Clinical implications of endoluminal ultrasonography using through-the-scope catheter probes

Basic Principles and Role of Endoscopic Ultrasound in Diagnosis and Differentiation of Pancreatic Cancer from Other Pancreatic Lesions: A Comprehensive Review of Endoscopic Ultrasound for Pancreatic Cancer

Pancreatic cancer is one of the leading causes of cancer-related deaths worldwide. Pancreatic lesions consist of both neoplastic and non-neoplastic lesions and often pose a diagnostic and therapeutic challenge due to similar clinical and radiological features. In recent years, pancreatic lesions have been discovered more frequently as incidental findings due to the increased utilization and widespread availability of abdominal cross-sectional imaging. Therefore, it becomes imperative to establish an early and appropriate diagnosis with meticulous differentiation in an attempt to balance unnecessary treatment of benign pancreatic lesions and missing the opportunity for early intervention in malignant lesions. Endoscopic ultrasound (EUS) has become an important diagnostic modality for the identification and risk stratification of pancreatic lesions due to its ability to provide detailed imaging and acquisition of tissue samples for analysis with the help of fine-needle aspiration/biopsy. The recent development of EUS-based technology, including contrast-enhanced endoscopic ultrasound, real-time elastography-endoscopic ultrasound, miniature probe ultrasound, confocal laser endomicroscopy, and the application of artificial intelligence has significantly augmented the diagnostic accuracy of EUS as it enables better evaluation of the number, location, dimension, wall thickness, and contents of these lesions. This article provides a comprehensive overview of the role of the different types of EUS available for the diagnosis and differentiation of pancreatic cancer from other pancreatic lesions while discussing their key strengths and important limitations.

Miniprobe Endoscopic Sonography for Gastrointestinal Tract Assessment: A Case Series of 1451 Procedures

Conventional endoscopic sonography has allowed precise diagnostics without disturbances, and miniprobes can be easily introduced through the biopsy channel of the endoscope. Miniprobe endoscopic sonography has many benefits compared with conventional endoscopic sonography. Although there are well-known indications for miniprobe endoscopic sonography in endoscopic digestive tract assessment, there is still a need for this method to be widely spread among physicians and commonly used by most endoscopists. The aim of this series was to describe a multicenter retrospective experience with 1451 procedures using miniprobes, presenting examples and the applicability and usefulness of this technology in the daily activities of an endoscopy department.

Discrepancy in diagnosis of gastric submucosal tumor among esophagogastroduodenoscopy, CT, and endoscopic ultrasonography: a retrospective analysis of 93 consecutive cases

PURPOSE

Evidences on diagnostic ability of esophagogastroduodenoscopy (EGD), CT, and endoscopic ultrasonography (EUS) for gastric submucosal tumor (SMT) are insufficient. For investigating a suitable diagnostic strategy, we retrospectively investigated diagnostic accuracy of EGD and CT for SMT, in comparison to EUS findings.

METHODS

Ninety-three consecutive lesions in which gastric SMT was suspected by EGD were investigated by EUS from March 2009 to June 2011, including 55 lesions evaluated also by CT 4 months before or after EUS. Frequency of possibly malignant SMTs as a detection rate of EGD, and sensitivity and specificity of CT in detection of SMT were retrospectively analyzed. Factors influencing the ability for CT to detect SMT were also investigated.

RESULTS

EUS revealed possibly malignant SMT in 60 cases (64.5%). In 32 out of 55 cases, possibly malignant SMT was suspected by CT. Sensitivity and specificity of CT was 80.6% and 84.2%, respectively. The mean size of possibly malignant SMT detected and not detected by CT was 27.4 and 11.0 mm, respectively, with a statistically significant difference (p = 0.0001).

CONCLUSION

This study elucidated that approximately one-third of suspected SMTs by EGD might not need clinical care. EUS for suspected SMTs is indispensable for extracting possibly malignant SMTs from others, and CT may be insufficient as an alternative to EUS in detecting especially small ones.

Appendiceal mucocele diagnosed in patients with inflammatory bowel disease using endoscopic ultrasound

When a bulging appendiceal orifice is observed during surveillance colonoscopy, the possibility of appendiceal mucocele must be considered. Appendiceal mucocele is a rare group of lesions characterized by mucinous distension of the appendiceal lumen with the dangerous potential to rupture, resulting in the development of pseudomyxoma peritonei. Early recognition and diagnosis of appendiceal mucocele can prevent the dreaded complication of pseudomyxoma peritonei but it requires a high index of suspicion. Patients with inflammatory bowel disease are at increased risk for colorectal neoplasm but neoplasm of the appendix is infrequently reported. We report two of the first cases of appendiceal mucoceles diagnosed in patients with inflammatory bowel disease using endoscopic ultrasound.

