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A new small probe for ultrasound imaging via conventional endoscope
A new small probe for ultrasound imaging via conventional endoscope Hiromitsu Saisho, Kaoru Sai, Toshio Tsuyuguchi, Taketo Yamaguchi, Shoichi Matsutani, Masao Ohto,
MD MD MD MD MD MD
Several types of small ultrasonic probes have been designed for imaging gastrointestinal structures under endoscopic visual control. 1-3 These devices can be introduced through the working channel of an endoscope and are intended to overcome the practical and technical problems often experienced at present in the use of conventional instruments for endoscopic ultrasonography (EUS). 1, s We used a new type of ultrasonic probe that incorporates a high-frequency radial scanner and is small enough to be introduced through the working channel of a conventional diagnostic endoscope4--features that may facilitate ultrasonic imaging of the site of interest during routine gastrointestinal endoscopy. In order to obtain high-quality images with this probe, a certain amount of deaerated water must usually be infused into the gastrointestinal lumen. Unfortunately, this treatment is cumbersome when used with a single-channel diagnostic endoscope. We describe here the quality of the images obtained using the new probe. Scanning techniques are also discussed, with special reference to contact scanning during air inflation. METHODS The new ultrasonic microprobe (Toshiba Medical Corp., Tokyo, Japan) has a diameter of 2.4 mm and a length of 160 cm. A mechanical 10-, 15-, or 20-MHz sector scanner is mounted in the tip to generate a 360~ view (Fig. 1). Clinical studies were performed with the probe during routine endoscopic examination of the gastrointestinal tract in 43 patients. These included 13 patients with esophagoReceived December 10, 1993. For revision March 16, 1994. Accepted April 18, 1994. From the First Department of Internal Medicine, Chiba University School of Medicine, Chiba, Japan. Reprint requests: Hiromitsu Saisho, MD, The First Department of Internal Medicine, Chiba University School of Medicine, 1-8-1, Inohana, Chuo-ku, Chiba (260), Japan. 0016-5107/95/4102-014153.00+ 0 GASTROINTESTINAL ENDOSCOPY Copyright 9 1995 by the American Society for Gastrointestinal Endoscopy 37/69/56952 VOLUME 41, NO. 2, 1995
Figure 1. The new ultrasonic microprobe and the 360o radial
high-frequency scanner
mounted in the tip.
gastric malignant tumors (advanced tumors in 4 and early cancer in 9), 6 with upper gastrointestinal polyps, 4 with submucosal tumors, 2 with gastric ulcers, 6 with esophagogastric varices, 1 with eosinophilic proctitis, and 11 with dyspepsia but no remarkable gastrointestinal abnormalities. All the endoscopes used for the procedure were conventional instruments: Olympus GIF type XQ20 and CF type 20I {Olympus Corp., Tokyo, Japan). Ultrasound imaging with the probe was performed by contact scanning during inflation with air or by underwater scanning after the lumen was deflated and 200 to 300 mL of deaerated water was infused. The images were continuously recorded with a videotape recorder. RESULTS Imaging of the gastric wall When the gastric wall was visualized with the probe during underwater scanning, seven to nine ultrasonically distinct layers were usually clearly imaged (Fig. 2). Of these layers, the five most obvious structures apparently corresponded to the anatomic strata of the gastric wall, as has been shown with conventional EUS.5, 6 In the muscularis propria, central linear reflections apparently separated the inner circular and outer longitudinal muscle bundles. In addition, with the 15- or 20-MHz probe, fine linear echoes often detected in the bottom of the mucosal layer allowed us to distinguish an additional thin layer, which appeared to correspond spatially to the lamina muscularis mucosae. Submucosal blood vessels were also observed (Fig. 3). Because of compression by the probe, contact scanning resulted in attenuation of the surface echoes; however, the other layers, including the submucosa and the muscularis propria, and their internal structures were still imaged well (Fig. 4). The thickness of each structural layer was measured GASTROINTESTINAL ENDOSCOPY 1 4 1
Figure. 3. Submucosal fine vessels (v) are well visualized with the probe.
