The diagnosis of chronic mesenteric ischaemia is typically based on angiographic findings along with a classic symptomatology. Only a few methods are available for functional testing to establish the diagnosis, such as indirect measurement of the splanchnic blood flow and hepatic vein oxygenation. The present case is a 76-year-old woman with weight loss and intermittent abdominal pain who was clinically suspected of chronic mesenteric ischaemia based on severe stenosis of the celiac artery and superior mesenteric artery. Measurement of the total splanchnic blood flow and hepatic vein oxygenation, however, showed a normal perfusion after meal stimulation, as well as an increased hepatic vein oxygenation, indicating normal flow reserves. This was likely due to a richly developed Riolan's anastomosis arising from the inferior mesenteric artery. The present case advocates the need for functional testing when diagnosing chronic mesenteric ischaemia.