"Probing" the endoscopic ultrasound (EUS) catheter probe: a small step for EUS or a giant leap?

A Transesophageal Cardiovascular Intervention

Endoscopic ultrasonography-guided transesophageal pericardiocentesis was performed for a posteriorly located effusion not amenable to transthoracic drainage in a 58-year-old woman with a history of recurrent breast adenocarcinoma who presented with dyspnea. The patient had a pericardial effusion that resulted in cardiac tamponade. Transthoracic pericardiocentesis was unsuitable because of the posterior location of the effusion. Pericardiocentesis via the transesophageal route was performed. The pericardial sac was punctured with a 19-gauge needle, and 245 mL of pericardial fluid were aspirated, resulting in the resolution of the tamponade physiology. Endoscopic ultrasonography-guided transesophageal drainage is a novel and promising therapeutic option for posteriorly located pericardial effusions.

Ultrasound capsule endoscopy: sounding out the future

Video capsule endoscopy (VCE) has been of immense benefit in the diagnosis and management of gastrointestinal (GI) disorders since its introduction in 2001. However, it suffers from a number of well recognized deficiencies. Amongst these is the limited capability of white light imaging, which is restricted to analysis of the mucosal surface. Current capsule endoscopes are dependent on visual manifestation of disease and limited in regards to transmural imaging and detection of deeper pathology. Ultrasound capsule endoscopy (USCE) has the potential to overcome surface only imaging and provide transmural scans of the GI tract. The integration of high frequency microultrasound (µUS) into capsule endoscopy would allow high resolution transmural images and provide a means of both qualitative and quantitative assessment of the bowel wall. Quantitative ultrasound (QUS) can provide data in an objective and measurable manner, potentially reducing lengthy interpretation times by incorporation into an automated diagnostic process. The research described here is focused on the development of USCE and other complementary diagnostic and therapeutic modalities. Presently investigations have entered a preclinical phase with laboratory investigations running concurrently.

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.

Role of endoscopic ultrasonography in diseases of the extrahepatic biliary system

Endoscopic ultrasonography (EUS) is one of the most recent advances in gastrointestinal endoscopy. Available EUS devices include echoendoscopes, such as radial scanning and linear array echoendoscopes, and catheter ultrasound probes. Endoscopic ultrasonography has various applications, such as staging of gastrointestinal malignancy, evaluation of submucosal tumors, and has grown to be an important modality in evaluating the pancreaticobiliary system. With regard to the biliary system, EUS is useful for the detection and staging of ampullary tumors, detection of microlithiasis and choledocholithiasis and evaluation of benign and malignant bile-duct strictures. Endoscopic ultrasonography may be used as an adjunct to transabdominal ultrasound for the detection and characterization of gallbladder polyps. In addition, EUS is helpful in the staging of gallbladder cancer as well as in diagnosing anomalous pancreaticobiliary junction with its associated pancreatobiliary diseases. The present paper reviews the current applications of EUS for imaging and intervention in diseases of the extrahepatic biliary system.

Differentiating pancreatic cancer from pseudotumorous chronic pancreatitis

The differentiation between pancreatic carcinoma and pseudotumorous pancreatitis continues to be a challenge. Several diagnostic imaging and endoscopic modalities can assist in making the differentiation, but the accuracy of each method varies. Radiologic imaging techniques include transabdominal ultrasound, computed tomography, magnetic resonance imaging, magnetic resonance cholangiopancreatography, and positron emission tomography. Endoscopic techniques include endoscopic ultrasonography, intraductal ultrasonography, and endoscopic retrograde cholangiopancreatography with brush cytology of pancreatobiliary strictures, endoscopic forceps biopsy, and analysis of pancreatic juices for malignant cells. Tumor markers appear to be promising, but further studies are needed to define the role of these markers.

Accuracy of EUS in the evaluation of Barrett's esophagus and high-grade dysplasia or intramucosal carcinoma

BACKGROUND

Nonoperative therapy with intent to cure may be considered for patients with Barrett's esophagus and high-grade dysplasia or intramucosal carcinoma. However, a more advanced stage of disease must be precluded before such treatment. The potential of EUS for this purpose was evaluated.

METHODS

EUS was performed in patients with Barrett's esophagus and high-grade dysplasia or intramucosal carcinoma based on endoscopy, endoscopic biopsies, and CT before esophagectomy. EUS findings were compared with surgical/pathologic evaluation.

RESULTS

EUS suggested submucosal invasion in 6 patients and lymph node involvement in 5 patients. By surgical/pathologic evaluation, 5 of 22 patients (23%) had unsuspected submucosal invasion and 1 had lymph node involvement. EUS detected all 5 instances of submucosal invasion and the single instance of lymph node involvement. EUS was falsely positive for submucosal invasion in 1 patient and for lymph node involvement in 4 patients. Sensitivity, specificity, and negative predictive values of preoperative EUS for submucosal invasion were 100%, 94%, and 100%, and for lymph node involvement were 100%, 81%, and 100%, respectively. A nodule or stricture noted by endoscopy was associated with an increased likelihood of submucosal invasion.

CONCLUSIONS

In patients with Barrett's esophagus and high-grade dysplasia or intramucosal carcinoma, EUS detected otherwise unsuspected submucosal invasion and lymph node involvement. Patients should be evaluated with EUS when nonoperative therapy is contemplated.

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.

Endoscopic ultrasound in pancreatic diseases. Indications, limitations, and the future

Endoscopic ultrasonography (EUS) is a significant advance in the diagnosis and management of pancreatic disease. This article reviews the application of endosonography for detection of pancreatic masses, staging of pancreatic cancer, detection of pancreatic endocrine tumors, management of cystic pancreatic lesion, diagnosis of chronic pancreatitis, and many other emerging indications. Indications and limitations of endosonography in pancreatic diseases are discussed. The exciting possibilities of EUS-guided intervention in pancreatic diseases and other futuristic indications are explored.