Figure. 2. The normal gastric wall visualized with the 15MHz ultrasonic microprobe: A, antrum; B, body, Seven to nine ultrasonically distinct layers, including interface echoes of the mural strata, are visible. The hyperechoic layer of the submucosa (sin) is the most prominent constituent in the gastric wall. The surrounding dominant hypoechoic layers are noted as the mucosa (m) and the muscularis propria (pm). Additionally, fine linear echoes (curved arrow) may separate a thin hypoechoic layer in the bottom of the mucosa, spatially representing the lamina muscularis mucosae (ram). The central echoes (open arrow) in the muscularis propria may reflect the border between the inner and outer muscle bundles. The external hyperechoic layer indicates the subserosa (ss). The hypoechoic layer of the muscularis propria in the prepyloric antrum appears much thicker.
on all sides of the gastric body, angulus, and antrum. The thickness of the submucosa and the muscularis propria was estimated in 22 patients by contact scanning and in 13 patients by underwater scanning. The angulus was omitted from the measurements in the latter patients because it could hardly be distinguished in the deflated stomach. It was possible to assess the mucosal layer only when it was imaged by the underwater scanning method. The gastric wall layers were fairly variable in thickness from site to site, even when measured in the same 142 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. 4. The gastric wall images obtained with the probe by contact scanning during air inflation: A, antrum; B, body. The submucosal layer (srn), the muscularis propria (pm), and the central echoes in the muscle layer (arrow) are well imaged despite compression on the mucosa.
segment and under the same condition. The measurements were mathematically averaged for each gastric segment (Table 1). In the deflated, water-filled stomach, the muscularis propria of the antrum was obVOLUME 41, NO. 2, 1995
Table 1. Thickness* of the gastric wall components for each segment measured with the ultrasonic microprobe Segment
m
sm
ti - 84184~
~
,,
pm
Results in the deflated condition under water immersion (n = 13) Body 0.8 (0.3) 1.0 (0.4) 0.8 (0.4) Antrum 0.9 (0.4) 1.1 (0.7) 1.6 (0.9) Results in the distended condition under air inflation (n = 22) Body -0.8 (0.4) 0.5 (0.3) Angulus -0.6 (0.2) 0.5 (0.3) Antrum -0.6 (0.2) 0.8 (0.5) *Mean (SD) in millimeters. m, Mucosa; sm, submucosa; p m , muscularis propria.
l!tlil il
,,:
. . . . . .
~
I*
Table 2. Imaging of gastrointestinal lesions with the ultrasonic microprobe Lesions
Underwater Contact scanning scanning
Early carcinomas (n = 9) Valid in: Tumor identification Observation of submucosal growth Benign polyps (n = 6) Valid in: Tumor identification Observation of inner structure Submucosal tumors (n = 3) Valid in: Tumor identification Observation of inner structure
9 8
5 5
6 6
4 4
3 2
2 2
served to be about two times thicker t h a n t h a t of the body, whereas the mucosal and submucosal layers seemed to be almost equal in thickness t h r o u g h o u t the stomach. T h e submucosa and muscularis propria as seen by contact scanning appeared to become t h i n n e r in the inflated stomach. However, their relative proportions in terms of thickness were found to be m u c h the same as those observed in the deflated stomach by u n d e r w a t e r scanning.
