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 byevidence of acute cholecystitis is a nonspecific find￾ing and is often noted in patients who have hepati￾tis [11] (see Fig. 6). Pericholecystic fluid is also a nonspecific finding, often occurring secondary to localized inflamma￾tion 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 adja￾cent to the gallbladder wall, is a nonspecific find￾ing (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 ex￾act 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 hyper￾alimentation that contribute to biliary stasis and functional obstruction of the cystic duct obstruc￾tion. Gangrene of the gallbladder develops in ap￾proximately 40% to 60% of patients who have an associated increased risk for perforation [2]. Mortal￾ity 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. Hepato￾biliary imaging and its pitfalls. Radiol Clin North Am 2004;42:257–78; with permission.) 396 Rubens