are imaged through the stomach and duodenum. Finding landmarks and organs through the stomach is more difficult than through the esophagus because of the former's larger capacity and greater anatomic variation (different shapes and sizes of the stomach in relation to surrounding organs). Again the major landm a r k or "home base" for imaging through the stomach is the abdominal aorta and the mesenteric vessels. The survey from the stomach begins at the gastroesophageal junction. With the transducer positioned in the cardia, the scope is rotated until the abdominal aorta is imaged longitudinally coming down from the thorax (station 1, Fig. 1, B). By advancing the scope a few centimeters along the aorta, the celiac trunk will then come into view as a longitudinal structure at about a 45 degree angle. Color flow and Doppler ultrasound can be used to verify the celiac artery, which has a typical mesenteric arterial waveform with a sharp upstroke followed by a substantial diastolic flow from the low resistance of the mesenteric vascular bed (Fig. 3, A). Finding the celiac artery is important both for identifying celiac nodes for EUS-guided FNA s and for performing celiac nerve blocks. 9 Advancing the scope I to 2 cm farther will image the superior mesenteric artery (SMA) coming off at about a 30 degree angle. Between the celiac trunk and the SMA (station 2, Fig. 1, B) the body of the pancreas can be imaged in cross section, with the pancreatic duct appearing as a small echolucent circle (Fig. 3, B). To view the distal pancreas (station 3, Fig. 1, B), left kidney, and spleen, rotate your shoulders to the right and fine-tune the image using the left/right control knob and a slight withdrawal of the scope. The tail of the pancreas can be seen with the splenic vein and artery below. The splenic artery is generally serpiginous, cephalad to the pancreas, and tends to be more circuVOLUME 43, NO. 2, P A R T 2, 1996
Figure 2. Linear array endosonographic views of mediastinum using Pentax-Hitachi FG32UA system at 7.5 MHZ (all station numbers refer to Fig. 1, A). A, Descending aorta at station 1. B, View from left atrium of mitral valve (M. V.) into the left ventricle and aortic outflow tract, station 1. C, View of subcarinal region, station 2, with cephalad portion of left atrium, pulmonary artery (P.A.), and the ascending aorta. D, View of arch with the take-off of the left subclavian artery (LSCA) at station 3. Deep to these structures is the innominate vein (IN. V.).
lar than the splenic vein, which is more oval and of a larger diameter. Deep to these vessels, the renal vein and artery can be imaged with the vein larger and closer to the transducer (station 4, Fig. 1, B). Further rotation and tip deflection will allow imaging of the left kidney and spleen (Fig. 3, C). The left adrenal gland can sometimes be seen medial to the left kidney (station 5, Fig. 1, B). After imaging the structures of the upper abdomen, the scope is advanced into the duodenum. From here, the pancreatic uncinate, head, and neck are imaged by withdrawing the scope in a continuous sweep from the duodenum to the a n t r u m and body of the stomach. After the ampulla of Vater is identified endoscopically, the transducer is placed against the mucosa with the water balloon inflated. The uncinate process is identified here (station 6, Fig. 1, B). All endosonographers, especially those embarking on EUS-guided FNA, VOLUME 43, NO. 2, P A R T 2, 1996
should be aware that the ventral pancreas is often hypoechoic and can mimic a "pseudotumor. ''1~ At the level of the ampulla, the head of the pancreas is imaged, with the common bile duct (CBD) and the pancreatic duct running parallel (Fig. 3, D). The CBD is always closer to the transducer. The extrapancreatic CBD is usually imaged adjacent to the distal duodenal bulb and appears in cross section. This is the ideal location for performing EUS cholangiogram where the EUS-guided fine-needle injection of contrast is performed through the duodenal wall into the CBD in patients with difficult ERCP cannulation. The portal vein confluence (PV) is imaged at the level of the proximal second portion of the duodenum or duodenal bulb and is deep to the pancreatic head and neck. Portal vein and splenic vein Doppler waveforms are similar and are characterized by a continuous venous hum that extends throughout the systole and diastole GASTROINTESTINAL E N D O S C O P Y
S45
E
C Figure 3. Linear array endosonographic views of abdomen. (all station numbers refer to Figure 1, B). A, Celiac artery with characteristic pulsewave, station 1. B, Body of pancreas with pancreatic duct demarcated, station 2. C, Tail of pancreas, kidney, and spleen, station 4.
