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INTRODUCTION Acute cholecystitis refers to a syndrome of right upper quadrant pain, fever, and leukocytosis associated with gallbladder inflammation, which is usually related to gallstone disease. In addition, two other forms of cholecystitis are commonly recognized:Acalculous cholecystitis is clinically identical to acute cholecystitis but is not associated with gallstones, and usually occurs in critically ill patients. It accounts for approximately 10 percent of cases of acute cholecystitis and is associated with high morbidity and mortality . (See "Acalculous cholecystitis").
The clinical manifestations, diagnosis, and pathogenesis of acute cholecystitis will be reviewed here. The treatment of acute cholecystitis, and acalculous, and the medical management of gallstone disease are discussed separately. (See appropriate topic reviews).
PATHOGENESIS In contrast to biliary colic, the development of acute cholecystitis is not fully explained by cystic duct obstruction alone. Studies in animals have demonstrated that ligation of the cystic duct does not result in acute cholecystitis [7,8]. However, acute cholecystitis can be produced experimentally by blockade of the cystic duct followed by deliberate irritation of the gallbladder mucosa (either mechanically with an indwelling catheter or by infusion of an irritant).
One such irritant used in experimental models, lysolecithin, is produced from lecithin, a normal constituent of bile. The production of lysolecithin from lecithin is catalyzed by phospholipase A, which is present in gallbladder mucosa. This enzyme may be released into the gallbladder following trauma of the gallbladder wall from an impacted gallstone . Supporting this hypothesis is the observation that lysolecithin (normally absent in bile) is detectable in gallbladder bile in patients with acute cholecystitis .
Once inflammation of the gallbladder begins, additional inflammatory mediators are released, further propagating gallbladder inflammation . Prostaglandins, which are involved in gallbladder contraction and fluid absorption, probably play a central role in this process. In experimental models using human gallbladder tissue, the main prostaglandins synthesized by inflamed human gallbladder microsomes were prostaglandin E2 and 6-keto-prostaglandin F1 alpha, the concentrations of which were increased four times above normal . The prostaglandin hypothesis is supported by the observation that prostaglandin inhibitors relieve biliary colic and can reduce intraluminal cystic pressure [12-14].
Infection of bile within the biliary system probably has a role in the development of cholecystitis; however, not all patients with cholecystitis have infected bile. This observation was illustrated in a study of 467 subjects in whom bile samples were obtained from the gallbladder and common bile duct for aerobic and anaerobic culture . Patients with a variety of hepatobiliary diseases and a healthy control group were included. Patients with gallstones, acute cholecystitis, and hydropic gallbladder had similar rates of positive cultures in the gallbladder and common bile duct, ranging from 22 to 46 percent; cultures were generally sterile in healthy subjects. The main species isolated were Escherichia coli, Enterococcus, Klebsiella, and Enterobacter.
Histologic changes of the gallbladder in acute cholecystitis can range from mild edema and acute inflammation to necrosis and gangrene. Occasionally, prolonged impaction of a stone in the cystic duct can lead to a distended gallbladder that is full of colorless, mucoid fluid. This condition, known as a mucocele with white bile (hydrops), is due to the absence of bile entry into the gallbladder and absorption of all the bilirubin within the gallbladder.
CLINICAL MANIFESTATIONS Patients with acute cholecystitis typically complain of abdominal pain, most commonly in the right upper quadrant or epigastrium. The pain may radiate to the right shoulder or back. Characteristically, acute cholecystitis pain is steady and severe. Associated complaints may include nausea, vomiting, and anorexia. There is often a history of fatty food ingestion about one hour or more before the initial onset of pain.
Prolonged or recurrent cystic duct blockage can progress to total obstruction causing acute cholecystitis. An episode of prolonged right upper quadrant pain (greater than four to six hours), especially if associated with fever, should arouse suspicion for acute cholecystitis as opposed to an attack of simple biliary colic. Symptoms that are not suggestive of a biliary etiology include fatty food intolerance not in the form of pain, nausea not in association with pain, pain only a few minutes after a meal, irregular bowel habits, or belching [16,17].
Physical examination Patients with acute cholecystitis are usually ill appearing, febrile, and tachycardic, and lie still on the examining table because cholecystitis is associated with true local parietal peritoneal inflammation that is aggravated by movement. Abdominal examination usually demonstrates voluntary and involuntary guarding.
