Boshell, Hunter MD; Ristagno, Ross L. MD
A 59-year-old man with endstage liver disease, portal hypertension, and suspected hepatocellular carcinoma presented with 3 days of anorexia, right upper quadrant abdominal pain, and nausea. Physical examination revealed right upper quadrant tenderness. The patient was afebrile with a white blood cell count of 6000/cubic millimeter. A contrast-enhanced computed tomography (CT) of the abdomen revealed gallbladder distention, pericholecystic inflammatory stranding, and multiple gallstones (Fig. 1). Ultrasound (US) revealed a thickened gallbladder wall and multiple gallstones (Fig. 2).
Based on clinical and imaging findings, acute calculous cholecystitis was diagnosed. Given the patient's significant comorbid conditions and estimated high risk of general anesthesia, a percutaneous cholecystostomy (PC) tube was placed using US and fluoroscopic guidance in the radiology department. An 8-French locking pigtail catheter was inserted into the gallbladder via the transhepatic approach using intravenous sedation and local anesthesia (Fig. 3). Culture of nonpurulent bile yielded Enterococcus and α-hemolytic streptococcus species. Based on culture results, the patient was started on intravenous piperacillin/tazobactam.
The patient's nausea and abdominal tenderness resolved within 24 hours after PC tube placement. He was discharged on the fourth hospital day with the cholecystostomy tube to bag drainage, a 14-day course of oral amoxicillin/clavulanate, and scheduled for follow-up in surgery clinic to determine optimal timing of cholecystectomy.
Acute calculous cholecystitis treated with PC.
Acute cholecystitis (AC) is a common clinical problem which may present in either the ambulatory or the critical care settings. The condition presents with a variety of clinical, laboratory, and imaging findings. Diagnosis and treatment are most challenging in patients who are advanced in age, critically ill, and with multiple comorbid conditions. Care of these patients requires a multidisciplinary team that may involve the primary care physician, infectious disease specialist, surgeon, and radiologist. This case report focuses on the imaging findings and the role of interventional radiology management in AC.
Most cases (90%-95%) of AC are caused by biliary calculi obstructing the cystic duct (ie, acute calculous cholecystitis). The consequences of cystic duct obstruction are gallbladder distention and increased intraluminal pressure, which may lead to gallbladder wall ischemia and subsequent necrosis.1 Acute inflammation of the wall may be related to chemical injury from bile salts or superimposed bacterial infection. Only 5% to 10% of cases of AC are caused by acute acalculous cholecystitis, which usually occurs in hospitalized patients. Predisposing factors include recent surgery, severe trauma, burns, and any severe debilitating illness. The pathophysiology of acute acalculous cholecystitis is incompletely understood. Underlying cystic duct obstruction may be caused by external compression (from kinking, adhesions, lymphadenopathy, local tumor, or anomalous vessel) or intrinsic cystic duct obstruction (caused by edema, stagnant bile, or cellular debris). In patients with acalculous cholecystitis without cystic duct obstruction, gallbladder inflammation is believed to result from sepsis, ischemia, or concentrated bile salts in the setting of bile stasis.2
Simple inflammation of the gallbladder wall (uncomplicated AC) can progress to complicated AC in 20% of patients. Complicated AC includes entities such as gangrenous cholecystitis, emphysematous cholecystitis, and gallbladder perforation. These entities are associated with significantly increased morbidity (10%) and mortality rates (15%). Patients with complicated AC usually require emergent surgical intervention and are at higher risk of surgical complications.3
Gangrenous cholecystitis is characterized by caseous necrosis of the gallbladder wall secondary to ischemia caused by increased intraluminal pressure.3 Gallbladder perforation occurs most commonly in patients with gangrenous cholecystitis. Subacute perforation progresses to pericholecystic abscess formation; less often, acute perforation leads to bile peritonitis.3 Emphysematous cholecystitis is a rare infection of the gallbladder associated with gas-forming bacteria in the gallbladder lumen or wall. Up to 40% of patients with emphysematous cholecystitis have diabetes mellitus.3 Emphysematous cholecystitis may lead to perforation.
Although the diagnosis of AC in an otherwise healthy patient is often straightforward, the diagnosis of calculous and especially acalculous cholecystitis in a critically ill patient can present quite a dilemma. Patients are often nonresponsive, and classic physical examination findings are difficult to elicit. Also in this setting, many laboratory and imaging abnormalities are nonspecific.