Evaluation of subepithelial abnormalities of the appendix by endoscopic ultrasound

Background. The use of through-the-scope (TTS) miniprobe catheter endoscopic ultrasound is a valuable technique for evaluating subepithelial lesions in the proximal colon. Few reports include the evaluation of the appendix by EUS. Objective. To describe endoscopic and endosonographic characteristics of subepithelial lesions of the appendix. Methods. Retrospective case series in a single academic medical center. Adult patients referred for evaluation of subepithelial lesions of the appendix identified by colonoscopy between April 1, 2003 to February 29, 2008. Data were abstracted from an electronic endoscopic database for all patients undergoing miniprobe endoscopic ultrasound examination of the appendix. Medical records were reviewed for patient followup and outcomes. Results. Nine cases were identified. Seven (78%) patients were female. Seven (78%) utilized the 12 MHz miniprobe device and two (22%) used the 20 MHz device. Three mucoceles were described and confirmed by surgical resection. Cases also included one inverted appendix, one gastrointestinal stromal tumor, and one lipoma. In three cases, no abnormality was found. Conclusions. EUS evaluation of the appendix is feasible with standard miniprobe devices and may assist in the selection of patients who may benefit from surgical management.

Diagnostic procedures for submucosal tumors in the gastrointestinal tract

This review is part one of three, which will present an update on diagnostic procedures for gastrointestinal (GI) submucosal tumors (SMTs). Part two identifies the classification and part three the therapeutic methods regarding GI SMTs. Submucosal tumors are typically asymptomatic and therefore encountered incidentally. Advances in diagnostic tools for gastrointestinal submucosal tumors have emerged over the past decade. The aim of this paper is to provide the readers with guidelines for the use of diagnostic procedures, when a submucosal tumor is suspected. Literature searches were performed to find information on diagnostics for gastrointestinal submucosal tumors. Based on the searches, the optimal diagnostic procedures and specific features of the submucosal tumors could be outlined. Standard endoscppy, capsule endoscopy and push-and-pull enteroscopy (PPE) together with barium contrast X-ray do not alone provide sufficient information, when examining submucosal tumors. Endoscopic ultrasound (EUS), computed tomography (CT), magnetic resonance imaging (MRI) and fluorodeoxyglucose-labeled positron emission tomography (FDG-PET) are recommended as supplementary tools.

The preferred choice for radial endosonographic staging of esophageal cancer: standard echoendoscope or nonoptic esophagoprobe?

BACKGROUND

The nonoptic esophagoprobe has been reported to be comparable to the standard echoendoscope in esophageal cancer staging, with a superior advantage of traversing more stenotic tumors because of its smaller diameter. The aim of this study was to see whether its use in a general population of esophageal cancer patients confers any significant clinical benefit.

METHODS

Five hundred seventy-seven consecutive patients referred for initial locoregional staging of esophageal cancer were analyzed retrospectively. Comparisons were made between the standard echoendoscope and the esophagoprobe.

RESULTS

Complete staging (95.2% vs 77.5%; p < 0.001) was significantly higher in the esophagoprobe group compared with that of the standard echoendoscope group (315 and 262 patients, respectively). In 146 patients with histopathologic verification without prior chemotherapy or radiotherapy, the esophagoprobe was comparable in T-staging accuracy to the standard echoendoscope in those with traversable tumors (89.2% vs. 82.8%; p = 0.213). However, the presence of a nontraversable stricture significantly decreased standard echoendoscope T-staging accuracy compared with a traversable stricture (33.3% vs. 82.8%, respectively; p < 0.001). The esophagoprobe also picked more advanced tumors and distal nodes.

CONCLUSIONS

The esophagoprobe is more accurate than the standard echoendoscope in the T staging of esophageal cancer because of its higher likelihood of traversing tumor stenosis. It can potentially reduce the necessity for dilation in stenotic tumors by four to five times. We propose using the esophagoprobe as the first choice for radial endoscopic ultrasound staging of esophageal cancer.

Prospective evaluation of high-frequency mini-probe ultrasound colonoscopic imaging in ulcerative colitis: a valid tool for predicting clinical severity

BACKGROUND

High-frequency mini-probe ultrasound imaging permits trans-mural cross-sectional imaging of the colorectal wall. In ulcerative colitis, prognosis is dependent on the severity of mucosal inflammatory change where accurate assessment of disease activity is required to optimize medical therapy. Furthermore, predicting relapse of disease using conventional endoscopic, histopathological and clinical criteria has not proven reliable.