Imaging of gastrointestinal lesions Early c a r c i n o m a o f the stomach. Nine patients (Table 2) with early gastric carcinoma included three with the superficial elevated type (IIa) and six with the superficial depressed type (IIc or IIc+III). W h e n imaged with the probe, the lesions a p p e a r e d hypoechoic. U n d e r w a t e r scanning was the b e t t e r procedure for visualizing the pathologic process as a whole. T h e ultrasound beam was usually able to p e n e t r a t e the tissue of interest in these lesions, providing quality images for the assessment of submucosal t u m o r growth (Figs. 5A, 6A). However, one type IIc + I I I lesion resisted the ult r a s o u n d beam penetration. V O L U M E 41, NO. 2, 1995
Figure 5. Early gastric carcinoma of type Ila+llc with a significant submucosal growth (T). A, Image by underwater scanning; B, image by contact scanning. The muscularis propria (pm) appeared intact. Contact scanning during air inflation was p e r f o r m e d in six of these patients. T h e lesions could be identified and submucosal t u m o r growth observed in five (Figs. 5B, 6B). In one patient, a tiny IIa lesion (about 4 m m in size) was missed by this technique. This failure was a t t r i b u t e d to the difficulty in maintaining p r o p e r contact with the surface of the small protrusion. P o l y p s o f the g a s t r o i n t e s t i n a l tract. B y underwater scanning, these polyps, either p e d u n c u l a t e d or of the sessile type, were well visualized (Table 2), with a high-quality view of the inner structure (Fig. 7A). A vessel-like structure was detected within the stalk of a p e d u n c u l a t e d polyp in one patient. P e d u n c u l a t e d or s e m i p e d u n c u l a t e d polyps were also visible by contact scanning with air inflation (Fig. 7B), although some distortion was inevitable from the probe contact. Small sessile polyps less t h a n 4 m m in size were hardly visualized by contact scanning. S u b m u c o s a l tumors. T h e submucosal tumors of three patients were easily located in the mural layers by u n d e r w a t e r scanning (Table 2). T h e cystic lesions were clearly delineated (Fig. 8), b u t the ultrasound beam became r e m a r k a b l y a t t e n u a t e d in one solid tuGASTROINTESTINAL ENDOSCOPY
143
Figure 6. Early gastric carcinoma of type IIc presenting a slightly thickened mucosal layer on ultrasonography. A, Image by underwater scanning; B, image by contact scanning. Both images demonstrate an intact muscularis mucosae (arrow) and submucosa (sm), suggesting the lesion to be limited to the mucosa.
mor, probably a leiomyoma, so that the inner structure could not be visualized aS all. Cystic submucosal tumors were also well demonstrated by contact scanning. However, this method did fail with one solid lesion found just below the gastric cardia because of technical difficulty in apposing the probe. O t h e r l e s i o n s . In five patients with esophagogastric varices, intramural dilated vessels were well visualized. Transmural edema of the rectum was revealed in one patient with eosinophilic proctitis. Regarding gastric ulcers, the ultrasound beam was significantly attenuated in these lesions. Considerable acoustic attenuation also occurred in advanced malignant tumors, including gastric carcinoma of Borrmann type III or IV, gastric malignant lymphoma, and advanced esophageal carcinoma, resulting in incomplete examination. DISCUSSION We found the short focus (focus zone of 1.5 to 6.5 mm) and the high-frequency scanning (10, 15, or 20 144 GASTROINTESTINAL ENDOSCOPY
Figure 7. Semipedunculated gastric polyp containing inner cystic components. A, Image by underwater scanning; B, image by contact scanning.
MHz) of the new Toshiba probe to provide high-quality, real-time images of the gastrointestinal wall. The structure of the gastric wall was clearly identifiable as being stratified in seven to nine layers. The submucosal small vessels and the internal and external components of the muscularis propria were distinctly presented. The muscularis mucosae, which had been reported to be visible with a linear 20-MHz probe, 7 was also often detectable with this radial 15- or 20-MHz probe. The normal thickness of the wall components could be assessed with this probe. The muscularis propria of the antrum was about two times thicker than that of the body, but the mucosal and submucosal layers appeared uniform in thickness throughout the stomach. However, several independent factors, such as the fluctuating strain of the wall, the compression caused by probe contact, and the direction of scanning, could account for some of the variations seen in the measurements. Our in vivo study shows that the high-resolution images achieved with this probe have the potential to provide precise evaluation of small gastrointestinal lesions, especially early carcinomas. Underwater scanVOLUME 41, NO. 2, 1995
Figure 1. CT scan showing large pseudocyst (large arrow) pressing closely against the posterior wall of the stomach
(small arrow).
Figure 3. Ultrasound catheter probe image of pseudocyst (curved arrows). The catheter probe is in the water-filled lumen (large arrow) and is pressing gentry against the gastric wall. The distance between the gastric wall mucosa and the pseudocyst is 3.6 mm (smallarrows), and there are no large intramural vascular structures.
Figure 2. Endoscopic ultrasound of pseudocyst (large solid arrows) as imaged from the posterior wall of the stomach using a mechanical radial scanner echoendoscope. Note the distance (small open arrow) between where the transducer is pushing on the gastric wall and the pseudocyst lumen is 3 mm.
g a s t r o s t o m y in a patient with no obvious pseudocyst bulge on endoscopy.
