US - Wall Echo Shadow Sign: Ultrasound of the Month
/The case presentation...
A young obese female with a history of hypertension and polycystic ovarian syndrome presents to the emergency department for evaluation of epigastric abdominal pain associated with nausea and vomiting. In fact, this is her third visit to an emergency department in the past week. At the initial visit she received an abdominal CT scan that was interpreted as negative for acute intra-abdominal pathology. The day prior to presentation, she was seen again, achieved symptomatic control with fluids, non-steroidal anti-inflammatories, and antiemetics, with an overall reassuring workup, including a normal hepatic function panel. However, her pain persisted, prompting her to return for a third visit.
The patient reported that she first noticed her symptoms after a meal of fried chicken, but aside from a few episodes of vomiting, she had been able to tolerate food and fluids without further post-prandial exacerbation. She denied changes in bowel habits, fevers, dysuria, and really any other complaints.
On presentation, she was somewhat hypertensive, but afebrile and in no acute respiratory distress. Her abdominal exam was notable for tenderness in the epigastrium and right upper quadrant. She received intravenous analgesia and laboratory analyses were repeated with no significant changes from her most recent visit. The providers decided to perform a POCUS biliary scan to evaluate for cholelithiasis.
And now for the ultrasound images...
+ What do you see on ultrasound?
The images here demonstrate a gallbladder that is full of stones. With the exception of the anterior wall, the gallbladder is not well-visualized. The stones that fill the gallbladder create an echogenic line and a dense shadow. Wall + Echo + Shadow = WES sign
Still image of wall-echo-shadow complex
+What is your diagnosis?
Cholelithiasis
Wall-echo-shadow (WES) sign
The WES sign was first described in 1981 by MacDonald et al. and has since been used to describe gallstones within a contracted gallbladder (1,2). It consists of two curvilinear echogenic lines separated by a thin hypoechoic space. The near line represents the gallbladder wall, the hypoechoic line is caused by a thin layer of bile, and the far line is caused by either many small stones or one large stone within the gallbladder lumen. The resultant image appears as a bright double-crescent casting a dark shadow posteriorly that appears quite different from normal gallbladder anatomy. When encountered for the first time it may fool the examiner into believing that they cannot visualize the gallbladder at all, or may be misinterpreted as a loop of bowel (2).
This finding is indicative of cholelithiasis. The patient may have cholecystitis, however, the secondary signs of cholecystitis are difficult to assess (e.g. wall thickening, pericholecystic fluid, and common bile duct diameter) when the WES sign is present. Impaction of stones in the gallbladder neck is also possible, however, it quite difficult to assess the mobility of stones.
Other important items on the differential of WES are porcelain gallbladder and emphysematous cholecystitis (3). Porcelain gallbladder is associated with chronic gallbladder inflammation, is associated with chronic cholelithiasis, and increases the risk of gallbladder cancer by 2-3%. The definitive test to rule out this process is CT scan, but abdominal plain films may also show characteristic findings. Emphysematous cholecystitis is a complication of cholecystitis resulting from gas-producing bacterial infection of the gallbladder. Air can also create a shadow, although typically it will produce a dirty shadow, rather than the dense shadow associated with stones, and is unlikely to be uniformly present throughout the gallbladder. Further, the characteristic wall-echo-shadow components will not be present. These patients are likely to appear systemically ill and may very rarely exhibit crepitus on exam when palpating the RUQ. These patients are at increased risk of gallbladder wall perforation, abscess, peritonitis, and sepsis.
You may be asking yourself, why did the CT scan failed to detect gallstones in this patient? Interestingly, CT is not the test of choice for diagnosis of biliary pathology. CT imaging is only 85% sensitive for cholelithiasis. A significant portion of stones have attenuation to bile and are likely to be missed missed with standard CT (4).
+Ultrasound pearls
In general when performing hepatobiliary scans, images are optimized by positioning your patient in the left lateral decubitus position. Various patient maneuvers will be beneficial to identifying the gallbladder in two orthogonal planes.
Recognizing the wall-echo-shadow sign can save you from misdiagnosing a loop of bowel or being fooled into thinking you haven’t found the gallbladder at all.
Correctly interpreting the wall-echo-shadow sign will set your patient on the right track, including potential early surgical intervention.
Authored by Jared Ham, MD
Peer Reviewed by Lori Stolz, MD, RDMS
References
Rybicki, F. J. (2000). The WES sign. Radiology, 214(3), 881.
MacDonald, F. R., Cooperberg, P. L., & Cohen, M. M. (1981). The WES triad - A specific sonographic sign of gallstones in the contracted gallbladder. Gastrointestinal Radiology, 6(1), 39-41.
George, N., Dawkins, A., & Disantis, D. (2015). The wall-echo-shadow (WES) sign. Abdominal Imaging, 40(7), 2903.
Aparici, C., & Win, A. (2016). Acute calculous cholecystitis missed on computed tomography and ultrasound but diagnosed with fluorodeoxyglucose-positron emission Tomography/Computed tomography.Journal of Clinical Imaging Science, 6(31).
