396 Rube 105cm Fig. 4. Peptic ulcer perforation and thick gallbladder wall. (A)Patient who had rUQ pain d elevate white blood cell count (WBC). Ultrasound shows focal gallbladder wall thickening(7 mm; cur ( asterisks) and could be interpreted as cholecystitis. the free air with reverberation shadow to the correct diagnosis could be easily overlooked. (B) Transverse ultrasound shows wall thicken so heads), cursors) and extraluminal accumulated air(paired arrowheads)in perforated duodenal ulcer(From Rubens D Hepato- biliary imaging and its pitfalls. Radiol Clin North Am 2004: 42: 257-78: with permission. evidence of acute cholecystitis is a nonspecific find- ing and is often noted in patients who have hepati- ute acalculous cholecystitis Pericholecystic fluid is also a nonspecific finding, 5%-14% of cases of acute cholecystitis//l,o Acute acalculous cholecystitis account for up often occurring secondary to localized inflamma- seen most commonly in critically ill patients often tion from other causes, such as peptic ulcer disease following trauma, surgery, or major burns. The ex- 31(see Fig. 4)or identified in patients who have act etiology is unknown, but ischemia, hypotension ascites. Teefey and colleagues [10 have described or sepsis are likely cotributing factors [12]. These two specific patterns of pericholecystic fluid. Type critically ill patients are often medicated witI L, a thin anechoic crescent-shaped collection adja- narcotics, placed on ventilators, and receive hyper cent to the gallbladder wall, is a nonspecific find- alimentation that contribute to biliary stasis and ing(see Fig. 4B). Type Il, a round or irregularly functional obstruction of the cystic duct obst aped collection with thick walls, septations, or tion. Gangrene of the gallbladder develops in ap- internal debris, is more likely to be associated proximately 40% to 60% of patients who have with gallbladder perforation and abscess formation associated increased risk for perforation 2 Mortal ity ranges from 6% to 44% but can be reduced by
evidence of acute cholecystitis is a nonspecific finding and is often noted in patients who have hepatitis [11] (see Fig. 6). Pericholecystic fluid is also a nonspecific finding, often occurring secondary to localized inflammation from other causes, such as peptic ulcer disease [3] (see Fig. 4) or identified in patients who have ascites. Teefey and colleagues [10] have described two specific patterns of pericholecystic fluid. Type I, a thin anechoic crescent-shaped collection adjacent to the gallbladder wall, is a nonspecific finding (see Fig. 4B). Type II, a round or irregularly shaped collection with thick walls, septations, or internal debris, is more likely to be associated with gallbladder perforation and abscess formation (Fig. 7). Acute acalculous cholecystitis Acute acalculous cholecystitis account for up to 5%–14% of cases of acute cholecystitis [11]. It is seen most commonly in critically ill patients often following trauma, surgery, or major burns. The exact etiology is unknown, but ischemia, hypotension or sepsis are likely cotributing factors [12]. These critically ill patients are often medicated with narcotics, placed on ventilators, and receive hyperalimentation that contribute to biliary stasis and functional obstruction of the cystic duct obstruction. Gangrene of the gallbladder develops in approximately 40% to 60% of patients who have an associated increased risk for perforation [2]. Mortality ranges from 6% to 44% but can be reduced by Fig. 4. Peptic ulcer perforation and thick gallbladder wall. (A) Patient who had RUQ pain, fever, and elevated white blood cell count (WBC). Ultrasound shows focal gallbladder wall thickening (7 mm; cursors) and gallstones (asterisks) and could be interpreted as cholecystitis. The free air with reverberation shadows (arrows) that leads to the correct diagnosis could be easily overlooked. (B) Transverse ultrasound shows wall thickening (cursors) and simple pericholecystic fluid (arrow). (C) CT image shows pericholecystic fluid (arrows), free air (arrowheads), and extraluminal accumulated air (paired arrowheads) in perforated duodenal ulcer. (From Rubens D. Hepatobiliary imaging and its pitfalls. Radiol Clin North Am 2004;42:257–78; with permission.) 396 Rubens