CASE REPORT A 37-year-old male alcoholic presented with acute pancreatitis which was complicated by a 5 • 6 x 7 cm pancreatic pseudocyst located in the mid-body on CT scan. This fluid collection was aspirated under CT guidance with removal of 30 ml of hemorrhagic, sterile fluid. Over the next 4 weeks the patient had increasing abdominal pain and a repeat CT scan revealed the pseudocyst to be 8 • 10 • 22 cm extending from the lesser curve of the stomach to just below the left renal hilum {Fig. 1). Initially, endoscopic ultrasound (EUS) with a 360-degree radial scanning echoendoscope at 7.5 MHz (GF-UM20, 146
GASTROINTESTINAL ENDOSCOPY
Olympus America Inc., Lake Success, N.Y.) was performed in order to determine if the pseudocyst was located less than 10 mm from the intestinal wall to allow endoscopic cystenterostomy, as well as to evaluate the pancreatic parenchyma for evidence of chronic pancreatitis, pancreatic duct dilitation, or pancreatic duct stones, which might affect endoscopic management. Upper gastrointestinal endoscopy immediately prior to EUS showed no obvious visible bulging into the gastric or duodenal lumen and no esophageal or gastric varices. EUS revealed a large pseudocyst adjacent to the antral and duodenal walls which measured 3 to 4 mm from the lumen to the pseudocyst (Fig. 2). The pancreas parenchyma had EUS changes of chronic pancreatitis consisting of a diffuse inhomogeneous echopattern with multiple hypoechoic areas suggesting cystic spaces and a thickened, hyperechoic, irregular main pancreatic duct. There were multiple benign-appearing peri-pancreatic lymph nodes, and poor visualization of the splenic vein suggesting splenic vein thrombosis. Gastric varices were present near the gastroesophageal junction. The following day the patient was taken to the fluoroscopy suite to have endoscopic cystenterostomy performed. The patient was placed in the standard prone position used for ERCP. No pseudocyst bulge was seen with the therapeutic duodenoscope (TJF-100, Olympus America Inc.). To determine the optimal site for pseudocyst puncture, a 6.2F, 20 MHz, 200 cm long, catheter-based ultrasound probe (EndoSound, Microvasive/Boston Scientific Inc, Watertown, Mass., and HP Sonos Intravascular Imaging System, Hewlett-Packard Company, Andover, Mass.) was passed through the working channel of the duodenoscope into the VOLUME 41, NO. 2, 1995
MD MD MD MD MD MD
Several types of small ultrasonic probes have been designed for imaging gastrointestinal structures under endoscopic visual control. 1-3 These devices can be introduced through the working channel of an endoscope and are intended to overcome the practical and technical problems often experienced at present in the use of conventional instruments for endoscopic ultrasonography (EUS). 1, s We used a new type of ultrasonic probe that incorporates a high-frequency radial scanner and is small enough to be introduced through the working channel of a conventional diagnostic endoscope4--features that may facilitate ultrasonic imaging of the site of interest during routine gastrointestinal endoscopy. In order to obtain high-quality images with this probe, a certain amount of deaerated water must usually be infused into the gastrointestinal lumen. Unfortunately, this treatment is cumbersome when used with a single-channel diagnostic endoscope. We describe here the quality of the images obtained using the new probe. Scanning techniques are also discussed, with special reference to contact scanning during air inflation. METHODS The new ultrasonic microprobe (Toshiba Medical Corp., Tokyo, Japan) has a diameter of 2.4 mm and a length of 160 cm. A mechanical 10-, 15-, or 20-MHz sector scanner is mounted in the tip to generate a 360~ view (Fig. 1). Clinical studies were performed with the probe during routine endoscopic examination of the gastrointestinal tract in 43 patients. These included 13 patients with esophagoReceived December 10, 1993. For revision March 16, 1994. Accepted April 18, 1994. From the First Department of Internal Medicine, Chiba University School of Medicine, Chiba, Japan. Reprint requests: Hiromitsu Saisho, MD, The First Department of Internal Medicine, Chiba University School of Medicine, 1-8-1, Inohana, Chuo-ku, Chiba (260), Japan. 0016-5107/95/4102-014153.00+ 0 GASTROINTESTINAL ENDOSCOPY Copyright 9 1995 by the American Society for Gastrointestinal Endoscopy 37/69/56952 VOLUME 41, NO. 2, 1995
Figure 1. The new ultrasonic microprobe and the 360o radial
high-frequency scanner
mounted in the tip.
