Endoscopic ultrasonography (EUS), also known as endosonography, is a highly effective procedure for the detailed assessment of conditions affecting the gastrointestinal tract and adjacent organs. It is particularly valuable in the staging of various cancers, including esophageal, gastric, rectal, pancreatic, and anal cancers, by precisely identifying the depth of tumor invasion and involvement of surrounding lymph nodes, blood vessels, and other vital structures. EUS enables the acquisition of detailed, close-up images due to its endoscopic approach, providing clear visualization of tissue layers. This capability is critical for accurate tumor staging and for characterizing sub-epithelial lesions. Furthermore, EUS facilitates therapeutic interventions such as targeted biopsies from tumors and lymph nodes, as well as the drainage of cysts and other fluid collections.