Stone in neck. This is also known as the “SIN” sign. A stone lodged in the neck of the gallbladder is much more likely to cause cholecystitis than a stone elsewhere such as in the fundus. To see if a stone is truly lodged in the neck of the gallbladder, the patient should also be scanned in the left lateral decubitus or prone position to see if it rolls away.
What is the structure labeled “B”?
Duodenal bulb. Be careful not to mistake this structure for the gallbladder. Remember to look for landmarks such as the portal triad and main lobar fissure to confirm that the structure you are seeing is really the gallbladder. The duodenum will also exhibit peristalsis if you watch carefully.
Let’s say the point of maximal tenderness was elicited when palpating with the probe while obtaining the above images, however the patient’s labs are completely normal including no leukocytosis or transaminitis. What diagnosis is most likely?
Acute cholecystitis. There is unfortunately no single laboratory or imaging finding to sufficiently rule in or out cholecystitis. While abnormal labs can help make the diagnosis, normal labs do not exclude it. The combination of certain findings, however, can make the diagnosis much more likely. This question describes the technique for the Sonographic Murphy Sign. It was found that a combination of the presence of gallstones with a positive Sonographic Murphy has a positive predictive value of 92% for acute cholecystitis. The presence of a SIN sign alone was found to has a PPV of 93% for acute cholecystitis.
What are the 5 sonographic signs associated with this diagnosis?
Stone in neck (SIN sign) – Sp 97%
Sonographic Murphy sign – Sn 86%, Sp 35%
Pericholecystic fluid (secondary finding, low specificity by itself)
Anterior gallbladder wall thickening (>4 mm is abnormal, secondary finding, low specificity by itself)
Gallbladder hydrops (distended gallbladder measuring greater than 10 cm in length and 5 cm in width [increased width more specific])