Gallbladder wall thickening is more commonly seen in diagnostic imaging. Historically, a thickened gallbladder wall was considered a manifestation of primary gallbladder disease and was thought to be a feature of acute cholecystitis. However, the presentation itself is not specific and can be found in many gallbladder lesions and extracholedochal lesions. Gallbladder that is dilated and edematous and congested due to obstruction by stones in the gallbladder neck or common bile duct. On ultrasonography, the normal gallbladder wall appears as a pencil-like linear echogenicity. The thickening of the gallbladder wall depends on the degree of gallbladder distension and pseudo-thickening of the gallbladder wall can occur after meals. Left: Fasting gallbladder wall shows a pencil-like ultrasound structure. On the right, postprandial gallbladder pseudobulbar wall thickening. Normal gallbladder on CT shows thin annular soft tissue density enhancement after contrast injection. Gallbladder wall thickening is relatively common in diagnostic imaging. A thickened gallbladder wall of more than 3 mm typically appears as a lamellar structure on ultrasound and as a periportal hypodense layer on CT due to a trace of peri-gallbladder fluid and subplasma edema. On the left, a 59-year-old woman with acute cholecystitis shows laminar thickening of the gallbladder wall with a hypoechoic area between the two echogenic layers. On the right, enhanced contrast CT shows thickening of the gallbladder wall containing a hypodense outer layer due to subplasma edema. Acute cholecystitis is the fourth leading cause of hospitalization in patients with acute abdomen, and the initial diagnosis is often associated with imaging findings of gallbladder wall thickening. However, this feature does not establish the diagnosis, and the presence of other imaging signs such as obstructive gallstones, dilated gallbladder edema and positive Murphy’s sign on ultrasound, peri-gallbladder steatitis or fluid, and energy Doppler with gallbladder wall congestion should confirm the diagnosis of acute gallstone cholecystitis. Enhanced contrast CT showed distended gallbladder (arrow) and mildly thickened wall, slight localized fatty infiltration (asterisk). There was an embedded stone in the neck of the gallbladder. Transverse ultrasound at the most sensitive point shows an incompressible edematous distended thick-walled gallbladder (arrow) with stones, sediment (or debris) visible in the lumen Enhanced contrast CT shows extensive fatty inflammatory changes (arrows) around the gallbladder (arrows) Acute stone free cholecystitis occurs mainly in critically ill patients, presumably due to increased bile viscosity due to fasting and drug-induced biliary sludge. These acute cholecystitis are characterized by the absence of stones on imaging and replaced by intra-biliary mud and sand. Because these gallbladder abnormalities usually occur in critically ill patients and are secondary to systemic disease, these cholecystitis are often difficult to diagnose. Performing a percutaneous cholecystostomy on them allows for both diagnosis and treatment. On the left, ultrasound at the most sensitive point shows a thickened gallbladder wall (arrow) and a gallbladder filled with sediment (asterisk) but no stones. On the right side, energy Doppler ultrasound shows the gallbladder wall enriched with blood vessels (arrows), a sign supporting inflammation. The term chronic cholecystitis is used for clinically symptomatic gallbladder stones leading to transient obstruction, resulting in low-grade inflammation and fibrosis. The associated imaging shows a mildly wall-thickened gallbladder containing stones with a corresponding clinical history. Longitudinal ultrasound of the gallbladder shows mild wall thickening (arrows) and intraluminal non obstructive stones. Yellow granulomatous cholecystitis is a rare variant of chronic cholecystitis characterized by a fat-rich inflammatory process, similar to yellow granulomatous pyelonephritis. Imaging studies show significant thickening of the gallbladder wall, often containing intramural nodules that appear hypoechoic on ultrasound and hypodense on CT, suggesting abscesses or focal yellow granulomatous inflammation. These features overlap with gallbladder cancer, making preoperative diagnosis difficult. Left, ultrasound showing a significantly thickened gallbladder wall and intramural hypoechoic nodules (arrows), and intraluminal stones (arrows). Right, enhanced contrast CT shows a malformed thickened gallbladder wall containing hypodense nodules. Yellow granulomatous cholecystitis. The hypodense nodules (arrows) suggest abscess or focal inflammation. Several stones (arrows) are present in the lumen. Porcelain-like gallbladder is another rare variant of chronic cholecystitis characterized by calcification of the gallbladder wall. Because of the association with gallbladder cancer, these patients often require prophylactic cholecystectomy. However, the risk of gallbladder cancer in porcelain gallbladders is not high. Porcelain-like gallbladder Gallbladder cancer is the fifth most common malignant lesion of the gastrointestinal tract and is found in 1-3% of surgical cholecystectomy specimens. Because of the lack of early or specific presentation, when detected, the lesion is usually at an advanced stage. Gallbladder cancer has a wide variety of imaging manifestations, ranging from intraluminal polyp-like lesions to masses that infiltrate the gallbladder wall and may also present as diffuse wall thickening. Associated features such as invasion of adjacent structures, secondary bile duct dilatation, liver or lymph node metastases can help differentiate gallbladder cancer from acute or yellow granulomatous cholecystitis. In the absence of these findings, it is difficult to differentiate between gallbladder cancer and yellow granulomatous cholecystitis. Ultrasound shows significant diffuse gallbladder thickening (arrows) in place of the gallbladder lumen. Multiple gallbladder stones (arrows) suggest that the lumen may be filled with stones. On the right, enhanced contrast CT depicts wall thickening of the gallbladder (arrows) with localized tumor invasion into the adjacent liver (arrows). Adenomyomatosis of the gallbladder is characterized by epithelial hyperplasia, muscular hypertrophy and intramural diverticula (ro-Archis sinus), which may cause segmental or diffuse gallbladder involvement. It is a benign lesion that requires no specific treatment and is found incidentally in 9% of cholecystectomy specimens. The diagnosis is strongly suggested by cholesterol crystals found within the thickened gallbladder wall, with a mixed echogenic artifact in the form of a “comet tail” on ultrasound. Air can also cause similar artifacts, however, patients with emphysematous cholecystitis usually have severe symptoms and can be differentiated from adenomyomatosis. MRI can also help to differentiate adenomyomatosis from gallbladder cancer because it can depict the Roche-Archis sinus. Ultrasound shows wall thickening and calcification, as well as a “comet tail” of mixed echogenic artifacts (arrows) due to small cholesterol crystals in the sinusoids (arrowheads) Systemic diseases such as hepatic insufficiency, heart failure or renal failure can also cause diffuse gallbladder wall thickening. The exact pathogenesis of these lesions leading to gallbladder wall edema is unclear, but may be related to increased portal venous pressure, increased venous pressure in the body circulation, and decreased intravascular osmotic pressure. Hypoproteinemia leading to exogenous gallbladder lesions has also been reported, but remains controversial.1, hepatitis; 2, cirrhosis; 3, congestive heart failure; 4, pancreatitis.