[Possibilities and limitations in endosonography of the gastrointestinal tract].

In addition to the endoscopic assessment of the mucosa, endoscopic ultrasonography allows the characterization of the gastrointestinal tract wall and the neighbouring structures. Due to the high ultrasonic frequencies employed, endoscopic images have a high resolution. Malignant tumours of the esophagus, stomach, periampullary region, and rectum are usually investigated both by computer tomography and endoscopic ultrasonography. The local T-N tumour stage is predominantly assessed by endoscopic ultrasonography. In contrast, the M stage is assessed predominantly by computed tomography. The local T-N stage, which ist decisive for the local tumour resectability, can only be assessed with sufficient accuracy by endoscopic ultrasonography.