Gallbladder folds arise due to the gallbladder wall folding onto itself. They are thick, junctional in nature and incomplete or non-continuous in appearance.
The posterior wall is usually involved, however, anterior wall folds may also occur 1. The folding may produce a bizarre or unusual shape on occasion. Sigmoid or an "s" shaped gallbladder and even a "boomerang" gallbladder have been documented in the literature 1.
Some specific folds are named:
Phrygian cap: gallbladder fundus folding back upon the body resembling the head garment worn by inhabitants of Phrygia (modern Türkiye) 1200-700 BCE 1,2
Hartmann pouch: fold or diverticulum near the neck of the gallbladder where gallstones can often collect ref
Radiographic features
Ultrasound
Gallbladder folds may produce an acoustic shadow and when partially visualized they can mimic a polyp or even a calculus. It is essential to assess the gallbladder in all planes to fully resolve normal variants and confirm or exclude pathology ref.