There are multiple imaging modalities that have been successfully used to evaluate patients for suspected AC. These include US, CT, and hepatobiliary scintigraphy.
Ultrasound is the most commonly used first-line imaging.1 There are several findings on US that may indicate acute calculous cholecystitis. These findings include the following: gallstones, sludge, gallbladder wall thickening (>3 mm), intramural edema, pericholecystic fluid, sloughing of the gallbladder wall, and a positive sonographic Murphy's sign (Figs. 2, 4, 5).4 By far, the most sensitive US findings for acute calculous cholecystitis are a combination of cholelithiasis with a positive sonographic Murphy sign that has been shown to have a positive predictive value of 92%.1,5 A positive Murphy sign is defined as maximal tenderness elicited by the US transducer over the gallbladder. Sonographic findings in acute acalculous cholecystitis are similar to those in acute calculous cholecystitis except for the absence of gallstones
Certain sonographic findings are seen more frequently in patients with complicated AC. Sloughing of the gallbladder wall is a specific finding for gangrenous cholecystitis but is only seen in 5% of patients with this entity (Fig. 5).3 Complex pericholecystic fluid collections are often seen in cases of gallbladder perforation with subsequent abscess formation. Emphysematous cholecystitis is difficult to evaluate with US but can present with antidependent gas shadows in the gallbladder lumen.3
Ultrasound findings of AC are very helpful in the appropriate clinical setting and are nonspecific in other circumstances. For example, gallbladder wall thickening and pericholecystic fluid usually indicate AC in the ambulatory patient, although these findings are frequently identified in patients without AC who have ascites or nearby local inflammation. Gallstones are found in 90% of patients with AC and present in at least 20% of asymptomatic individuals older than 55 years.2
Although US is the first-line imaging for gallbladder pathology, the pervasive use of CT, which is more helpful than US in evaluation of other abdominal pathologies, has led to more frequent visualization of AC by CT.6 The CT findings of AC include gallstones, gallbladder distention, gallbladder wall thickening (>3 mm), pericholecystic fluid and inflammatory stranding, lack of gallbladder wall enhancement, intraluminal membranes, and gas in the gallbladder wall (Figs. 1, 6, 7).5,6 Most of these CT findings are similar to the findings seen on US. Computed tomography is less sensitive than US for imaging gallstones because only 75% are detected (depending on calcium content of the stone). A finding which is unique to CT is focal enhancement of the hepatic parenchyma adjacent to the gallbladder.5,7 Pericholecystic inflammatory change is a more specific CT finding than gallbladder distension and wall thickening, which may simply represent edema and do not necessarily indicate inflammation (Fig. 1).5
As with US, certain CT findings are more indicative of complicated AC. Gangrenous cholecystitis is often characterized by intraluminal membranes or lack of gallbladder wall enhancement. A pericholecystic abscess is the most common CT finding in gallbladder perforation. Computed tomography is much more sensitive than US for emphysematous cholecystitis which is characterized by gas in the lumen or wall (Fig. 7).3,5
Hepatobiliary scintigraphy with 99mTc-iminodiacetic acid is another frequently used imaging modality for the evaluation of AC. Hepatobiliary scintigraphy demonstrates high sensitivity (up to 95%) and specificity (>90%) for acute calculous cholecystitis.2 Findings in acute acalculous cholecystitis are similar in sensitivity but are much less specific. Findings indicative of acute calculous cholecystitis are nonfilling of the gallbladder with normal hepatic uptake and biliary excretion (Fig. 8).2 An infrequently identified but very specific hepatobiliary scintigraphic finding is focally increased hepatic scintigraphic uptake surrounding the gallbladder fossa known as the "rim sign."2
Biliary stasis, which is commonly found in hospitalized AC patients with prolonged fasting or receiving total parenteral alimentation, leads to a high rate of false-positive hepatobiliary scintigraphy.8 The number of false-positive scans can be decreased by augmenting the scan with intravenous morphine or cholecystokinin or by performing delayed images.
In summary, each imaging modality-US, CT, and hepatobiliary scintigraphy-has a role in the evaluation of AC. Ultrasound is the most commonly used first-line imaging modality because it is a simple bedside test which provides rapid results. Computed tomography is a more useful diagnostic test if other abdominal pathologies are under consideration. Hepatobiliary scintigraphy is the most sensitive and specific of the imaging modalities for diagnosis of AC in the noncritically ill patient. The diagnostic accuracy of each imaging modality depends on the patient's clinical scenario. Consultation with the radiologist can often clarify which imaging test will be the most helpful.
