Acute acalculous cholecystitis refers to the development of cholecystitis in the gallbladder either without gallstones or with gallstones where they are not the contributory factor. It is thought to occur most often due to biliary stasis and/or gallbladder ischemia.
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Epidemiology
Acute acalculous cholecystitis represents 5-10% of cases of acute cholecystitis.
Risk factors
Risk factors and preceding contributory insults associated with the development of acute acalculous cholecystitis include 2:
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severe tissue injury
including major trauma and burns
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postoperative
especially following major surgery e.g. valvular replacement 13
malignancy
vasculitis
shock
cardiac arrest
advanced age 12
concomitant opioid therapy
positive-pressure ventilation (PPV)
total parenteral nutrition (TPN)
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viral infections
dengue, Epstein-Barr, hepatitis (A-C), cytomegalovirus, disseminated varicella-zoster, Zika, and HIV 15
Pathology
Acute acalculous cholecystitis usually occurs in critically ill or injured patients (e.g. trauma, burns, sepsis). The risk factors listed above may affect the perfusion of the gallbladder and favor bile stasis leading to injury and inflammation. Subsequent ischemia-reperfusion injury to the gallbladder is also a central pathogenic feature 2,9.
A rare cause of acalculous cholecystitis occurring in patients with advanced cancer is gallbladder metastases 10. Case reports have also described acute acalculous cholecystitis likely precipitated by snake envenomation 16, as well as a presenting feature in a patient with Kawasaki disease 17.
Radiographic features
Generally, ultrasound is needed to confidently exclude the presence of gallstones.
Ultrasound
May show gallbladder wall edema, pericholecystic fluid, and gallbladder distention (the first two considered the two most important criteria 2). The sonographic Murphy sign may be positive. A sonolucent intramural layer or “halo” that represents intramural edema may also be present.
A sonogram may be considered highly suggestive of the diagnosis with two of the following major criteria, or one major and two minor criteria fulfilled 14;
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major criteria
wall striation
pericholecystic fluid
intramural gas
mucosal sloughing
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minor criteria
echogenic bile or sludge in the lumen
transverse diameter >5 cm
Scintigraphy
Tc-99m iminodiacetic acid cholescintigraphy is considered a highly reliable test and may be performed even in acutely ill patients. Ideally, there is non-visualization of the gallbladder.
Treatment and prognosis
The importance of recognizing acalculous cholecystitis lies in the fact that these patients have a high rate of recurrence when treated with medical management. As such, cholecystectomy is the definitive treatment. However, patients that are not fit for surgery can undergo percutaneous or endoscopic biliary drainage as an alternative therapy, though cholecystectomy may still be performed when the patient improves.