Case:
66 yo female with PMH of HTN, DM presented with pain in subxiphoid area x 1 day. The pain was severe and associated with nausea and vomiting. She denied diarrhea, fever, SOB. There was no history of previous abdominal surgeries. VSS. Physical exam was notable for epigastric tenderness. POCUS of the RUQ showed the following:
Case Conclusion:
The patient had a negative ACS workup in addition to normal LFTs and lipase. She was diagnosed with cholelithiasis based on the WES sign appreciated on her POCUS. Her symptoms, suspected to be due to biliary colic, resolved in the ED. She was discharged with outpatient follow-up and return precautions.
WES Sign:
This case highlights the Wall Echo Shadow (WES) sign. This sign can be difficult to appreciate and should be a consideration when you are having trouble visualizing the gallbladder (in addition to, of course, an "occult" history of cholecystectomy). The WES sign is often mistaken for a loop of bowel. It occurs when the gallbladder is either filled with multiple stones or one large stone immediately beneath the GB wall, preventing the passage of the ultrasound waves into the lumen of the gallbladder. The WES sign consists of three findings: the white (hyperechoic) line of the gallbladder wall, the hyperechoic echo from the stone(s) right below the anterior wall, and then a strong posterior shadow from the echo to the bottom of the screen, where the ultrasound waves do not penetrate. There is a small sliver of bile visualized between the wall and the echo.
If you see a WES sign, this is sufficient to diagnose cholelithiasis. It can also be present in cholecystitis, depending on the clinical picture, but a WES sign alone without other signs of cholecystitis does not signify more serious pathology than visualizing one smaller stone in the GB - both are cholelithiasis and can be asymptomatic or symptomatic. In other words, a WES sign is not a marker of severity of cholelithiasis but is indicative of its presence.
Pitfalls:
The WES sign has a similar appearance to a porcelain gallbladder, but a porcelain gallbladder lacks the thin hypoechoic (dark) stripe of bile that is appreciated in the WES sign between the stones and gallbladder wall. See below for an example of a porcelain gallbladder on EMBU:
The WES sign may also be confused with a collapsed duodenum, which can appear similar. Air in the duodenum can create a posterior shadowing effect that mimics a WES sign. Try repositioning the patient and rescanning to see if the WES sign is still appreciated. You can also watch carefully for signs of peristalsis which is consistent with an image of a duodenum.
- Jessica Patterson, MD, Emergency Medicine Ultrasound Fellow
References:
1. http://pubs.rsna.org/doi/full/10.1148/radiographics.20.3.g00ma16751
2. http://www.jem-journal.com/article/S0736-4679(11)00002-3/pdf
3. https://www.ultrasoundoftheweek.com/uotw-8-answer/
4. http://www.christem.com/acmcem-conf-notes/2016/10/29/conference-notes-10-26-2016