Imaging findings, as previously discussed, pertain to AC as defined by inflammation of the gallbladder wall on pathological examination without regard to the presence of bacteria. Studies have shown that 40% to 50% of patients with AC have positive bile cultures.9 The lower than expected culture positivity may be caused by previous antimicrobial coverage and a more advanced stage of AC.10 The finding of bactibilia is of particular interest because these patients have been shown to be at higher risk for sepsis and gallbladder rupture and may require more aggressive medical and interventional therapies.10
Bactibilia is believed to result from superinfection of stagnant bile. The most commonly encountered organisms in infected bile are constituents of normal intestinal flora including gram-negative bacilli such as Escherichia coli and species of Enterobacter and Klebsiella. Enterococcus species and anaerobes including Bacteroides, Fusobacterium, and clostridia species are less commonly isolated.11 Studies by Beardsley et al10 and Sosna et al9 have sought to determine if certain imaging characteristics are helpful in predicting bactibilia. Unfortunately, both studies demonstrated that no single imaging finding was either sensitive or specific. Furthermore, Beardsley et al10 found that no single or combination of imaging findings was predictive of bactibilia.
The treatment of choice for AC in otherwise healthy patients is laparoscopic or open cholecystectomy. However, in critically ill and elderly patients with multiple comorbidities, surgical mortality rates are as high as 14% to 30%.12 This is a relatively common problem because as many as 50% to 70% of patients who present with AC are elderly and have multiple comorbidities.13 Patients who are considered poor surgical candidates are provided intravenous fluids and broad-spectrum antibiotics initially. If the patient fails to improve clinically, a viable alternative to surgery is PC.
First performed in 1980,12 PC has been proven to be an effective bridge for patients with AC compared with emergent cholecystectomy and has led to lower mortality rates of less than 1%.11-14 In many patients with acalculous cholecystitis treated with PC, a cholecystectomy is not necessary.12
Percutaneous cholecystostomy is usually performed using the Seldinger technique under US guidance while the patient receives intravenous sedation and local anesthesia. The procedure is performed in the radiology department or at the patient's bedside in the intensive care unit. If adequate visualization of the gallbladder with sonography is not achievable, CT guidance may be used.13 Two routes of PC catheter insertion are used, transhepatic and transperitoneal. The transhepatic route is generally preferred because of a lower risk of significant bile leak into the peritoneal cavity and increased catheter stability. The transperitoneal approach may be preferred in patients with coagulopathy or severe liver disease.12 Locking pigtail drainage catheters (8-10 French) are generally used to decrease the risk of catheter dislodgment. Bile is drained through the catheter to bag drainage or Jackson-Pratt bulb suction. If possible, a small amount of contrast may be injected under fluoroscopy to document PC tube position. A definitive cholangiogram is delayed until the patient has clinically improved to decrease the risk of sepsis.12,14 Of paramount importance is that the PC catheter is not removed prematurely because of risk of bile leak and consequent bile peritonitis. Percutaneous cholecystostomy catheters should be left in place for 3 to 6 weeks to ensure adequate tract formation.15
The efficacy and safety of PC in patients with AC with severe comorbid conditions is well documented.12-14 The technical success rate approaches 100%.13,14 A rapid clinical response (defervescence, cessation of symptoms, and return of white blood cell to normal) is seen in 83% to 98% of patients within 24 to 72 hours of PC.12,13 Complications of PC include catheter dislodgement, bile leak, hemorrhage, pneumothorax, bowel perforation, and vasovagal reactions. Percutaneous cholecystostomy complications are rare except for catheter dislodgement (5%-10%).13 Death resulting from bile peritonitis has been reported.14
Although PC is an established treatment modality for AC, some investigators maintain that PC has a diagnostic (and therapeutic) role in patients with sepsis of unknown etiology in the intensive care unit.15,16 This application of PC results in a greater than 50% clinical response. Although it may seem that many patients undergo an unnecessary procedure, it can be argued that the definitive exclusion of the gallbladder as the cause of sepsis is worthwhile, given the low procedural risk of PC.15,16
Acute cholecystitis is a common and complex clinical problem particularly in critically ill and elderly patients. Awareness of pertinent imaging findings and minimally invasive treatment options is necessary for adequate diagnosis and management of patients with this potentially fatal disease.
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