Stone-In-Neck or the ‘SIN’ sign is when you see an immobile stone lodged in the gallbladder neck, without any anechoic space between the neck and the stone. It is suggestive of cholecystitis even in the absence of other sonographic signs such as thickened gall bladder wall, Pericholecystic fluid, sonographic Murphy’s sign etc. One small study found that the sensitivity of this sign is 56.5% and the specificity 97% for cholecystitis.