GI obstruction often leads to intractable vomiting, the consequences of which can be life-threatening. For diagnosing, an ileus clinical examination with abdominal radiographs or ultrasonographs are chosen routinely. The purpose of the study was to determine the incidence of GI obstruction among animals with gastrointestinal symptoms and to define ultrasonographic accuracy in detecting these GI obstructions. 38 animals (31 dogs and 7 cats) were included in the study. At the first consultation they presented gastrointestinal symptoms. A clinical examination with palpation of the abdomen was made. An ultrasound examination was made by an experienced radiologist. 17 of the 38 animals were diagnosed with obstructive ileus. In 15 of these 17 the ileus was confirmed, and in the remaining 2 only functional obstruction and enteritis was found. For the other 21 of the 38 animals the ileus was excluded. The animals with GI obstruction accounted for 39.5% of all animals with GI symptoms. The ultrasound examination was effective in 88.2% of cases. Intestinal obstruction is common in patients with gastrointestinal symptoms. Vomiting, diarrhoea and constipation are the main symptoms. Abdomen pain is rare. Ultrasound is a valuable and safe method for detecting GI obstructions. In only 2 animals was ileus misdiagnosed.