AIM

To evaluate the correlation of high-frequency mini-probe imaging with standardized measures of clinical, endoscopic and histopathological severity.

METHODS

High-frequency ultrasound images were obtained from the caecum to rectum in 200 patients. Tsuga colorectal ultrasound criteria were then compared to the endoscopic Baron score, Seo activity score and Matts histopathological grade.

RESULTS

For rectal disease, the kappa coefficient between Tsuga criteria I/II and Matts grade 1/2 was 0.78 (95% CI, 0.67-0.89), 0.57 (95% CI, 0.46-0.68) and 0.48 (95% CI, 0.34-0.62) for Tsuga class IIIa/b, IVa/b and Matts grade 3a/b and 4, respectively. Colonic imaging showed a kappa coefficient between Tsuga class I/II and Matts grade1/2 of 0.76 (95% CI, 0.72-0.8). Tsuga class IIIa-IIIb/IVa-IVb as compared to Matts grade 3a-3b/4 yielded kappa coefficients of 0.49 (95% CI, 0.43-0.55) and 0.62 (95% CI, 0.56-0.69), respectively. In the rectum both the total wall thickness, mucosa and submucosa were significantly thicker in Matts grade 3b and 4 disease as compared to Matts grade 1/2 (P < 0.02) for all parameters. A significant increase in colonic total wall thickness was observed between Matts score 4 and Tsuga grade 1-3a disease (P < 0.001).

CONCLUSIONS

High-frequency ultrasound is a valid adjunctive 'tool' for the trans-mural assessment of the colorectal wall in ulcerative colitis. This technique may aid in the initial diagnosis, and ongoing chronic management of disease.

Prospective evaluation of a jelly-like conducting medium for catheter US probe imaging of esophageal and duodenal lesions

BACKGROUND

The catheter probe EUS(C-EUS) relies on luminal water for acoustic coupling. However, in tubular structures, such as the esophagus and the duodenum, instilled water drains away rapidly. The use of water-filled balloons is limited by air artifact and other problems. This study evaluated the image quality, the penetration depth, the tumor staging accuracy, and the safety of C-EUS by using carboxymethylcellulose, an edible, nontoxic, transparent jelly-like substance (JC-EUS).

METHODS

Forty patients with an esophageal or a duodenal submucosal lesion or an esophageal carcinoma were evaluated prospectively in a crossover study with both C-EUS and JC-EUS when using a 12-MHz US catheter probe. Based on still images, depth of US penetration and image quality (by using a predefined 1 to 5 scale) were assessed by a blinded, independent endosonographer.

OBSERVATIONS

JC-EUS was superior in image quality compared with C-EUS overall (mean score: 4.9 vs. 2.6; p <0.001), as well as in each subgroup (esophageal carcinoma, esophageal submucosal lesion, duodenal submucosal lesion). Penetration depth was not significantly different (2.5 cm). Staging was 100% accurate in 14 patients with esophageal cancer who underwent surgery. There was no procedure-related complication.

CONCLUSIONS

JC-EUS is safe, provides superior image quality to C-EUS, and is accurate for local staging of esophageal cancer.

A resource utilization projection study of EUS

BACKGROUND

EUS has emerged as standard practice with respect to the diagnosis and staging of GI malignancies. Whether currently available resources are sufficient to meet the potential need for EUS is uncertain. This study examines the hypothetical demand for EUS in the United States.

METHODS

EUS cases performed at 3 centers with well-established expertise in EUS in 1997 were retrospectively reviewed and trends were extrapolated to national cancer statistics. Indications for EUS fell into 3 categories: (1) diagnosis/staging of esophageal, gastric, pancreatic, or rectal cancers (established indications); (2) suspected GI malignancy (obligate "rule out"); and (3) "other" (emerging indications). Hypothetical total numbers of cases in which EUS could be performed in the United States were calculated taking into consideration the expected number of GI malignancies for which EUS would be appropriate (based on cancer statistics for 2000), the fraction unresectable by CT, the fraction of elderly nonsurgical candidates, proportionate "rule out" cases, as well as "other" emerging indications.

RESULTS

The calculated hypothetical number of cases (United States) in which EUS would be indicated is 79,568 per year (10,287 esophagus, 10,666 stomach, 23,069 pancreas, and 35,546 rectal). If "other" indications remained constant at 12%, there would potentially be 89,116 EUS procedures performed per year, with a conservative estimate of 79,572 per year.

CONCLUSIONS

This model suggests that currently available EUS resources are not sufficient to meet hypothetical demand. Future considerations include the number of endoscopy units in which EUS is performed, the capacity of individual units, and the implications for training programs in the United States.

