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.
1. Hanbidge AE, Buckler PM, O'Malley ME, et al. Imaging evaluation for acute pain in the right upper quadrant. Radiographics
. 2004;24: 1117-1135.
2. Ziessman HA. Acute cholecystitis, biliary obstruction, and biliary leakage. Semin Nucl Med
3. Rubens DJ. Hepatobiliary imaging and its pitfalls. Radiol Clin North Am
4. Bortoff GA, Chen MY, Ott DJ, et al. Gallbladder stones: imaging and intervention. Radiographics
5. Bennett GL, Balthazar EJ. Ultrasound and CT evaluation of emergent gallbladder pathology. Radiol Clin North Am
6. Singh AK, Sagar P. Gangrenous cholecystitis: prediction with CT imaging. Abdom Imaging
7. Yamashita K, Jin MJ, Hirose Y, et al. CT finding of transient focal increased attenuation of the liver adjacent to the gallbladder in acute cholecystitis. AJR Am J Roentgenol
8. Mirvis SE, Vainright JR, Nelson AW, et al. The diagnosis of acute acalculous cholecystitis: a comparison of sonography, scintigraphy, and CT. AJR Am J Roentgenol
9. Sosna J, Kruskal JB, Copel L, et al. US-guided percutaneous cholecystostomy: features predicating culture-positive bile and clinical outcome. Radiology
10. Beardsley SL, Shlansky-Goldberg RD, Patel A, et al. Predicting infected bile among patients undergoing percutaneous cholecystostomy. Cardiovasc Intervent Radiol
11. Johannsen EC, Madoff LC. Infections of the liver and biliary system. In: Mandell GL, Bennett JE, Dolin R, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases
. 6th ed. Philadelphia, PA: Elsevier; 2005:951-959.
12. Spira RM, Nissan A, Zamir O, et al. Percutaneous transhepatic cholecystostomy and delayed laparoscopic cholecystectomy in critically ill patients with acute calculus cholecystitis. Am J Surg
. 2002;183: 62-66.
13. Berber E, Engle KL, String A, et al. Selective use of tube cholecystostomy with interval laparoscopic cholecystectomy in acute cholecystitis. Arch Surg
14. McGahan JP, Lindfors KK. Percutaneous cholecystostomy: an alternative to surgical cholecystectomy for acute cholecystitis? Radiology
15. Boland GW, Lee MJ, Leung J, et al. Percutaneous cholecystostomy in critically ill patients: early response and final outcome in 82 patients. AJR Am J Roentgenol
© 2007 Lippincott Williams & Wilkins, Inc.
16. Lee MJ, Saini S, Brink JA, et al. Treatment of critically ill patients with sepsis of unknown cause: value of percutaneous cholecystostomy. AJR Am J Roentgenol