This patient presented with right upper quadrant abdominal pain. There was RUQ tenderness on exam, but no fever, rebound or Murphy sign. A point-of-care ultrasound was performed to assess for signs of cholecystitis and the following image was obtained. This prompted the operator to ask, “What the heck?”
The normal gallbladder wall should measure less than 3-4mm. It is recommended that this measurement be taken through the anterior wall of the gallbladder, since posterior acoustic enhancement will often make posterior measurements inaccurate. The image above was taken in a patient with cirrhosis, chronic ascites, and no acute complaints of upper abdominal pain. While a thickened gallbladder wall is one sign of cholecystitis, there are a number of normal and pathologic states which can lead to this finding as well.
- Normal contracted gallbladder
- Alcoholic liver disease
- Increased portal venous pressure
- Acute viral hepatitis
- Heart failure
- Renal disease
Why does this occur? A normal gallbladder can exhibit a thickened wall of 4-5mm due to contraction alone. Typically this will occur in the setting of a lower-than-normal gallbladder volume.
For the rest, hypoalbuminemia is a major culprit in gallbladder wall thickening; alone or as a secondary mechanism in patients with cirrhosis, heart failure or renal disease. Other speculated mechanisms of gallbladder wall thickening in the disease states above are increased portal venous pressure and generalized edema. Going back through radiology journal articles older than the ones below (1970s-80s), the same mechanisms are invoked repeatedly, and other older articles are referenced. There seems to be no definitive mechanism proven to cause the gallbladder wall thickening, though many articles demonstrate that it does in fact occur, and distinct from incomplete contraction of the gallbladder itself.
Gallbladder wall thickening is often evident in adenomyomatosis and gallbladder cancer as well. In these settings the gallbladder wall diameter is directly a part of the pathology, and not a side effect of some other process as in the cases above.
Thus, this finding is not specific to acute cholecystitis. It is present in many other disease states and may even signal the clinician that there is some other pathology at play.
- Wegener M, Borsch G, Schneider J et al. Gallbladder wall thickening: a frequent finding in various nonbiliary disorders–a prospective ultrasonographic study. J Clin Ultrasound 1987 Jun;15(5):307-12. (PMID: 3149957)
- van Breda Vriesman AC, Engelbrecht MR, Smithuis RH et al. Diffuse gallbladder wall thickening: differential diagnosis. Am J Roentgenol 2007 Feb;188(2):495-501. (PMID: 17242260)
One of the most common pitfalls in gallbladder sonography is confusion with the structure which abuts it in the right upper quadrant – the duodenum. This loop of bowel can easily be mistaken for the gallbladder especially if it contains a mixture of fluid and solid materials. So how can we tell them apart?
- has a bright (echogenic) wall
- is surrounded by liver
- attaches to the middle hepatic ligament
- is a contained structure
- can be traced to the portal vein
- has a darker (hypoechoic) wall
- is next to the liver, not in it
- cannot be traced to the middle hepatic ligament
- is a tubular structure
- does not connect to the portal vein
More images and explanation after the break!