Elicitation of "Murphy's sign" may be a useful diagnostic maneuver. While palpating the area of the gallbladder fossa just beneath the liver edge, the patient is asked to inspire deeply, causing the gallbladder to descend toward the examining fingers. Patients with acute cholecystitis commonly experience increased discomfort and may have an associated inspiratory arrest. The sensitivity of Murphy's sign may be diminished in the elderly .
Complications Left untreated, symptoms of cholecystitis may abate within 7 to 10 days. However, complications can occur at alarmingly high rates. The most common complication is the development of gallbladder gangrene (up to 20 percent of cases) with subsequent perforation (2 percent of cases) .
Gangrene Gangrenous cholecystitis is the most common complication of cholecystitis, particularly in older patients, diabetics, or those who delay seeking therapy . The presence of a sepsis-like picture in addition to the other symptoms of cholecystitis should suggest the diagnosis, but gangrene may not be suspected preoperatively.
Perforation Perforation of the gallbladder usually occurs after the development of gangrene. It is often localized, resulting in a pericholecystic abscess. Less commonly, perforation is free into the peritoneum, leading to generalized peritonitis. Such cases are associated with a high mortality.
Cholecystoenteric fistula A cholecystoenteric fistula may result from perforation of the gallbladder directly into the duodenum or jejunum. Fistula formation is more often due to long standing pressure necrosis from stones than to acute cholecystitis .
Gallstone ileus Passage of a gallstone through a cholecystoenteric fistula may lead to the development of mechanical bowel obstruction, usually in the terminal ileum (gallstone ileus) . (See "Gallstone ileus").
Emphysematous cholecystitis Emphysematous cholecystitis is caused by secondary infection of the gallbladder wall with gas-forming organisms (such as Clostridium welchii) [22,23]. Other organisms that may be isolated include Escherichia coli (15 percent), staphylococci, streptococci, Pseudomonas, and Klebsiella .
Affected patients are more commonly men in their fifth to seventh decade , and approximately one-third to one-half are diabetic [23-25]. Gallstones are present in about one-half of patients.
Like other patients with acute cholecystitis, patients with emphysematous cholecystitis usually present with right upper quadrant pain, nausea, vomiting, and low-grade fever. Peritoneal signs are usually absent, but crepitus in the abdominal wall adjacent to the gall bladder may rarely be detected. When such crepitus is present, it is an important clue to the diagnosis. The presence of mild to moderate unconjugated hyperbilirubinemia (caused by hemolysis induced by clostridial infection). (See "Extrinsic nonimmune hemolytic anemia due to systemic disease"). The ultrasound report may erroneously note the presence of "overlying bowel gas making adequate visualization of the gallbladder difficult" while in reality this reflects air in the wall of the gallbladder.
Emphysematous cholecystitis often heralds the development of gangrene, perforation, and other complications [23-25]. In a review of 20 patients, gallbladder perforation occurred in seven, pericholecystic abscess in nine, and bile peritonitis in three .
Removal of the gallbladder and antibiotic therapy are essential for effective treatment . Antibiotic regimens should be administered parenterally and must contain a drug with activity against Clostridium spp. Single drug choices include ampicillin-sulbactam or piperacillin-tazobactam. An alternative is the combination of an aminoglycoside or a quinolone with clindamycin or metronidazole.
There is controversy as to whether or not laparoscopic cholecystectomy should be attempted. Although several cases of successful laparoscopic cholecystectomies have been reported, it may not be feasible in many patients  and many patients require conversion to an open procedure .
DIAGNOSIS Acute cholecystitis should be suspected when a patient presenting with the clinical manifestations outlined above is found to have gallstones on an imaging study. However, the mere presence of gallstones is not a sine qua non for acute cholecystitis, since asymptomatic cholelithiasis is a common condition in the general population. Thus, confirmation of the diagnosis must be based upon a combination of physical findings, laboratory studies, and imaging tests (show algorithm 1).
The basis for this recommendation was underscored in a systematic review that focused on 17 studies examining the role of the history, physical examination and/or laboratory tests in adults with abdominal pain or suspected acute cholecystitis . No single clinical or laboratory finding was sufficiently accurate to rule-in or rule-out the diagnosis. The most accurate physical finding was a positive Murphy sign (positive likelihood ratio (LR) 2.8, 95 percent CI 0.8 to 8.6) and right upper quadrant tenderness (negative LR 0.4, 95 percent CI 0.2 to 1.1). On the other hand, the correct diagnosis (confirmed at surgery) was frequently achieved by the clinical impression in which the history, physical examination, laboratory and radiologic findings were considered together (LR ranging from 25 to 30).