gastric malignant tumors (advanced tumors in 4 and early cancer in 9), 6 with upper gastrointestinal polyps, 4 with submucosal tumors, 2 with gastric ulcers, 6 with esophagogastric varices, 1 with eosinophilic proctitis, and 11 with dyspepsia but no remarkable gastrointestinal abnormalities. All the endoscopes used for the procedure were conventional instruments: Olympus GIF type XQ20 and CF type 20I {Olympus Corp., Tokyo, Japan). Ultrasound imaging with the probe was performed by contact scanning during inflation with air or by underwater scanning after the lumen was deflated and 200 to 300 mL of deaerated water was infused. The images were continuously recorded with a videotape recorder. RESULTS Imaging of the gastric wall When the gastric wall was visualized with the probe during underwater scanning, seven to nine ultrasonically distinct layers were usually clearly imaged (Fig. 2). Of these layers, the five most obvious structures apparently corresponded to the anatomic strata of the gastric wall, as has been shown with conventional EUS.5, 6 In the muscularis propria, central linear reflections apparently separated the inner circular and outer longitudinal muscle bundles. In addition, with the 15- or 20-MHz probe, fine linear echoes often detected in the bottom of the mucosal layer allowed us to distinguish an additional thin layer, which appeared to correspond spatially to the lamina muscularis mucosae. Submucosal blood vessels were also observed (Fig. 3). Because of compression by the probe, contact scanning resulted in attenuation of the surface echoes; however, the other layers, including the submucosa and the muscularis propria, and their internal structures were still imaged well (Fig. 4). The thickness of each structural layer was measured GASTROINTESTINAL ENDOSCOPY 1 4 1
Figure. 3. Submucosal fine vessels (v) are well visualized with the probe.
Figure. 2. The normal gastric wall visualized with the 15MHz ultrasonic microprobe: A, antrum; B, body, Seven to nine ultrasonically distinct layers, including interface echoes of the mural strata, are visible. The hyperechoic layer of the submucosa (sin) is the most prominent constituent in the gastric wall. The surrounding dominant hypoechoic layers are noted as the mucosa (m) and the muscularis propria (pm). Additionally, fine linear echoes (curved arrow) may separate a thin hypoechoic layer in the bottom of the mucosa, spatially representing the lamina muscularis mucosae (ram). The central echoes (open arrow) in the muscularis propria may reflect the border between the inner and outer muscle bundles. The external hyperechoic layer indicates the subserosa (ss). The hypoechoic layer of the muscularis propria in the prepyloric antrum appears much thicker.
on all sides of the gastric body, angulus, and antrum. The thickness of the submucosa and the muscularis propria was estimated in 22 patients by contact scanning and in 13 patients by underwater scanning. The angulus was omitted from the measurements in the latter patients because it could hardly be distinguished in the deflated stomach. It was possible to assess the mucosal layer only when it was imaged by the underwater scanning method. The gastric wall layers were fairly variable in thickness from site to site, even when measured in the same 142 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. 4. The gastric wall images obtained with the probe by contact scanning during air inflation: A, antrum; B, body. The submucosal layer (srn), the muscularis propria (pm), and the central echoes in the muscle layer (arrow) are well imaged despite compression on the mucosa.
segment and under the same condition. The measurements were mathematically averaged for each gastric segment (Table 1). In the deflated, water-filled stomach, the muscularis propria of the antrum was obVOLUME 41, NO. 2, 1995
Table 1. Thickness* of the gastric wall components for each segment measured with the ultrasonic microprobe Segment
m
sm
ti - 84184~
~
,,
pm
Results in the deflated condition under water immersion (n = 13) Body 0.8 (0.3) 1.0 (0.4) 0.8 (0.4) Antrum 0.9 (0.4) 1.1 (0.7) 1.6 (0.9) Results in the distended condition under air inflation (n = 22) Body -0.8 (0.4) 0.5 (0.3) Angulus -0.6 (0.2) 0.5 (0.3) Antrum -0.6 (0.2) 0.8 (0.5) *Mean (SD) in millimeters. m, Mucosa; sm, submucosa; p m , muscularis propria.
l!tlil il
,,:
. . . . . .