Utility of an upper echoendoscope for endoscopic ultrasonography of malignant and benign conditions of the sigmoid/left colon and the rectum

OBJECTIVE

The majority of data on colonic endoscopic ultrasound (EUS) are limited to malignant lesions in the rectum and diseases of the anal sphincter. The forward-oblique-viewing upper echoendoscope has been mostly applied for staging rectal cancer. A front-viewing echocolonoscope is available but has not been widely used because of limited indications and the expense of buying another instrument. The purpose of our study was to evaluate the utility of a forward-oblique-viewing upper echoendoscope for EUS of malignant and benign lesions of the sigmoid/left colon and the rectum.

METHODS

Thirty-two EUS exams were performed for a variety of indications in the rectum and the sigmoid/left colon. The patients were prepared for the exam in a manner similar to the performance of flexible sigmoidoscopy. Flexible sigmoidoscopy was performed in all cases before performing EUS. Surgical path data were reviewed in all cases if the patient had surgery after EUS.

RESULTS

Twenty-six exams were done for staging of rectosigmoid carcinoma, follow-up after chemotherapy and/or radiation, or to look for recurrence after resection of colorectal cancer. Surgical pathology results were available in 20 patients. The accuracies of EUS were 85% for T staging and 80% for N staging. Six EUS exams were for benign causes, including evaluation for the presence of a perirectal abscess in two (no abscess found), to rule out rectal varices in one (EUS confirmed rectal varices), and evaluation of submucosal lesions. One patient subsequent to EUS imaging also underwent a linear EUS-guided fine-needle aspiration of a submucosal mass in the rectum with the fine-needle aspirate consistent with a myogenic tumor.

CONCLUSIONS

The forward-oblique-viewing upper echoendoscope is a versatile instrument that can be applied for EUS imaging of malignant and benign indications not only in the rectum but also in the sigmoid/left colon.

Prospective evaluation of balloon-sheathed catheter US system

BACKGROUND

Catheter US probes must rely on luminal water to create images because they do not incorporate a water-filled balloon such as that used with a designated echoendoscope. The purpose of this study is to determine the effectiveness and safety of a balloon sheath for the US catheter system.

METHODS

Catheter EUS was performed on 50 patients by using a 2.3 mm 12 MHz or 20 MHz catheter probe. Catheter EUS was used in 47 cases, and a newly developed water-filled balloon sheath was used in 41 cases. Both devices were used in 39 cases. Procedure time, depth of ultrasound penetration, and a subjective assessment of image quality and ease of use were recorded, along with TMN stage as applicable. Catheter EUS findings were confirmed with a standard radial scanning echoendoscopy (S-EUS) in 18 cases.

RESULTS

Catheter probe EUS (C-EUS) and catheter probe plus balloon (CB-EUS) imaging was obtained of 25 esophageal, 8 gastric, 4 rectal, 1 biliary, and 1 duodenal lesion. Time required for the ultrasound portion of the examination was identical with C-EUS and CB-EUS. Depth of penetration increased with CB-EUS with both the 12 MHz and 20 MHz probes (p < 0.05). Subjective assessment of image clarity improved when CB-EUS was used in the esophagus. C-EUS failed to identify 2 esophageal cancers and 2 sets of paraesophageal lymph nodes, and understaged 1 esophageal cancer. The remaining 14 cancers were staged identically by both modalities. The catheter probes with and without the balloon sheath were easy to use, even in markedly narrow esophageal strictures. CB-EUS did not significantly improve resolution in the stomach or rectum. S-EUS confirmed findings of CB-EUS in all 18 cases in which both instruments were used. There were no procedure-related complications.

CONCLUSIONS

For esophageal lesions, CB-EUS improves images compared with C-EUS, and enhances depth of penetration without prolonging or encumbering the examination. CB-EUS offers no advantage over C-EUS in organs other than the esophagus. S-EUS, when possible, remains the preferred imaging modality for esophageal cancers because of the ability to image the celiac axis and other deep structures.

Intraductal ultrasound in the biliary tract

Although endoscopic ultrasonography (EUS) represents a major advance in endoscopic imaging, endosonography using dedicated echoendoscopes has some serious drawbacks, including the diameter of the echoendoscope (12 to 13 mm), the lack of intraluminal examination of the pancreatobiliary duct system due to the size of the instrument, unsatisfactory image quality and resolution for small lesions, and the need for a second examination separate from the previous routine endoscopy. Recently developed ultrasonographic miniprobes (diameter, about 2 mm; frequency, 12 to 20 MHz) can be passed through the working channel of standard endoscopes to provide high-frequency ultrasound images. These miniprobes may overcome some of the noted drawbacks and add to the safety and convenience of patients. Moreover, in various diseases of the gastrointestinal tract and the pancreatobiliary ductal system, the diagnostic accuracy of miniprobe ultrasonography has been proven to be superior to that of EUS. Miniprobe ultrasonography is a promising tool that adds new capabilities to the armamentarium of gastroenterologic diagnostic assessment.