Laboratory evaluation Initial evaluation should include a white blood cell count with differential, which often shows leukocytosis with an increased number of band forms (ie, a left shift). Elevation in the serum total bilirubin and alkaline phosphatase concentrations are not common in uncomplicated cholecystitis, since biliary obstruction is limited to the gallbladder; if present, they should raise concerns about complicating conditions such as cholangitis, choledocholithiasis, or the Mirizzi syndrome (a gallstone impacted in the distal cystic duct causing extrinsic compression of the common bile duct). (See "Mirizzi syndrome").
However, a mild elevation in serum aminotransferases and amylase, and hyperbilirubinemia with jaundice have been reported even in the absence of these complications . These abnormalities may be due to the passage of small stones, sludge, or pus.
Imaging studies Physical examination alone often cannot determine which of the abdominal viscera is the source of inflammation and pain. Thus, patients presenting with clinical features suggesting acute cholecystitis should undergo imaging tests to confirm the diagnosis. Ultrasonography is usually the first test obtained and can often establish the diagnosis. Nuclear cholescintigraphy may be useful in cases in which the diagnosis remains uncertain after ultrasonography.
Ultrasonography The presence of stones in the gallbladder in the clinical setting of right upper quadrant abdominal pain and fever supports the diagnosis of acute cholecystitis but is not diagnostic (show radiograph 2). Additional sonographic features include:Gallbladder wall thickening (greater than 4 to 5 mm) or edema (double wall sign).
Several studies have evaluated the accuracy of ultrasonography in the diagnosis of acute cholecystitis [28,30-34]. A particularly informative systematic review summarized the results of 30 studies of ultrasonography for gallstones and acute cholecystitis . Adjusted sensitivity and specificity for diagnosis of acute cholecystitis were 88 percent (95 percent CI 0.74 to 1.00) and 80 percent (95 percent CI 0.62 to 0.98), respectively.
The sensitivity and specificity of ultrasonography for detection of gallstones are in the range of 84 (95 percent CI 0.76 to 0.92) and 99 (95 percent CI .97 to 1.00) percent, respectively . Ultrasonography may not detect small stones or sludge as illustrated in a study that compared ultrasonography with direct percutaneous mini-endoscopy in patients who had undergone topical gallstone dissolution . Ultrasonography was negative in 12 of 13 patients in whom endoscopy demonstrated 1 to 3 mm stones or fragments (show endoscopy 1) .
Cholescintigraphy Cholescintigraphy (generically referred to as a HIDA scan) is indicated if the diagnosis remains uncertain following ultrasonography. This nuclear medicine examination uses a technetium labeled hepatic iminodiacetic acid (HIDA), which is injected intravenously and is then taken up selectively by hepatocytes and excreted into bile. If the cystic duct is patent, this agent will enter the gallbladder, leading to its visualization without the need for concentration. The HIDA scan is also useful for demonstrating patency of the common bile duct and ampulla. Visualization of contrast within the common bile duct, gallbladder, and small bowel occurs within 30 to 60 minutes (show radiograph 3). The test is positive if the gallbladder does not visualize, which is invariably due to cystic duct obstruction, usually from edema associated with acute cholecystitis or an obstructing stone.
Cholescintigraphy has a sensitivity and specificity of approximately 97 and 90 percent, respectively [32,36]. Cystic duct obstruction with a stone or tumor in the absence of acute cholecystitis can cause a false positive test. Other conditions can cause false positive results in which the gallbladder does not visualize in spite of a nonobstructed cystic duct. These include:Severe liver disease, which may lead to abnormal uptake and excretion of the tracer.
False negative results are uncommon, since most patients with acute cholecystitis have obstruction of the cystic duct. When they occur, they may be due to incomplete cystic duct obstruction.
Morphine cholescintigraphy A modified version of the HIDA scan has been described, in which patients are given intravenous morphine during the examination. Morphine increases sphincter of Oddi pressure, thereby causing a more favorable pressure gradient for the radioactive tracer to enter the cystic duct. This modification is thought to be particularly useful in critically ill patients, in whom standard HIDA scanning may be associated with false positive results [38,39]. However, the test has not been well standardized, and has not gained wide acceptance.
