On CT abdomen in a patient with appendicitis, the 'arrowhead sign' refers to:

• A Contrast material filling the appendiceal lumen confirming patent appendix
• B Mesenteric fat stranding around the appendix creating a wedge-shaped opacity
• C Thickened cecal apex directing toward an inflamed, non-filling appendix ✓
• D Appendicolith casting a shadow with V-shaped configuration

Explanation

The CT arrowhead sign in appendicitis describes contrast material filling the cecal apex up to the appendiceal orifice, with the thickened, edematous cecal wall forming the 'arrowhead' shape that points toward the non-filling, obstructed appendix. This sign helps identify the appendiceal orifice when the appendix itself is collapsed or difficult to trace. It is a secondary sign of appendiceal obstruction. The absence of contrast in the appendix despite cecal filling suggests obstruction. Mesenteric fat stranding is a separate finding indicating peri-appendiceal inflammation.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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