Endoscopic ultrasonography

Endoscopic ultrasonography is a new and interesting technique. It is the only imaging technique that provides images of the gastrointestinal wall. Because of the high frequency used in EUS, it may provide high resolution images of gastrointestinal organs such as the pancreas. Although the equipment used for EUS is similar to that used for more familiar diagnostic and therapeutic endoscopic procedures, there are substantial differences as well. The EUS procedure is more complex and difficult than many standard endoscopic procedures, and it requires close cooperation between the endoscopist, nurse and the patient. Despite the cost and difficulties of establishing this procedure in an endoscopy unit, EUS offers considerable promise as a new method of investigation.     

Endoscopic ultrasonography

Increasing research related to endoscopic ultrasonography is published every year. A welcome trend towards outcomes-oriented research, evaluating the impact of endoscopic ultrasonography on patient management, is continuing. As experience regarding the safety and efficacy of endosonography-guided fine-needle aspiration in different clinical settings accumulates, this procedure is rapidly becoming a key component of endoscopic ultrasonography. Although promising developments in the fields of guided tissue sampling and image acquisition and analysis are being reported, innovative technical ideas need to be incorporated into the existing endoscopic ultrasound technology to take it to the next level of applications, such as endosurgery.     

Endoscopic ultrasonography

This review again uses a practical arrangement of the topics of endoscopic ultrasonography (EUS) into clinical categories rather than single diseases. The clinical categories include established indications, such as staging of gastrointestinal tract cancers, differential diagnosis of submucosal tumors, evaluation of solid and cystic pancreatic masses, detection of lymph nodes, evaluation of the biliary tree, and fine-needle aspiration (FNA). In addition to established indications, surgical and investigational techniques are presented, such as fine-needle therapeutic procedures and methods of studying portal hypertension and hepatic, abdominal, and retroperitoneal masses. This year, the new techniques and instruments presented have not included new probes or endoscopes, as these have already gained wide application in published papers and clinical practice. However, new techniques capable of facilitating the use of existing equipment are discussed, such as computer-aided EUS image analysis. Finally, some fascinating studies investigated outcomes with EUS and the cost-effectiveness of the method - stimulating both endosonographers and non-endosonographers to think about current practices and ways of improving them.     

Endoscopic ultrasonography

Endosonography is primarily a diagnostic imaging modality, but new therapeutic applications are being developed. Miniprobe technology (ultrasound catheter probes) has led to new clinical applications. The staging of gastrointestinal cancers remains the major accepted indication for endosonography. Other conditions, such as chronic pancreatitis, portal hypertension, and inflammatory bowel diseases, are also being evaluated with endosonographic imaging.     

Endoscopic ultrasonography

Twenty years after the introduction of endoscopic ultrasonography, many papers on the topic are still being published every year in the medical literature. Along with established clinical indications, such as gastrointestinal and pancreatic cancer staging and differential diagnosis of submucosal tumors, new applications have been suggested, such as mediastinal and liver tumor sampling with fine-needle aspiration. Improved accuracy and cost-effectiveness have been demonstrated in comparison with other imaging techniques. Reports of large series of fine-needle aspiration procedures have described a high level of accuracy for EUS in the diagnosis of lymph nodes and perivisceral masses. Pancreatic and ampullary tumors still represent a major challenge, as shown by numerous articles describing differential-diagnostic criteria and cytological sampling techniques. A few papers have also been published on the topic of portal hypertension, but it seems questionable whether there is any real advantage for endoscopic ultrasonography over traditional endoscopy here. New techniques such as radiofrequency tumor ablation are promising, while others such as three-dimensional imaging and the use of contrast enhancement have not yet met with routine clinical application. Finally, some of the papers published during the last year have studied the technique of endoscopic ultrasonography itself, dealing with issues of outcome, current clinical availability and use, and the learning curve. Evidently, endoscopic ultrasonography is still widely underused - not only among general practitioners and physicians in other specialties, but even by gastroenterologists. Although endoscopic ultrasonography is already 20 years old, considerable efforts are still needed, therefore, to ensure that it becomes more widely accepted in clinical practice.     

Endoscopic ultrasonography

This paper covers the literature published between June 2003 and August 2004 on endoscopic ultrasonography (EUS) and EUS-guided fine-needle aspiration (FNA). During this period, more than 120 original studies were published on the topic, not to mention editorials and case reports--indirect evidence of the ever-increasing importance of EUS in everyday clinical practice. However, due to limitations of space, this review will focus only on a few articles selected for their importance and originality. The studies presented deal either with the outcome of EUS--i. e., its real importance in affecting the choices physicians are faced with in their clinical work--or definitively clarify certain technical issues that have often been a matter of debate at EUS meetings. Finally, a few papers describing new potential diagnostic or interventional applications of EUS are presented. Many other relevant papers in addition to those discussed in detail are cited in the references.     

Placental ultrasonography

Ultrasonography is the preferred technique for placental localization. It permits a comparatively precise estimate of the separation of the lower placental margin and internal cervical os. Six false positive diagnoses of placenta previa occurred in a series of 244 patients. There were no false negative diagnoses. The diagnosis of placenta previa was confirmed as correct in ten patients. Determination of the location of the lower margin of a posterior placenta obscured by the overlying fetus may be assisted by measurement of the separation of the anterior sacral margin and the fetal head when the latter is dipping into the pelvis. A separation of greater than 15 millimeters usually indicates extension of the lower placental margin over the sacral promontory and onto the lower uterine segment.     

Endoscopic ultrasonography

Areas of application for endosonography can be roughly divided into three categories: standard diagnostic examination; operative diagnostic examination (fine-needle aspiration); and operative therapeutic procedures. Nevertheless, endoscopic ultrasonography remains a single technique, in which the physician can not only raise a suspicion of a particular disease, but can also obtain cytological confirmation when needed and carry out a therapeutic procedure when indicated. Widely accepted indications for endosonography are the staging of esophageal and rectal cancer, and the visualization of submucosal lesions and gastric wall diseases; other indications, such as imaging of the pancreas and biliary tree, are still being discussed.