Magnetic resonance cholangiography Magnetic resonance cholangiography (MR cholangiography) is a noninvasive technique for evaluating the intrahepatic and extrahepatic bile ducts. Its role in the diagnosis of acute cholecystitis was evaluated in a series that included 35 patients with symptoms of acute cholecystitis who underwent both ultrasound and MR cholangiography prior to cholecystectomy . MR cholangiography was superior to ultrasound for detecting stones in the cystic duct (sensitivity 100 versus 14 percent) but was less sensitive than ultrasound for detecting gallbladder wall thickening (sensitivity 69 versus 96 percent). At the present time its role in the diagnosis of acute cholecystitis should remain within clinical trials. (See "Magnetic resonance cholangiopancreatography").
CT scan Abdominal computed tomography (CT) is usually unnecessary in the diagnosis of acute cholecystitis, although it is can easily demonstrate gallbladder wall edema associated with acute cholecystitis (show radiograph 1). Other CT findings include pericholecystic stranding and fluid, and high-attenuation bile [40,41]. CT can be useful when complications of acute cholecystitis (such as emphysematous cholecystitis or gallbladder perforation) are suspected or when other diagnoses are considered.
Oral cholecystography Oral cholecystography has no role in the diagnosis of acute cholecystitis since it cannot show gallbladder wall edema and requires days to complete.
DIFFERENTIAL DIAGNOSIS The greatest initial challenge in the diagnosis of acute cholecystitis is distinguishing it from the more benign condition of biliary colic. Biliary colic is usually caused by the gallbladder contracting in response to a fatty meal, pressing a stone against the gallbladder outlet or cystic duct opening, and leading to increased intragallbladder pressure and pain. As in acute cholecystitis, biliary colic causes pain in the right upper quadrant. However, unlike acute cholecystitis, the pain is entirely visceral in origin, without true gallbladder wall inflammation. As the gallbladder relaxes, the stones often fall back from the cystic duct. As a result, the attack reaches a crescendo over a number of hours and then resolves completely.
Most patients who develop acute cholecystitis have had previous attacks of biliary colic, which may further confuse the diagnosis or lead patients to delay seeking medical attention. The following features may help to distinguish an attack of biliary colic from acute cholecystitis. However, such patients usually require imaging studies to help establish the diagnosis:The pain of biliary colic typically reaches a crescendo, and then resolves completely. Pain resolution occurs when the gallbladder relaxes, permitting stones to fall back from the cystic duct. An episode of right upper quadrant pain lasting for more than four to six hours should raise suspicion for acute cholecystitis.
A variety of other conditions can give rise to symptoms in the upper abdomen, which may be confused with biliary colic or acute cholecystitis. These include:Acute pancreatitis
These conditions can usually be differentiated by the clinical setting in which they occur and by obtaining the appropriate diagnostic studies.
SUMMARY AND RECOMMENDATIONS Acute cholecystitis refers to a syndrome of right upper quadrant pain, fever, and leukocytosis associated with gallbladder inflammation and is usually related to gallstone disease.
Patients with acute cholecystitis typically complain of abdominal pain, most commonly in the right upper quadrant or epigastrium. The pain may radiate to the right shoulder or back. Characteristically, acute cholecystitis pain is steady and severe. Associated complaints may include nausea, vomiting, and anorexia.
Acute cholecystitis must be distinguished from the more benign condition of biliary colic, which presents with the same type of pain. Biliary colic is usually caused by the gallbladder contracting in response to a fatty meal, pressing a stone against the gallbladder outlet or cystic duct opening, and leading to increased intragallbladder pressure and pain. As in acute cholecystitis, biliary colic causes pain in the right upper quadrant. However, unlike acute cholecystitis, the pain is entirely visceral in origin, without true gallbladder wall inflammation. As the gallbladder relaxes, the stones often fall back from the cystic duct. As a result, the attack reaches a crescendo over a number of hours and then resolves completely.
Left untreated, symptoms of cholecystitis may abate within 7 to 10 days. However, complications can occur at alarmingly high rates, which is why urgent plans for treatment must be entertained. The most common complication is the development of gallbladder gangrene (up to 20 percent of cases) with subsequent perforation (2 percent of cases) .
Acute cholecystitis should be suspected when a patient presenting with the clinical manifestations outlined above is found to have gallstones on an imaging study. However, the mere presence of gallstones is not a sine qua non for acute cholecystitis, since asymptomatic cholelithiasis is a common condition in the general population. Thus, confirmation of the diagnosis must be based upon a combination of physical findings, laboratory studies, and imaging tests (show algorithm 1).
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