398 Rub in association with gangrenous cholecystitis 3 The fundus is the most common site for perfora- tion, because it has the least blood supply. Acute gallbladder perforation with an intraperitoneal bile leak will result in peritonitis but is much less common than subacute perforation, which typi cally leads to pericholecystic abscess formation 12 These abscesses may occur within or adjacent to the gallbladder wall in the gallbladder fossa, within the liver, parenchyma, or along the free margin of the gallbladder within the peritoneal avity 10. These are complex fluid collections Inflammatory changes in the adjacent fat can be detected ultrasound or ig.7C)|21 Patients who have intraperitoneal abscesses re- quire immediate surgery, although liver abscesses can be treated effectively with percutaneous drain Fig. 6. Hepatitis with striated gallbladder wall thick ladder with a thickened striated wall(arrowy) e/k age Abscesses in the gallbladder wall or gallblad- ening. Longitudinal ultrasound of contracted g der fossa may espond to conservative ternating echogenic and hypoechoic layers. This pa management 161 Pericholecystic fluid adjacent to the gallbladder ests, and a negative sonographic Murphy sign. She wall may mimic perforation. However, with careful tested positive for hepatitis b and also had clinically inspection, the gallbladder wall will be intact, and pecific for gallbladder disease. (From Hazle H, collecting within the gallbladder wall has been re- Rubens D. The liver. In: Dogra V, Rubens D, editors. ported in one case to precede perforation 1 Ultrasound secrets. Philadelpha: Hanley and Belfus; However, no other specific ultrasound features 2004. p. 130-49: with permission. have been identified that will accurately predict which inflamed gallbladders will perfo orbidity(10%)and mortality(15%)[14 and require emergency surgery 2 - There is also approx imately a 30%conversion rate for laparoscopic cho- Emphysematous cholecystitis lecystectomy to an open procedure in the setting of This is a rare complication of acute cholecystitis, ac- complicated cholecystitis 14 counting for less than 1% of all complicated cases of acute cholecystitis, and is caused by gas-forming Gangrenous cholecystitis bacteria in the gallbladder lumen or in the gallblad der wall. As many as 40% of patients who have Gangrenous cholecystitis is defined histologically emphysematous cholecystitis have diabetes 21 as coagulative necrosis of the mucosa or the entire Emphysematous cholecystitis is more common in gallbladder wall associated with acute or chronic men and patients often do not have gallstones inflammation (10 It occurs in up to 20% of pa- The clinical course is rapidly progressive, with tients who have acute cholecystitis and has an in- a 75% indidence of gallbladder ganges p8 creased risk for perforation 3]. Unfortunately a 20% incidence of gallbladder perforation ultrasound is nonspecific for the diagnosis of Emphysematous cholecystitis can be recognized eno on US examination by the extremely echogenic graphic Murphy sign is absent in up to two thirds gas which casts a distal shadow and layers nonde- of patients [15 A specific finding is the presence pendently within the gallbladder lumen(Fig. 10) of intraluminal membranes or stranding caused Intramural gas is more difficult to identify, because by sloughing of the gallbladder mucosa, necrosis it may mimic the mural calcification seen in a porce- of the gallbladder wall or fibrous exudate lain gallbladder. The type of shadowing(ie,clean (Fig 9). This finding is present on US examina versus"dirty")does not differentiate between cal- tion, however, in only 5% of patients 101 cium and air. The nondependent location of the mobile echoes within the lumen or mobile bubbles Gallbladder perforation within the wall can document gas. If the US find ings are equivocal, either CT or plain film radiogra- Perforation of the gallbladder occurs in 5% to 10% phy can be used to differentiate between gas and of patients who have acute cholecystitis, most often calcification 191morbidity (10%) and mortality (15%) [14] and require emergency surgery [2]. There is also approx￾imately a 30% conversion rate for laparoscopic