Endosonography
Endosonography ( EUS , from endoscopic ultrasound ) is an ultrasound examination (sonography) carried out not from the outside through the skin , but from the inside . The ultrasound head is brought into direct contact with internal surfaces (for example the esophageal mucosa ) using special equipment (usually endoscopes ) . An ultrasound image is then created there.
Compared to the ultrasound examination through the outer skin, this method has the advantage that it means that the target organ is closer to the ultrasound head and can therefore be displayed more sharply and more precisely or it is possible to display it in the first place. There are two different types of endoscopic ultrasound devices. Radial transducers allow a 360 ° view and have a balloon at the tip of the endoscope, which is filled with water to achieve better coupling to the mucous membrane. Devices with a longitudinal transducer have a restricted viewing angle, but in contrast to radial devices, they have the option of sonographically supported punctures, e.g. B. for obtaining tissue samples. Endosonography makes it possible to depict internal organs in large animal medicine in the first place.
Depending on the area of application, different devices are used for endosonography. A flexible endoscope is used to examine the esophagus , stomach , the adjoining duodenum and bronchial tubes, at the tip of which there is a miniaturized ultrasound head in addition to the optics. This endoscopic sonography endoscope is slightly thicker than a normal endoscope.
Gastroenterological endosonography has established itself as an essential component in the diagnosis of benign and malignant processes in the esophagus , mediastinum , stomach , bile , pancreas and rectum since around 1995 . Interventional techniques guided by endoscopic ultrasound are also spreading more and more. A puncture needle is passed through the endoscopic ultrasound device and a sample is taken from a finding under ultrasound view. In addition to endoscopic skill, endosonography requires subtle knowledge of anatomy and ultrasound anatomy and is one of the most difficult endoscopically-assisted procedures to learn.
Endosonography as part of other examination methods
The following examination methods can be supplemented by an endosonography:
- Esophago-gastro-duodenoscopy
- Bronchoscopy
- Rectoscopy
- Vaginal ultrasound
- Endoscopic retrograde cholangiopancreatography (ERCP), but only as mini-probe endosonography, see below
Mini-probe endosonography
Mini-probe systems are related to endosonography : instruments that can also be used e.g. B. can be pushed through a so-called biopsy channel. They have a much thinner probe than with conventional endoscopic ultrasound. The radius of the penetration depth of the ultrasound is also smaller (penetration depth of the mini probes is limited to approx. 3 cm). In contrast to conventional endoscopic ultrasound, one works here with fixed frequencies (5 / 7.5 / 10/12/20/25 MHz). Mini-probe endosonography is particularly suitable, for. B. for the targeted examination of a polyp or to estimate the penetration depth of a tumor .
A mini-probe endosonography of the last part of the bile duct (ductus choledochus) as part of an ERCP is known as intraductal ultrasound (IDUS).
Web links
- Endosonography Atlas very good collection of endosonography images
Individual evidence
- ↑ Dissertation on endoscopic ultrasound
- ↑ B. Braden et al .: Intraductal Ultrasound (IDUS) . In: Christoph Frank Dietrich (Ed.): Endosonography: Guide and Atlas . Georg Thieme Verlag, 2008, ISBN 978-3-13-155531-1 , p. 27.
