Intraluminal Changes

Gallstones are the classic example of mobile changes within the gallbladder. The wellknown mnemonic of “the five Fs”—fat, female, fertile, forty, fair—characterizes the segment of the population most at risk for cholecystolithiasis.

Typically, gallbladder stones are mobile and differ in their extent of posterior shadowing (depending on the size of the calculus) as well as in their intrinsic pattern ( 3.7). The sonographic morphology of the stones depends on their size, shape, and composition. Usually, the gallstones are a mixture of cholesterol, calcium, and bilirubin and are located at the most dependent part of the gallbladder. When looking for calculi it should be remembered that with the patient supine the stones are more likely to

be found in the neck of the gallbladder, while in the left lateral decubitus position they tend to collect in the region of the fundus/body ( 3.7a–c). Fairly large pure cholesterol stones (up to 60 mm) may float in the liquid bile.

Shadowing can be observed in gallstones with a diameter down to about 2–3 mm, depending on the quality of the stone as well as the equipment used and the frequency employed. Calculi with a diameter of less than 5 mm are called microliths. From a diameter of 8 mm and upward, subtle differentiation of the gallstones into cholesterol, calcium, and pigmented calculi usually does not present any problem.12 In microliths with a diameter of less than 5 mm, assessment of the intrinsic echo pattern may become difficult. Here, addi-

tional data such as tabular structure and comet-tail artifacts as well as any flotation of the stones (rich in cholesterol) and their size and shape (usually hyperechoic microliths dependent in the gallbladder are of mixed calcium composition) have to be taken into account (Table 3.4). Ultrasound morphology is essential when planning possible lysis or shock-wave lithotripsy.

Differentiating gallstones. The criteria for differentiating gallstones are their intrinsic echo pattern, surface echo, and posterior shadowing (3.7 d–i). Although gallstones are best visualized at the focus of the transducer, the quality and settings of the platform used are extremely important as well. Optimized differentiation of

b Left lateral decubitus—the calculi will be located at the fundus/body of the gallbladder.

e Calcium stone: shell-like surface echo, pronounced posterior shadowing, inhomogeneous intrinsic echo pattern.

c Typical gallstone with the patient supine: bright echo of the stone, classic posterior shadowing.

f Mixed pigment gallstone: inhomogeneous intrinsic echo pattern with black voids (pigment), soft surface echo, weak posterior shadowing.

Hypoechoic

sludge in the gallbladder may be differentiated as shown in Table 3.6 and 3.8. Dysfunctional motility or ejection is a precondition.

Hemobilia

Hemobilia is a well-known complication of tumor or, less commonly, inflammatory and traumatic gallbladder lesions. A fresh clot within the gallbladder may mimic hypoechoic sludge. Older traumatic clots adherent to the wall will display as hyperechoic mass (Fig. 3.66). During anticoagulation and known gallbladder disease hemobilia must be considered in the case of an obscure anemia.

Conclusion

These findings demonstrate the enormous capabilities offered by a subtle ultrasound study in the differential diagnosis of gallbladder disease. Ultrasound is the diagnostic modality of choice in all disorders of the gallbladder, since its resolution is much better than that of all the other modalities. Therefore, sonography is the linchpin in the diagnostic work-up of the gallbladder.

Fig. 3.66 Hemobilia in the fundus of the gallbladder, trau- matic-related hemorrhage, spontaneous resolution within 4 weeks.