How to diagnose intestinal obstruction, which is a common acute abdomen condition in surgery. If symptoms such as cessation of passing gas or stools, abdominal pain, and vomiting occur, it may suggest the presence of an intestinal obstruction. The simplest diagnostic method for intestinal obstruction is to perform an upright abdominal plain film to assess the degree of obstruction, based on the presence or absence of fluid levels. Furthermore, identifying the fundamental cause of the obstruction is essential; this can be achieved through enhanced abdominal CT and colonoscopy to make a determination. An abdominal ultrasound can also be performed, which provides a better understanding of the condition of the intestinal obstruction. Using abdominal ultrasound, the presence of effusion can be detected, and by aspirating the effusion, its properties can be analyzed to determine if there is a condition such as bowel necrosis.