Ultrasound Imaging of the Biliary Tract 397 B RT X LP GB X DEC A=1.38cm 2.36cm cursors an ic fluid within the wall. B) Transverse ultrasound of the lower pole of the enuation area of focal pyelonephritis(arrows).(From Rubens D. Hepatobi and its pitfalls. Radiol Clin North Am 2004: 42: 257-78: with permission. diagnosis and therapy [12 However, the diag- congestive heart failure(CHF), or liver disease are of acalculous cholecystitis is difficult to make considered unlikely to be the cause(Fig. 8). CT clinically and by US, because gallstones are absent can be used to assess for pericholecystic inflamma and the sonographic Murphy sign may not be de- tion to improve diagnostic specificity in patients tected because of diminished mental status, medi- who have a thick gallbladder wall and multiple cation and co-morbid illness. In the series potential etiologies [ 2, 13 reported by Cornwall and colleagues [12 only 50% of patients who had acalculous cholecystitis Complicated cholecystitis had a positive Murphys sign. The diagnosis is therefore, made by distension of the gall bladder Gangrenous cholecystitis, emphysematous chole in a suspicious clinical setting the presence of intra- cystitis, and perforation of the gallbladder occur luminal debris, gallbladder tenderness when in up to 20% of patients who have acute cholecys- resent (w50%)and gallbladder wall thickening titis 5 These complications are important to rec- when other etiologies, such as hypoalbuminemia, ognize, because they are associated with increased
early diagnosis and therapy [12]. However, the diagnosis of acalculous cholecystitis is difficult to make clinically and by US, because gallstones are absent and the sonographic Murphy sign may not be detected because of diminished mental status, medication and co-morbid illness. In the series reported by Cornwall and colleagues [12], only 50% of patients who had acalculous cholecystitis had a positive Murphy’s sign. The diagnosis is, therefore, made by distension of the gall bladder in a suspicious clinical setting, the presence of intraluminal debris, gallbladder tenderness when present (~50%) and gallbladder wall thickening when other etiologies, such as hypoalbuminemia, congestive heart failure (CHF), or liver disease are considered unlikely to be the cause (Fig. 8). CT can be used to assess for pericholecystic inflammation to improve diagnostic specificity in patients who have a thick gallbladder wall and multiple potential etiologies [2,13]. Complicated cholecystitis Gangrenous cholecystitis, emphysematous cholecystitis, and perforation of the gallbladder occur in up to 20% of patients who have acute cholecystitis [5]. These complications are important to recognize, because they are associated with increased Fig. 5. Pyelonephritis with gallbladder wall thickening. (A) Gallbladder wall shows marked 1.3-cm thickening (cursors) and hypoechoic fluid within the wall. (B) Transverse ultrasound of the lower pole of the right kidney shows a 3-cm echogenic mass (arrows). (C) CT through the right lower pole shows a characteristic round, heterogeneous, decreased attenuation area of focal pyelonephritis (arrows). (From Rubens D. Hepatobiliary imaging and its pitfalls. Radiol Clin North Am 2004;42:257–78; with permission.) Ultrasound Imaging of the Biliary Tract 397
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 191
morbidity (10%) and mortality (15%) [14] and require emergency surgery [2]. There is also approximately a 30% conversion rate for laparoscopic cholecystectomy 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 patients who have acute cholecystitis and has an increased risk for perforation [3]. Unfortunately ultrasound is nonspecific for the diagnosis of gangrenous cholecystitis. This is because the sonographic 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 examination, 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 perforation, 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 typically 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 require immediate surgery, although liver abscesses can be treated effectively with percutaneous drainage. Abscesses in the gallbladder wall or gallbladder 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 reported 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, accounting 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 gallbladder 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 nondependently within the gallbladder lumen (Fig. 10). Intramural gas is more difficult to identify, because it may mimic the mural calcification seen in a porcelain gallbladder. The type of shadowing (ie, ‘‘clean’’ versus ‘‘dirty’’) does not differentiate between calcium and air. The nondependent location of the mobile echoes within the lumen or mobile bubbles within the wall can document gas. If the US findings are equivocal, either CT or plain film radiography can be used to differentiate between gas and calcification [19]. Fig. 6. Hepatitis with striated gallbladder wall thickening. Longitudinal ultrasound of contracted gallbladder with a thickened striated wall (arrows) with alternating echogenic and hypoechoic layers. This patient 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