Most fasting gallbladders with low or no fluid levels result from cystic duct obstruction (Fig. 3.43).

Inflammatory atrophy of the gallbladder with its lack of fluid is usually caused by chronic cholecystitis, where the shape of the gallbladder is irregular and its wall thickened and inhomogeneous (hyperechoic) (Fig. 3.45, Fig. 3.46). During acute exacerbation, hypo-

echoic areas in the wall may also be visualized. A typical finding would be several, sometimes even encrusted, intraluminal gallstones. In the end the atrophic gallbladder can only be identified by the encrusted calculi within the scar tissue.

This contracted gallbladder with its gallstones is characterized by a crescent-shaped band of echoes without demonstration of the

posterior wall. Sometimes even the anterior wall with its scar contraction may hardly be delimited from the gallstone echoes (Fig. 3.46). In these patients, differentiation of a possible concurrent gallbladder carcinoma can be problematic.

Acute Cholecystitis

Acute and chronic cholecystitis is characterized by uneven thickening of the gallbladder wall with irregular echo pattern. The typical finding in acute cholecystitis is the tensely distended afunctional/dysfunctional gallbladder with its hypoechoic wall that is tender on palpation (positive Murphy’s sign). Another sign is the ill-defined intraluminal and extraluminal contour of the wall, accompanied by hypoechoic inflammation of the surrounding tissue (pericholecystitis). Ultrasound morphology of the gallbladder wall spans the spectrum from diffuse hypoechoic thickening with poorly delim-

ited contour of the wall ( 3.6a,b) through hypoechoic necrosis all the way to complete destruction of the wall ( 3.6c; see Table 3.2).9 Intraluminal hyperechoic or inhomogeneously echogenic material can point the way to the diagnosis of cholecystic empyema.

Advanced and severe courses of acute cholecystitis may result in necrosis of the mucosa and filiform detachment of the tunica mucosa ( 3.6e). Usually, these cases present with hyperechoic inhomogeneous necrotic debris within the gallbladder. A pericholecystic film is typical of localized perforation ( 3.6 d,e).

Lacelike structures with hypoechoic necrotic areas are infrequent findings.

Imminent perforation may be preceded by ascites, ulcers of the gallbladder wall, or pericholecystic infiltrates/abscesses ( 3.6f). Hypervascularization of the gallbladder wall in color-flow duplex scanning of cholecystitis is by no means mandatory. The histological grading of edematous, phlegmonous, and gangrenous cholecystitis cannot be differentiated very well by ultrasound.

Chronic cholecystitis

Normal or atrophied

Round

Hyperechoic

Small or lacking

Thickened

This entity is almost impossible to differentiate from gallbladder carcinoma on the basis of sonographic morphology alone.

spontaneous passage of stones up to 5.7 cm in diameter. Most often the stones perforate from the gallbladder into the duodenum (52%); perforation into the stomach occurs rather infrequently (ca. 3%), while the remainder of the gastrointestinal tract is affected in 45% of cases. The ultrasound signs of a perforated stone are its atypical anatomical location, gas echoes (pneumobilia) (Fig. 3.49b) within the lumen of the gallbladder (may not be present in case of fistulas), demonstration of a fistula, and atrophic gallbladder with visualization of calculi (Fig. 3.48, Fig. 3.49).

Porcelain gallbladder is considered a precancerous condition because in 10–60% of all cases gallbladder carcinoma will develop. Porcelain gallbladder is characterized by intramural shell-like calcification that may affect the entire wall or (more commonly) just parts of it (e. g., the fundus) (Fig. 3.50a,b, Fig. 3.52). Depending on the thickness of the calcified layer, the gallbladder wall may be sonolucent. In cases of severe calcification, any ultrasound differentiation of possible malignancy may prove to be infeasible. In the diffuse type there is complete calcification of the gallbladder wall, which may not be penetrated by the ultrasound beam in severe cases. If porcelain gallbladder is suspected, a plain radiograph of the gallbladder should be obtained (Fig. 3.50b).

Fig. 3.50

a Classic diffuse porcelain gallbladder: visualization of a broad calcified intramural crescent.

b Plain film of the gallbladder: typical radiographic image of diffuse porcelain gallbladder.

Based on the morphology of the outflow obstruction in gallbladder anomalies, the inflammatory changes of the gallbladder wall may be focal (e. g., inflammation of the fundus in Phrygian cap). The sonographic morphology of focal inflammatory lesions resembles that of the diffuse changes (Fig. 3.51). Just as in diffuse calcification, focal calcium deposits are classified as porcelain gallbladders (see above) (Fig. 3.52). Cholecystitis in focal porcelain gallbladder may be hard to differentiate.

Fig. 3.51 Focal cholecystitis (in Phrygian cap).

Fig. 3.52 Porcelain gallbladder with sonolucent wall: fine focal calcification of the fundus wall with translucent lumen of the gallbladder and identifiable cholecystolithiasis (with sludge) (image courtesy of Dr. W.B. Stelzel, Frankfurt, Germany).