~
I*
Table 2. Imaging of gastrointestinal lesions with the ultrasonic microprobe Lesions
Underwater Contact scanning scanning
Early carcinomas (n = 9) Valid in: Tumor identification Observation of submucosal growth Benign polyps (n = 6) Valid in: Tumor identification Observation of inner structure Submucosal tumors (n = 3) Valid in: Tumor identification Observation of inner structure
9 8
5 5
6 6
4 4
3 2
2 2
served to be about two times thicker t h a n t h a t of the body, whereas the mucosal and submucosal layers seemed to be almost equal in thickness t h r o u g h o u t the stomach. T h e submucosa and muscularis propria as seen by contact scanning appeared to become t h i n n e r in the inflated stomach. However, their relative proportions in terms of thickness were found to be m u c h the same as those observed in the deflated stomach by u n d e r w a t e r scanning.
Imaging of gastrointestinal lesions Early c a r c i n o m a o f the stomach. Nine patients (Table 2) with early gastric carcinoma included three with the superficial elevated type (IIa) and six with the superficial depressed type (IIc or IIc+III). W h e n imaged with the probe, the lesions a p p e a r e d hypoechoic. U n d e r w a t e r scanning was the b e t t e r procedure for visualizing the pathologic process as a whole. T h e ultrasound beam was usually able to p e n e t r a t e the tissue of interest in these lesions, providing quality images for the assessment of submucosal t u m o r growth (Figs. 5A, 6A). However, one type IIc + I I I lesion resisted the ult r a s o u n d beam penetration. V O L U M E 41, NO. 2, 1995
Figure 5. Early gastric carcinoma of type Ila+llc with a significant submucosal growth (T). A, Image by underwater scanning; B, image by contact scanning. The muscularis propria (pm) appeared intact. Contact scanning during air inflation was p e r f o r m e d in six of these patients. T h e lesions could be identified and submucosal t u m o r growth observed in five (Figs. 5B, 6B). In one patient, a tiny IIa lesion (about 4 m m in size) was missed by this technique. This failure was a t t r i b u t e d to the difficulty in maintaining p r o p e r contact with the surface of the small protrusion. P o l y p s o f the g a s t r o i n t e s t i n a l tract. B y underwater scanning, these polyps, either p e d u n c u l a t e d or of the sessile type, were well visualized (Table 2), with a high-quality view of the inner structure (Fig. 7A). A vessel-like structure was detected within the stalk of a p e d u n c u l a t e d polyp in one patient. P e d u n c u l a t e d or s e m i p e d u n c u l a t e d polyps were also visible by contact scanning with air inflation (Fig. 7B), although some distortion was inevitable from the probe contact. Small sessile polyps less t h a n 4 m m in size were hardly visualized by contact scanning. S u b m u c o s a l tumors. T h e submucosal tumors of three patients were easily located in the mural layers by u n d e r w a t e r scanning (Table 2). T h e cystic lesions were clearly delineated (Fig. 8), b u t the ultrasound beam became r e m a r k a b l y a t t e n u a t e d in one solid tuGASTROINTESTINAL ENDOSCOPY
143
Figure 6. Early gastric carcinoma of type IIc presenting a slightly thickened mucosal layer on ultrasonography. A, Image by underwater scanning; B, image by contact scanning. Both images demonstrate an intact muscularis mucosae (arrow) and submucosa (sm), suggesting the lesion to be limited to the mucosa.
mor, probably a leiomyoma, so that the inner structure could not be visualized aS all. Cystic submucosal tumors were also well demonstrated by contact scanning. However, this method did fail with one solid lesion found just below the gastric cardia because of technical difficulty in apposing the probe. O t h e r l e s i o n s . In five patients with esophagogastric varices, intramural dilated vessels were well visualized. Transmural edema of the rectum was revealed in one patient with eosinophilic proctitis. Regarding gastric ulcers, the ultrasound beam was significantly attenuated in these lesions. Considerable acoustic attenuation also occurred in advanced malignant tumors, including gastric carcinoma of Borrmann type III or IV, gastric malignant lymphoma, and advanced esophageal carcinoma, resulting in incomplete examination. DISCUSSION We found the short focus (focus zone of 1.5 to 6.5 mm) and the high-frequency scanning (10, 15, or 20 144 GASTROINTESTINAL ENDOSCOPY
Figure 7. Semipedunculated gastric polyp containing inner cystic components. A, Image by underwater scanning; B, image by contact scanning.
