Figure 6. "Arrowhead" sign. 64-year-old man with 3-day history of colicky lower abdominal pain and right iliac fossa tenderness. CT shows an "arrowhead" sign (arrow) with peri-appendiceal inflammation. The arrowhead sign results from the accumulation of gastrointestinal contrast medium between a symmetrically thickened caecal apex; the intraluminal collection of contrast "points" at the occluded orifice of the appendix.