(Fig. 3, E). Color flow at this level may enhance the endosonographer's ability to assess portal vein invasion in patients with pancreatic head cancer. The neck of the pancreas is imaged from either the duodenal bulb or the antrum. Decreasing the amount of water in the balloon will help facilitate the transition from S46 G A S T R O I N T E S T I N A L E N D O S C O P Y
Figure 3. Cont'd D, Head of pancreas at level of ampulla. C, Common bile duct; P, pancreatic duct; PV, portal vein, station 6. E, PV, Portal vein; characteristic venous hum on Doppler, station 6 or 7. F, Neck/body of pancreas with SMA, Superior mesenteric artery; PV, merging of superior mesenteric vein with splenic vein to form portal vein, station 8.
the bulb to the antrum and prevent "popping" out of the pylorus. At the pancreatic neck, the superior mesenteric vein (SMV) and splenic vein (SV) may be seen merging into the portal vein; the SMA is usually seen longitudinally and running parallel below the SMV/PV (Fig. 3, F). When the scope is further withdrawn into the body of the stomach, the pancreatic body is imaged. Occasionally one can orient the transducer to VOLUME 43, NO. 2, P A R T 2, 1996
image the pancreas and splenic vein transversely; the SMA then appears in cross section (similar to radial scanning). The inferior vena cava (IVC) and abdominal aorta can be imaged from the duodenum. The IVC has a typical pulsatile "sawtooth" waveform with some reversal of flow due to right atrial contraction. The gallbladder is best imaged from the duodenum or antrum. EUS imaging of the gallbladder may be important in patients with idiopathic biliary pain. 11 CONCLUSION Linear array endosonography, with its capacity to perform EUS-guided FNA and EUS-guided injections, as well as color mapping and Doppler ultrasonography, is becoming an important instrument for the endosonographer. Familiarity with linear array anatomy, as introduced here, is the critical foundation on which these diagnostic and therapeutic procedures can be performed safely and effectively. REFERENCES 1. Chang KJ, Katz KD, Durbin TE, et al. Endoscopic ultrasoundguided fine-needle aspiration. Gastrointest Endosc 1994;40: 694-9. 2. Wiersema MJ, Kochman ML, Cramer HM, et al. Endosonography guided real-time fine-needleaspiration biopsy. Gastrointest Endosc 1994;40:700-7.
VOLUME 43, NO. 2, P A R T 2, 1996
3. Wegener M, Adamek RJ, Wedmann B, Pfaffenbach B. Endosonographically guided fine-needle aspiration puncture of paraesophagogastric mass lesions: preliminary results. Endoscopy 1994;26:586-91. 4. Vilmann P, Hancke S, Henriksen FW, Jacobsen GK. Endoscopic ultrasonography guided fine-needle aspiration biopsy of lesions in the upper gastrointestinal tract. Gastrointest Endosc 1995;41:230-5. 5. GiovanniniM, Seitz JF, Monges G, et al. Fine-needleaspiration cytology guided by endoscopic ultrasonography: results in 141 patients. Endoscopy 1995;27:171-7. 6. Chang KJ, Albers CG, Nguyen P. Endoscopic ultrasoundguided fine-needle aspiration of pleural and ascitic fluid. Am J Gastroenterol 1995;90:148-50. 7. Gress F, Savides T, Ikenberry S, et al. A prospective comparison study of endoscopic ultrasound (EUS), computed tomography (CT) and EUS directed fine-needle aspiration biopsy (EUS/FNA) of the mediastinum in the preoperative staging of non-small cell lung cancer (NSCLCA) [Abstract]. Gastrointest Endosc 1995;41:304. 8. Chang K, Durbin T, Katz K, et al. Endoscopic ultrasound (EUS) guided fine-needle aspiration (FNA) of upper gastrointestinal peri-luminal and celiac lymph nodes (LN) [Abstract]. Gastrointest Endosc 1994;40(Pt 2):62. 9. Wiersema M, Sandusky D, Carr R, et al. Endosonography guided celiac plexus neurolysis (EUS CPN) in patients with pain due to intra-abdominal (IA) malignancy [Abstract]. Gastrointest Endosc 1995;41:315. 10. Savides TJ, Gress FG, Zaidi SA, et al. EUS detects the pancreatic ventral anlage [Abstract]. Gastrointest Endosc 1995;41: 312. 11. Dill J. Comparative accuracy of endoscopic ultrasound, transabdominal ultrasound and biliary drainage in the diagnosis of cholecystitis [Abstract]. Gastroenterology 1995;108:A414.
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