Gastrointestinal miniprobe sonography: the current status

Endoscopic ultrasonography (EUS) represents a major advance in endoscopic imaging. The usefulness and effectiveness of EUS have been established during the past few years. However, endosonography using dedicated echoendoscopes (7.5/12 MHz) has some serious drawbacks, as follows: 1) Combining endoscopy and ultrasonography in one instrument increases the diameter of such echoendoscopes (12-13 mm); 2) Because of the large diameter, complete passage of severe strictures is often not possible and, for examination of the pancreatobiliary duct system, is not feasible at all; 3) Image quality and resolution for small lesions is not always satisfactory; and 4) Conventional endosonography requires a second examination separate from the previous routine endoscopy. Recently developed ultrasonographic miniprobes (diameters about 2 mm; frequencies 12-20 MHz) can be passed through the working channel of standard endoscopes to provide high frequency ultrasound images. These miniprobes might overcome some of the above-mentioned drawbacks and contribute to patients' security and convenience. Moreover, in various diseases of the GI tract and the pancreatobiliary duct system, diagnostic accuracy of miniprobe ultrasonography has been shown to be even superior to that of EUS. In summary, miniprobe ultrasonography seems to be a promising tool in the armamentarium of gastroenterological diagnostics.

Dilation of malignant esophageal stenosis to allow EUS guided fine-needle aspiration: safety and effect on patient management

BACKGROUND

Endoscopic ultrasonography (EUS) with fine-needle aspiration identifies patients with esophageal cancer who are unlikely to be cured by surgery. In approximately 30% of patients the staging procedure cannot be completed without dilation of an obstructing tumor.

METHODS

All EUS examinations for esophageal cancer requiring dilation from July 1995 to December 1998 were included. Yield was defined as newly diagnosed metastatic (celiac lymph nodes) or locally invasive disease that could not have been detected without dilation.

RESULTS

EUS was performed in 132 patients. Forty-two (32%) required 44 dilations. No complications occurred. Of the 42 patients with obstruction, 18 (43%) had celiac adenopathy of which 7 had malignant cells confirmed histologically, 3 had benign adenopathy, and 8 did not undergo fine-needle aspiration due to T4 stage disease (5) or intervening vessels (3). Two patients were upstaged after successful dilation from T2 N1 Mx to T4 N1 Mx and from T3 Nx Mx to T3 N1 M1. Overall, dilation allowed detection of advanced disease in 8 of 42 (19%) patients. Dilation to 11 to 12.8 mm was insufficient (36% success rate) to complete EUS compared with dilation to 14 to 16 mm (87%, p < 0.01).

CONCLUSION

Dilation of obstructing esophageal tumors allows identification of a large number of patients with advanced stage malignancy. Dilation to 14 to 16 mm is sufficient for complete staging in almost all patients.

Catheter probe assisted endoluminal US in inflammatory bowel disease

BACKGROUND

Use of an echocolonoscope to examine patients with inflammatory bowel disease is technically difficult. Catheter probe assisted endoluminal ultrasonography (US) may be a feasible alternative.

METHODS

Determination of demographic information and clinical disease activity was followed by colonoscopy with biopsy. Catheter probe assisted endoluminal US was performed with measurements of thickness of the intestinal wall and evaluation of the structure of the sonographic layers.

RESULTS

Twenty-eight patients, 7 with ulcerative colitis, 11 with Crohn's disease, and 10 healthy control subjects participated in a prospective study. Mean colonic wall thickness was 2.2 +/- 0.1 mm (controls) compared with 4. 1 +/- 0.4 mm (ulcerative colitis) (p < 0.001) and 4.4 +/- 0.4 mm (Crohn's disease) (p < 0.001). Among patients with ulcerative colitis, colonic wall thickness correlated with severity of colonoscopic changes (r = 0.84, p = 0.02). Among patients with Crohn's disease, loss of endosonographic layer structure correlated with disease activity score (r = 0.8, p = 0.003), and colonic wall thickness correlated with the severity of histologic changes (r = 0. 62, p = 0.04).

CONCLUSIONS

Catheter probe assisted endoluminal US is technically feasible in the care of patients with inflammatory bowel disease. Endosonographic measurements of colonic wall thickness and layer structure provide clinically significant information.