Gastrointestinal sonography plays an increasingly important role in the nutritional management of critically ill patients, particularly in assessing gastric emptying and enteral feeding tolerance. Traditional methods such as scintigraphy and isotope breath testing, though considered gold standards, are impractical in intensive care settings due to their complexity and limited bedside applicability. In contrast, ultrasound has emerged as a noninvasive, real-time imaging technique that allows for reliable assessment of gastric residual volume (GRV) and gastrointestinal motility. This chapter explores the principles and clinical applications of gastric ultrasound, detailing its role in estimating GRV using standardized models such as the Bouvet and Perlas methods. It also discusses its integration into critical care protocols like the gastrointestinal ultrasound (GUTS) and abdominal gastrointestinal ultrasound (AGIUS) scores, which aid in predicting enteral feeding intolerance. Additionally, sonographic techniques for confirming nasogastric tube placement are presented as a safer alternative to radiographic verification. By providing real-time insights into gastrointestinal function, gastric sonography enhances clinical decision-making, reduces complications associated with enteral feeding, and minimizes reliance on radiological methods. While further standardization is needed, its ease of use and bedside availability make it a valuable addition to intensive care nutrition management.