MHz) of the new Toshiba probe to provide high-quality, real-time images of the gastrointestinal wall. The structure of the gastric wall was clearly identifiable as being stratified in seven to nine layers. The submucosal small vessels and the internal and external components of the muscularis propria were distinctly presented. The muscularis mucosae, which had been reported to be visible with a linear 20-MHz probe, 7 was also often detectable with this radial 15- or 20-MHz probe. The normal thickness of the wall components could be assessed with this probe. The muscularis propria of the antrum was about two times thicker than that of the body, but the mucosal and submucosal layers appeared uniform in thickness throughout the stomach. However, several independent factors, such as the fluctuating strain of the wall, the compression caused by probe contact, and the direction of scanning, could account for some of the variations seen in the measurements. Our in vivo study shows that the high-resolution images achieved with this probe have the potential to provide precise evaluation of small gastrointestinal lesions, especially early carcinomas. Underwater scanVOLUME 41, NO. 2, 1995
Figure 1. CT scan showing large pseudocyst (large arrow) pressing closely against the posterior wall of the stomach
(small arrow).
Figure 3. Ultrasound catheter probe image of pseudocyst (curved arrows). The catheter probe is in the water-filled lumen (large arrow) and is pressing gentry against the gastric wall. The distance between the gastric wall mucosa and the pseudocyst is 3.6 mm (smallarrows), and there are no large intramural vascular structures.
Figure 2. Endoscopic ultrasound of pseudocyst (large solid arrows) as imaged from the posterior wall of the stomach using a mechanical radial scanner echoendoscope. Note the distance (small open arrow) between where the transducer is pushing on the gastric wall and the pseudocyst lumen is 3 mm.
g a s t r o s t o m y in a patient with no obvious pseudocyst bulge on endoscopy.
CASE REPORT A 37-year-old male alcoholic presented with acute pancreatitis which was complicated by a 5 • 6 x 7 cm pancreatic pseudocyst located in the mid-body on CT scan. This fluid collection was aspirated under CT guidance with removal of 30 ml of hemorrhagic, sterile fluid. Over the next 4 weeks the patient had increasing abdominal pain and a repeat CT scan revealed the pseudocyst to be 8 • 10 • 22 cm extending from the lesser curve of the stomach to just below the left renal hilum {Fig. 1). Initially, endoscopic ultrasound (EUS) with a 360-degree radial scanning echoendoscope at 7.5 MHz (GF-UM20, 146
GASTROINTESTINAL ENDOSCOPY
Olympus America Inc., Lake Success, N.Y.) was performed in order to determine if the pseudocyst was located less than 10 mm from the intestinal wall to allow endoscopic cystenterostomy, as well as to evaluate the pancreatic parenchyma for evidence of chronic pancreatitis, pancreatic duct dilitation, or pancreatic duct stones, which might affect endoscopic management. Upper gastrointestinal endoscopy immediately prior to EUS showed no obvious visible bulging into the gastric or duodenal lumen and no esophageal or gastric varices. EUS revealed a large pseudocyst adjacent to the antral and duodenal walls which measured 3 to 4 mm from the lumen to the pseudocyst (Fig. 2). The pancreas parenchyma had EUS changes of chronic pancreatitis consisting of a diffuse inhomogeneous echopattern with multiple hypoechoic areas suggesting cystic spaces and a thickened, hyperechoic, irregular main pancreatic duct. There were multiple benign-appearing peri-pancreatic lymph nodes, and poor visualization of the splenic vein suggesting splenic vein thrombosis. Gastric varices were present near the gastroesophageal junction. The following day the patient was taken to the fluoroscopy suite to have endoscopic cystenterostomy performed. The patient was placed in the standard prone position used for ERCP. No pseudocyst bulge was seen with the therapeutic duodenoscope (TJF-100, Olympus America Inc.). To determine the optimal site for pseudocyst puncture, a 6.2F, 20 MHz, 200 cm long, catheter-based ultrasound probe (EndoSound, Microvasive/Boston Scientific Inc, Watertown, Mass., and HP Sonos Intravascular Imaging System, Hewlett-Packard Company, Andover, Mass.) was passed through the working channel of the duodenoscope into the VOLUME 41, NO. 2, 1995