Phrygian Cap

A Phrygian cap is a congenital anatomical variant of the gallbladder in which the fundus is folded over the body, producing a distinctive shape that resembles the eponymous Greek/Roman headwear. It is one of the most common gallbladder anatomical variants, present in roughly 4% of the population, and is almost always an incidental finding on ultrasound, CT, MRI, or HIDA scan.

The clinical importance of a Phrygian cap is mostly in not mistaking it for pathology. The fold can mimic a septated gallbladder, an intraluminal mass, an adenomyomatosis, or a duplicated gallbladder. The fold itself is not a risk factor for cholelithiasis or gallbladder dysfunction, although a Phrygian cap can complicate cholecystectomy if not anticipated.

Recognition on cross-sectional imaging is straightforward: a smooth fold separating the fundus from the body, with the fundus tilted toward the body or porta hepatis. No intervention is required for an asymptomatic Phrygian cap.