cho￾lecystectomy to an open procedure in the setting of complicated cholecystitis [14]. Gangrenous cholecystitis Gangrenous cholecystitis is defined histologically as coagulative necrosis of the mucosa or the entire gallbladder wall associated with acute or chronic inflammation [10]. It occurs in up to 20% of pa￾tients who have acute cholecystitis and has an in￾creased risk for perforation [3]. Unfortunately ultrasound is nonspecific for the diagnosis of gangrenous cholecystitis. This is because the sono￾graphic Murphy sign is absent in up to two thirds of patients [15]. A specific finding is the presence of intraluminal membranes or stranding caused by sloughing of the gallbladder mucosa, necrosis of the gallbladder wall or fibrous exudate (Fig. 9). This finding is present on US examina￾tion, however, in only 5% of patients [10]. Gallbladder perforation Perforation of the gallbladder occurs in 5% to 10% of patients who have acute cholecystitis, most often in association with gangrenous cholecystitis [3]. The fundus is the most common site for perfora￾tion, because it has the least blood supply. Acute gallbladder perforation with an intraperitoneal bile leak will result in peritonitis but is much less common than subacute perforation, which typi￾cally leads to pericholecystic abscess formation [2]. These abscesses may occur within or adjacent to the gallbladder wall in the gallbladder fossa, within the liver, parrenchyma, or along the free margin of the gallbladder within the peritoneal cavity [10]. These are complex fluid collections. Inflammatory changes in the adjacent fat can be detected on ultrasound or CT (Fig. 7C) [2]. Patients who have intraperitoneal abscesses re￾quire immediate surgery, although liver abscesses can be treated effectively with percutaneous drain￾age. Abscesses in the gallbladder wall or gallblad￾der fossa may respond to conservative management [16]. Pericholecystic fluid adjacent to the gallbladder wall may mimic perforation. However, with careful inspection, the gallbladder wall will be intact, and the fluid is typically anechoic (see Fig. 4B). Fluid collecting within the gallbladder wall has been re￾ported in one case to precede perforation [17]. However, no other specific ultrasound features have been identified that will accurately predict which inflamed gallbladders will perforate. Emphysematous cholecystitis This is a rare complication of acute cholecystitis, ac￾counting for less than 1% of all complicated cases of acute cholecystitis, and is caused by gas-forming bacteria in the gallbladder lumen or in the gallblad￾der wall. As many as 40% of patients who have emphysematous cholecystitis have diabetes [2]. Emphysematous cholecystitis is more common in men and patients often do not have gallstones. The clinical course is rapidly progressive, with a 75% incidence of gallbladder gangrene and a 20% incidence of gallbladder perforation [18]. Emphysematous cholecystitis can be recognized on US examination by the extremely echogenic gas which casts a distal shadow and layers nonde￾pendently within the gallbladder lumen (Fig. 10). Intramural gas is more difficult to identify, because it may mimic the mural calcification seen in a porce￾lain gallbladder. The type of shadowing (ie, ‘‘clean’’ versus ‘‘dirty’’) does not differentiate between cal￾cium and air. The nondependent location of the mobile echoes within the lumen or mobile bubbles within the wall can document gas. If the US find￾ings are equivocal, either CT or plain film radiogra￾phy can be used to differentiate between gas and calcification [19]. Fig. 6. Hepatitis with striated gallbladder wall thick￾ening. Longitudinal ultrasound of contracted gall￾bladder with a thickened striated wall (arrows) with alternating echogenic and hypoechoic layers. This pa￾tient had RUQ pain, fever, abnormal liver function tests, and a negative sonographic Murphy sign. She tested positive for hepatitis B and also had clinically acute alcoholic hepatitis. The striated wall is not specific for gallbladder disease. (From Ghazle H, Rubens D. The liver. In: Dogra V, Rubens D, editors. Ultrasound secrets. Philadelpha: Hanley and Belfus; 2004. p. 130–49; with permission.) 398 Rubens